First Discovery of Late Triassic Tuffs in the South Qilian Basin: Geochemical Characteristics, Zircon LA-ICP-MS U-Pb Ages and Potential Source Regions  

作　　者：Fangpeng Du Furong Tan Shiming Liu Xiaochen Zhao Yingtao Chen Junwei Qiao 

机构地区：[1]School of Petroleum Engineering and Environmental Engineering,Yan'an University,Yan'an 716000,China [2]China National Administration of Coal Geology,Beijing 100038,China [3]State Key Laboratory of Continental Dynamics,Department of Geology,Northwest University,Xi'an 710069,China [4]Key Laboratory of Resource Exploration Research of Hebei Province,Hebei University of Engineering,Handan 056038,China [5]College of Geology and Environment,Xi'an University of Science and Technology,Xi'an 710054,China

出　　处：《Journal of Earth Science》2023年第6期1692-1703,共12页地球科学学刊（英文版）

基　　金：supported by the National Natural Science Foundation of China(Nos.41702144,42002194);the Natural Science Basic Research Plan of Shaanxi Province,China(Nos.2019JQ-991,2020JQ-746).

摘　　要：This investigation reports the first discovery of more than 70 tuff intervals in the Upper Triassic,South Qilian Basin.Petrographic and geochemical analyses were carried out on ten tuff samples and zircon U-Pb dating were on three.Thin section and X-ray diffraction(XRD)results indicate that the tuffs were composed of crystal shards and altered glass shards;crystal shards include plagio-clase and quartz.Most of the tuffs had been transformed into illite/smectite mixed-layers(I/S).In addition,calcite,pyrite,dolomite and siderite were also identified in some of the tuff samples.Analysis of major elements suggests that the tuffs are peraluminous high-K calcalkaline series.Trace elements indicate that the tuffs are enriched in high field strength elements(HFSE),including Th,U,Ta,Zr and Hf.Geochemical characteristics suggest that the tuffs originated from comendite pantellerite and rhyolite from within plate setting.Zircon U-Pb dating(236.0±1.7,231.4±1.6,and 223.1±3.9 Ma)indicate that the tuffs were erupted in the Late Triassic.Comparative chronology and geochemical analyses suggest that the West Qinling belt and the East Kunlun belt are the potential source regions of these tuffs,and they originated from the within plate magma during a post-collisional period.

关 键 词：TUFF South Qilian Basin Late Triassic U-Pb isotopic dating source regions zircon geo-chemistry 

分 类 号：P534.51[天文地球—古生物学与地层学] P588.2[天文地球—地质学] P597.3