摘要
粤北大宝山矿区一带出露一套与层状Fe-Cu-Pb-Zn矿化紧密共生的层状火成岩。层状火成岩产状与上覆页岩及大理岩和下伏碳质页岩基本一致。本文通过层状火成岩显微特征及锆石年龄探讨火成岩形成环境及时代。层状火成岩为斑状结构,块状构造,局部发育条带状构造及流动构造。层状火成岩的斑晶主要由火山喷发形成的棱角明显石英、斜长石、钾长石、少量角闪石、黑云母及黄铁矿等晶屑及少量岩屑组成,基质为火山熔浆凝结形成的全晶质矿物,主要由粒度极细的石英、钾长石、绢云母、白云母及少量黑云母等组成,石英和钾长石构成典型的霏细结构。层状火成岩含大量火山碎屑及具流动构造等现象表明其为火山碎屑熔岩类,主要为英安质凝灰熔岩、流纹质凝灰熔岩及角砾熔岩。大宝山矿区中部流纹质凝灰熔岩和东部丘坝一带英安质凝灰熔岩的锆石LA-ICP-MS U-Pb年龄分别为436.4±4.1Ma,MSWD=0.94和434.1±4.4Ma,MSWD=1.9,是加里东期形成的。据大宝山矿区熔岩锆石U-Pb年龄,结合层状熔岩和灰岩及碳质页岩紧密共生及区域深大断裂构造活动特征,我们认为大宝山与层状矿化关系密切的层状火成岩为加里东期海相火山熔岩,粤北一带加里东期海相火山活动可能和形成于加里东期的吴川-四会深大断裂活动有关。
Layered igneous rocks associated closely with stratiform Fe-Cu-Pb-Zn mineralization are widely exposed in the Dabaoshan mining area in northern Guangdong Province. The layered igneous rocks are overlaid conformably by shale and marble and underlaid conformably by carbonaceous shale, respectively. Our work discusses the forming environment and age of the layered igneous rocks. The layered igneous rocks characterized by porphyritic texture, massive structure, with banded structure and flow structure locally, are composed of crystal fragments, small amount of rock debris and matrix. The layered igneous rocks have crystal fragments Of quartz, plagioclase, K-feldspar, small amount of amphibole, muscovite and pyrite and with pleocrystalline matrix which are made up of small grain of quartz, K-feldspar, serieite, muscovite and small amount of biotite, Graphic texture made up of small grain quartz and K- feldspar is popular in the matrix of the Dabaoshan layered igneous rocks. The above characteristics of the Dabaoshan layered igneous rocks suggest that the layered igneous rocks belong to volcanic clastic lava. Based on the mineral association and grain size of minerals, the Dabaoshan layered igneous rocks could be divided into dacite tufflava, rhyolitic tufflava, and breccia lava. Rhyolitic tufflava in the middle of the Dabaoshan mining area and dacite tufflava from the Qiuba in the eastern part of the Dabaoshan mining area bav'e zircon LA-ICP-MS U-Pb age of 436.4 +4. 1Ma, with MSWD =0.94 and 434. 1 _+4.4Ma, with MSWD = 1.9, respectively, suggesting that the lavas in the Dabaoshan area were formed in Caledonian Period. Based on the zircon age of the Dabaoshan lavas and closely association between the lavas and the limestone as well as carbonaceous shale, together with activities of deep fault in the region, it is concluded that the Dabaoshan layered igneous rocks associated closely with stratiform Fe-Cu-Pb-Zn are formed in Caledonian Period in marine environment. The formation of the Caledonian volcanic rocks in the Dabaoshan mining area is suggested to be related to the activities of the Wuchuan-Sihui deep fault.
出处
《岩石学报》
SCIE
EI
CAS
CSCD
北大核心
2014年第4期1145-1154,共10页
Acta Petrologica Sinica
基金
国家"深部探测技术与实验研究"专项课题(SinoProbe-03-01)
国家自然科学基金项目(41172080
41121002
41272099
41342084)
中国科学院国际合作项目(GJHZ1127)联合资助
关键词
加里东期火山岩
锆石年龄
华南粤北
Caledonian volcano rock
Zircon age
Northern Guangdong of South China