Geochemistry of sedimentary rocks from Permian–Triassic boundary sections of Tethys Himalaya: implications for paleo-weathering, provenance, and tectonic setting  

作　　者：Akhtar R.Mir V.Balaram Javid A.Ganai Shamim A.Dar A.Keshav Krishna 

机构地区：[1]Department of Earth Sciences,University of Kashmir,Srinagar 190006,India [2]CSIR-National Geophysical Research Institute,Hyderabad 500007,India [3]Department of Geology,S.P.College,Srinagar 190008,India

出　　处：《Acta Geochimica》2016年第4期428-436,共9页地球化学学报（英文）

摘　　要：The geochemical characteristics of two sections—the Permian–Triassic boundary(PTB) Guryul Ravine section, Kashmir Valley, Jammu and Kashmir,India; and the Attargoo section, Spiti Valley, Himachal Pradesh, India—have been studied in the context of provenance, paleo-weathering, and plate tectonic setting.These sections represent the siliciclastic sedimentary sequence from the Tethys Himalaya. The PTB siliciclastic sedimentary sequence in these regions primarily consists of sandstones and shales with variable thickness. Present studied sandstones and shales of both sections had chemical index of alteration values between 65 and 74; such values reveal low-to-moderate degree of chemical weathering. The chemical index of weathering in studied samples ranged from 71 to 94, suggesting a minor K-metasomatism effect on these samples. Plagioclase index of alteration in studied sections ranged from 68 to 92, indicating a moderate degree of weathering of plagioclase feldspars. The provenance discriminant function diagram suggests that the detritus involved in the formation of present studied siliciclastic sedimentary rocks fall in quartzose sedimentary and felsic igneous provenances. These sediments were deposited in a passive continental margin plate tectonic setting according to their location on a Si_2 O versus K_2O/Na_2 O tectonic setting diagram.The geochemical characteristics of two sections-the Permian-Triassic boundary （PTB） Guryul Ravine section, Kashmir Valley, Jammu and Kashmir, India; and the Attargoo section, Spiti Valley, Himachal Pradesh, India-have been studied in the context of provenance, paleo-weathering, and plate tectonic setting. These sections represent the siliciclastic sedimentary sequence from the Tethys Himalaya. The PTB siliciclastic sedimentary sequence in these regions primarily consists of sandstones and shales with variable thickness. Present studied sandstones and shales of both sections had chemical index of alteration values between 65 and 74; such values reveal low-to-moderate degree of chemical weathering. The chemical index of weathering in studied samples ranged from 71 to 94, suggesting a minor K-metasomatism effect on these samples. Plagioclase index of alteration in studied sections ranged from 68 to 92, indicating a moderate degree of weathering of plagioclase feldspars. The provenance discriminant function diagram suggests that the detritus involved in the formation of present studied siliciclastic sedimentary rocks fall in quartzose sedimentary and felsic igneous provenances. These sediments were deposited in a passive continental margin plate tectonic setting according to their location on a Si2O versus K2O/ Na2O tectonic setting diagram.

关 键 词：GEOCHEMISTRY Permian-Triassic boundary - Guryul Ravine Tectonic settings 

分 类 号：P588.2[天文地球—岩石学]