| 固相线以下变质过程中水的行为 |
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| 引用本文： | 魏春景,张景森.固相线以下变质过程中水的行为[J].高校地质学报,2007,13(3):507-514. |
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| 作者姓名： | 魏春景 张景森 |
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| 作者单位： | 造山带与地壳演化教育部重点实验室,北京大学,地球与空间科学学院,北京,100871 |
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| 基金项目： | 国家自然科学基金资助项目(40525006) |
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| 摘 要： | 在p–T视剖面上定量计算全岩饱和水含量等值线可以更有效地讨论变质矿物组合的演化。Guiraud等认为在封闭体系中发生的变质作用通过递进脱水作用使岩石向水含量降低方向演化,脱出的水离开岩石体系。当变质过程向水含量增加方向演化时,岩石会很快变成流体缺失状态,不利于变质矿物组合的进一步演化。因此,从岩石中的实际矿物组合所得到的"变质峰期"应该理解为脱水反应结束,并可能发生少量水化反应的位置,并不一定对应p–T轨迹所经历的实际峰期温度或压力。利用p–T视剖面图和饱和水含量等值线的行为研究阿尔泰造山带泥质岩石的中低压变质作用发现,阿尔泰地区红柱石型变质带的发生与蓝晶石型变质带的抬升有关,主要发生铝硅酸盐矿物之间的同质多相转变,低压变质矿物组合未能达到热力学平衡状态。与泥质岩中低压变质演化明显不同的是超高压榴辉岩在峰期以后的减压过程中仍然发生递进脱水作用。
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| 关 键 词： | p-T视剖面图 饱和水等值线 变质相平衡 变质作用p-T轨迹 |
| 文章编号： | 1006-7493（2007）03-0507-08 |
| 修稿时间： | 2007-04-27 |
H2O Behaviour in Subsolidus Metamorphic Processes |
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| WEI Chun-jing,ZHANG Jing-sen.H2O Behaviour in Subsolidus Metamorphic Processes[J].Geological Journal of China Universities,2007,13(3):507-514. |
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| Authors: | WEI Chun-jing ZHANG Jing-sen |
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| Institution: | Key Laboratory of Orogenic Belts and Crustal Evolution of Ministry of Education, School of Earth and Space Sciences, Peking University, Beijing 100871, China |
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| Abstract: | Contours of H2O-content saturated to a mineral assemblage in the calculated p-T psaeudosections can provide much useful information on plausible evolution for the mineral assemblage. Guiraud et al. proposed that metamorphism in a closed system can only evolve via progressive dehydration, crossing contours of decreasing H2O- content, the fluid being lost from the rocks. If the metamorphic process crosses contours of increasing H2O-content, the mineral assemblage starts to become a fluid-absent state, which does not favor the further evelution of the mineral assemblage. Thus, a metamorphic peak should represent a point at which the metamorphic p-T path becomes tangential to a H2O-content contour or at which dehydration reactions complete and just start to rehydrate. It may not correspond to the maximum temperature and pressure reached along a p-T path. Using p-T pseudosections with contours of H2O-contents, the medium-low pressure metamorphism for pelite from the Altai orogen was documented. We proposed that the andalusite-type metamorphic zones in Altai were related to the uplifting of kyanite-type zones and are characteristic of isomorphic transformation between aluminosilicates. Generally, it is difficult for the low-pressure metamorphic assemblages to reach an equilibrium state. Distinctive from the low-medium pressure metamorphism of pelite, progressive dehydrations proceed even in the decompression process post metamorphic peak of UHP eclogites. |
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| Keywords: | p-T pseudosection isopleth of H_2O-content saturated to mineral assemblage metamorphic phase equilibria metamorphicp-T path |
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