Temperature and isotopic relations in carbonate minerals in the Middle Jurassic sideritic rocks of central and southern Poland

Abstract

1 Pol ish Geo log i cal In sti tute -Na tional Geo log i cal In sti tute, Rakowiecka 4, 00-975 Warszawa, Po land Jarmo³owicz-Szulc, K., Koz³owska, A., 2016. Tem per a ture and iso to pic re la tions in car bon ate min er als in the Mid dle Ju rassic si der it ic rocks of cen tral and south ern Po land. Geo log i cal Quar terly, 60 (4): 881-892, doi: 10.7306/gq.1323The pres ent study as sesses the physico-chem i cal char ac ter of the flu ids re spon si ble for the gen e sis of car bon ate min er als in the Mid dle Ju ras sic si der it ic rocks at the north east ern mar gin of the Holy Cross Mts. and in the Czêstochowa re gion. These rocks oc cur at pres ent at depths be tween 30 and 600 m. Fluid in clu sion and iso to pic anal y ses have been per formed in the car bon ate min er als from si der it ic sand stones, clayey siderites and si der it ic coquinas. Sid er ite is the main car bon ate min eral of the si der it ic rocks. Cal cite and an ker ite are also pres ent. The sid er ite is rep re sented by two va ri et ies, Mg-rich sid er ite (sideroplesite, less com monly -pistomesite) and sid er ite. Two gen er a tions of sid er ite have been dis tin guished -an early and a late one. The early sid er ite was formed at tem per a tures of about 20°C in the zone of mi cro bi o log i cal methanogenesis from ma rine wa ters with some in flu ence of me te oric wa ters (d 18 O from -7.84 to -1.92‰ VSMOW). The late sid er ite crys tallized at tem per a tures of about 62-110°C from pore wa ters en riched in 18 O (d 18 O >0‰ VSMOW) as com pared with the iso topic com po si tion of the wa ters re spon si ble for the early sid er ite gen er a tion. The con ducted fluid in clu sion anal y ses point to for ma tion of the ce ments from com plex flu ids of brine and car bon di ox ide char ac ter, with den si ties slightly ex ceed ing 1 g/cm 3 and sa lini ties vary ing from 10.5 to 16.9 wt.% NaCl eq. and from 6.4 to 14.0 wt.% NaCl eq. in the Holy Cross Mts. and in the Czêstochowa re gion, re spec tively. The ho mog e ni za tion tem per a tures lie in the in ter vals of 62-110°C and 60-97°C, re spectively and rep re sent el e vated val ues com pared with data from the Pol ish Low lands. Apart from burial, other heat sources must have been im por tant for the lithogenesis of the Mid dle Ju ras sic de pos its.Key words: fluid in clu sions, iso topes, car bon ate min er als, si der it ic rocks, Mid dle Ju ras sic.

Diagenesis and the Conditions of Deposition of the Middle Jurassic Siderite Rocks from the Northern Margin of the Holy Cross Mountains (Poland)

“…The rhombohedral crystals of sideroplesite and pistomesite were formed at a later stage of diagenesis, which was supported by the isotope data (Table S5) and the homogenization temperature of fluid inclusions in the range of 62.0-110.0 °C [29] from the Węglany borehole. These minerals precipitated from pore water (from approximately −5.00 to +3.50‰VSMOW) more enriched in the 18 O isotope compared to water from which the early diagenetic sideroplesite precipitated, probably as a result of internal sedimentwater reactions, due to sediment burial [120].…”

“…SEM Quant software (Great Britain) was used for the X-ray quantitative analysis when examining micro areas. Fluid inclusion studies were performed on two-sided polished preparations using the Linkam THMS600 heating and freezing stages mounted on a Nikon Eclipse LV100 Pol polarizing microscope (Japan, see References [29,30]). X-ray investigations of selected samples were carried out on an X'Pert PW 3020 X-ray diffractometer from Philips Company (Enschede, Netherlands) (see Reference [28]).…”

“…This may correspond to seawater or a mixture of seawater and meteoric water. To sum up, the pore waters, from which the diagenetic sideroplesite crystallized, were not homogeneous and originated from both marine and meteoric waters [29]. The average δ 13 C and δ 18 O values of sideroplesite in a given age range are as follows: −7.02 and −1.52‰VPDB for the Aalenian, −5.80 and −0.77‰VPDB for the Bajocian, and −12.26 and −0.52‰VPDB for the Bathonian.…”

“…Mineralogical studies of siderite interbeds in Middle Jurassic siliciclastic rocks from the Polish Lowlands were conducted by Maliszewska [19] and Maliszewska et al [20][21][22][23]. Kozłowska's studies provided petrographic analyses of siderite rocks from the northeastern margin of the Holy Cross Mountains [24][25][26][27][28][29][30] and the Częstochowa region [26,[28][29][30][31].…”