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Open AccessArticle

Geochemical Significance of Clay Minerals and Elements in Paleogene Sandstones in the Center of the Northern Margin of the Qaidam Basin, China

1
Northwest Institute of Eco-Environment and Resources, Chinese Academy of Sciences, Lanzhou 730000, China
2
Key Laboratory of Petroleum Resources, Lanzhou 730000, China
3
University of Chinese Academy of Sciences, Beijing 100049, China
4
Research Institute of Petroleum Exploration and Development-Northwest, Petrochina, Lanzhou 730020, China
*
Author to whom correspondence should be addressed.
Minerals 2020, 10(6), 505; https://doi.org/10.3390/min10060505
Received: 24 April 2020 / Revised: 29 May 2020 / Accepted: 30 May 2020 / Published: 31 May 2020
(This article belongs to the Special Issue Clays, Clay Minerals and Geology)
The average thickness of Paleogene sandstones reaches about 3000–4000 m at the northern margin of the Qaidam Basin. However, the provenance and sedimentary environment of these sandstones are uncertain; thus, more comprehensive research is needed. Integrated research is conducted on the provenance and weathering process based on petrographic characteristics, clay minerals, and geochemical compositions of sandstones in the center of the northern Qaidam Basin. The results of lithofacies analysis show that the Paleogene sandstones were mainly derived from an active continental magmatic arc, subduction accretion, or a fold-thrust belt. The average illite content in the Paleogene clay minerals is more than 50%, followed by chlorite and smectite, which reflect climatic and environmental characteristics that were arid to semi-arid, whereas the characteristics of carbon–oxygen isotopes reveal a mainly freshwater sedimentary environment. The corrected chemical index of alteration (CIAcorr) is between 56.3 and 75.7, with an average value of 66.5. These results indicate that the provenance of the Paleogene sandstones in the center of the northern Qaidam Basin mainly formed under cold and dry climatic conditions and experienced limited chemical weathering with a small amount that underwent intermediate chemical weathering under warm and humid conditions. View Full-Text
Keywords: framework petrography; clay minerals; elements; Paleogene sandstones; sedimentary environment; Qaidam Basin framework petrography; clay minerals; elements; Paleogene sandstones; sedimentary environment; Qaidam Basin
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Sun, G.; Wang, M.; Guo, J.; Wang, Y.; Yang, Y. Geochemical Significance of Clay Minerals and Elements in Paleogene Sandstones in the Center of the Northern Margin of the Qaidam Basin, China. Minerals 2020, 10, 505.

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