木兰山蓝片岩中两种文石的产出特征及其动力学意义

赵文俞; 刘嵘; 王勤燕; 彭长琪; 张清杰

木兰山蓝片岩中两种文石的产出特征及其动力学意义

1.
武汉理工大学材料研究与测试中心, 湖北武汉 430070
2.
中国地质大学地球科学学院, 湖北武汉 430074

基金项目:

国家自然科学基金资助项目 49802004

详细信息

中图分类号: P588.33
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出版历程
- 收稿日期: 2001-01-02
- 刊出日期: 2001-11-25

ARAGONITE FROM MULANSHAN GLAUCOPHANE SCHIST: IMPLICATIONS FOR REGIONAL EVOLUTION OF SOUTHWESTERN DABIE MOUNTAINS, CENTRAL CHINA

1.
Center of Material Research and Analysis, Wuhan University of Technology, Wuhan 430070, China
2.
Faculty of Earth Sciences, China University ofGeosciences, Wuhan 430074, China

摘要

摘要: 微米-纳米尺度显微超显微研究表明, 木兰山蓝片岩中存在微米级粒间文石和亚微米级文石包裹体, 它们是木兰山蓝片岩快速折返动力学机制的证据.并指出木兰山蓝片岩区硬柱石和绿纤石等Ca-Al硅酸盐矿物的缺失与本区变质流体中CO₂浓度较高和(或) 岩石中含方解石/文石有关.
- 木兰山蓝片岩 /
- 粒间文石 /
- 文石包裹体 /
- Ca-Al硅酸盐 /
- 快速折返
Abstract: The aragonite, an index mineral of glaucophane schist facies, has not been confirmed in the Dabie Mountains high-pressure and ultrahigh-pressure metamorphic belts. The Mulanshan glaucophane schist in Huangpi County, Hubei Province, is located in the southwestern Dabie mountains, central China. The micro-sized inter-granular aragonite is confirmed with optical microscope (OM) and electron probe microanalysis (EPMA) in the glaucophane schist. The submicrometer-sized ellipse aragonite inclusion is observed by using bright-field image (BFI), X-ray energy-damage spectrograph (EDS), and selected area electron diffraction (SAED) with transmission electron microscope in the quartz lens of glaucophane-albite-epidote-chlorite schist from the Mulanshan. The presence of aragonite indicates not only the average geothermal gradient of the Mulanshan glaucophane schist less than 10 ℃/km, which is very close to that of eclogite in the Dabie Mountain metamorphic belts, but also the relatively higher concentration of CO₂ during the metamorphic process. In addition, the glaucophane schist free of such index minerals as lawsonite, prehnite, and pumpellyite, has been attributed to the effect of CO₂ on the stability of calcium aluminum silicate minerals during the low-grade metamorphism. EDS and SAED analysis results show that the host of aragonite inclusion is amorphous SiO 2. The occurrence of amorphous SiO 2 indicates a quick cooling process during the exhumation of the Mulanshan glaucophane schist. These results suggest that the rapid exhumation mechanism of the glaucophane schist, the same as that of eclogite in the Dabie Mountain metamorphic belts, occurred in the geodynamic context of subduction-obduction.
- Mulanshan glaucophane schist /
- intergranular aragonite /
- aragonite inclusion /
- calcium aluminum silicate minerals /
- rapid exhumation
注释:

1) ①赵文俞.木兰山低温高压微变质体中SiO₂非晶相的特征和意义.岩石学报(待刊).

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图 1 含粒间文石(Arg) 微区的背散射电子像

Ab.钠长石; Cli.斜黝帘石; Ep.绿帘石; Sph.榍石

Fig. 1. Backscattered electron image of intergranular aragonite-bearing microarea (Arg)

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图 2 含亚微米级文石包裹体微区的背散射电子像

Q.石英; Cro.青铝闪石; Chl.绿泥石; Sph.榍石; Act.阳起石

Fig. 2. Backscattered electron image of aragonite-bearing quartz lens

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图 3 图 2所示微区的透射电子显微分析

a.非晶SiO₂ (Ho) 中亚微米文石包裹体(Arg) 的透射电子像; b, c.分别为非晶SiO₂的X射线能量损失谱和选区电子衍射花样; d.文石包裹体的X射线能量损失谱; e.文石包裹体的选区电子衍射花

Fig. 3. TEM investigations of the microarea shown in

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表 1 木兰山蓝片岩部分组成矿物的化学成分

Table 1. Chemical compositions of mineral assemblage of the aragonite-bearing glaucophane-albite-epidote-chlorite schist

表 2 包裹体选区电子衍射花样的标定及其与文石晶体的X射线衍射数据的对比

Table 2. Possible chemical compounds consisting of calcium and light and ultralight elements

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