摘要
月田岩体位于扬子地块与华夏地块拼合带的西南段,对该岩体片麻状花岗闪长岩样品进行了LAICP-MS锆石U-Pb测年,获得206Pb/238U年龄加权平均值为433.6±4.8 Ma(MSWD=2.9),说明该岩体形成于加里东期。该花岗闪长岩体SiO2含量在61.31%~69.42%,K2O+Na2O为3.48%~5.91%,且K2O/Na2O为0.88~5.57,具有钙碱性-高钾钙碱性、强过铝质特征的S型花岗岩,兼具有I型花岗岩特征;明显亏损Ba、Sr、Ta、Nb、P、Ti等元素,相对富集Rb、Th、U、Ce、Zr、Hf、Y、La、Nd等元素,总体属于低Ba-Sr花岗岩范畴;稀土总量((199.52~252.15)×10^-6)较高,LREE/HREE为5.38~11.29,轻稀土富集,轻稀土分馏程度中等,δEu为0.40~0.64,δCe为0.90~1.04。锆石的εHf(t)值在-10.01^-3.22,二阶段模式年龄T2DM在1.62~2.06 Ga,暗示物源来自元古代地壳物质。结合前人研究资料认为,月田花岗岩是由元古代基底物质发生深熔作用形成,是华南地区加里东期陆内造山作用的响应。
Yuetian pluton was found in the southwest orogenic belt of the Yangtze block and the Cathaysia block,and the pluton has important geological significance to analyze the regional tectonic evolution of South China.A gneissic granodiorite sample from Yuetian pluton was selected for LA-ICP-MS zircon U-Pb dating,the weighted average age of U-Pb is 433.6±4.8Ma(MSWD=2.9),which indicates Yuetian pluton,was formed in Caledonian orogeny.The content of SiO2 of Yuetian granodiorite is 61.31%-69.42%,K2O+Na2O is 3.48%-5.91%,and K2O/Na2O is 0.88-5.57.The data show that Yuetian pluton belongs to S-type granite with calc-alkaline and high-K calc-alkaline series,and the characteristics of I-type granite.In trace elements,the Yuetian pluton is enriched in Rb,Th,U,Ce,Zr,Hf,Y,La and Nd,depleted in Ba,Sr,Ta,Nb,P and Ti,and a low Ba-Sr granite on the whole.The total REE content((199.52-252.15)×10^-6)is relatively high,LREE/HREE is 5.38-11.29,showing LREE enrichment.LREE fractionation degree is medium.TheδEu is 0.40-0.64,and theδCe is 0.90-1.04.The Hf isotopic compositions of zircons show that the rocks haveεHf(t)values of-10.01 to-3.22,and T2DM(Hf)model ages are mainly concentrated from 1.62 to 2.06 Ga,implying that the magma was derived from the crust formed in the Mesoproterozoic.In combination with previous studies,Yuetian pluton probably was resulted from partial melting of the Proterozoic materials due to the Caledonian orogeny in South China.
作者
黄锡强
王国灿
农军年
郭尚宇
孙明行
周秋娥
HUANG Xi-qiang;WANG Guo-can;NONG Jun-nian;GUO Shang-yu;SUN Ming-hang;ZHOU Qiu-e(Faculty of Earth Sciences,China University of Geosciences,Wuhan 430074,China;Guangxi Institute of Geological Survey,Nanning 530023,China)
出处
《桂林理工大学学报》
CAS
北大核心
2020年第2期251-262,共12页
Journal of Guilin University of Technology
基金
中国地质调查局项目(DD20160035,DD20190047)。
