In clu sions in anhydrite crys tals from blue ha lite veins in the K³odawa Salt Dome (Zechstein, Po land)
Tomasz TOBO£A1, *
1 AGH Uni ver sity of Sci ence and Tech nol ogy, Fac ulty of Ge ol ogy, Geo phys ics and En vi ron men tal Pro tec tion, al.
A. Mickiewicza 30, 30-059 Kraków, Po land
Tobo³a, T., 2016. In clu sions in anhydrite crys tals from blue ha lite veins in the K³odawa Salt Dome (Zechstein, Po land). Geo - log i cal Quar terly, 60 (3): 572–585, doi: 10.7306/gq.1274
The oc cur rence of both the blue and vi o let halites is one of the most in ter est ing phe nom ena in na ture. De spite nu mer ous lab - o ra tory and field works, their or i gin in nat u ral evaporitic en vi ron ments has not been sat is fac to rily ex plained. In the K³odawa Salt Dome (Zechstein, Cen tral Po land), blue or vi o let halites oc cur rel a tively fre quently. Their ac cu mu la tions dif fer in size and in ten sity of colours. In this pa per, pet ro log i cal fea tures of anhydrite crys tals de rived from one of the larg est out crops of the blue ha lite at the K³odawa Salt Mine are pre sented. Anhydrite is one of solid in clu sions en coun tered in blue-col oured ha - lite crys tals. Spe cial at ten tion was paid to fluid in clu sions pres ent in this anhydrite. The microthermometric mea sure ments showed two di rec tions of ho mog e nisation, i.e., to wards the liq uid phase (LG®L, LL®L) or to wards the gas phase (LG®G).
In the for mer case, the tem per a tures ranged from 174 to 513°C, whereas in the lat ter one, the val ues from 224 to 385°C were mea sured. The com po si tion of in clu sions is rel a tively vari able. We can ob serve trans par ent and opaque daugh ter min er als as well as CO2 in the liq uid phase ac com pa nied by a vari able amount of meth ane or hy dro gen sul phide. These fea tures of in - clu sions in di cate that anhydrite crys tals and, thus, blue ha lite were formed un der the in flu ence of hy dro ther mal con di tions.
Ob ser va tions in the mine work ings com bined with pet ro log i cal stud ies en able to con clude that blue colouration of ha lite crys - tals is con trolled by three fac tors: a high tem per a ture, re duc ing con di tions and de fects in ha lite lat tice re lated to tec tonic stress.
Key words: blue ha lite, hy dro ther mal en vi ron ment, salt domes, anhydrite, epigenetic salt.
INTRODUCTION
The blue or vi o let ha lite crys tals are very rare in na ture al - though they were no ticed in many salt for ma tions of var i ous ages. They were found, inter alia, in Cam brian KCl-de pos its from the south ern part of the Si be rian plat form (Pustyl’nikov, 1975), Mis sis sip pian rocks of east ern Can ada (Roulston and Waugh, 1983; Waugh and Urquhart, 1983; Davison, 2009), Lower Perm ian of the Solikamsk De pres sion in the Ural Foredeep (Vinokurov, 1958; Ivanov and Voronova, 1972;
Smetannikov, 2011), within the Verkhnepechora Ba sin (Ivanov and Voronova, 1968) as well as in the Kramatorsk Se ries of Donbass (Bobrov et al., 1968), Up per Perm ian of the Del a ware Ba sin, south east ern New Mex ico, USA (Bickham, 2012), Up per Perm ian (Zechstein) salt de pos its of Ger many (Borchert, 1959), Cre ta ceous to Paleogene (Maha Sarakham For ma tion) of the Khorat Pla teau, north east ern Thai land (Suwanich, 1983;
Tabakh et al., 1999), Paleogene and Neo gene of North ern and Cen tral Iran (Rahimpour-Bonab and Alijani, 2003; Baikpour et al., 2010), and Mio cene of the Carpathian Foredeep in Ukraine
(Koriñ, 1994). The na ture of such colouration has been in ves ti - gated for over 150 years by many re search ers rep re sent ing var - i ous fields. One of the first sci en tists who un der took in-depth anal y sis of blue ha lite was Kreutz (1892). He ana lysed the re - sults of ex per i ments and ob ser va tions made by pre vi ous au - thors, and com pleted a se ries of his own ex per i ments on nat u ral and syn thetic ha lite crys tals. Based on these data Kreutz (1892) con cluded that: (1) blue col our does not fade when ha lite crys - tals are heated in ox y gen-free at mo sphere, but dis ap pears un - der “flame of ox i da tion”; (2) pre vi ously dis col oured and nat u rally colour less ha lite crys tals be come col oured when heated in po - tas sium or so dium va pours, al though not all orig i nally colour - less crys tals be come col oured; and (3) un der the same ex per i - men tal con di tions, syn thetic ha lite crys tals are not col oured.
These and other ob ser va tions and ex per i ments en abled Kreutz (1892) to pres ent the the ory that the col our of ha lite crys - tals orig i nated from very small ad mix tures of iron or other met - als, which were be low the de tec tion lim its of an a lyt i cal meth ods used at that time.
The de vel op ment of mod ern an a lyt i cal meth ods since the late 19th cen tury has pro vided new valu able data. The new stud ies (see Sonnenfeld, 1995) fo cused mostly on lab o ra tory anal y ses of blue ha lite prop er ties and on the meth ods of its colouration, and they gave rise to new hy poth e ses on the or i gin of col our in nat u ral ha lite. It was found that, in ad di tion to the above-men tioned fac tors, colouration of ha lite can be ob tained by crystallisation from NaCl- and KCl-sat u rated so lu tions con -
* E-mail: tob@geolog.geol.agh.edu.pl
Received: October 13, 2015; accepted: December 11, 2015; first published online: February 2, 2016
tain ing 320 g/l MgCl2, by elec tric spark punc ture and by the ac - tion of ion iz ing UV, a, b and g ra di a tions. More over, it was also ob served that the physico-chem i cal prop er ties of ar ti fi cially col - oured ha lite crys tals dif fer from the nat u ral ones. A large num - ber of pa pers con cern ing ha lite crys tals colouration were re - viewed and dis cussed by Sonnenfeld (1995). He con cluded that most of ex per i men tal re sults were ob tained un der con di - tions which do not oc cur in the na ture. He has also ques tioned the widely ac cepted view that the col our of nat u ral ha lite re sults from ra di a tion caused by ra dio ac tive de cay of 40K iso tope.
In re cent years, de tailed ob ser va tions and stud ies on the oc cur rence of blue ha lite were car ried on at the K³odawa Salt Dome (Natkaniec-Nowak and Tobo³a, 2003; Tobo³a et al., 2007; Janiów et al., 2008). As a re sult of this re search, 19 key ex po sures were de scribed to gether with their re la tions to the sur round ing rocks and min eral com po si tion, as well as with vi - sual es ti ma tion of the in ten sity, vari abil ity, hue and sat u ra tion of col our. Stan dard mi cro scopic ex am i na tions of thin sec tions of blue ha lite re vealed the pres ence of birefringent ar eas in the crys tals. Un for tu nately, their cor re la tion with col oured ar eas was dif fi cult be cause ha lite colours are in vis i ble in thin sec tions (Heflik et al., 2008). Sim i larly, in thick sec tions, in which blue col our is clearly vis i ble un der trans mit ted light, char ac ter is tic bi - refrin gence does not co in cide with col oured ar eas, but both fea - tures co ex ist side by side. More over, ob ser va tions of thick sec - tions re vealed also the com mon pres ence of inter growths, both trans par ent and opaque. The SEM-EDS ex am i na tions showed that trans par ent inter growths are the mix tures of so dium, mag - ne sium and po tas sium chlo rine com pounds, whereas opaque inter growths are iron sulphides, al though their crys tal hab its do not cor re spond to well-known and most com mon min er als, such as py rite or marcasite (Tobo³a and Natkaniec-Nowak, 2008). The fluid in clu sion stud ies dem on strated the pres ence of sev eral in clu sion types dif fer ing in geo met ric pat terns. The in - clu sions are filled with highly con cen trated brines as well as with gases (CO2, CO, COS, O2, N2, CH4, C3H8), with ar o matic hy dro - car bons and with liq uid, long-chained hy dro car bons (Tobo³a and Wese³ucha-Birczyñska, 2008; Wese³ucha-Birczyñska et al., 2008). Struc tural stud ies of ha lite sam ples with vary ing de - grees of stain ing showed de for ma tion of the sym me try of reg u - lar struc ture (Zelek et al., 2007, 2014; Stadnicka and Zelek, 2008). All these data clearly dem on strated the com plex ity of pro cesses lead ing to the for ma tion of col oured va ri et ies of ha lite in the salt dome.
The aim of pres ent stud ies is to es ti mate the for ma tion tem - per a ture of the blue salts. Pre vi ous in ves ti ga tions car ried out for blue ha lite crys tals sug gested in some cases high tem per a tures, up to 347°C (Tobo³a and Wese³ucha-Birczyñska, 2008). How - ever, these data should be treated with cau tion be cause of some ha lite prop er ties such as easy recrystallisation and re ac tion with so lu tions con tained in in clu sions (e.g., Roedder, 1984b). Hence, more pre cise and cred i ble data can be ob tained for min er als co - ex ist ing with the blue ha lite. Anhydrite, ac com pa nied by iron sulphides (py rite) and quartz, is the most com mon min eral. Such paragenesis as well as the fluid in clu sions as sem blage (FIA) in anhydrite crys tals doc u ment atyp i cal con di tions of the blue ha lite for ma tion and the ther mal im pact on salt rocks.
