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A strongly positive sulphur isotopic shift in late Ediacaran-early Cambrian seawater : evidence from evaporites in the Salt Range Formation, northern Pakistan

Meng Fanwei, Zhang Zhili, Bukowski Krzysztof, Zhuo Qingong, Ahsan Naveed, Ur-Rehman Saif, Ni Pei

Geological Quarterly

2021

Vol. 65, No. 2

art. no. 30

The Salt Range Formation in northern Pakistan is globally well-known for its extremely large evaporite deposits dated to the upper Ediacaran-lower Cambrian. This huge evaporite belt formed an area covering present-day parts of India, Pakistan, Iran, Oman, and even South China (~200,000 km2 in South China). Sulphate minerals, including anhydrite and gypsum, can continuously record seawater sulphur isotopic composition. Until now, there was only one dataset reporting the isotopic composition of evaporites in Pakistan. This study reports new data, which points to a strongly positive sulphur isotopic shift (>+30‰, VCDT values) in the Salt Range Formation in Pakistan. Based on the stratigraphic position, similarity in lithology, age, and sulphur isotope data of the evaporitic sequences, it can be inferred that the Neoproterozoic Indo-Pakistan Plate and the Yangtze Platform were closely related palaeogeographically during the terminal Neoproterozoic. This interpretation can improve understanding of the palaeogeographical evolution of the area during the Neoproterozoic, with particular reference to the origin of biogeochemical cycles and the diagenetic evolution of the evaporitic deposits.

Calculation of salt basin depth using fluid inclusions in halite from the Ordovician Ordos Basin in China

Galamay Аnatolіy R., Meng Fanwei, Bukowski Krzysztof, Lyubchak Aleksandr, Zhang Yongsheng, Ni Pei

Geological Quarterly

2019

Vol. 63, No. 3

619--628

During the Middle Ordovician, the salt deposits of the Majiagou Formation of the Ordos Basin in North China formed, the halite including various genetic types of fluid inclusion. In this study, fit-testing of primary inclusions was performed to reconstruct the physical and chemical conditions during original halite sedimentation. During the post-sedimentation stage, salt was subjected to elevated temperatures (62-70°C) and pressures of tens of megapascals. From these measurements and mathematical calculations, the gas pressure was identified in the primary fluid inclusions, which allowed us to estimate that the brine column thickness in the salt basin was approximately 40 m.