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

发布时间：2018-05-20 00:43

本文选题：鄂东南地区 + 殷祖岩体　；参考：《地质学报》2017年02期

【摘要】：殷祖岩体是鄂东南地区六大岩体之一,也是目前该地区唯一不成矿的大岩体。LA-ICP-MS锆石UPb年代学数据显示,殷祖岩体至少有两次岩浆侵位活动。该岩体的主体岩性为石英闪长岩,侵位于148±1 Ma,早期黑云角闪辉长岩侵位于151±1 Ma。这一研究结果表明,鄂东南地区乃至长江中下游地区中生代的岩浆活动在~150 Ma时已经开始。根据野外侵入接触关系及元素地球化学特征,殷祖岩体的岩石类型大致可以分为两组:第一组为闪长-辉长岩类,包括闪长岩、黑云辉长岩和黑云角闪辉长岩,具有低SiO_2,低Ba、Sr含量,高TiO_2、FeOT、MgO及Y、Yb含量;第二组包括石英闪长岩和花岗闪长斑岩,具有高SiO_2,高Ba、Sr含量,低TiO_2、FeOT、MgO及Y、Yb含量。石英闪长岩的(87Sr/86Sr)i和εNd(t)值分别为0.70638~0.70719和-9.56~-7.59,锆石εHf(t)值为-10.21~-1.15,Nd-Hf同位素基本耦合;黑云角闪辉长岩的(87Sr/86Sr)i和εNd(t)值分别为0.70742和-9.79,锆石εHf(t)值为-24.58~-15.22,Nd-Hf同位素出现解耦。综合两期岩浆活动的侵位时间、地球化学以及Sr-NdHf同位素特征,推测它们可能是同一岩浆源区演化的产物,即均主要来源于富集岩石圈地幔。分离结晶作用在主体岩性石英闪长岩的形成过程中起了主导作用。早期小规模的辉长岩类出现Nd-Hf同位素解耦现象可能与石榴子石效应有关。
[Abstract]:The Yanzu rock body is one of the six major bodies in southeast Hubei, and is the only large rock mass in this area. LA-ICP-MS zircon UPb geochronology data show that there are at least two magmatic emplacement activities in the Yanzu rock mass. The main lithology of the body is quartz diorite, which is transgressive at 148 卤1 Ma, and early black cloud amphibolite at 151 卤1 Ma. The results show that the Mesozoic magmatic activity in southeastern Hubei and even in the middle and lower reaches of the Yangtze River began at 150 Ma. According to the intrusive contact relationship in the field and the geochemical characteristics of elements, the rock types of the Yanchu rock body can be divided into two groups: the first group is diorite-gabbro, including diorite, biotite gabbro and black cloud hornblende diorite. The second group includes quartz diorite and granodiorite porphyry with high SiO2, BaOSr, TiO2FeOTOTMgO and YYb contents, and low TiO2FeOTMgO and YYb contents with high SiO2, BaOSr, low TiO2FeOTMgO and YYb contents. For quartz diorite, the values of ~ (87) Sr ~ (86) Sr ~ (+) I and 蔚 Ndndt) are 0.70638 ~ (0.70719) and -9.56 ~ (-7.59), respectively, and the zircon 蔚 -Hft) values are -10.21 ~ (-1.15) Nd-Hf isotopic coupling, and the values of 87 Sr ~ (86) Sr ~ (6) Sr ~ (6) Sr ~ (+) and 蔚 Ndt ~ (t) of the amphiolite are 0.70742 and -9.79, respectively, and the zircon 蔚 Hftt) values are -24.58 ~ (-15.22) Nd-Hf ~ f isotopic decoupling. Based on the emplacement time, geochemistry and Sr-NdHf isotopic characteristics of the magmatic activities in the two periods, it is assumed that they may be the product of the evolution of the same magmatic source, that is, they are mainly derived from the enriched lithospheric mantle. Separation and crystallization play a leading role in the formation of the main lithologic quartz diorite. The Nd-Hf isotopic decoupling in the early small-scale gabbro may be related to the pomegranate effect.
【作者单位】：中国地质调查局武汉地质调查中心;中国地质调查局花岗岩成岩成矿地质研究中心;
【基金】：中国地质调查局地质调查项目(编号1212011120863&12120114005901)资助的成果
【分类号】：P597.3;P587

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