矿床地质2018，Vol.37Issue(2)：311-338,28.DOI:10.16111/j.0258-7106.2018.02.006
内蒙古大苏计斑岩钼矿床花岗质杂岩年代学、地球化学、Hf同位素组成及其地质意义
Geochronology, geochemistry and Hf isotope of granitic complex in Dasuji porphyry Mo deposit of Inner Mongolia and their geological implications
摘要
Abstract
The Dasuji porphyry molybdenum mineralization is closely related to the Dasuji granitic complex (quartz porphyry,syenogranite porphyry,and granite porphyry) in the Dasuji ore district of Zhuozi County,Inner Mongolia.LA-ICP-MS zircon U-Pb dating for the quartz porphyry,syenogranite porphyry and granite porphyry yielded ages of (234 ± 3) Ma,(225 ± 4) Ma,and (220 ± 4) Ma,respectively.The granitic rocks all have high content of SiO2 (70.37％ ～ 78.84％) and total alkali (K2O + Na2O =4.52％ ～ 8.77％),thus belonging to high-K calc-alkaline series.The granitic complex generally has a low Na2O content (0.15％ ～ 2.69％) and high aluminum index (ASI ranging from 1.13 to 3.35).The values of total rare earth elements (REEs) for the granitic rocks range from 48.2 × l0-6 to 527.0 × 10-6;of them,the REE content of quartz porphyry is the lowest (48.2 × 10-6 ～ 83.1 ×10-6);syenogranite porphyry has the highest REE content (272.1 × 10-6 ～ 527.0 × 10-6),and the REE content of the granite porphyry ranges from 162.5 × 10-6 to 236.8 × 10-6.The δEu value of the complex ranges from 0.15 to 0.93,and (La/Yb) N value ranges from 3.0 to 65.5.From the syenogranite porphyry through granite porphyry to quartz porphyry,the δEu value gradually increases,while (La/Yb) N value decreases gradually.The three rocks are all enriched in Rb,Th,U,K,Nd,Zr and Hf,but strongly depleted in Sr,P and Ti;moreover,the syenogranite porphyry reveals medium depletion of Ba,Ta,and Nb.Both quartz porphyry and granite porphyry are highly fractionated granite,while syenogranite porphyry is a typical I-type granite.The characteristics of the major,REE,and trace elements indicate that the Dasuji complex has affinity to post-collision or post-orogenic granites,suggesting that the complex formed in a post-collision or post-orogenic environment.The εHf(t) values of zircons from the three types of rocks range from-21.1 to-8.1,and their Hf two-stage model ages (tDM2(Hf)) range from 1775 to 2587 Ma.The Hf isotope compositions suggest that the quartz porphyry was most likely formed by partial melting of a Paleoproterozoic crust,the syenogranite porphyry was most likely formed by partial melting of a late Paleoproterozoic crust,and the granite porphyry was mainly formed by partial melting of a Paleoproterozoic crust with the addition of a small amount of the Neoarchaean crust.关键词
地球化学/LA-ICP-MS锆石U-Pb定年/Hf同位素/大苏计杂岩体/内蒙古/华北克拉通北缘Key words
geochemistry/LA-ICP-MS zircon U-Pb dating/Hf isotope/Dasuji complex/Inner Mongolia/the northern margin of the North China craton分类
天文与地球科学引用本文复制引用
吴昊,武广,陶宏,张明玉,王国瑞,陈军其,杨宁宁..内蒙古大苏计斑岩钼矿床花岗质杂岩年代学、地球化学、Hf同位素组成及其地质意义[J].矿床地质,2018,37(2):311-338,28.基金项目
本文得到国家自然科学基金项目(编号:41572061)、内蒙古自治区地质勘查基金项目(编号:2012-03-YS01)和中国地质调查局中国矿产地质与成矿规律综合集成和服务(矿产地质志)项目(编号:DD20160346)的资助 （编号:41572061）
