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Early Cretaceous redbeds from the Minle Basin, Hexi Corridor, northwest China; mineralogy and geochemistry implications for paleoweathering, provenance, and tectonic settings

Sun Yaxiong, Ding Wenlong, Gu Yang, Zhao Gang, Shi Siyu, Jiao Baocheng and Ji Xiang
Early Cretaceous redbeds from the Minle Basin, Hexi Corridor, northwest China; mineralogy and geochemistry implications for paleoweathering, provenance, and tectonic settings
Interpretation (Tulsa) (May 2019) 7 (2): T525-T545

Abstract

Redbeds with a large thickness in the Lower Cretaceous record abundant geologic information in the Minle Basin. We have conducted the paleoweathering conditions, provenance, and tectonic settings based on mineralogy and geochemistry. Our results indicate that mudstone samples are characterized by abundant illite with negligible amounts of K-feldspars and analcime. The lower part of the Lower Cretaceous is rich in quartz, whereas the upper part is dominated by dolomite and analcime. We suggest that this is caused by the decreasing input of the clastic influx during the middle-late Early Cretaceous. High index of compositional variation values (average 1.33) indicate first-cycle sediment supply, suggesting an overall compositional immaturity and short-distance transportation. These characteristics are consistent with an active regional extension tectonic setting. The M (super +) -4Si-R (super 2+) system (M (super +) = Na (super +) + K (super +) + 2Ca (super 2+) ; 4Si = Si/4;R (super 2+) = Fe (super 2+) + Mg (super 2+) ) and Th/U versus Th consistently reveal that the Lower Cretaceous experienced a positive gradient in chemical weathering from young to old formations. Although the patterns of trace elements in three formations of the lower Cretaceous are different, those of the rare earth elements (REEs) tend to be consistent. The significant enrichment of light REEs, heavy REEs fractionation, and distinctive negative Eu anomalies suggest derivation from an old, upper continental crust composed of predominantly felsic sediments. This interpretation is supported by several discrimination diagrams such as titanium dioxide-nickel (Ti (sub 2) O-Ni), which shows the characteristics of immature recycled sediments. A few sensitive elements, ratios, and normalized REE patterns indicate a provenance of an active continental margin and a continental island arc (CIA). The La-Th-Sc, Th-Co-Zr/10, and Th-Sc-Zr/10 discrimination plots further confirm the CIA signature. Thus, we conclude that the Early Cretaceous redbeds in the Minle Basin, Hexi Corridor, were deposited in a dustpan-shaped half-graben basin in a CIA setting when northwest China was influenced by intense regional extension.


ISSN: 2324-8858
EISSN: 2324-8866
Serial Title: Interpretation (Tulsa)
Serial Volume: 7
Serial Issue: 2
Title: Early Cretaceous redbeds from the Minle Basin, Hexi Corridor, northwest China; mineralogy and geochemistry implications for paleoweathering, provenance, and tectonic settings
Affiliation: China University of Geosciences, School of Energy Resources, Beijing, China
Pages: T525-T545
Published: 201905
Text Language: English
Publisher: Society of Exploration Geophysicists, Tulsa, OK, United States
References: 91
Accession Number: 2019-036108
Categories: Isotope geochemistrySedimentary petrology
Document Type: Serial
Bibliographic Level: Analytic
Annotation: Technical papers
Illustration Description: illus. incl. strat. col., sects., 6 tables, geol. sketch map
N38°00'00" - N39°30'00", E99°45'00" - E101°45'00"
Secondary Affiliation: SINOPEC, CHN, China
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2019, American Geosciences Institute. Reference includes data supplied by Society of Exploration Geophysicists, Tulsa, OK, United States
Update Code: 201909
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