摘要
内蒙古莲花山铜银矿是大兴安岭南段成矿带上的一个重要矿床,成矿与斜长花岗斑岩密切相关。对矿区内斜长花岗斑岩体进行LA-MC-ICP-MS锆石U-Pb测年结果表明,其形成年龄为(236.8±0.77)Ma(MSWD=0.85)和(237.9±0.71)Ma(MSWD=1.02),为中三叠世岩浆活动产物,而不是前人认为的中侏罗世。莲花山斜长花岗斑岩的εHf(t)=+5.6-+11.5,具有较高的176Hf/177Hf比值(0.282 762-0.282 954)和年轻的二阶段Hf同位素模式年龄(477-810 Ma),综合研究表明其主要源自从亏损地幔中新增生的年轻地壳物质的部分熔融,也暗示兴安地块新元古代—早古生代曾发生一次重要的地壳增生事件。对兴蒙造山带及邻区近1 100个岩浆岩中锆石Hf同位素数据整理研究后发现,兴安地块、松嫩地块和佳木斯地块属性相似,其与额尔古纳地块和华北板块北缘各自具有不同的地壳增生历史,揭示它们具有不同的早期地壳演化过程。
The Lianhuashan Cu-Ag deposit of Inner Mongolia is an important deposit in southern Da Hinggan Mountains metallogenic belt,and its mineralization is closely related to the plagioclase granite porphyry.Zircon LA-MC-ICP-MS dating of the plagioclase granite porphyry shows that its formation ages range from 236.8±0.77Ma（MSWD=0.85） to 237.9±0.71Ma（MSWD=1.02）,suggesting that it is a product of the Triassic magmatism rather than the Middle Jurassic magmatic activity.The Lianhuashan plagioclase granite porphyry has εHf（t） values range from ＋5.6 to ＋11.5 with relatively high 176Hf/177Hf values and younger two-stage model ages（477-810Ma）,indicating that it was mainly derived from the partial melting of the new-born lower crust that originated from the depleted mantle,and that there probably existed an important crustal growth event in Hinggan massif which occurred in the early Paleozoic-late Proterozoic period.Based on a systematical study of -1100 zircon Hf isotope data from the magmatic rocks in the Xingmeng orogenic belt,the authors found that the Hinggan,Songnen and Jiamusi massifs have similar properties,and these three massifs,the Ergun massif and the North China plate margin have their respective crustal accretion histories,revealing that they had different early crustal evolution processes.
出处
《中国地质》
CAS
CSCD
北大核心
2012年第6期1472-1485,共14页
Geology in China
基金
中国地质调查局地质调查项目(1212011085260)
内蒙古重要矿产资源潜力评及区域成矿规律研究项目(2006-02-YS01)联合资助
