摘要
本文围绕泰国沙蒙矿床锡成矿相关的中粗粒黑云母花岗岩及远离矿体的细粒角闪石黑云母花岗岩开展了全岩地球化学、锆石U-Pb年代学及原位Hf同位素研究。锆石U-Pb年龄显示两类花岗岩分别形成于210.9±1.1 Ma和206.5±1.0 Ma。二者均具有富碱(全碱含量为5.81%~8.22%)、弱过铝—强过铝(A/CNK=1.01~1.14)、相对富集Rb、Th、Pb等元素、低的TFeO/MgO(0.75~3.54)和10000Ga/Al(2.21~2.66)比值等特征。中粗粒黑云母花岗岩具有原生白云母,高的K_(2)O/Na_(2)O(1.56~2.50)和Rb/Sr(2.26~2.60)比值,且其锆石具有较高的P含量,属于典型的S型花岗岩。而细粒角闪石黑云母花岗岩普遍发育角闪石,具有低的K_(2)O/Na_(2)O(0.45~1.11)和Rb/Sr(0.54~1.18)比值,且其锆石具有较低的P含量,应属于典型的I型花岗岩。两种花岗岩具有截然不同的Hf同位素组成,其中中粗粒黑云母花岗岩具有明显低的ε_(Hf)(t)值(-20.0~-8.9),对应的二阶段模式年龄tDM2值为2.5~1.8 Ga(平均值为2.0 Ga),而细粒角闪石黑云母花岗岩具有偏高的ε_(Hf)(t)值(-4.6~5.5),二阶段模式年龄tDM2值为1.5~0.9 Ga(平均值为1.1 Ga)。它们均形成于古特提斯洋闭合的碰撞后挤压向伸展转换构造背景下,具有相近的岩浆温度和中等演化程度(DI=79.6~88.0、SiO_(2)=67.57%~72.97%及锆石Zr/Hf=29.8~64.9)。中粗粒黑云母花岗岩可能起源于古元古代的变质杂砂岩的部分熔融且具有较低的岩浆氧逸度(ΔFMQ平均为-4.93),而细粒角闪石黑云母花岗岩源区主要为新元古代新生地壳,并具有部分古老地壳变沉积岩源区物质的加入,具较前者相对偏高的岩浆氧逸度(ΔFMQ平均为-2.76)。源区性质和岩浆氧逸度条件可能是制约沙蒙矿区花岗岩锡成矿最重要的控制因素。
Our study involved zircon U-Pb dating and in-situ Hf isotope,and whole-rock geochemical analyses for the medium-coarse-grained biotite granites associated with tin mineralization and the fine-grained hornblende biotite granites far away from the ore bodies from the Samoeng deposit,in Thailand.Zircon U-Pb ages show that the two granites were formed at 210.9±1.1 Ma and 206.5±1.0 Ma,respectively.Both granites are characteristic of rich in alkali with total alkali content of 5.81%~8.22%,relatively rich in Rb,Th,and Pb,weakly to strongly peraluminous(A/CNK=1.01~1.14)and low in TFeO/MgO(0.75~3.54)and 10000Al/Ga(2.21~2.66)values.The medium-coarse-grained biotite granites have primary muscovite and relatively high K_(2)O/Na_(2)O(1.56~2.50)and Rb/Sr(2.26~2.60)ratios,with high P content in their zircons,belonging to typical S-type granites.While the fine-grained amphibole biotite granites are wide development of amphibole,and have relatively low K_(2)O/Na_(2)O(0.45~1.11)and Rb/Sr(0.54~1.18)ratios,with low content of P in their zircons,which can be classified as typical I-type granites.The two granites have quite different Hf isotopic compositions.The medium-coarse-grained biotite granites have relatively lowε_(Hf)(t)values(-20.0 to-8.9),with the corresponding two-stage Hf model age of 1.8 to 2.5 Ga(average values of 2.0 Ga).In contrast,the fine hornblende biotites granite have relatively highε_(Hf)(t)values(-4.6 to 5.5),with the two-stage Hf model age of 0.9 to 1.5 Ga(average values of 1.1 Ga).Both two granites were formed in a post-collisional tectonic transition(from compression to extension)related to the closed Paleo-Tethys Ocean,and have similar magmatic temperatures and moderate fractionated(DI=79.6~88.0,SiO_(2)=67.57%~72.97%,and zircon Zr/Hf values=29.8~64.9).The mid-coarse-grained biotite granites were suggested to be derived from Paleoproterozoic metagreywackes with low magmatic oxygen fugacities(averageΔFMQ-4.93),whereas the fine-grained amphibolite biotite granites mainly originated from juvenile meta-igneous rocks with the input of ancient meta-sedimentary component,and have relatively high magmatic oxygen fugacities(averageΔFMQ-2.76).We think the nature of the source region and magmatic oxygen fugacity condition could be the most important controlling factors for tin mineralization in the Samoeng deposit.
作者
张博
刘亮
阳杰华
钟宏
符亚洲
毛伟
张兴春
ZHANG Bo;LIU Liang;YANG Jiehua;ZHONG Hong;FU Yazhou;MAO Wei;ZHANG Xingchun(State Key Laboratory of Ore Deposit Geochemistry,Institute of Geochemistry,Chinese Academy of Sciences,Guiyang,Guizhou550081,China;University of Chinese Academy of Sciences,Beijing 100049,China)
出处
《地质学报》
EI
CAS
CSCD
北大核心
2023年第4期1228-1244,共17页
Acta Geologica Sinica
基金
中国科学院国际合作局国际伙伴计划项目(编号E1ZK251)
中国科学院“西部之光”人才培养计划项目
中国科学院青年创新促进会项目(编号2020393)
贵州省高层次留学人才创新创业择优项目(编号(2020)03号)
国家自然科学基金项目(编号42272096,42073046)
贵州省科学技术基金资助项目(编号黔科合LH字[2017]7055号)
贵州省教育厅青年科技人才成长项目(编号黔教合KY字[2017]280)联合资助的成果。
关键词
花岗岩成因
物理化学条件
锡成矿作用
东南亚
泰国沙蒙矿床
petrogenesis of granite
physic-chemical conditions
tin mineralization
Southeast Asia
Samoeng deposit in Thailand