GEOLOGICAL SETTING
The K³odawa Salt Dome is lo cated in the Kujawy re gion (Cen tral Po land, Fig. 1). This re gion is char ac ter ized by the most com plete lithostratigraphic suc ces sion and the max i mum thick ness of the Zechstein salt-bear ing for ma tion. De tailed data con cern ing the re la tion ships of salt-bear ing for ma tion to the
sur round ing rocks, its tec ton ics, lithostratigraphy and fa cies changes can be found in a num ber of pub li ca tions (see e.g., Dadlez, 2003; Dadlez et al., 1995; Krzywiec, 2004, 2006). The K³odawa Salt Dome be longs to the Izbica Kujawska–£êczyca salt ridge, which is con sid ered as the larg est salt diapir in Po - land. Stud ies on the diapir struc ture in di cated its strong NW–SE elon ga tion. The length of the diapir is about 26 km, and its width var ies from 0.5 to 2 km (e.g., Werner et al., 1960; Tarka, 1992;
Burliga, 2014; Burliga et al., 1995). The geo log i cal cross-sec - tions show the asym met ri cal shape of the diapir: its NE slope dips mod er ately east ward at 55–70°, but its SW slope is al most ver ti cal. The diapir is en closed within de formed Me so zoic (Tri - as sic–Ju ras sic) and, partly, Neo gene de pos its, and is cov ered by Qua ter nary and Neo gene sed i ments. The K³odawa salt de - posit is built mainly of rocks rep re sent ing fully de vel oped Zechstein PZ2–PZ4 cyclothems. These are claystones, dolomites, an hyd rites, rock salts and K-Mg salts. The low er - most Zechstein cyclothem PZ1 is known only as tec toni cally trans ported blocks (Charysz, 1973; Burliga et al., 1995).
The in ter nal struc ture of the K³odawa Salt Dome is com pli - cated due to de for ma tion of salt se ries. The main ef fect of salt move ment dur ing the diapir ris ing is the pierc ing of the Older Ha lite (Na2) by the Youn ger (Na3) and the Youn gest (Na4) halites, as well as the oc cur rence of tec tonic pinch-outs and high-am pli tude nar row folds. Such com pli cated de for ma tion re - sulted from dif fer ent rhe o log i cal prop er ties of rocks. In gen eral, two NW–SE elon gated anticlines pre dom i nate in the SW and NE parts of the diapir (Fig. 2). These are sep a rated by a deep cen tral syncline built of the youn gest salt lay ers (Charysz, 1973;
Tarka, 1992; Burliga, 1994).
An im por tant role in the in ter nal struc ture of the salt dome is played by epigenetic salts. Their pres ence is closely as so ci ated with salt de for ma tion pro cesses that fa cil i tated mi gra tion of so - lu tions. In the K³odawa Salt Dome the epigenetic salts form veins and ac cu mu la tions of vari able size. Their min eral com po - si tion in cludes large ha lite crys tals as well as polyhalite, car nal - lite and sylvite (Stañczyk, 1970; Stañczak-Stasik, 1976).
OCCURRENCE OF THE BLUE HALITE IN THE K£ODAWA SALT DOME
The blue ha lite is rel a tively com mon at the K³odawa Mine. It was found at all main min ing lev els and in many interlevel work - ings, in var i ous rocks of the PZ2, PZ3 and PZ4 cyclothems (Natkaniec-Nowak and Tobo³a, 2003; Tobo³a et al., 2007;
Janiów et al., 2008). The blue ha lite forms very di verse con cen - tra tions with re spect to its size and col our, its con tact with the sur - round ing rocks, and the oc cur rence of ac com pa ny ing min er als.
The ha lite usu ally forms very small ac cu mu la tions (from a few to sev eral centi metres across) hosted in small veins or ir reg u lar ac - cu mu la tions of recrystallised salt. Salt crys tals some times con - tain inter growths of sylvite, car nal lite and polyhalite (Fig. 3A). The blue col our ap pears as point clus ters or small streaks within sin - gle ha lite crys tals. Such ac cu mu la tions are most com mon within the Older Ha lite (Na2) or Youn ger Ha lite (Na3).
The larger ac cu mu la tions of blue-col oured ha lite crys tals reach from a few to, oc ca sion ally, sev eral tens of metres in length. Their out crops were en coun tered at min ing lev els 525, 562, 600 and 750. At the level 525, a con tin u ous zone of blue ha lite was rec og nized within the Older Ha lite (Na2), over 50 m long and from 4 to 15 m wide. It ex tends from the KS29–KS21 cham bers through the area of KSc18 and KSc12 cy lin dri cal cham bers, and con tin ues to wards the KS16a cham ber as well as gal ler ies lead ing to the above-men tioned work ings. A char - ac ter is tic fea ture of this zone is the oc cur rence of both
Fig. 1. Part of the Zechstein lithofacies map, and location of salt structures in Poland (after Garlicki and Szybist, 1986)
Fig. 2. Geological cross-section through the upper part of the K³odawa Salt Dome (after Burliga et al., 1995, simplified)
Fig. 3A – small clus ters and streaks of blue col our within ha lite crys tal ac com pa nied by car nal lite and polyhalite (min ing level 600 m, cham ber KS1d); B – larger, ir reg u lar con cen tra tion of blue ha lite within striped salt (Older Ha lite) (min ing level 525 m, cham - ber KSc14); C – coarse-crys tal line ha lite with small inter growths of sylvite (marked by ar rows) with blue rim (min ing level 630 m, gal lery be tween cham bers KS16b and KS17b); D – streaks and elon gated con cen tra tion of blue ha lite in white ha lite and sylvite (min ing level 562 m, ven ti la tion gal lery be tween cham bers KS38 and KS39); E – blocks of pri mary striped salt (Older Ha lite) with blue rims em bed ded within white epigenetic vein of ha lite and sylvite (min ing level 600 m, roof of cham ber KS39); F – large blue-col - oured ha lite crys tals in side a vein of white car nal lite with ad mix ture of sylvite (min ing level 750 m, cross ing of gal ler ies GPT2 and GPT2a)
epigenetic structureless veins and nests of large ha lite crys tals, and rock salt ag gre gates with pre served re sid ual “striped”
struc ture (Tobo³a et al., 2007; Janiów et al., 2008). In the ha lite crys tals, blue colouration shows var i ous pat terns. The most com mon fea tures of the “striped” halites are ir reg u lar, spotty ac - cu mu la tions with fuzzy con tours and vary ing de grees of blue col our sat u ra tion (Fig. 3B). In the structureless salt ag gre gates, where ha lite crys tals oc ca sion ally ex ceed 20 cm in di am e ter, blue col our is much rarer. It can be ob served only in some ha lite crys tals as sin gle spots or spot clus ters, up to sev eral milli - metres across. Blue colouration is of ten as so ci ated also with trans par ent solid in clu sions vary ing in size from 0.5 to 2–3 mm, em bed ded within ha lite crys tals which show thin blue rims (Fig. 3C).
One of the larg est ac cu mu la tions of the colour ful ha lite, ex - tend ing over a dis tance of 12 metres (Fig. 3D), is lo cated at the min ing level 562, in the ven ti la tion gal lery be tween cham bers KS38 and KS39, within the Older Ha lite (Na2). The main mass com prises trans par ent or white ha lite and sylvite in var i ous pro - por tions. The col oured ha lite forms strongly elon gated streaks of dif fused bound aries, up to sev eral centi metres thick, ex tend - ing con tin u ously through the en clos ing white salts. The col our of these streaks changes from light blue through blu ish-vi o let to dark navy blue. Lo cally, even pur ple or yel low ha lite crys tals can be found (Tobo³a et al., 2007; Janiów et al., 2008).
At the min ing level 600 in the end part of cham ber KS39, there is an ex ten sion of the above-men tioned out crop of blue ha lite. How ever, in con trast to the ac cu mu la tion at the level 562, the great est amounts of blue salt oc cur at the con tact of striped pri mary salts (Na2) and epigenetic syl vin ite. Streaks or in di vid - ual small light-blue ha lite crys tals are ob served much more rarely. The most in tense blue col our ap pears along the edges of tec tonic blocks of striped ha lite (Na2) em bed ded within syl vin ite veins (Fig. 3E).
Other ma jor ex po sures at this min ing level were found in the gal ler ies NW I and NE VII (Tobo³a et al., 2007; Janiów et al., 2008). They are hosted in side lam i nated salt of the Youn ger Ha lite (Na3). Sim i larly to the above-men tioned oc cur rences in the ven ti la tion gal lery and cham ber KS39, the ma trix of the vein con sists of white epigenetic syl vin ite, within which the blue ha - lite forms blurry streaks, up to about 20–30 cm thick and gen er - ally par al lel to the course of that epigenetic vein. The larg est con cen tra tions of ha lite show ing the high est in ten sity of blue col our are lo cated at the con tact of the vein and the Youn ger Ha lite (Na3).
