摘要
首次发现扬子克拉通西缘古元古代晚期海孜斜长花岗斑岩岩体。本文报道了其锆石的LA-ICP-MSU-Pb年龄,为1730±15Ma(MSWD=4.0,n=15)。岩石具有高SiO2(69.77%～73.83%)、高碱(ALK=5.46～6.65)、低钾(K2O/Na2O=0.02～0.14)含量。里特曼指数1.04～1.65,A/CNK值为1.11～1.25,平均值为1.18(>1.1),10000Ga/Al=3.96～7.34(均值为5.18>2.6),较高的含铁指数[FeO/(FeO+MgO)=0.95～0.99],总体显示了低钾钙碱性过铝质(SP)铁质A型花岗岩的特点。岩石富集Nb、Ta、Zr和Hf等高场强元素,强烈亏损K、Sr和Ba等大离子亲石元素,稀土元素总量∑REE=390.70×10-6～674.91×10-6,LREE/HREE=1.74～3.29(均值2.18),轻稀土分异作用明显,相对富集,表现出强烈的负Eu异常。地球化学特征显示,海孜花岗斑岩岩体为形成于板内伸展构造环境,可能与同期基性岩浆活动的底侵作用相关。海孜花岗岩的年龄和地球化学表明,扬子克拉通西缘存在古元古代晚期与全球性Columbia超级大陆裂解同期的双峰式岩浆岩组合。
The late Paleoproterozoic Haizi plagioclase granite porphyry was discovered for the first time in the western margin of the Yangtze Craton.The paper reported that the LA-ICP-MS zircon U-Pb age is 1730± 15Ma （ MSWD=4.0 ） .The granite is characterized by high SiO2 , ALK and low K20 / Na20 （ SiO2 = 69.77%～73.83% , AlK （ K20＋Na20 ） =5.46～6.65and K20 / Na20=0.02～0.14 ）, Rittman indexσ= 1.04～1.65 , A / CNK=1.11～1.25 with an average of 1.18 （ 1.1 ）, 10000 Ga / Al=3.96～7.34 （ the average is 5.182.6 ）, high Fe number （ FeO /（ FeO＋MgO ） =0.95～0.99 ）, suggesting the characters of low-K and calc-alkaline SP A-type granites.The granites are rich in high strength field elements （ Nb , Ta , Zr , Hf ）, and obvious depletion of large ion lithophile elements （ K , Sr , Ba ）, The gross amount of REE is 390.70×10 -6 ～674.91×10 -6 , LREE / HREE=1.74～3.29 （ the average is 2.18 ）, the LREE is rich and have distinct fractionation ; the REE shows significant negative Eu anomaly.The petrochemical and trace elements shows that the granite was formed in an intraplate extension environment , and its formation can be related to the magma underplating of the same period basipetalous igneous activities.Thedating and geochemistry of Haizi granite porphyry represents that there exist the pattern of bimodel magmatic rocks in late Paleoproterozoic which is the same period as the global Columbia supercontinent Cracking event.
出处
《地质学报》
EI
CAS
CSCD
北大核心
2013年第7期931-942,共12页
Acta Geologica Sinica
基金
国土资源大调查项目(编号1212011120640
1212010911064
1212010813066)
国家重点基础研究发展规划"973"项目(编号2009CB421006)
国家自然科学基金项目(编号40830425
40173025)联合资助成果
作者简介
王子正，男，1981年生。工程师，从事区域地质矿产调查及前寒武地层研究工作。Email：15523327@qq．com。
