摘要
云南宾川小龙潭矿区斑岩体位于扬子板块西缘程海断裂带东侧,属金沙江‒红河富碱侵入岩带组成部分。本文对矿区内与成矿密切相关的花岗斑岩进行了岩石学、年代学及地球化学研究。结果显示:花岗斑岩由二长花岗斑岩(MGP)和钾长花岗斑岩(KGP)组成,二者岩相学特征相似,空间上无明显分带关系,呈过渡渐变关系,具典型斑状结构。二长花岗斑岩和钾长花岗斑岩均具富碱、低钛和准铝质‒弱过铝质特征,属准铝质‒弱过铝质钾玄岩系列富碱斑岩;二者富集轻稀土元素(LREE)和大离子亲石元素(Rb、Ba、U),亏损重稀土元素(HREE)和高场强元素(Ta、Nb、Ti,Zr,Hf),具有较高Sr含量和Sr/Y值,中等负Eu异常(δEu=0.39~0.78),表现出C型埃达克质岩地球化学特征。二长花岗斑岩和钾长花岗斑岩具相似的地球化学特征,表明它们属同源岩浆演化产物。二长花岗斑岩锆石U-Pb年龄为34.7±0.3 Ma,反映其形成于古近纪始新世,与金沙江‒红河富碱侵入岩活动高峰期(45~30 Ma)吻合。综合研究表明,小龙潭矿区花岗斑岩属具C型埃达克质岩地球化学特征的花岗岩,起源于底侵作用带来的幔源岩浆与石榴角闪岩相加厚下地壳部分熔融的混合岩浆,是印度‒欧亚板块晚碰撞期力学性质由挤压向伸展转化动力学背景下的产物,具备成矿作用发生的物质基础,有较好的成矿潜力。
The granite porphyries in the Xiaolongtan mining area, located to the east of the Chinghai fault belt, are an important part of the Jinshajiang-Red River alkali-rich intrusive rock belt in the western Yangtze Block. This paper reports petrological, chronological and whole-rock geochemical results of the ore-related granite porphyries in the mining area. The results show that the granite porphyries consist of monzonitic granite porphyry(MGP) and K-feldspar granite porphyry(KGP). They are petrographically similar, showing typical porphyritic structures, and exhibit transitional contact. Both MGP and KGP are rich in alkali, low in Ti, metaluminous to weak peraluminpous. These results show they belong to the metaluminous to weak peraluminous and shoshonite series. Both of them are relatively enriched in LREE, LILE(Rb, Ba, and U) and depleted in HREE and HFSE(Ta, Nb, Ti, Zr, and Hf), with relatively high Sr contents and Sr/Y ratios, and mild negative Eu anomalies(δEu=0.39–0.78), showing geochemical affinity of C-type adakitic rocks. The similar geochemical characteristics of MGP and KGP indicate that they are products of homologous magmatic evolution. The LA-ICP-MS zircon U-Pb age is 34.7±0.3 Ma, reflecting that it was formed in the Paleogene Eocene, which coincides with the peak period of the Jinshajiang-Honghe alkali-rich intrusive rock activity(45–30 Ma).Hence, we propose that the granite porphyries in the Xiaolongtan mining area are granites with C-type adakitic geochemical characteristics. They were likely derived from the mixed magma by partial melting of the pomegranate amphibolite lithofacies over-thickened lower crust and underplating mantle magma under transition from compressional to extensional setting after the collision between the India and Eurasia plates. Combined with previous studies, it can be seen that the crust-mantle mixed source characteristics of the granite porphyries may account for the promising ore mineralization potential.
作者
徐恒
周家喜
豆松
姜永果
刘文佳
郑晓军
曾敏
XU Heng;ZHOU Jiaxi;DOU Song;JIANG Yongguo;LIU Wenjia;ZHENG Xiaojun;ZENG Min(Yunnan Nonferrous Metals Geological Bureau,Kunming 650051,Yunnan,China;School of Earth Sciences,Yunnan University,Kunming 650500,Yunnan,China;Survey and Design Institute,Yunnan Province Nonferrous Geological Bureau,Kunming 650106,Yunnan,China;Yunnan Copper Mining and Mineral Resources Exploration and Development Co.,Ltd.,Kunming 650051,Yunnan,China)
出处
《大地构造与成矿学》
EI
CAS
CSCD
北大核心
2021年第5期934-950,共17页
Geotectonica et Metallogenia
基金
云南省技术创新人才培养对象项目(202105AD160003)
第二次青藏高原综合科学考察研究项目(2019QZKK0802)
中国地质调查局项目(1212011120607)
云南省整装勘查项目(201100024)
云南省有色地质局项目(2013100001)联合资助
关键词
花岗斑岩
锆石U-PB年龄
地球化学
岩石成因
小龙潭矿区
宾川
granite porphyry
zircon U-Pb dating
geochemistry
petrogenesis
Xiaolongtan mining area
Binchuan city
作者简介
第一作者:徐恒(1981-),男,博士,高级工程师,主要从事地质科研与矿产勘查工作。Email:306551439@qq.com。
