知识与财富的链接
云南省武定地区广泛出露元古宙辉绿岩体,本文报道了武定地区海孜辉绿岩的地球化学特征及锆石的LA-ICP-MS U-Pb年龄,结果为1767±15Ma(MSWD=0.19,n=17),表明本区广泛出露的辉绿岩群侵位时代为古元古代晚期。辉绿岩岩石化学表现为低SiO2、MgO以及高TiO2(3.24%~4.02%)、碱(K2O+Na2O)和P2O5含量(0.32%~0.45%),具有偏碱性的拉斑质玄武岩的岩石化学特征。辉绿岩的大离子半径元素如K、Rb、Ba等富集,高场强元素如Ta、Nb和Zr、Hf没有明显的亏损,其地球化学参数也多与夏威夷碱性洋岛玄武岩相近。辉绿岩的微量、稀土元素的配分模式与典型的OIB和峨眉山高Ti玄武岩具有高度一致性。海孜辉绿岩原始岩浆形成于相对较富集的过渡型地幔的部分熔融,其源区为尖晶石橄榄岩相,演化过程中,有少量下地壳物质的加入。海孜辉绿岩与扬子地台西南缘广泛出露古元古代晚期的岩浆岩一致,形成于全球性Columbia超级大陆裂解的大地构造背景。海孜辉绿岩OIB的地球化学属性,为古元古代晚期全球性Columbia超级大陆裂解的地幔柱活动提供了最重要的地球化学证据。
There exist a number of diabase rock bodies in Wuding area, Yunnan Province, and the geochemistry and La-ICP-MS U-Pb age for zircons in Haizi diabase are reported in this paper. The U-Pb age of 1767±15 Ma(MSWD=0.19,n=17) reflected that the widely spread diabases in Wuding area intruded in the late Paleoproterozoic. The petrochemistry of Haizi diabase characterized by low SiO2, MgO and high TiO2(3.24%～4.02%), alkaline(K2O+Na2O) and P2O5(0.32%～0.45%) content, which has the petrochemical characteristics of the tholeiitic basalt. The large ion lithophile elements(LILE) are enriched and the high field strength elements(HFSE) express without obviously anomaly for Haizi diabase, and the other geochemical parameters are also similar to the characteristics of Hawaii alkaline island basalt. The MORB normalized trace elements and chondrite normalized REE patterns of Haizi diabase are highly in accordance with the tipical OIB and high-Ti basalt in Emeishan. The resource area of primitive magma for Haizi diabase which derived from the patial melting of relatively enriched transitional mantle is spinel-bearing peridotite. A little lower crustal material was contaminated during the primitive magma evolution. The Haizi diabse and the other paleoproterozoic magmatic rocks which widely spread in the southwest of Yangtze block, formed in the tectonic background of the global Columbia supercontinent breakup. The typical OIB characteristics for Haizi diabase provides the most important geochemical evidence for mantle plume activity which result in the breakup of Columbia supercontinent.