An other va ri ety of large ha lite ac cu mu la tion is lo cated at the min ing level 750 (Tobo³a et al., 2007; Janiów et al., 2008) within the Youn ger Pot ash Salts (K3). The wall-rocks of the vein are com posed of epigenetic car nal lite with an ad mix ture of sylvite, in which sin gle crys tals of light-blue ha lite are em bed ded (Fig. 3F). The col oured ha lite is gen er ally scat tered in the vein as sin gle crys tals or small ag gre gates. Larger ac cu mu la tions in the form of streaks of darker-blue ha lite are ob served at the con tact of the vein with K-Mg salts (K3), es pe cially where these salts are ac com pa nied by the rock salt.
MATERIALS AND ANALYTICAL METHOD
For microthermometric stud ies we se lected anhydrite crys - tals form ing solid in clu sions in the blue ha lite. Ha lite sam ples were col lected from one of the larg est doc u mented ex po sure of blue salts lo cated in the ven ti la tion gal lery at the min ing level 562. In these sam ples, anhydrite crys tals are com monly as so ci - ated with streaks or nests of opaque min er als (Heflik et al.,
2008) or form scat tered sin gle crys tals. Anhydrite crys tals to - gether with other in sol u ble min er als were sep a rated by dis so lu - tion of blue ha lite. Then, anhydrite crys tals were gently crushed be cause their sur face rough ness causes dif fi cul ties dur ing mi - cro scopic ex am i na tions. To tally, about 200 anhydrite crys tals were se lected from 67 sam ples. Microthermometric mea sure - ments were car ried on for groups of fluid in clu sions which were clearly vis i ble un der the trans par ent light and which con tained two phases with a con stant vapour/liq uid ra tio.
Microthermometric mea sure ments were con ducted with a Linkam THMSG600 Ge ol ogy Heat ing and Freez ing Stage mounted on a NIKON ECLIPSE E600 mi cro scope, us ing 20´, 50´ and 100´ ob jec tives. The stage was cal i brated us ing pure CO2 syn thetic in clu sions (Tm = –56.6°C) and known ho mogeni - sa tion tem per a ture of pure H2O in clu sions. A heat ing-freez ing rate of 5°C/min was ap plied with the ac cu racy of 0.1°C. In di vid - ual anhydrite crys tals were mea sured only once in or der to avoid the ef fect of in clu sion stretch ing out side the ob ser va tion field of the mi cro scope, where in clu sion can not be di rectly ob - served. Cy cling was at tempted in all ho mogeni sa tion runs, in or der to ob serve the proper ho mogeni sa tion tem per a tures (Goldstein and Reynolds, 1994). An at ten tion was paid also to the changes of in clu sion shapes (Vanko and Bach, 2005). In case of no tice able changes, the mea sure ments were in ter - rupted.
In ad di tion, se lected sam ples were ana lysed with the Thermo Sci en tific TM DXR Raman Mi cro scope work ing in con fo - cal mode, us ing 780 nm ex ci ta tion line (di ode la ser, power:
24 mW). The Olym pus mi cro scope with 10´, 50´ and 100´ ob - jec tives was used for la ser fo cus ing.
RESULTS
SOLID INCLUSIONS IN ANHYDRITE CRYSTALS
Anhydrite crys tals are among the most fre quent solid inter - growths ob served in the blue ha lite crys tals (Tobo³a and Natkaniec-Nowak, 2007, 2008). Such inter growths vary in size from about 0.1 to 1 mm. Their shapes are usu ally anhedral or rarely subhedral, of ten with slightly rounded edges. The ma jor - ity of stud ied anhydrite crys tals are char ac ter ized by rough and scaly sur face (Fig. 4A). Un der trans mit ted light, opaque inter - growths can be seen within some anhydrite grains, usu ally as scat tered sin gle grains or, less com monly, as small ag gre gates (Fig. 4B) from a few micrometres to about 20 mm across. Their shapes vary from reg u lar for the larger grains (Fig. 4C) through partly reg u lar to rarely ir reg u lar for smaller ex am ples. The Raman spec tros copy re vealed that these solid inter growths are py rite grains (Fig. 4D). Oc ca sion ally, the large crys tals oc cur within the fluid in clu sion and oc cupy sig nif i cant parts of their vol - ume (Fig. 4E). As shown be low, very small opaque min er als are rel a tively com mon in fluid in clu sions.
Quartz is an other in ter est ing min eral en coun tered in blue-col oured ha lite. It was ini tially iden ti fied us ing the SEM-EDS method (Tobo³a and Natkaniec-Nowak, 2007, 2008). Sep a rated quartz crys tals are al ways euhedral and form elon gated hex ag o nal prisms (Figs. 4F and 5A). Sim i larly to the anhydrite crys tals, their sur face is very of ten rough (Fig. 4F), which pre vents ob ser va tion of in ter nal struc ture. More smooth sur faces are dis played only by rare crys tals which form short prisms (Fig. 5A). Un der the trans par ent light, such crys tals re - veal opaque inter growths as well as very small (a few mm) fluid in clu sions. Quartz crys tals are not only as so ci ated with ha lite but are also closely re lated to anhydrite. Such as so ci a tion de -
Fig. 4. Microscopic images
A – rough sur face of anhydrite crys tals; B – inter growths of opaque min er als within anhydrite crys tals (trans mit ted light); C – euhedral py rite inter growths in anhydrite crys tal (re flected light); D – Raman spec tra of py rite inter growth in C; E – solid inter growths as so ci ated with two-phase fluid in clu sion (trans mit ted light); F – euhedral quartz crys tal with rough sur face (trans mit ted light)
Fig. 5. Microscopic images (transmitted light)
A – short euhedral quartz crys tals with smoother sur face and small opaque inter growths; B – anhydrite crys tal (A) with inter growths of euhedral quartz (Q); C – densely packed FIA in a part of anhydrite crys tal, two shapes of in clu sions are vis i ble: reg u lar, cuboid (on the left), and highly elon gated, tu bu lar (on the right and in the up per part), some in clu sions con tain opaque (mainly tu bu lar) or trans par ent (mainly cuboid) min er als; D – one of the larg est flat tened two-phase in clu sions; E – the group of small opaque min er als in large in clu sion; F – tu bu lar in clu sion with sin gle opaque min er als lo cated at its ter mi na tions and in the cen tre (sin gle in clu sion), note that the min eral in the cen tre di vides the in clu sion into two parts of dif fer ent di am e ters
pends on the co ex is tence of both min er als when the quartz crys tals are over grown by the anhydrite ones (Fig. 5B). In some euhedral anhydrite crys tals, ob served un der trans mit ted light, small (up to 20 mm) quartz grains can be seen, too.
FLUID INCLUSIONS – PETROGRAPHY AND MICROTHERMOMETRIC DATA
In most anhydrite crys tals, fluid in clu sions were ab sent or oc curred only as sin gle, ran domly dis trib uted spe cies. Clus ters com posed of sev eral small in clu sions were also rel a tively un - com mon al though hunted be cause such forms pro vide more use ful data. Larger ac cu mu la tions of densely packed in clu sions were ob served only oc ca sion ally (Fig. 5C).
Two types of FIA were dis tin guished, de pend ing on their re - la tion ships to crys tal lo graphic axes and mode of oc cur rence:
pri mary and sec ond ary (pseudosecondary) (e.g., Roedder, 1984a; Goldstein and Reynolds, 1994). The most com mon in - clu sions were those iden ti fied as pri mary. Among the whole pop u la tion of the in ves ti gated crys tals these in clu sions dif fer in shape, size and fill ing ma te ri als.
Con cern ing the shape of in clu sions, two groups were dis tin - guished: the first one com prises reg u lar, cuboid in clu sions usu - ally slightly ex tended along the Z axis (rarely per pen dic u lar to the Z axis) or show ing square cross sec tions. Their size var ied from a few to sev eral micrometres but oc ca sion ally ex ceeded 20 mm. In clu sions ex ceed ing 50 mm in size were found only in a few crys tals (Fig. 5D). Un der the trans mit ted light the ma jor ity of these in clu sions seem to be flat tened. Thicker and larger in clu - sions very of ten con tain groups of opaque min er als in the form of small (up to about 2 mm), ir reg u lar, oc ca sion ally spher i cal grains (Fig. 5E). Fur ther more, we ob served also trans par ent daugh ter min er als of reg u lar, cu bic shapes in di cat ing the pres - ence of ha lite and sylvite, and rounded crys tals.
The sec ond group con sists of tu bu lar in clu sions, strongly elon gated along the Z axis (Fig. 5F). Their length ex ceeds 50 mm and the width is up to a few micrometres (3–5 mm). Such in clu sions very of ten con tain small opaque min er als in their end parts.
In clu sions of both groups show very com plex phase re la - tions and chem i cal com po si tions. The phase ra tios are highly vari able be tween sam ples, but they ap pear highly or fully con - sis tent in sin gle crys tals or in FIA. There fore, the high est vari - abil ity was ob served be tween the crys tals. In most crys tals, gas to liq uid (GL) or liq uid CO2 to liq uid H2O (LL) ra tios are in the range from 5 to 30% (Fig. 6A). An other group of FIA con sists of in clu sions con tain ing 85–95% of vapour phase (Fig. 6B). Be - tween these two types there are nu mer ous FIAs which com - prise in clu sions show ing in ter me di ate or highly vari able val ues of phase ra tios (Fig. 6C).
