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CLAY MINERALS ASSOCIATIONS OF THE UPPER NEOPROTEROZOIC-LOWER CAMBRIAN MARLS OF THE SALT RANGE FORMATION, PAKISTAN

Home > Archive > No. 1–2 (197–198) 2025 > 91–110


Geology & Geochemistry of Combustible Minerals No. 1–2 (197–198) 2025, 91–110

https://doi.org/10.15407/ggcm2025.197-198.091

Yaroslava YAREMCHUK1, Fanwei MENG2, Sophiya HRYNIV1, Serhiy VOVNIUK1, Nadiya HORODECHNA1

1 Institute of Geology and Geochemistry of Combustible Minerals of National Academy of Sciences of Ukraine, Lviv, Ukraine, e-mail: slava.yaremchuk@gmail.com
2 China University of Mining and Technology (CUMT), Xuzhou, Jiangsu Province, China, e-mail: fwmeng@isl.ac.cn

Abstract

The peculiarities of the mineral composition of the pelitic fraction of marls of the Upper Neoproterozoic- Lower Cambrian Salt Range Formation are considered as a reflection of the influence of regional and global factors on the formation of clay minerals.

The pelitic fraction of 53 marl samples of Salt Range Formation taken in the Salt Range in the Khewra Gorge was studied: from the Sahwal Marl Member (48 samples), the Bhandar Kas Gypsum Member (2 samples), and the upper part of the Billianwala Salt Member (3 samples).

According to a set of analyzes (X-ray diffraction (XRD), scanning electron microscopy (SEM) with energydispersive X-ray microanalysis (EDX)), the determined association of clay minerals is represented by illite, chlorite, corrensite, chlorite-corrensite, chlorite-smectite, smectite, illite-smectite and in some samples also defective chlorite and defective corrensite occurs. Smectite, chlorite, and mixed-layer chlorite-smectite are magnesian trioctahedral minerals, illite is ferruginous dioctahedral, indicating their authigenic origin. A significant amount of labile minerals and phases in the associations is caused by a combination of the effects of contemporary volcanism, low brine concentration of the evaporite basin, and the presence of organic matter, mainly bitumen. Volcanic activity together with low brine concentration contributed to the formation of labile clay minerals and mixed-layer phases, and their interaction with organic compounds slowed down the processes of aggradation transformation.

The increased magnesium content and the presence of magnesian clay minerals in the pelitic fraction of the studied deposits are characteristic of evaporite deposits formed from SO4-rich seawater type, which is consistent with the sulfate seawater type in the Neoproterozoic.

Keywords

Neoproterozoic, clay minerals, X-ray diffraction, marls, Salt Range Formation, Pakistan

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CLAY MINERALS FROM ROCK SALT OF BAHADUR KHEL FORMATION, EOCENE, PAKISTAN

Home > Archive > No. 1 (182) 2020 > 87-100


Geology & Geochemistry of Combustible Minerals No. 1 (182) 2020, 87-100.

https://doi.org/10.15407/ggcm2020.01.087

Yaroslava YAREMCHUK, Serhiy VOVNYUK

Institute of Geology and Geochemistry of Combustible Minerals of National Academy of Sciences of Ukraine, Lviv, Ukraine, е-mail: slava.yaremchuk@gmail.com

Mohammad TARIQ

Baluchistan University of Information Technology, Engineering and Management Sciences, Department of Petroleum and Gas Engineering, Quetta, Pakistan

Abstract

According to studies of the pelitic fraction of the water-insoluble residue of 10 samples of Eocene rock salt of the Bahadur Khel Formation (Pakistan), it was determined that the clay minerals association contains swelling chlorite, chlorite-smectite, illite and kaolinite; chlorite was identified in three samples. Non-clay minerals are represented by quartz, dolomite, less often – magnesite; one sample contains impurities of both carbonates. Swelling chlorite, chlorite and mixed-layer minerals are trioctahedral, and illite and kaolinite are dioctahedral. All identified clay minerals, with the exception of kaolinite, are authigenic.

The presence of swelling chlorite in Eocene rock salt is probably caused by changes in the concentration of brines in the basin against the background of complex geological processes of this era (climate change from thermal maximum to global cooling, changes in water circulation in oceans, changes in isotopic composition of carbonates).

The association of clay minerals of Eocene rock salt, taking into account the peculiarities of its composition and the presence of swelling chlorite in it, we attributed to that formed during the SO4-rich seawater chemical type. This is also confirmed by two finds of swelling chlorite in the Triassic evaporites (rock salt of the Western Moroccan Basin, Midland marl) described in the literature, which are known to have been deposited from SO4-rich seawater.

The presence of kaolinite in almost all samples is caused by its largest accumulation in sediments of this time period – terrigenous kaolinite came in large quantities from dry land and did not transform even at the stage halite precipitation.

Keywords

clay minerals, swelling chlorite, rock salt, Eocene, Bahadur Khel Salt, Pakistan.

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