摘要
广西大厂矿田中部的笼箱盖岩体是一个多期次侵入的复式岩体,尽管前人对其中个别阶段岩体进行过年龄精测,但迄今还没有对多期岩体进行过系统的年代学精测。本文在运用阴极发光技术对岩体中锆石进行细致的内部结构分析的基础上,利用LA-MC-ICP-MS锆石U-Pb原位定年方法,系统测定了岩体中单颗粒锆石的206Pb/238U年龄,结果显示出,笼箱盖复式岩体形成经历了103.8～102Ma、96.6～93.86Ma、90.1～85.1Ma3期活动,其中96.6～93.86Ma为主体形成时期,其第一阶段形成中细粒含斑黑云母花岗岩(96.6±2.5Ma)、细粒含斑的黑云母花岗岩(94.3±2.2Ma),第二阶段形成中细粒等粒状黑云母花岗岩(96.1±2.0Ma),第三阶段形成似斑状黑云母花岗岩(93.86±0.84Ma)。这些岩体之间界限清晰、无明显冷凝边,说明岩浆活动是一种连续的脉动过程。大厂矿田的锌铜矿体、锡多金属矿体的形成主要与笼箱盖复式岩体的第二期岩浆活动密切相关,成矿过程在短暂时间完成。笼箱盖复式岩体的形成时期与中国东部110～80Ma大规模成矿过程是吻合的,成岩成矿作用可能与岩石圈伸展作用有关。
The Longxianggai pluton is a multiple-intruded in the middle of the Dachang ore field of Guangxi.Although the former researchers had carried out some dating on the rock intruded in some stages,so far systematic chronology study about its multi-stage magmatic intrusions has not done.Based on analyzing the interior structures of zircons by the CL technology,in-situ zircon U-Pb dating was performed with LA-MC-ICP-MS and reliable 206Pb/238U age data in fine-grained zircon were obtained.The results show that Longxianggai pluton was formed in three staged,that is,103.8~102Ma,96.6~93.86Ma and 91~85.1Ma,and 96.6~93.86Ma is the main magmatic period.In the first stage,medium-fine-grained biotite granite with porphyritic （96.6±2.5Ma） and fine-grained biotite granite with porphyritic （94.3±2.2Ma） was formed.In the second stage,medium-fine-grained equigranular biotite granite （96.1±2.0Ma）.In the third stage,the porphyraceous biotite granite （93.86±0.84Ma） was formed.The boundary between the rocks is clear and has no chilled margin,which indicates that magmatism forming Longxiagngai pluton is a continuous pulse process.The formation of zinc-copper ore body and tin-polymetallic ore body is closely related with the second magmatic period of the Longxianggai pluton and the mineralization process was completed in a short time.This information period of the Longxianggai pluton is the same as the large-scale mineralization of 110~80Ma in eastern China,and its digenesis and mineralization may be related to lithosphere extension.
出处
《岩石学报》
SCIE
EI
CAS
CSCD
北大核心
2011年第6期1624-1636,共13页
Acta Petrologica Sinica
基金
国土资源部公益性行业科研专项(21011046
200911007-6)
国家危机矿山综合研究项目(20089946)联合资助
