地质学报2017，Vol.91Issue(2)：362-383,22.
鄂东南地区殷祖岩体的成因及其地质意义:年代学、地球化学和Sr-Nd-Hf同位素证据
Petrogenesis and Implications of the Yinzu Pluton in Southeast Hubei Province: Evidence from Geochronology, Geochemistry, and Sr-Nd-Hf Isotopes
摘要
Abstract
The Yinzu pluton,one of the six large intrusions in southeastern Hubei Province,is the only barren large intrusion in the region.LA-ICPMS zircon U-Pb dating results show that the Yinzu pluton experienced at least two episodes of magmatism.The pluton is composed mainly of quartz diorites and was emplaced in 148±1 Ma,with the early biotite hornblende gabbro emplaced at 151±1 Ma.The study indicates that the Mesozoic magmatic activities in southeastern Hubei Province and even the Middle and Lower Yangtze River began in ca.150Ma.Based on their contact relation in the field and element chemical characteristics,the rock types of the Yinzu pluton can be divided into two groups.The first is dioritegabbro,including diorite,biotite gabbro and biotite hornblende gabbro,which have low SiO2,Ba,Sr and high TiO2,FeOT,MgO,Y and Yb contents.The second includes quartz diorite and granodiorite porphyry,which have high SiO2,Ba,Sr and low TiO2,FeOT,MgO,Y and Yb contents.(87Sr/86Sr)i and εNa(t) values of quartz diorite are 0.70638～0.70719 and-9.56～-7.59,separately,which are coupled with zircon εHf (t) values ranging from-10.21 to-1.15.(87 Sr/86 Sr) i and εNd (t) and of biotite hornblende gabbro are 0.70742 and-9.79,separately,and zircon εHf (t) values vary from-24.58 to-15.22,showing that Nd and Hf isotopic compositions are decoupled.Combined with emplacement time and geochemical and Sr-Nd-Hf isotopic characteristics of two magmatic activities,it can be inferred that the pluton should be evolvement products of the same magmatic source area,i.e.from enriched lithospheric mantle.Fractional crystallization played a dominant role in the formation of quartz diorite.Nd-Hf isotope decoupling of the early small scale gabbros is probably related to the effect of garnet.关键词
鄂东南地区/殷祖岩体/锆石U-Pb年龄/黑云角闪辉长岩/Nd-Hf同位素解耦Key words
southeastern Hubei Province/Yinzu pluton/zircon U-Pb age/biotite hornblende gabbro/Nd-Hf isotope decoupling引用本文复制引用
丁丽雪,黄圭成,夏金龙..鄂东南地区殷祖岩体的成因及其地质意义:年代学、地球化学和Sr-Nd-Hf同位素证据[J].地质学报,2017,91(2):362-383,22.基金项目
本文为中国地质调查局地质调查项目(编号1212011120863&12120114005901)资助的成果. （编号1212011120863&12120114005901）