Both the sec ond ary and pseudosecondary in clu sions in anhydrite crys tals are more rare than the pri mary FIAs. These are ar ranged in nar row, some times curved or oblique rows (Fig. 6D). Such FIAs al ways con sist of very small in clu sions, up to a few micrometres across (rarely reach ing 10 mm). Their shapes are ir reg u lar and rounded. In all cases these are liq uid in clu sions with small (up to 15%) bub bles of gas phase.
In ad di tion to the above-men tioned types, in a few cases we ob served sep a rate in clu sions of ques tion able or i gin. Their shapes are ei ther rounded and slightly elon gated (Fig. 6E) or strongly elon gated and tu bu lar (Fig. 6F). The for mer are filled with the gas and liq uid phases in sim i lar pro por tions (~50%
V/L), whereas the lat ter are filled mostly with the gas phase
host ing trans par ent daugh ter min er als which sep a rate smaller parts of in clu sion filled prob a bly with the liq uid phase.
Microthermometric mea sure ments showed highly di ver si - fied be hav iour of in clu sions. Dur ing the heat ing, most of stud ied in clu sions un der went decrepitation with a rapid jump ing of crys - tals, which pre vented fur ther ob ser va tions, or with a dis tinct un - seal ing, with of ten vis i ble per co la tion of flu ids through the cleav - age planes. The tem per a tures of decrepitation and un seal ing var ied in a wide range, from 116 to 530°C, but the most com - mon val ues were from 350 to 450°C (Fig. 7). This in di cates a high pres sure within the in clu sions and the pos si ble pres ence of CO2 (e.g., Di a mond, 2001). Such in ter pre ta tion is sup ported by a com mon “swell ing” of in clu sions and evo lu tion of their shapes to oval at higher tem per a tures (Vanko and Bach, 2005).
Re li able re sults of to tal ho mogeni sa tion tem per a tures were ob tained for only twenty-seven FIAs mea sured. The pro cess of ho mogeni sa tion showed two paths: to the liq uid phase (LG®L or LL®L) or to the gas phase (LG®G), as re vealed by the phase ra tio. The first path was ob served in in clu sions with very low (5–10%) gas/liq uid of liq uid/liq uid ra tios. The low est ho mogeni - sa tion tem per a ture (174°C) was ob served in a sin gle in clu sion, whereas other in clu sions in this FIA re mained unhomogenised, show ing only shrink age and move ments of bub bles. At higher tem per a tures these in clu sions showed un seal ing or decrepitation. In the re main ing eight in clu sions, ho mogeni sa tion tem per a tures var ied from 371 to 513°C (Fig. 7). In the his to gram (Fig. 7), the value >520°C re fers to the in clu sions in which ho - mogeni sa tion could not be ob served di rectly be cause the heat - ing was con ducted to the max i mum tem per a ture of 550°C. How - ever, these in clu sions showed some fea tures in di cat ing the ap - proach ing ho mogeni sa tion, e.g., grad ual shrink age of the bub - bles and their rapid move ments (Roedder, 1984a).
The sec ond ho mogeni sa tion path (to wards the gas phase) pro vided re li able ho mogeni sa tion tem per a tures only for nine in - clu sions, in which, af ter cool ing to room tem per a ture, the phase ra tios re turned to the ini tial val ues. We re jected all in clu sions in which phase ra tios did not re turn ex actly to the orig i nal state due to un seal ing in vis i ble un der the mi cro scope. We also re - jected the in clu sions in which changes in shape (swell ing) were ob served. Gen er ally, ho mogeni sa tion to wards the gas phase was found in gas-dom i nated in clu sions, but it was also re - corded in in clu sions with a sim i lar phase ra tio (Fig. 6E). In com - par i son to the first ho mogeni sa tion path (i.e., to wards the liq uid phase), the mea sured tem per a tures were lower and more con - sis tent: from 224 to 385°C (Fig. 7).
For both the sec ond ary and pseudosecondary in clu sions, heat ing caused ho mogeni sa tion only to wards the liq uid phase (LG®L). Mea sured tem per a tures var ied in a wide range from 325 to 451°C al though most such in clu sions ho mogen ised in the range of 400–500°C (Fig. 7).
Dur ing the cool ing, highly vari able be hav iour of in clu sions was ob served. In some crys tals of the two-phase (LL) in clu - sions, cool ing caused nu cle ation of gas bub ble within the orig i - nal liq uid bub ble. This per fectly proves the pres ence of CO2 in the liq uid phase (Sterner and Bodnar, 1991; Schmidt et al., 1995; Kirill and Gra ham, 1999; Bakker and Di a mond, 2000;
Schmidt and Bodnar, 2000; Di a mond, 2001, 2003; Van den Kerkhof and Thiéry, 2001). In such cases, ho mogeni sa tion tem per a tures (Thcar) var ied in a wide range (from –42 to 5.8°C), in di cat ing vari able den sity of CO2.
Dur ing the sub se quent cool ing down to the tem per a ture of –192°C, no vis i ble changes were ob served in most of the in clu - sions. Such be hav iour may re sult from sev eral rea sons. First of
Fig. 6. Microscopic images (transmitted light)
A – FIA with con stant and low gas/liq uid ra tio (marked by ar rows); B – FIA with a sig nif i cant prev a lence of gas phase (marked by ar rows); C – in clu sions with highly vari able gas/liq uid ra tio (marked by ar rows); D – sec ond ary or pseudo-sec ond ary in clu sions; E – sin gle in clu sion (cen - tre) filled with liq uid and gas phases in sim i lar pro por tions; F – tu bu lar in clu sion (cen tre) filled with gas phase (lower part of darker rim)
all, both the small size of in clu sions and their flat tened (tab u lar) shapes of ten pre cluded proper ob ser va tions and in ter pre ta tion (see e.g., Bodnar, 2003). The sec ond rea son can be the metastability of flu ids pre sum ably re lated to high sa lin ity of the aque ous phase. As stated above, some ob served in clu sions con tained daugh ter min er als (ha lite or sylvite) in di cat ing that the mi grat ing so lu tion was fully sat u rated with re spect to chlo - rine salts. In ad di tion, we found inter growths of sylvite and car - nal lite in blue ha lite, sug gest ing the pres ence of large amounts of po tas sium and mag ne sium in the per co lat ing brines. Such a high sa lin ity of brines en closed in in clu sions may re sult in their metastability dur ing the cool ing (Roedder, 1984a; Bodnar, 2003; Di a mond, 2003). An other rea son of metastability may be the ad mix ture of other volatiles, as CH4 or H2S (Di a mond, 2003). The pres ence of such gases was re corded in a few sin - gle-phase liq uid in clu sions, which nu cle ated gas bub bles dur ing the cool ing be low –100°C and freez ing be low –140°C. The melt ing tem per a tures were in the range from –87.9°C to –87.1°C and the ho mogeni sa tion tem per a tures var ied from –61.5°C to –60.5°C. Such val ues may sug gest the pres ence of CH4 in amounts of 80 mol.% (Di a mond, 2003).
DISCUSSION
The pre vi ous stud ies of the blue ha lite from the K³odawa Salt Dome showed that its oc cur rences are closely con nected with the epigenetic rocks and that it does not oc cur in pri mary salts, as yet (Natkaniec-Nowak and Tobo³a, 2003; Tobo³a et al., 2007; Janiów et al., 2008). The for ma tion of such rocks was re - lated to the mi gra tion of so lu tions rich in po tas sium and mag ne - sium. The larger ac cu mu la tions of blue ha lite were also re lated to dis junc tive tec tonic dis tur bances. Such a po si tion of blue ha - lite in the K³odawa Salt Dome is in ac cor dance with the oc cur - rence of blue salts in other for ma tions (Borchert, 1959; Boborov et al., 1968; Ivanov and Voronova, 1968, 1972; Roulston and Waugh, 1983; Waugh and Urquhart, 1983; Koriñ, 1994;
Sonnenfeld, 1995; Tabakh et al., 1999; Davison, 2009;
Smetannikov, 2011). They oc cur most fre quently in the vi cin ity
of frac tures, shear zones or faults where salts are sub jected to crush ing and brecciation. These pro cesses fa cil i tated the per - co la tion of so lu tions, and recrystallisation and crystallisation of epigenetic salts (sylvite or car nal lite). Within the blue ha lite crys tals, solid in clu sions of sylvite sur rounded by colour less halo of ha lite were some times no ticed. It may be an ar gu ment against the in flu ence of ra dio ac tiv ity orig i nat ing from po tas sium (Sonnenfeld, 1995). In the K³odawa Salt Dome, sim i lar fea tures of blue ha lite were no ticed very of ten (Heflik et al., 2008). More - over, the blue ha lite veins also con tain colour less ha lite crys tals or large parts of crys tals de void of blue colouration with nu mer - ous sylvite in clu sions. It may very well sup port the idea of in suf - fi cient ef fect of ra di a tion of 40K from sylvite.
