云开地块印支期变质-深熔作用：混合岩、片麻岩锆石U-Pb年代学和Hf同位素证据
Indosinian Metamorphism and Anatexis in Yunkai Massif: Evidences from Zircon Geochronology and Hf Isotopes of Migmatites and Gneisses

云开地块中生代构造演化是华南地区的研究热点之一.通过对云开地块变质基底中的混合岩、片麻岩(5个样品)和花岗岩(1个样品)开展锆石LA-ICP-MS U-Pb定年，获得440.3±3.3 Ma、230.2±2.9 Ma、230.7±1.3 Ma、459.5±2.7 Ma、431.5± 4.3 Ma、229.2±5.4 Ma、229.7±2.7 Ma 7组变质(深熔)或岩浆年龄和2组(样品1432-1和ID7-3)碎屑锆石年龄，碎屑锆石年龄范围均为太古代-新元古代，且具有～1.0 Ga年龄主峰，与天堂山岩群和云开群碎屑锆石年龄谱相似.区域资料表明云开地块天堂山岩群和云开群具有相似的物质组成，均形成于早古生代-新元古代，存在变质程度和物质面貌的差异；在加里东期构造-热事件的基础上，广泛叠加了印支期区域变质(深熔)-构造-流体作用影响.4个样品中(1431-1、1432-1、D116-3和ID7-3)锆石原位Lu-Hf同位素组成显示，加里东期变质和深熔锆石Lu/Hf同位素组成基本一致，应继承了原岩的同位素组成特征.印支期变质和深熔锆石Lu/Hf同位素组成不同，可能主要由变质作用和深熔作用的差异所致.以古-中元古代为主的地壳物质参与了加里东期和印支期变质-深熔作用，在加里东期和印支期深熔作用过程中，均有少量幔源物质的加入，印支期幔源物质的贡献相对显著.
The Mesozoic tectonic evolution in Yunkai massif have always been one of hot topics in South China. Zircons from five metamorphic rocks including migmatite and gneiss and one granite from the metamorphic basement in Yunkai massif were measured by the LA-ICP-MS U-Pb dating method, yielding 7 metamorphic (anatectic) or granitic ages (440.3±3.3 Ma、 230.2±2.9 Ma 、230.7±1.3 Ma、459.5±2.7 Ma、431.5±4.3 Ma、229.2±5.4 Ma、229.7±2.7 Ma) and 2 groups of detrital ages. Both the detrital zircons showed Archaean-Neoproterozoic age range with ～1.0Ga age peaks, which were similar with those of the Tiantangshan Group complex and the Yunkai Group. Together with the regional data, it was concluded that the Tiantangshan Group complex and the Yunkai Group, which were analogous in provenance and formed in Early Palaeozoic-Neoproterozoic, were broadly overprinted by the Indosinian metamorphism (anatexis)-deformation-fluid activity after the Caledonian tectonicthermal events，resulting in differences in metamorphic grade and appearance. In situ zircon Lu-Hf isotopic analysis from four samples showed that both the isotopic compositions of Caledonian metamorphic and anatectic zircons were similar with each other, which was ascribe to inheriting the compositions of provenance rocks, whereas the different isotopic compositions of Indosinian metamorphic and anatectic zircons could be caused by individual mechanism of metamorphic and anatectic processe. It was inferred that the dominant Paleo-Mesoproterozoic crustal material played important role in the metamorphism and anatexis processe in Caledonian and Indosinian, and a few mantle-derived material was added in the anatectic processe in Caledonian and Indosinian with relatively remarkable contribution of mantle-derived material in Indosinian