江西冷水坑矿床含矿花岗斑岩的Sr-Nd及锆石Hf-O同位素研究  

Sr-Nd and zircon Hf-O isotopic constraints on the petrogenesis of the orebearing granitic porphyry at Lengshuikeng, Jiangxi Province

作　　者：龚雪婧 曾建辉 曹殿华[1,2] GONG Xuejing;ZENG Jianhui;CAO Dianhua(Chinese Academy of Geological Sciences, Beijing 100037, China;SinoProbe Center, Chinese Academy of Geological Sciencesand China Geological Survey, Beijing 100037, China;No. 912 Geological Party of Jiangxi Bureau of Geology and Mineral Exploration and Development, Yingtan 335001, Jiangxi, China)

机构地区：[1]中国地质科学院,北京100037 [2]中国地质调查局-中国地质科学院地球深部探测中心,北京100037 [3]江西省地质矿产勘查开发局九一二大队,江西鹰潭335000

出　　处：《中国地质》2019年第4期818-831,共14页Geology in China

基　　金：中国地质调查局项目（DD20160082,DD20190012）;国家自然科学基金（41802097）;国家重点研发计划“深地资源勘查开采”重点专项（2016YFC0600201）联合资助~~

摘　　要：江西冷水坑铅锌矿床是武夷成矿带北段的典型矿床,矿区内含矿花岗斑岩锆石U-Pb年龄为(162.0±2.0)Ma,岩浆分异程度较高,具有高SiO2(69.46%~75.52%)、高K2O(K2O/Na2O>3.22)、强过铝质(ASI=1.20~1.96)的特征。岩体发育较明显的Eu负异常,富集强不相容元素Rb、Th、U,而亏损高场强元素Ba、Sr、Nb、Ta、P、Ti。全岩同位素测试结果显示,冷水坑含矿花岗斑岩具有极高的87Sr/86Sr初始比值(0.74005~0.76518)与低的εNd值(-11.48^-10.78),锆石Hf-O同位素测定值变化范围较小,176Hf/177Hf介于0.282317~0.282460,具有负的εHf(t)值(-12.39^-7.62)和相对较高的δ18O值(7.23‰~8.81‰),指示岩浆主要来自于成熟地壳,可能起源于北武夷地区变质基底,源岩为基底变质岩,这可能与古太平洋板块俯冲形成的挤压背景下的地壳熔融有关。The Lengshuikeng lead-zinc deposit in Jiangxi Province is a typical deposit in the northern section of the Wuyi metallogenic belt. The zircon SHRIMP U-Pb age of the ore-bearing granite porphyry in the mining area is(162.0±2.0) Ma. The granite porphyries are highly evolved, with high SiO2(69.46%~75.52%), high K2 O(K2 O/Na2 O>3.22) and strong peraluminous(ASI=1.20~1.96). The negative Eu anomalies of the rock mass are relatively strong, and enriched in LILE such as Rb, Th, and U, while the HFSE such as Ba, Sr, Nb, Ta, P, and Ti are depleted. In this study, the authors also report Sr-Nd and zircon Hf-O isotopic compositions of the granitic porphyries at Lengshuikeng. The results show that the granitic porphyries have relatively high initial87 Sr/86 Sr ratios(0.74005~0.76518) and negative εNd values(-11.48^-10.78) as well as the zircon Hf-O isotope measurement value. The variation range of176 Hf/177 Hf values(0.282317~0.282460) is small, with negative εHf(t) values(-12.39^-7.62) and relatively high δ18 O values(7.23‰~8.81‰), indicating that the magma mainly came from the mature crust, which may have originated from metamorphic basement of North Wuyi area, and the source rocks were probably the metamorphic basement. The magmatic activity was probably related to the crust melting under the compressive background formed by northwestward subduction of the Paleo-Pacific Plate.

关 键 词：Sr-Nd-Hf-O同位素 花岗斑岩 冷水坑 武夷成矿带 华南 

分 类 号：P588.13[天文地球—岩石学] P597[天文地球—地质学]