摘要
川-滇-黔地区是地质学者一直以来重点关注的地区之一,也是我国重要的有色金属基地之一,是滇东北成矿带的重要组成部分。本次在云南巧家县谓姑地区坪子地新发现一处石英斑岩体,该岩体岩性单一,并伴有铜矿化。本文在野外地质调查基础上,对该石英斑岩体进行了锆石LA-ICP-MS U-Pb定年、Lu-Hf同位素分析和岩石地球化学研究,以限定石英斑岩体侵位时代,反演岩体岩浆源区特征,总结石英斑岩体成因,并探讨其构造背景。结果显示,谓姑地区石英斑岩属高硅(SiO 2=70.41%~77.65%)、过铝质(A/CNK=1.29~5.37)岩石。岩石具较高的稀土总量(∑REE为1017.12×10-6~1325.20×10-6),(La/Yb)N为22.87~42.78,(Lm/Sm)N为4.84~5.61,轻稀土富集明显,铕负异常明显(δEu=0.21~0.25),相对富集K、Rb、Th、U、Zr、Nb、Sm等大离子亲石元素和高场强元素,形成于伸展拉张构造背景。石英斑岩体的锆石LA-ICP-MS U-Pb年龄为795.4±5.8 Ma,表明其形成于新元古代青白口纪;锆石的εHf(t)=-7.43~-5.76,平均-6.61,二阶段模式年龄值在2.063~2.146 Ga,显示源区来源于古元古代古老地壳部分熔融。结合区域地质资料,认为该岩体是Rondnia超大陆裂解阶段的产物。
The Sichuan-Yunnan-Guizhou area is one of the key areas among geologists,and is also one of the important non-ferrous metal bases in China.It is an important part of the Northeast Yunnan metallogenic zone.A new quartz porphyry was discovered in the Weigu area of Yunnan Province,which has single lithology and is accompanied by copper mineralization.Based on the field geological survey,this work conducted zircon LA-ICP-MS U-Pb dating,Lu-Hf isotope analysis and geochemical analysis to determine the emplacement age,characteristics of magatic source area and genesis of this quartz porphyry,and thus to discuss the tectonic setting.It is indicated that the quartz porphyry belongs to high silicon(Si02=70.41%~77.65%)and superaluminum(A/CNK=1.29~5.37)rock.The rock has a high total rare earth(∑REE=1017.12×10-6~1325.20×10^(-6)),(La/Yb)N is 22.87~42.78,(Lm/Sm)N is 4.84~5.61,light rare earth enrichment,obvious negative europum(δEu=0.21~0.25),relatively rich K,Rb,Th,U,Zr,Nb,Sm and high-field strong elements.The zircon LA-ICP-MS U-Pb age of the quartz porphyry is 795.4±5.8 Ma,indicating it was formed in the Neo-Proterozoic era.For the zircons,theεHf(t)values range from-7.43 to-5.76,-6.61 on average,and have a secondary mode age peak between 20.63 Ga and 21.46 Ga,showing that the magma derived from ancient crustal melting.Combined with the rock body formation age and geochemical characteristics,this rock body is the product of Rondnia supercontinental pyrolysis stage.
作者
金建才
曾礼传
赵勇
黄跃
胡清华
张尔新
孙涛
JIN Jiancai;ZENG Lizhuan;ZHAO Yong;HUANG Yue;HU Qinghua;ZHANG Erxing;SUN Tao(Institute of Yunnan Geological Survey,Kunmning,Yunnan 650216;MNR Key Laboratory of Sanjiang Metallogeny and Resources Exploration&Utilization,Kunming,Yunnan 650051;School of Earth Sciences,Yunnan University,Kunming,Yunnan 650500;Key Laboratory of Critical Minerals Metallogeny in Universities of Yunnan Province,Kunming,Yunnan 650500)
出处
《地质与勘探》
CAS
CSCD
北大核心
2021年第4期920-934,共15页
Geology and Exploration
基金
中国地质调查局整装勘查区矿地质调查与找矿预测项目(编号:D20190159-2020-12)资助。
