Mineralogical and geochemical characteristics of altered volcanic ashes (tonsteins and K-bentonites) from the latest Permian coal-bearing strata of western Guizhou Province, southwestern China
Mineralogical and geochemical characteristics of altered volcanic ashes (tonsteins and K-bentonites) from the latest Permian coal-bearing strata of western Guizhou Province, southwestern China
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贵州省西部最新二叠纪含煤地层蚀变火山灰（吨斯坦岩和钾膨润土）的矿物学和地球化学特征
DOI：
10.1016/j.coal.2021.103707
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发表时间：
2021-02
影响因子：
5.6
通讯作者：
Xuanhao Xie
中科院分区：
文献类型：
--
作者：
Minglian Shen;Shifeng Dai;Ian Graham;Victor Nechaev;David French;Fenghua Zhao;Longyi Shao;Sh;e Liu;Jianping Zuo;Jingtao Zhao;Kun Chen;Xuanhao Xie
尽管对中国南方二叠纪-三叠纪边界（PTB）广泛分布的火山灰的地球化学和矿物学特征及其来源进行了深入研究，但对二叠纪末大规模灭绝（EPME）之前的火山灰的研究却很少。本文介绍了中国西南地区最新二叠纪含煤地层火山灰的矿物学和地球化学成分。根据高岭石和混合层伊利石/蒙脱石（I/S）的相对丰度，本研究中的火山灰可分为以高岭石和I/S为主的吨斯坦岩和钾膨润土。钾膨润土中的 I/S 是在非海洋环境中的埋藏成岩作用过程中形成的，其硫含量低和 Sr/Ba 比率低表明了这一点。根据煤的一般地温梯度和镜质体反射率，推断I/S是在低于100℃的温度下形成的。总的来说，在吨斯坦石样品中发现的蠕虫状高岭石以及高温石英和自形原生锆石表明火山灰的中长英质火山碎屑起源，而吨斯坦石和钾膨润土中的圆形石英和云母颗粒则反映了沉积物源区侵蚀的产物。负Eu异常、稀土元素(REY)分布模式、低Sc、V、Cr、Co、Ni和Zn含量以及Al2O3/TiO2值，表明吨斯坦岩和钾膨润土与长英质火山喷发有关。 Al2O3/TiO2 与 Al2O3 之间的关系Nb/Yb 和 Al2O3/TiO2 对比。 Zr/TiO2比率表明，吨斯坦岩和钾膨润土至少来自两个长英质来源：（1）一些远端火山弧和（2）康甸高地顶部暴露出峨眉山羽流减弱活动期间形成的碱性长英质火山岩，康甸高地基底暴露出较古老的长英质岩石。
Although the geochemical and mineralogical characteristics and provenance of Permian-Triassic boundary (PTB) widespread volcanic ashes from southern China have been well investigated, the volcanic ashes just prior to the end-Permian mass extinction (EPME) have rarely been studied. This paper presents the mineralogical and geochemical compositions of volcanic ashes from the latest Permian coal-bearing strata of southwest China. Based on the relative abundances of kaolinite and mixed-layer illite/smectite (I/S), the volcanic ashes in the present study can be divided into tonsteins and K-bentonites, which are dominated by kaolinite and I/S, respectively. The I/S in K-bentonites formed during burial diagenesis in a non-marine environment, indicated by their low contents of sulfur and low ratios of Sr/Ba. Based on the general geothermal gradient and vitrinite reflectance of coals, the I/S was deduced to have formed under a temperature less than 100 °C. Collectively, the occurrence of vermicular kaolinite, as well as high-temperature quartz and euhedral primary zircon identified in tonstein samples indicate an intermediate-felsic pyroclastic origin for the volcanic ashes, while rounded quartz and mica grains both in tonsteins and K-bentonites reflect the products of erosion from sediment source regions. The negative Eu anomalies, rare earth elements (REY) distribution patterns, low contents of Sc, V, Cr, Co, Ni and Zn, and Al2O3/TiO2values, suggest that the tonsteins and K-bentonites are related to felsic volcanic eruptions. The relationship between Al2O3/TiO2vs. Nb/Yb and Al2O3/TiO2vs. Zr/TiO2ratios indicate that the tonsteins and K-bentonites were derived from at least two felsic sources: (1) some distal volcanic arc(s) and (2) the top of the Kangdian Upland exposing the alkaline-felsic volcanic rocks formed during the waning activity of the Emeishan plume and the basement of the Kangdian Upland exposing older felsic rocks.
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影响因子：
3.3
作者：
Fenlian Wang;C. Wang;T. Zhao
通讯作者：
Fenlian Wang;C. Wang;T. Zhao
影响因子：
5.6
作者：
S. Dai;Yiping Zhou;Mingquan Zhang;Xibo Wang;Jumin Wang;Xiaolin Song;Yao-fa Jiang;Yangbing Luo-
通讯作者：
S. Dai;Yiping Zhou;Mingquan Zhang;Xibo Wang;Jumin Wang;Xiaolin Song;Yao-fa Jiang;Yangbing Luo-
影响因子：
5.3
作者：
He, B;Xu, YG;Wang, Y
通讯作者：
Wang, Y
影响因子：
3.5
作者：
Hu Huang;Peter A. Cawood;Mingcai Hou;S. Ni;Jianghai Yang;Yuansheng Du;Huaguo Wen
通讯作者：
Hu Huang;Peter A. Cawood;Mingcai Hou;S. Ni;Jianghai Yang;Yuansheng Du;Huaguo Wen
影响因子：
3.9
作者：
Dai, Shifeng;Wang, Xibo;Zou, Jianhua
通讯作者：
Zou, Jianhua