The discovery of eclogite-high-pressure granulite association from Hainan Island, South China
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摘要:
在海南木栏头地区首次发现了一套榴辉岩-高压麻粒岩组合。该岩石产出于沿海潮间带中，主要由石榴子石、绿辉石、角闪石、石英和金红石组成，含或不含黝帘石和（或）斜长石。由传统的地质温压计计算获得岩石峰期变质作用的温压条件约为800~850℃、>1.5GPa，锆石U-Pb定年得到的变质时代为340~300Ma。榴辉岩-高压麻粒岩组合的发现对于深入理解海南岛构造属性、古特提斯洋东域构造演化过程等均具有重要意义。
Abstract:An eclogite-high-pressure (HP) granulite association were firstly discovered in the Mulantou area, northeastern Hainan Island, South China. The HP rocks occur in the coastal intertidal zone, and consist mainly of garnet, omphacite, hornblende, quartz and rutile, with or without zoisite or plagioclase. Peak p-t conditions of the rocks obtained by conventional geothermobarometers are about 800~850° C and >1.5GPa. U-Pb zircon dating yields metamorphic ages of about 340~300Ma. The occurrence of HP granulite-eclogite association is of great significance for understanding the tectonic affinity of Hainan Island and the tectonic evolution of the eastern Paleo-Tethys.
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Keywords:
- eclogite /
- high-pressure granulite /
- Hainan Island
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致谢: 在岩石样品采集过程中得到中国地质科学院地质力学研究所有关团队成员的大力协助，审稿专家提出了细致、中肯的建议，在此表示衷心的感谢。
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图 1 亚洲东部大地构造纲要图（A）和海南岛区域地质简图（B）(据参考文献[4]修改)
Figure 1. Schematic map illustrating the major tectonic units of eastern Asia(A) and simplified geological map of Hainan Island, South China(B)
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图 2 榴辉岩-高压麻粒岩组合显微照片
A—榴辉岩矿物组合；B—高压麻粒岩矿物组合；C—石榴子石边缘转变为角闪石+斜长石后成合晶；D—绿辉石边缘转变为透辉石+斜长石后成合晶。Amp—角闪石；Di—透辉石；Grt—石榴子石；Ilm—钛铁矿；Omp—绿辉石；Pl—斜长石；Qtz—石英；Rt—金红石
Figure 2. Microphotographs of eclogite-HP granulite association
表 1 海南岛榴辉岩中代表性石榴子石及绿辉石化学成分
Table 1 Chemical compositions of representative garnet and omphacite from eclogite, Hainan Island
% 矿物 部位 SiO2 TiO2 Al2O3 Cr2O3 FeO* MnO MgO CaO Na2O K2O 总量 石榴子石 核 39.31 0.10 20.67 0.01 20.77 0.82 6.77 10.77 0.04 0.00 99.26 边 39.66 0.00 21.03 0.12 20.14 0.41 8.68 9.04 0.02 0.00 99.10 绿辉石 核 52.45 0.36 9.62 0.04 4.96 0.03 9.83 17.43 4.40 0.00 99.12 边 52.32 0.32 9.71 0.00 5.07 0.00 9.95 18.20 3.83 0.00 99.40 
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