Anal y ses of anhydrite crys tals sep a rated from the larg est ac cu mu la tion of blue ha lite in the K³odawa Salt Dome al lowed us to de ter mine their or i gin more pre cisely. Pet ro log i cal ob ser - va tions and, es pe cially, microthermometric stud ies re vealed that the con di tions of their for ma tion were highly com pli cated and con sid er ably dif fer ent from the com monly ac cepted for ma - tion mod els of epigenetic evaporites in salt domes (e.g., Borchert and Muir, 1964; Kühn, 1968; Stañczyk, 1970;
Braitsch, 1971; Stañczyk-Stasik, 1976). In these mod els, the main source of wa ter is de com po si tion of hy drated min er als dur ing the burial of salt for ma tions (i.e., un der in creas ing tem - per a ture and pres sure) and the re ac tions be tween min er als.
Such so lu tions have spe cific physicochemical prop er ties con - trolled by the re la tion ships be tween evaporite min er als and the burial depths. In this con text, both the chem i cal and phys i cal prop er ties of so lu tions from which the anhydrite and other min - er als (py rite, quartz) as well as blue ha lite and other chlo rine min er als have crys tal lised seem to be very vari able.
The first in di ca tion of such un usual prop er ties of so lu tions is the oc cur rence of euhedral py rite and quartz within the anhydrite crys tals (Figs. 4C, F and 5A, B). Their euhedral hab - its sug gest that these min er als crys tal lised at the first stage, un der free crys tal growth con di tions, from so lu tions with in - creased con cen tra tions of iron, sul phide and sil ica. It is sug - gested that these min er als were the nu clei for sub se quently crystallising anhydrite.
Fig. 7. Histogram of temperatures of:
A – decrepitation, B – primary fluid inclusions homogenising towards liquid phase, C – primary fluid inclusions homogenising towards gas phase, D – secondary fluid inclusions homogenising
towards liquid phase
The iron sulphides were still pres ent in so lu tion dur ing the crystallisation of anhydrite crys tals. These min er als crys tal lised at the sur face of anhydrite, in the form of small subhedral crys - tals. Lo cated close to each other, such em bry onic crys tals cre - ated bar ri ers to the growth of anhydrite, and, thus, lim ited the for ma tion of tu bu lar in clu sions (Fig. 5F) or more iso met ric in clu - sions (Fig. 5C, E) if larger ac cu mu la tions were ob served. Such gen e sis of in clu sions is a rel a tively com mon phe nom e non (e.g., Roedder, 1984a; Goldstein and Reynolds, 1994).
Microthermometric mea sure ments in di cated very clearly that anhydrite was formed un der high-tem per a ture con di tions, i.e., at tem per a tures ex ceed ing in most cases 250°C. In some ana lysed crys tals, for ma tion tem per a tures sig nif i cantly ex - ceeded the crit i cal point of wa ter, which in di cates high sa lin ity of so lu tions (Knight and Bodnar, 1989). Such a tem per a ture range can not be ex plained in terms of burial of salt for ma tion and de - vel op ment of the K³odawa Salt Dome. Ac cord ing to the re sults of geo log i cal and geo phys i cal stud ies, the Zechstein salt for ma - tion and the salts in the K³odawa dome were not bur ied suf fi - ciently deep to at tain such high tem per a tures (e.g., Dadlez et al., 1995; Dadlez, 2003; Krzywiec, 2004, 2006). It is par tic u larly valid for salts en closed in the salt domes be cause the up lift of domes started in the Early and Mid dle Tri as sic (Krzywiec, 2004), and be cause the domes have not been cov ered by thick over bur den.
Other im por tant fea tures which can be ge netic in di ca tors of so lu tions in clude the chem i cal com po si tion and gen eral be hav - iour dur ing heat ing and cool ing. Ob ser va tions of in clu sions con - firmed the pres ence of liq uid CO2 with con sid er able amounts of CH4 and, prob a bly, also H2S. The oc cur rence of these com po - nents in the whole pop u la tion of in clu sions is highly vari able, but in a sin gle FIA or in frag ments of anhydrite crys tals the chem i cal com po si tion is quite sta ble. This sug gests that the mi gra tion en - vi ron ment was rather ho mo ge neous, but it was sub jected to rapid chem i cal changes in time. Con sid er ing the P-T con di - tions, the vari abil ity of mi gra tion en vi ron ment is also very well-pro nounced by dif fer ent di rec tions of ho mogeni sa tion (i.e., to wards the liq uid or gas eous phases), which in di cates that the en trap ment of flu ids in in clu sions took place first of all un der highly vari able pres sures. Cal cu la tion of ho mogeni sa tion pres - sure in in clu sions us ing the pro grams of Bakker (2003, 2009, 2012) re veal the pres sure in the range of 8.0–73.1 MPa for ho - mogeni sa tion to ward the liq uid phase and 3.9–27.2 MPa for ho - mogeni sa tion to ward the gas phase. There fore, so lu tion den si - ties (mo lar vol umes) were also highly vari able (see e.g., Roedder, 1984a; Goldstein and Reynolds, 1994; Di a mond, 2003). On the con trary, for ma tion tem per a tures seem to be less vari able be cause no sig nif i cant dif fer ences were ob served be - tween the tem per a tures of ho mogeni sa tion to wards the liq uid and gas phases. Such be hav iour of in clu sions com bined with high tem per a tures of ho mogeni sa tion may be re lated to mi gra - tion of hy dro ther mal so lu tions. Ac cord ing to nu mer ous au thors (e.g., Di a mond, 1990, 2001; Xu and Pol lard, 1999; Yao et al., 1999; Xu, 2000; Baker and Lang, 2001; Graupner et al., 2001;
Wilkinson, 2001; Fedele et al., 2005), hy dro ther mal sys tems re - veal high vari abil ity of the amount of vol a tile (gas eous) and non-vol a tile com po nents, their mu tual re la tions as well as P-T con di tions. The most com mon min er als which crys tal lise in such en vi ron ments are quartz and nu mer ous sulphides of heavy met als. This paragenesis was also found in the stud ied blue ha lite crys tals ac com pa ny ing the anhydrite. The quan ti ta - tive pre dom i nance of the anhydrite over quartz and sulphides in blue salts is prob a bly re lated to the sec ond ary en rich ment of pri mary hot so lu tions in cal cium sul phate, which took place dur - ing mi gra tion through the salt for ma tion.
A wide range of ho mogeni sa tion tem per a tures mea sured in ana lysed anhydrite crys tals is also typ i cal of an en vi ron ment in which sev eral for ma tion stages of dif fer ent tem per a tures and pres sures can be dis tin guished. Fur ther more, in the hy dro ther - mal veins, lo cal pock ets of vapour phases are com mon (Di a - mond, 1990, 2001). This fairly well ex plains the pres ence of the groups of in clu sions within anhydrite crys tals, which show ho - mogeni sa tion to wards the gas phase.
The oc cur rence of hy dro ther mal veins in the up per part of the K³odawa Salt Dome is a re sult of geo log i cal evo lu tion of this struc ture, par tic u larly of the tec ton ics of the sub-Zechstein base ment. Anal y sis of seis mic data from the K³odawa re gion re - vealed a sys tem of faults in the base ment, which were re spon si - ble for tec tonic sub si dence dur ing the Zechstein sed i men ta tion.
Such tec tonic ac tiv ity in flu enced the de vel op ment of salt struc - tures (Wag ner et al., 2002; Krzywiec, 2004). Si mul ta neously, these faults might have been the path ways for mi gra tion of hy - dro ther mal so lu tions (Fig. 8). When mi grat ing through the salt for ma tion, these so lu tions must have changed their chem i cal com po si tion by dis so lu tion of rocks in the old est Zechstein cyclothems (Lower Anhydrite, Old est Ha lite, prob a bly also Old - est Pot ash and Up per Anhydrite). In this way, the so lu tions be - came en riched in Ca, Na, K and Mg sulphates and chlo rides.
Fur ther as cen sion of hy dro ther mal so lu tions through the grow - ing salt struc ture caused their grad ual cool ing and pre cip i ta tion
Fig. 8. Scheme of deformation evolution of salt structure with migration paths of hydrothermal solutions
(after Koyi et al., 1993, modified)
White arrows – salt movement direction, grey arrows – direction of hydrothermal solutions migration
of some min er als due to their sol u bil i ties at higher tem per a - tures. Such mech a nism ex plains very well the oc cur rence of nu - mer ous inter growths of sylvite or car nal lite in blue ha lite (Tobo³a and Natkaniec-Nowak, 2007, 2008).
The pres ence of hy dro ther mal so lu tions be neath the salt for - ma tion might have played a cru cial role in the tec tonic evo lu tion of the K³odawa Salt Dome. The mi gra tion of hot, high-pres sured so lu tions through the salt for ma tions sig nif i cantly fa cil i tated the ver ti cal flow of salt masses. The leach ing prop er ties of so lu tions com bined with high tem per a ture and pres sure might have in flu - enced the tec tonic move ments be cause the so lu tions worked like a lu bri cant be tween the salt blocks. More over, their mi gra tion af fected chem i cally and ther mally the sur round ing salts caus ing, for ex am ple, pre cip i ta tion of min er als which are not ge net i cally re lated to the ma rine evaporites, e.g., bo rates (Wachowiak and Pieczka, 2012; Wachowiak and Tobo³a, 2014).
