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Petrography and geochemistry of upper T riassic sandstones from the T umengela F ormation in the W oruo M ountain area, N orth Q iangtang B asin, T ibet: I mplications for provenance, source area weathering, and tectonic setting
Author(s) -
Wang Zhongwei,
Wang Jian,
Fu Xiugen,
Feng Xinglei,
Wang Dong,
Song Chunyan,
Chen Wenbin,
Zeng Shengqiang
Publication year - 2017
Publication title -
island arc
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.554
H-Index - 58
eISSN - 1440-1738
pISSN - 1038-4871
DOI - 10.1111/iar.12191
Subject(s) - provenance , geology , felsic , petrography , weathering , geochemistry , plagioclase , source rock , lithic fragment , maturity (psychological) , mineralogy , feldspar , clastic rock , quartz , mafic , sedimentary rock , structural basin , geomorphology , paleontology , psychology , developmental psychology
Abstract The petrography and major and trace element concentrations of the sandstones from the T umengela F ormation in the W oruo M ountain area, N orth Q iangtang B asin, are studied to determine their provenance, intensity of weathering and tectonic setting. The detrital compositions of the T umengela sandstone samples are dominated by quartz (58.0–70.1 %, average 64.7 %) and lithic fragments (21.8–35.9 %, average 27.3 %), but low in feldspar content (4.9–12.9 %, average 8.0 %). The sandstones can be classified as litharenite and feldspathic litharenite according to their detrital compositions, which is consistent with the geochemical data. The detrital modal compositions reflect that these sandstones are probably derived from a recycled orogenic source. The index of chemical variability ( ICV ) and SiO 2 / A l 2 O 3 ratio values suggest that the compositional maturity and recycling were moderate. The weathering indices such as the chemical index of alteration ( CIA ), plagioclase index of alteration ( PIA ), chemical index of weathering ( CIW ), and A l 2 O 3 –( C a O * + N a 2 O )– K 2 O ( A – CN – K ) diagram indicate that the intensities of weathering in the source area were moderate. The A l 2 O 3 / T i O 2 , T h/ C o, L a/ S c, L a/ C o, T h/ S c, C r/ T h ratio values and the discriminant function of the T umengela sandstones indicate that the sediments were mainly derived from felsic source rocks, while also mixed with intermediate source rocks. The comparison of rare earth element patterns and its E u anomalies to the probable source rocks infer that the sandstones were derived from the combination of granite, rhyolite, dacite, and gneisses. The proximal central uplift belt was probably the primary provenance area as evidenced by the petrographical and geochemical features of the T umengela sandstones. The multidimensional tectonic discrimination diagram based on major elements show a collision setting (80 %) combined with a rift setting (20 %) for the T umengela sandstones, which is consistent with the general geology of the study areas.