青海东昆仑哈西亚图铁多金属矿区石英闪长岩LA-ICP-MS锆石U-Pb年龄和岩石地球化学特征

东昆仑地区是青海省重要的夕卡岩型铁多金属矿成矿带,哈西亚图铁多金属矿是近年来首例在东昆仑金水口岩群中发现的与中酸性岩体有关的夕卡岩型矿床,目前铁、金、锌矿已达中型。其成矿作用与矿区东北部石英闪长岩关系密切,矿体产于石英闪长岩的外接触带。采用LA-ICP-MS同位素测定技术,测得石英闪长岩锆石U-Pb年龄为246.8±1.8Ma(MSWD=0.074),形成于早三叠世,表明东昆仑地区早三叠世存在夕卡岩成矿作用。地球化学研究表明,石英闪长岩为高钾钙碱性系列,具有安第斯型活动大陆边缘火成岩的构造属性。研究认为,石英闪长岩是阿尼玛卿洋盆向北俯冲,致使壳幔岩浆发生混合,后经侵位、结晶分异形成的。

LA-ICP-MS zircon U-Pb age and geochemical characteristics of quartz diorite from the Haxiyatu iron-polymetallic ore district in Eastern Kunlun

Eastern Kunlun region is an important skarn-type iron-polymetallic metallogenic belt in Qinghai Province, and the Haxiyatu iron-polymetallic deposit is related to the intermediate intrusive body discovered in recent years in the area of Jinshuikou rock group. The iron, gold and zinc reserves of the deposit have reached a medium-size deposit. The mineralization has a close relationship with quartz diorite in northeast mining area, and the orebody occurs in the outer contact zone of quartz diorite. LA-ICP-MS isotope dating of zircons from the quartz diorite yielded an age of 246.8±1.8Ma (MSWD=0.074), suggesting that the quartz diorite was formed before Early Triassic and that there existed skarn mineralization in Eastern Kunlun area in Early Triassic. Geochemical studies indicate that quartz diorite is of high-K calc-alkaline series and has the attribute of Andean type epicontinental igneous tectonics. It is thus held that the quartz diorite was formed after the northward subduction of Animating ocean basin which caused the mixing, emplacement and crystallization differentiation of the crust mantle magma.