The other ef fect of mi gra tion of high-tem per a ture so lu tions within the salt dome is the ap pear ance of blue or vi o let colouration of ha lite crys tals hosted within the salt lay ers. The colouration of ha lite is closely re lated to high tem per a tures (above 250°C) pro vid ing en ergy as well as re lated to re duc ing con di tions doc u mented by the ap pear ance of sulphides. The above-men tioned fac tors are prob a bly re spon si ble for the cre - ation of de fects, their mi gra tion and ag gre ga tion in the ha lite crys tal struc ture. Pre sum ably, an im por tant role was played also by the high con tents of po tas sium and so dium in so lu tions.
Such con di tions are in ac cor dance with lab o ra tory ex per i ments of Kreutz (1892) who found that such col our of ha lite may be ob - tained by heat ing its crys tals in po tas sium or so dium va pours, al though this mech a nism ap plies only to some nat u ral crys tals.
Sim i larly lim ited is the the ory of ra dio ac tive dam age of ha lite lat - tice caused by ra di a tion from 40K iso tope. Such mech a nism of blue colouration of ha lite crys tals is ei ther not sup ported in nat u - ral en vi ron ments or it plays rather mi nor role, as dem on strated by Sonnenfeld (1995) who sum ma rized ar gu ments against the ra di a tion as the cause of ha lite colouration. How ever, even if tem per a ture is con sid ered as a main rea son of ha lite colouration, un solved re main the prob lems of col our vari a tions and of the forms of colouration ob served on the mi cro-scale within the sin gle crys tals (Heflik et al., 2008) and on the scale of par tic u lar ex po sures in mine work ings (Natkaniec-Nowak and Tobo³a, 2003; Tobo³a et al., 2007; Janiów et al., 2008). Vari abil - ity of blue colouration was ob served also in ar ti fi cially ir ra di ated nat u ral ha lite crys tals (Schléder and Urai, 2005, 2007; Schléder et al., 2007, 2008) and in ter preted gen er ally as a re sult of stress. It must be em pha sized that dur ing the gamma-ir ra di a - tion, the blue colouration of ha lite was ob tained at the tem per a - ture of 100°C, whereas at lower tem per a ture (35°C) the brown col our ap peared.
Both the ir ra di a tion and the tem per a ture can not af fect se - lec tively only par tic u lar parts of ha lite ac cu mu la tions. There fore, ad di tional fac tors are ex pected for both the emer gence and the con sol i da tion of col our. Some ob ser va tions made at the K³odawa Salt Mine sug gest that the tec tonic stress and, par tic u - larly, the strain de vel op ing in the shear zones may af fect the crys tal lat tice of ha lite. Such ev i dence was found in the ex po - sure lo cated in cham ber KS39, at the min ing level 600 m (Fig. 3E) where the ha lite of in tense blue col our oc curs only at the con tact of pri mary striped salts and the epigenetic ha - lite-sylvite vein. Sim i lar po si tion of the main con cen tra tion of blue ha lite was ob served in the ex po sure at the min ing level 750 m (Janiów et al., 2008). Still, how ever, sin gle blue ha lite crys tals were en coun tered there within the car nal lite vein (Fig. 3F). This po si tion of blue ha lite sug gests that these crys - tals are of pri mary or partly sec ond ary (recrystallised) or i gin and they un der went tec tonic dis tur bances. Such tec tonic in volve -
ment caused de fects of the ha lite struc ture, whilst colour less crys tals might have pre cip i tated in the veins dur ing the later mi - gra tion of the so lu tions. The blue ha lite streaks or sin gle crys - tals in side the veins of epigenetic salts may be rel ics of the de - fected crys tals. The smaller ex po sures in the K³odawa Salt Dome do not show such un equiv o cal ev i dence, but all of them are strictly as so ci ated with shear zones (Tobo³a et al., 2007;
Janiów et al., 2008).
These con di tions of blue ha lite for ma tion ex plain very well why there is no blue ha lite in the pri mary po tas sium-mag ne sium salts de spite the pres ence of ra dio ac tive po tas sium iso tope 40K in the ra tio, nor mal for such sed i ments. More over, the mi gra tion of hy dro ther mal so lu tions through the K³odawa Salt Dome might have re sulted in the ap pear ance of min er als which are not di - rectly re lated to these for ma tions, as boracite and congolite (Wachowiak and Pieczka, 2012; Wachowiak and Tobo³a, 2014).
In flu ence of in creas ing tem per a ture in the diapir was also men - tioned by Wag ner and Burliga (2014) for the Stink ing Shale and the Main Do lo mite. It was de ter mined on the ba sis of mea sure - ments of ran dom reflectance of or ganic mat ter.
It should be pointed out that the con tri bu tion of tem per a ture to the for ma tion of blue ha lite in some salt de pos its, as well as their as so ci a tion with ig ne ous rocks or mag matic so lu tions, such as those found in salt de pos its in Ger many, is sig nif i cant (Borchert, 1959). More over, blue ha lite was also found in a kimberlite pipe in the form of xe no liths (Polozov et al., 2008).
CONCLUSIONS
The or i gin of blue or vi o let ha lite crys tals in nat u ral en vi ron - ments has not been ad e quately ex plained so far. Nu mer ous lab o ra tory ex per i ments us ing var i ous meth ods of ha lite colouration do not re flect the nat u ral con di tions (Sonnenfeld, 1995). The most com mon opin ion that ra dio ac tive de cay of po - tas sium 40K iso tope is re spon si ble for ha lite colouration does not ex plain ad e quately the ac cu mu la tion of blue ha lite in the salt for ma tions be cause, up to now, blue ha lite has not been found in the pri mary po tas sium salt beds.
Stud ies on anhydrite inter growths in blue ha lite from one of the larg est un der ground ex po sures in the K³odawa Salt Dome in di cate that blue colouration of ha lite is a com bined ef fect of at least three fac tors: (1) high tem per a tures (above 250°C) re sult - ing from mi gra tion of hy dro ther mal so lu tions within the salt for - ma tion, (2) re duc ing con di tions, as dem on strated by the oc cur - rence of sul phide min er als, (3) de fects of crys tal struc ture, caused by the tec tonic ac tiv ity and, es pe cially, by the stress de - vel oped in the shear zone.
The or i gin of hy dro ther mal so lu tions is re lated to the base - ment of Zechstein salt for ma tions and to the de vel op ment of salt diapirs (cf. Wag ner and Burliga, 2014). Their mi gra tion through the salt for ma tion caused the evo lu tion of their chem i - cal com po si tion. First of all, the so lu tions be came en riched in some ions: K, Mg, Ca, Na, Cl and SO4 due to dis so lu tion of the lower part of the Zechstein salt for ma tions. The pro cesses of dis so lu tion and recrystallisation fa cil i tated the tec tonic move - ments and the de vel op ment of the salt diapir but they also re - sulted in changes of min eral com po si tion of beds within the salt dome and in the ap pear ance of min er als which are not typ i cal of ma rine evaporites.
Ac knowl edge ments. The in ves ti ga tions were sup ported by the AGH Uni ver sity of Sci ence and Tech nol ogy in Kraków, grant No. 11.11.140.320. Help ful com ments by the ref er ees, G. Czapowski and an anon y mous one, are ap pre ci ated.
REFERENCES
Baikpour, S., Zulauf, G., Sebti, A., Kheirolahi, H., Dietl, C., 2010.
An a logue and geo phys i cal mod el ling of the Garmsar Salt Nappe, Iran: con straints on the evo lu tion of the Alborz Moun - tains. Geo phys i cal Jour nal In ter na tional, 182: 599–612.
Baker, T., Lang, J.R., 2001. Fluid in clu sion char ac ter is tic of in tru - sion-re lated gold min er al iza tion, Tomb stone-Tung sten mag - matic belt, Yu kon Ter ri tory, Can ada. Mineralium Deposita, 36:
563–582.
Bakker, R.J., 2003. Pack age FLUIDS 1. Com puter pro grams for anal y sis of fluid in clu sion data and for mod el ling bulk fluid prop - er ties. Chem i cal Ge ol ogy, 194: 3–23.
Bakker, R.J., 2009. Pack age FLUIDS. Part 3: cor re la tions be tween equa tions of state, ther mo dy nam ics and fluid in clu sions.
Geofluids, 9: 63–74.
Bakker, R.J., 2012. Pack age FLUIDS. Part 4: ther mo dy namic mod - el ling and purely em pir i cal equa tions for H2O-NaCl-KCl so lu - tions. Min er al ogy and Pe trol ogy, 105: 1–2.
Bakker, R.J., Di a mond, L.W., 2000. De ter mi na tion of the com po si - tion and mo lar vol ume of H2O-CO2 fluid in clu sions by microthermometry. Geochimica et Cosmochimica Acta, 64:
1753–1764.
Bickham, M., 2012. Chem i cal anal y sis of blue ha lite. South-Cen tral Sec tion – 46th An nual Meet ing (8–9 March 2012). GSA, Ab - stracts with Pro grams, 44: 8.
Bobrov, V.P., Korenievski, S.M., Rabitchenko, O.P., 1968. Li thol - ogy and stra tig ra phy of Kramatorskya for ma tion of Donbass and min er al og i cal-pet ro graph i cal char ac ter is tics of pot ash ho ri zons (in Rus sian). Pro ceed ings of the Rus sian Geo log i cal Re search In sti tute (VSEGEI), 161: 80–116.
