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引用本文:李宏卫,屈尚侠,林小明,肖光铭,黄建桦,廖冰冰. 广东新丰新坪花岗闪长岩(104 Ma)地球化学、锆石U-Pb年龄和Hf同位素研究[J]. 中国地质, 2021, 48(5): 1524-1539.
LI Hongwei,QU Shangxia,LIN Xiaoming,XIAO Guangming,HUANG Jianhua,LIAO Bingbing. Petrogeochemistry, zircon U-Pb age and Hf isotope of Xinping granodiorite(104Ma) in Xinfeng area, Guangdong Province[J]. Geology in China, 2021, 48(5): 1524-1539(in Chinese with English abstract).
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广东新丰新坪花岗闪长岩(104 Ma)地球化学、锆石U-Pb年龄和Hf同位素研究
李宏卫1, 屈尚侠2, 林小明1, 肖光铭1, 黄建桦1, 廖冰冰3
1.广东省地质调查院, 广东 广州 510080;2.广州市地质调查院, 广东 广州 510440;3.广东省地质实验测试中心, 广东 广州 510080
摘要:
新坪铜钼矿化花岗闪长岩体位于佛冈复式岩体中北部,LA-ICP-MS锆石U-Pb年龄为(104.6±1.8)Ma(MSWD=1.2),侵位时间为早白垩世晚期。岩石呈中酸性(SiO2=63.43%~65.27%)、准铝质(ACNK=0.76~0.92)、中等碱含量(ALK=6.09%~7.63%)和富钾钙碱性特征,富集轻稀土,LREE/HREE=8.26~13.20,(La/Yb)N=8.17~16.64,轻微的铕亏损(δEu=0.73~0.87),富集Rb、U、Th和La,亏损Nb、Ta、Ti和P、Ba、Sr。锆石εHft)值为-3.0~0.2,Hf二阶段模式年龄tDM2=1.16~1.36Ga,镁指数(Mg#)=42.64~46.95,表明源岩主要为中元古代地壳物质,并有亏损地幔组分的参与。Nb/U和Nb/La比值分别为0.20~0.38和1.7~2.2,显示源区受古太平洋板块俯冲流体交代作用的影响。研究表明,新坪岩体成岩过程主要受部分熔融作用控制,形成于燕山晚期古太平洋板片俯冲消减作用下的伸展拉张环境,与玄武质岩浆底垫诱发中元古代结晶基底的部分熔融有关。早白垩世晚期为中国东南部晚中生代重要的Cu-Au-Mo成矿期,位于南岭中东段的新坪花岗闪长岩体与邻区闽西南紫金山铜多金属岩(矿)体形成时代一致、岩石地球化学特征较为相似,且野外能观察到明显的铜钼矿化,因此具有较好的铜钼找矿前景。
关键词:  花岗闪长岩  铜钼矿化  U-Pb年龄  地球化学  Hf同位素  矿产资源调查工程  新丰  广东
DOI:10.12029/gc20210516
分类号:P588.12
基金项目:中国地质调查局项目“广东1∶5万周陂公社、隆街公社、新丰县、马头圩区域地质矿产调查”(12120113063100)、广东省国土资源保护与治理专项(2017201)和广州南沙区地质环境调查项目(22001130106)联合资助。
Petrogeochemistry, zircon U-Pb age and Hf isotope of Xinping granodiorite(104Ma) in Xinfeng area, Guangdong Province
LI Hongwei1, QU Shangxia2, LIN Xiaoming1, XIAO Guangming1, HUANG Jianhua1, LIAO Bingbing3
1.Guangdong Geological Survey, Guangzhou 510080, Guangdong, China;2.Geological Survey Institute of Guanghzou, Guangzhou 510440, Guangdong, China;3.Guangdong Geological Experiment and Testing Center, Guangzhou 510080, Guangdong, China
Abstract:
Located in the north-central part of the Fogang complex pluton, the Xinping Cu-Mo mineralization granodiorite pluton formed in late Early Cretaceous, and its LA-ICP-MS zircon U-Pb age is (104.6±1.8)Ma(MSWD=1.2). The granodiorite is characterized by medium acidity (SiO2=63.43%-65.27%), quasi-aluminium(ACNK=0.76-0.92), medium alkali(ALK=6.09%-7.63%) and high-K Calc-alkaline. It shows enrichment in light rare earth elements Rb, U, Th and La, and the ratio of LREE/HREE is 8.26-13.20 while (La/Yb)N is 8.17-16.64. Otherwise, it shows depletion in Nb, Ta, Ti, P, Ba and Sr, with minor loss of Eu (δEu=0.73-0.87). The εHf(t) range from -3.0 to +0.2, and the two-stage model age of Hf(tDM2) is 1.16-1.36Ga, and the index of Mg(Mg#) is 42.64-46.95. All of these indicate that the source rocks are mainly crustal materials formed in Mesoproterozoic, with the participation of deficient mantle components. The ratio of Nb/U and Nb/La is respectively 0.20-0.38 and 1.7-2.2, which indicates that the source area is affected by the fluid metasomatism in subduction of Paleo-Pacific Plate. This study shows that the Xinping granodiorite is dominated by partial melting in process of diageneesis. The Xinping pluton formed in the extensional setting under the subduction of the Paleo-Pacific plate in late Yanshanian period, which is related to the partial melting of the Mesoproterozoic crystalline basement induced by the basaltic magma. In late Early Cretaceous, it was an important Cu-Au-Mo mineralization period in late Mesozoic in southeastern China, while the Xinping granodiorite, located in the middle east of Nanling mountains, coincide with the diagenetic age of the Zijinshan copper polymetallic rocks or ores in the southwestern Fujian Province, with similar petrochemical characteristics. Also, the obvious copper-molybdenum mineralization can be observed in the field, so it will have a good prospecting prospect for copper-molybdenum deposits.
Key words:  granodiorite  Cu-Mo mineralization  U-Pb age  geochemistry  Hf isotope  mineral survey engineering  Xinfeng  Guangdong