吉林中东部季德屯钼矿床含矿岩体地质、地球化学及年代学研究

季德屯钼矿床是近年内在吉林中东部地区发现并初步探明的一个大型斑岩型钼矿床,钼矿体主要赋存在花岗闪长岩体内和花岗闪长岩体与二长花岗岩体的接触带及其附近。花岗闪长岩和二长花岗岩岩体的地质、岩石地球化学和单颗粒锆石U-Pb年代学研究揭示:它们均属于偏铝质、高钾钙碱性系列的I型花岗岩;均富集Rb、K等大离子亲石元素,亏损Nb、Ta、P、Ti、Y等高场强元素;锆石U-Pb年龄分别为(180.2±0.8)Ma和(180.1±0.6)Ma;矿床辉钼矿Re-Os同位素等时线年龄为(169±3)Ma。综合研究表明,季德屯斑岩型钼矿床类型属于与钙碱性、高钾钙碱性岩石系列有关的深成侵入体型钼矿床,形成于古太平洋板块俯冲背景下形成的活动大陆板块边缘岩浆弧环境,其成矿物质主要来源于地壳,从岩体侵位成岩到最终形成钼矿床大致经历了11 Ma。

Geology, geochemistry and geochronology of ore-bearing intrusions in Jidetun molybdenum deposit in mid-east Jilin Province

The Jidetun molybdenum deposit is a newly discovered and also preliminarily explored large porphyry type deposit in mid-east Jilin Province. The molybdenum orebodies are hosted in the granodiorite intrusion and at the contact zone between the granodiorite and monzonitic granite intrusions. In this study, geological and geochemical features of the ore-bearing intrusions were inveitigated and their zircon U-Pb ages were determined. The results show that the ore-bearing granodiorite and monzonitic granite belong to metaluminous I-type granites of the high-K cale-alkalic series, and are enriched in large-ion lithophile elements such as Rb and K and depleted in high field strength elements such as Nb, Ta, P, Ti and Y. The LA-ICP-MS zircon U-Pb ages of ore-bearing intrusions are (180.2±0.8) Ma and (180.1±0.6) Ma respectively. The Re-Os isotope isochron age of molybdenite of the ore is (169±3) Ma. The present research shows that the Jidetun molybdenum deposit belongs to the so-called plutonic type porphyry molybdenum deposit related to calc-alkaline, high-K cale-alkaline series of granodiorite and monzonitic granite. It is believed that the Jidetun molybdenum deposit was formed on the igneous arc margin of the active continental plate under a converging subduction system of the paleo-pacific plate. The ore-forming materials, including sulfur and metals, were derived mainly from the crust. The interval between the emplacement and solidification of the ore-bearing intrusions and the final molybdenum mineralizing roughly last for about 11 Ma.