Bodnar, R.J., 2003. In ter pre ta tion of data from aque ous-elec tro lyte fluid in clu sions. Min er al og i cal As so ci a tion of Can ada. Short Course Se ries, 32: 81–100.
Borchert, H., 1959. Ozeane Salzlagerstätten. Gebrûder Borntraeger, Berlin.
Borchert, H., Muir, R.O., 1964. Salt De pos its. The Or i gin, Meta mor - phism and De for ma tion of Evaporites. D. Van Nostrand Com - pany, Ltd, Lon don.
Braitsch, O., 1971. Salt De pos its. Their Or i gin and Com po si tion.
Springer, New York.
Burliga, S., 1994. Ten sion gashes in the Platy Do lo mite (Zechstein) of SW part of the K³odawa Diapir (Cen tral Po land) – ki ne matic im pli ca tion) (in Pol ish with Eng lish sum mary). Przegl¹d Geologiczny, 42: 99–102.
Burliga, S., 2014. Het er o ge ne ity of fold ing in Zechstein (Up per Perm ian) salt de pos its in the K³odawa Salt Struc ture, cen tral Po - land. Geo log i cal Quar terly, 58 (3): 565–576.
Burliga, S., Kolonko, P., Misiek, G., Czapowski, G., 1995.
K³odawa salt mine. In: Up per Rotliegend – Zechstein: Ter res trial – Ma rine Sed i men tary Suc ces sion in Pol ish Perm ian Ba sin (ed.
J. Ma³ecka): 45–54. XIII In ter na tional Con gress on Car bon if er - ous-Perm ian, Au gust 28–Sep tem ber 2, 1995, Guide to Ex cur - sion A3, Kraków, Po land.
Charysz, W., 1973. Zechstein stage of Youn ger Salts (Z3) in Kujawy re gion (in Pol ish with Eng lish sum mary). Prace Geologiczne, 75: 1–68.
Dadlez, R., 2003. Me so zoic thick ness pat tern in the Mid-Pol ish Trough. Geo log i cal Quar terly, 47 (3): 223–240.
Dadlez, R., Narkiewicz, M., Stephenson, R.A., Visser, M.T.M., van Wees, J.D., 1995. Tec tonic evo lu tion of the Mid-Pol ish Trough: mod el ling im pli ca tions and sig nif i cance for cen tral Eu - ro pean ge ol ogy. Tectonophysics, 252: 179–195.
Davison, I., 2009. Fault ing and fluid flow through salt. Jour nal of the Geo log i cal So ci ety, 166: 205–216.
Di a mond, L.W., 1990. Fluid in clu sion ev i dence for P-V-T-X evo lu - tion of hy dro ther mal so lu tions in Late-Al pine gold-Quartz veins at Brusson, Val d’Ayas, NW Ital ian Alps. Amer i can Jour nal of Sci ence, 290: 912–958.
Di a mond, L.W., 2001. Re view of the sys tem at ics of CO2–H2O fluid in clu sions. Lithos, 55: 69–99.
Di a mond, L.W., 2003. In tro duc tion to gas-bear ing, aque ous fluid in - clu sions. Min er al og i cal As so ci a tion of Can ada, Short Course Se ries, 32: 101–158.
Fedele, L., Raia, F., Sasaki, M., Sawaki, T., Tarzia, M., Sasada, M., 2005. Fluid in clu sion study con strain ing the hy dro ther mal evo lu - tion of cal dera-form ing vol ca nic sys tems in the Sengan Area, North ern Hon shu, Ja pan. Min er al ogy and Pe trol ogy, 84:
189–213.
Garlicki, A., Szybist, A., 1986. Sa line de pos its of Pol ish Zechstein with pot ash salts (in Pol ish with Eng lish sum mary). Gospodarka Surowcami Minerlnymi, 2: 389–404.
Goldstein, R.H., Reynolds, T.J., eds., 1994. Sys tem at ics of fluid in - clu sions in diagenetic min er als. SEPM Short Course, 31.
Graupner, T., Bray, C.J., Spooner, E.T.C., Herzig, P.M., 2001.
Anal y sis of fluid in clu sions in seafloor hy dro ther mal pre cip i tates:
test ing and ap pli ca tion of an in te grated GC/IC tech nique. Chem - i cal Ge ol ogy, 177: 443–470.
Heflik, W., Natkaniec-Nowak, L., Tobo³a, T., 2008. Badania mikroskopowe soli niebieskich (in Pol ish) In: Sole niebieskie w wysadzie k³odawskim (eds. T. Tobo³a and L. Natkaniec-Nowak):
56–69. Uczelniane Wyd. Nauk.-Dydaktyczne AGH.
Ivanov, A.A., Voronova, M.L., 1968. Ge ol ogy of the Verkhnepetchora sed i men tary ba sin and its pot ash bear ing fea - tures (in Rus sian). Pro ceed ings of the Rus sian Geo log i cal Re - search In sti tute (VSEGEI), 161: 3–79.
Ivanov, A.A., Voronova, M.L., 1972. Salt-bear ing For ma tions (in Rus sian). Rus sian Geo log i cal Re search In sti tute (VSEGEI).
Edi tion NEDRA, Mos cow.
Janiów, S., Misiek, G., Tobo³a, T., Natkaniec-Nowak, L., 2008.
Wystêpowanie soli niebieskich w kopalni K³odawa (in Pol ish) In:
Sole niebieskie w wysadzie k³odawskim (eds. T. Tobo³a and L.
Natkaniec-Nowak): 24-53. Uczelniane Wyd. Nauk.-Dydak - tyczne AGH.
Kirill, I., Gra ham, C.M., 1999. An ex per i men tal study of phase equi - lib ria in the sys tem H2O-CO2-NaCl at 800°C and 9 kbar. Con tri - bu tions to Min er al ogy and Pe trol ogy, 136: 247–257.
Knight, C.L., Bodnar, R.J., 1989. Syn thetic fluid in clu sions: IX. Crit - i cal PVTX prop er ties of NaCl-H20 so lu tions. Geochimica et Cosmochimica Acta, 53: 3–8.
Koriñ, S.S., 1994. Budowa geologiczna mioceñskich formacji solonoœnych ukraiñskiego Przedkarpacia (in Pol ish). Przegl¹d Geologiczny, 42: 744–747.
Koyi, H., Jenyon, M.K., Petersen, K., 1993. The ef fects of base - ment fault ing on diapirism. Jour nal of Pe tro leum Ge ol ogy, 16:
285–312.
Kreutz, F., 1892. O przyczynie niebieskiego zabarwienia soli kuchennej: 194–205 Akademia Umiejêtnoœci, Kraków.
Krzywiec, P., 2004. Tri as sic evo lu tion of the K³odawa salt struc ture:
base ment-con trolled salt tec ton ics within the Mid-Pol ish Trough (Cen tral Po land). Geo log i cal Quar terly, 48 (2): 123–134.
Krzywiec, P., 2006. Struc tural in ver sion of the Pom er a nian and Kuiavian seg ments of the Mid-Pol ish Trough lat eral vari a tions in tim ing and struc tural style. Geo log i cal Quar terly, 50 (1):
151–168.
Kühn, R., 1968. Geo chem is try of Ger man pot ash de pos its. GSA Spe cial Pa pers, 88: 427–504.
Natkaniec-Nowak, L., Tobo³a, T., 2003. Blue salt from K³odawa (Kujawy, Po land) (in Pol ish with Eng lish sum mary). Przegl¹d Geologiczny. 51: 435–438.
Polozov, A.G., Sergey, S., Sukhov, S.S., Gornova, M.A., Grishina, S.N., 2008. Salts from Udachnaya-East kimberlite pipe (Yakutia, Rus sia): oc cur rences and min eral com po si tion.
9th In ter na tional Kimberlite Con fer ence Ex tended Ab stract No.
9IKC-A-00247: 1–3.
Pustyl’nikov, A.M., 1975. Or i gin of blue color in ha lite in Cam brian salt de pos its of the Si be rian Plat form (in Rus sian). Litologiya i Poleznye Iskopaemye, 10: 388–389.
Rahimpour-Bonab, H., Alijani, N., 2003. Pe trog ra phy, diagenesis and depositional model for pot ash de pos its of north Cen tral Iran,
and use of bro mine geo chem is try as a pros pect ing tool. Car bon - ates and Evaporites, 18: 19–28
Roedder, E., 1984a. Fluid in clu sions. Re views in Min er al ogy, 12:
1–644.
Roedder, E., 1984b. The fluid in salt. Amer i can Min er al o gist, 69:
413–439.
Roulston, B.V., Waugh, D.C.E., 1983. Strati graphic com par i son of the Mis sis sip pian pot ash de pos its in New Bruns wick, Can ada.
Sixth In ter na tional Sym po sium on Salt, 1: 115–129.
Schléder, Z., Urai, J.L., 2005. Microstructural evo lu tion of de for ma - tion-mod i fied pri mary ha lite from the Mid dle Tri as sic Röt For ma - tion at Hengelo, The Neth er lands. In ter na tional Jour nal of Earth Sci ences, 94: 941–955.
