Geochronology of two kinds of Paleozoic granitic plutons from Sangewatang in Subei, the western margin of Central-South Qilian and their geological implications

中南祁连西缘三个洼塘附近花岗质岩石由花岗岩、石英闪长岩和花岗闪长岩构成。LA-ICP-MS锆石U-Pb年龄测定结果表明,花岗岩、石英闪长岩和花岗闪长岩侵位年龄分别为416.7±4.3Ma(MSWD=0.52)、442.5±4.7Ma(MSWD=0.46)和443.9±1.3Ma(MSWD=0.17),指示本区发生了两期岩浆活动事件。花岗质岩石均表现为过铝质,花岗岩高钾、K/Na,低Mg、Fe、Ca的主量元素特征,富集高场强元素,亏损大离子亲石元素,∑REE为122.0×10-6,δEu为0.05,具明显负铕异常。花岗闪长岩和石英闪长岩多数富钠,高场强元素含量相对花岗岩较低,而大离子亲石元素含量...The granitoids from Sangewatang in the western margin of Central-South Qilian are composed of granites, quartz diorites and granodiorites. LA-ICP-MS zircon U-Pb age of granite is 416.7 +/- 4.3Ma (MSWD = 0.52), while that of quartz diorite and granodiotite are 442.5 +/- 4.7 (MSWD = 0.46) and 443.9 +/- 1.3Ma (MSWD = 0.17) respectively, indicating that two magmatic events have occurred in the study area The granite is peraluminous with high K/Na and K content, and low Mg, Fe and Ca content Meanwhile, it is enriched in high field strength elements, and depleted in large ion lithophile elements. Its Sigma REE is 122.0 x 10(-6) and delta Eu is 0.05 with significant Eu negative anomaly. In contrast, the granodiorite and quartz diorite are also peraluminous but are enriched in Na. They have a lower content of high field strength elements and a slightly higher content of large ion lithophile elements. Their Sigma REE range from 133.3 x 10(-6) to 247.6 x 10(-6) and delta Eu range from 0.73 to 1.09, showing no significant Eu anomalies. Based on these geochemical characteristics, we conclude that the granites belong to I-type granites and were produced by partial melting of continental crust in a post-orogenic extensional setting. In contrast, the granodiorites and quartz diorites are I-type granites and are likely to be the product of island arc magmatism, associated with oceanic subduction. These results are of key importance to constrain the tectonic evolution of Central-South Qilian.http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000349509300013&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=8e1609b174ce4e31116a60747a720701SCI(E)中文核心期刊要目总览(PKU)中国科技核心期刊(ISTIC)中国科学引文数据库(CSCD)2zhiwenluoluo@163.com; zczhang@pku.edu.cn01176-1883