摘要
老君山花岗岩体位于滇东南地区的文山州麻栗坡县境内,是个旧-薄竹山-老君山岩浆-成矿系统中最东部的一个岩体。该岩体侵入到老君山地区前寒武纪变质地层中,是一个多期次岩浆侵入形成的复式岩体,其岩性主要为似斑状黑云母花岗岩,粗粒-中粗粒黑云母/二云母花岗岩,中粗粒黑云母/二云母二长花岗岩。本文提供了老君山花岗岩6个锆石的LAICP-MS U-Pb定年结果,为88.9±1.1Ma^93.9±2.0Ma之间,表明老君山花岗岩是白垩世晚期岩浆作用产物。全岩化学分析结果显示老君山花岗岩属过铝质高钾钙碱性S型花岗岩。锆石的εHf(t)值变化于-9.94^-5.01之间,平均值为-7.29,锆石Hf的两阶段模式年龄为t DM C=1.8~1.4Ga,上述特点表明,老君山花岗岩浆的源岩是滇东南地区早元古代结晶基底中的变泥砂质岩类。结合前人的研究资料,论证了老君山花岗岩的成因及其与区域成矿作用的关系,提出老君山花岗岩及其附近的钨锡多金属矿床同属于岩石圈板块强烈伸展作用下的产物,其中钨锡多金属矿床的形成与早期岩石圈板块的伸展及基底变质岩中成矿物质的活化迁移有关,而老君山花岗岩是在燕山晚期岩石圈强烈伸展与地幔物质上涌的背景下,由基底变泥砂质岩石的部分熔融作用形成的。燕山晚期岩石圈的强烈伸展、地幔上涌及花岗岩浆作用,不仅为成矿物质的活化迁移提供了热动力条件,而且还可能提供了成矿物质。正是因为燕山晚期岩石圈的强烈伸展、地幔上涌及花岗岩浆作用对早期矿床的叠加与改造,可能是该区大规模成矿作用的主要机制,也可能是形成该区大型与超大型钨锡多金属矿床的主要原因之一。
The Laojunshan granitoids located in Malipo County of the Wenshan Autonomous Prefecture,in southeastern Yunnan Province,is the most eastern intrusion of the Gejiu-Bozhushan-Laojunshan magma-metallogenic system. The intrusion is a multistage complex granite intrusion and intruded into the Cambrian metamorphic strata in Laojunshan areas,it mainly composed of porphyritoid biotite granite,coarse-medium to coarse biotite/mica granite,coarse-medium to coarse biotite / mica monzonitic granite. Six zircon UPb ages from 88. 9 ± 1. 1Ma to 93. 9 ± 2. 0Ma,indicated that Laojunshan granitoids are the product of Late Cretaceous magmatism. The geochemical signatures showed that the pluton is high-K calc-alkaline peraluminous S-type granite. The zircon εHf（ t） values（- 9. 94to- 5. 01）,and the weighted average of 7. 29,the two stage Hf model ages（ 1. 8Ga to 1. 4Ga）,these signatures indicated that the granite originated from the metamorphic sandstone of the Early Proterozoic crystalline basement in southeastern Yunnan areas. This study also demonstrated the genesis of the Laojunshan granitoids and its relationship with regional mineralization combined with the previous research,and presented that the granite and its nearby W,Sn polymetallic deposits are formed in the strong extension of the lithosphere plate. Thereinto,the W,Sn polymetallic deposits are related to the extension of lithosphere plate in early phase and the mineral activation migration in basement metamorphic rocks,while the Laojunshan granitoids are formed from the partial melting of the basal metamorphous pelitic-sandy rock in the setting of the lithosphere plate extension and mantle material upwelling in Late Yanshanian. During Late Yanshanian,the lithosphere plate extension,mantle material upwelling and granitic magmatism are not only provided the thermodynamic conditions for mineral activation migration,but also the metallogenic material. These acting on the early superposition and transformation,may be the primary mechanism for large-scale minera
出处
《岩石学报》
SCIE
EI
CAS
CSCD
北大核心
2014年第11期3271-3286,共16页
Acta Petrologica Sinica
基金
中国地质调查工作项目(1212011220928)
县校合作项目联合资助