Schléder, Z., Urai, J.L., 2007. De for ma tion and recrystallization mech a nisms in mylonitic shear zones in nat u rally de formed ex - tru sive Eocenee-Oligocene rocksalt from Eyvanekey pla teau and Garmsar hills (cen tral Iran). Jour nal of Struc tural Ge ol ogy, 29: 241–255.
Schléder, Z., Burliga, S., Urai, J.L., 2007. Dy namic and static recrystallization-re lated micro struc tures in ha lite sam ples from the Klodawa salt wall (cen tral Po land) as re vealed by gamma-ir - ra di a tion. Neues Jahrbuch für Mineralogie Abhandlungen, 184:
17–28.
Schléder, Z., Urai, J.L., Nollet, S., Hilgers, C., 2008. So lu tion-pre - cip i ta tion creep and fluid flow in ha lite: a case study of Zechstein (Z1) rocksalt from Neuhof salt mine (Ger many). In ter na tional Jour nal of Earth Sci ences, 97: 1045–1056.
Schmidt, C., Bodnar, J., 2000. Syn thetic fluid in clu sions: XVI.
PVTX prop er ties in the sys tem H2O-NaCl-CO2 at el e vated tem - per a tures, pres sures, and sa lini ties. Geochimica et Cosmochimica Acta, 64: 3853–3869.
Schmidt, C., Rosso, K.M., Bodnar, J.R., 1995. Syn thetic fluid in - clu sions: XIII. Ex per i men tal de ter mi na tion of PVT prop er ties in the sys tem H2O + 40 wt% NaCl + 5 mol% CO2 at el e vated tem - per a ture and pres sure. Geochemica et Cosmochimica Acta, 59:
3953–3959.
Smetannikov, A.F., 2011. Hy dro gen gen er a tion dur ing the radiolysis of crys tal li za tion wa ter in car nal lite and pos si ble con - se quences of this pro cess. Geo chem is try In ter na tional, 49:
916–924.
Sonnenfeld, P., 1995. The color of rock salt – a re view. Sed i men tary Ge ol ogy, 94: 267–276.
Stadnicka, K., Zelek, S., 2008. Badania strukturalne soli niebieskich oraz faz sta³ych z inkluzji w halicie (in Pol ish). In:
Sole niebieskie w wysadzie k³odawskim (eds. T. Tobo³a and L.
Natkaniec-Nowak): 100–116. Uczelniane Wyd. Nauk.-Dydak - tyczne AGH.
Stañczyk, I., 1970. Polyhalite in the salt mines of the Kujawy re gion (in Pol ish with Eng lish sum mary). Acta Geologica Polonica, 20:
805–821.
Stañczyk-Stasik, I., 1976. Les dépots èpigénétiques dans les mines de sel de la région de Kujawy (in Pol ish with French sum - mary). Prace Geologiczne, 90: 1–64.
Sterner, S.M., Bodnar, R.J., 1991. Syn thetic fluid in clu sions. X: Ex - per i men tal de ter mi na tion of P-V-T-X prop er ties in the sys tem CO2-H2O sys tem to 6 KB and 700 C. Amer i can Jour nal of Sci - ence, 291: 1–54.
Suwanich, P., 1983. Pot ash and rock salt in Thai land. Con fer ence on Ge ol ogy and Min eral Re sources of Thai land, Bang kok, 19–28 No vem ber: 241–252.
Tabakh, M.E., Utha-Aroon, Ch., Schreiber, B.Ch., 1999.
Sedimentology of the Cre ta ceous Maha Sarakham evaporites in the Khorat Pla teau of north east ern Thai land. Sed i men tary Ge ol - ogy, 123: 31–62.
Tarka, R., 1992. Tec ton ics of some salt de pos its in Po land based on mesostructural anal y sis) (in Pol ish with Eng lish sum mary).
Prace Pañstwowego Instytutu Geologicznego, 137: 1–47.
Tobo³a, T., Natkaniec-Nowak, L., 2007. Solid phase in clu sions in blue ha lite from Klodawa Salt Mine in the light of SEM-EDS anal - y sis. XII In ter na tional Salt Sym po sium „Quo Vadis Sal”. Oc to ber 10–11, 2007, K³odawa.
Tobo³a, T., Natkaniec-Nowak, L., 2008. Badania mikroskopem elektronowym (SEM-EDS) inkluzji sta³ych (in Pol ish). In: Sole niebieskie w wysadzie k³odawskim (eds. T. Tobo³a and L.
Natkaniec-Nowak): 70–80. Uczelniane Wyd. Nauk.-Dydak - tyczne AGH.
Tobo³a, T., Wese³ucha-Birczyñska, A., 2008. Inkluzje fluidalne w halicie niebieskim (in Pol ish). In: Sole niebieskie w wysadzie k³odawskim (eds. T. Tobo³a and L. Natkaniec-Nowak): 81–99.
Uczelniane Wyd. Nauk.-Dydaktyczne AGH.
Tobo³a, T., Natkaniec-Nowak, L., Szybist A., Misiek, G., Janiów, S., 2007. Blue salts in K³odawa Salt Mine (in Pol ish with Eng lish sum mary). Gospodarka Surowcami Mineralnymi, 23: 117–132.
Van den Kerkhof, A.M., Thiéry, R., 2001. Car bonic in clu sions.
Lithos, 55: 49–68.
Vanko, D.A., Bach, W., 2005. Heat ing and freez ing ex per i ments on aque ous fluid in clu sions in anhydrite: rec og ni tion and ef fects of stretch ing and the low-tem per a ture for ma tion of gyp sum. Chem - i cal Ge ol ogy, 223: 35–45.
Vinokurov, V.M., 1958. Blue rock salt from the Solikamsk dis trict (in Rus sian). Zapisy Vsesoyuznogo Mineralogicheskogo Obshchestva (Pro ceed ings of the All-Un ion Min er al og i cal So ci - ety), 87: 504–507.
Wachowiak, J., Pieczka, A., 2012. Congolite and trembatite from the K³odawa Salt Mine, cen tral Po land: re cord of the ther mal his tory of the pa ren tal salt dome. The Ca na dian Min er al o gist, 50: 1387–1399.
Wachowiak, J., Tobo³a, T., 2014. Phase tran si tions in the bo rate min er als from the K³odawa Salt Dome (Cen tral Po land) as in di - ca tors of tem per a ture pro cesses in salt diapirs. Geo log i cal Quar terly, 58 (3): 543–554.
Wag ner, M., Burliga, St., 2014. Coalified bi tu mens from the K³odawa Salt Struc ture (cen tral Po land) as ev i dence of mi gra - tion of hy dro ther mal flu ids in Zechstein (Up per Perm ian) de pos - its. Geo log i cal Quar terly, 58 (3): 555–564.
Wag ner, R., Leszczyñski, K., Pokorski, J., Gumulak, K., 2002.
Palaeotectonic cross-sec tions through the Mid-Pol ish Trough.
Geo log i cal Quar terly, 46 (3): 293–306.
Waugh D.C.E., Urquhart, B.R., 1983. The ge ol ogy of Denison-Potacan’s New Bruns wick pot ash de posit. Sixth In ter - na tional Sym po sium on Salt, 1: 85–98.
Werner, Z., Poborski, J., Orska, J., B¹kowski, J., 1960. A geo log i - cal and min ing out line of the K³odawa salt de posit (in Pol ish with Eng lish sum mary). Prace Instytutu Geologicznego, 30:
467–495.
Wese³ucha-Birczyñska, A., Tobo³a, T., Natkaniec-Nowak, L., 2008. Raman mi cros copy of in clu sions in blue halites. Vi bra - tional Spec tros copy, 48: 302–307.
Wilkinson, J.J., 2001. Fluid in clu sions in hy dro ther mal ore de pos - its. Lithos, 55: 229–272.
Xu, G., 2000. Fluid in clu sions with NaCl–CaCl2–H2O com po si tion from the Cloncurry hy dro ther mal sys tem, NW Queensland, Aus - tra lia. Lithos, 53: 21–35.
Xu, G., Pol lard P.J., 1999. Or i gin of CO2-rich fuid in clu sions in synorogenic veins from the East ern Mount Isa Fold Belt, NW Queensland, and their im pli ca tions for min er al iza tion.
Mineralium Deposita, 34: 395–404.
Yao, Y., Morteani, G., Trumbull, R.B., 1999. Fluid in clu sion microthermometry and the P-T evo lu tion of gold-bear ing hy dro - ther mal fuids in the Niuxinshan gold de posit, east ern Hebei prov ince, NE China. Mineralium Deposita, 34: 348–365.
Zelek, S., Stadnicka, K., Szklarzewicz, J., Natkaniec-Nowak, L., Tobo³a, T., 2007. Ha lite from K³odawa: an at tempt of cor re la tion be tween the de gree of crys tal struc ture de for ma tion and the spec tro scopic prop er ties in UV-VIS range. XII In ter na tional Salt Sym po sium „Quo Vadis Sal”. Oc to ber 10–11, 2007, K³odawa:
61-62.
Zelek, S., Stadnicka, K., Tobo³a, T., Natkaniec-Nowak, L., 2014.
Lat tice de for ma tion of blue ha lite from Zechstein evaporite ba - sin: K³odawa Salt Mine, Cen tral Po land. Min er al ogy and Pe trol - ogy, 108: 619–631.
