桂东南糯垌—安平地区(变质)中—基性火成岩的年代学、地球化学特征及其构造意义

文章对桂东南糯垌—安平地区出露的阳起石化斜长角闪岩(变质基性岩)和中—基性火山角砾岩进行了锆石U-Pb年代学和全岩地球化学分析研究,结果表明,糯垌地区岩体的形成时代晚于123 Ma,安平地区火山角砾岩记录了两期重要的岩浆活动,一组为燕山期(或之后),年龄上限为～138 Ma,一组为早古生代加里东期(452～450 Ma...

Geochronology,Geochemistry and Tectonic Significance of Metamorphic Intermediate-Basic Igneous Rocks in Nuodong-Anping Area,Southeastern Guangxi

Zircon U-Pb dating and geochemical data are reported for actinolitization amphibolites (metamorphic basic rocks) and intermediate-basic volcanic breccias of Nuodong-Anping plutons, southeastern Guangxi. The data show that the formation age of the Nuodong pluton is later than 123 Ma, and the Anping pluton record two important magmatic activities. One was in Yanshanian period (or later) with the youngest age of ~138 Ma, and the other was in Early Paleozoic (452-450 Ma). A large number of captured zircons ranging from Middle Archean-Paleoproterozoic (3076-1806 Ma), Mesoproterozoic-Neoproterozoic to Early Paleozoic in both plutons indicate the existence of the Middle Archean-Paleoproterozoic basement materials and the Mesoproterozoic, Neoproterozoic and Early Paleozoic magmatism. Geochemical data exhibit that the Nuodong pluton is characterized by a flat or slightly loss rare earth elements (REEs) distribution model, with relatively enriched in large-ion lithophile elements (LILEs) (Th, U and Pb) and depleted in high-field-strength elements (HFSEs) (Nb, Ta, Zr, Hf and Ti). The Anping pluton is also enriched in LILEs (Rb, Ba, Th, U and Pb) and depleted in HFSEs (Nb, Ta, P and Ti), but they show enrichment in light REEs and depletion in heavy REEs contents. The geochemical characteristics are similar to the Caledonian (metamorphic) basic rocks in the study area, indicating that the geochemical characteristics of rocks have limitations and multiple solutions in determining the tectonic setting.