Monazite behaviour during isothermal decompression in pelitic granulites: a case study from Dinggye, Tibetan Himalaya
Monazite behaviour during isothermal decompression in pelitic granulites: a case study from Dinggye, Tibetan Himalaya
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泥质麻粒岩等温减压过程中独居石的行为：以西藏喜马拉雅山定结为例
DOI：
10.1007/s00410-017-1400-y
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发表时间：
2017-09
影响因子：
3.5
通讯作者：
Yang Lei
中科院分区：
文献类型：
--
作者：
Wang Jia-Min;Wu Fu-Yuan;Rubatto Daniela;Liu Shi-Ran;Zhang Jin-Jiang;Liu Xiao-Chi;Yang Lei
独居石是变质地质年代学的重要副矿物，但其在高温变质和深熔作用中获得的复杂化学和年龄分带的解释仍然是一个挑战。研究了藏南定结地区大喜马拉雅结晶杂岩（GHC）中含有独居石的泥质麻粒岩和砂质麻粒岩的岩石学、压力-温度和变质时间。这些岩石在750-830°C的温度下经历了从> 10 kbar到~ 5 kbar的等温减压，记录了蓝晶石（M1）、硅线石（M2）和堇青石-尖晶石（M3）三个变质阶段。独居石和锆石晶体通过微束技术以颗粒分离或薄片形式进行测年。U-Th-Pb年龄与矿物生长的特定条件有关，其基础是分区模式、微量元素特征、定年域中的指标矿物包裹体（熔融包裹体、硅线石和钾长石）以及与共存矿物的结构关系。结果表明，独居石中即使在麻粒岩相条件下也保留了继承畴（500- 400 Ma）。很少有独居石或锆石产生与M1阶段有关的年龄（~30- 29 Ma），可能对应于白云母脱水的岩浆熔融。在等温减压的早期阶段，绝大多数样品中的继承性独居石或嵌布性独居石溶解在黑云母脱水熔融形成的熔体中。大多数独居石颗粒从熔体中结晶到减压结束（M3阶段，21- 19 Ma），并与石榴石分解反应有关。独居石生长的另一个高峰出现在熔体结晶的最后阶段（~ 15 Ma），这些独居石颗粒是不分带的，成分均匀。在区域背景下，我们的压力-温度-时间数据限制GHC内的峰值高压变质作用在定结喜马拉雅约30- 29 Ma。我们的研究结果是符合熔融辅助折返的GHC岩石。
Monazite is a key accessory mineral for metamorphic geochronology, but interpretation of its complex chemical and age zoning acquired during high-temperature metamorphism and anatexis remains a challenge. We investigate the petrology, pressure–temperature and timing of metamorphism in pelitic and psammitic granulites that contain monazite from the Greater Himalayan Crystalline Complex (GHC) in Dinggye, southern Tibet. These rocks underwent isothermal decompression from pressure of >10kbar to ~5kbar at temperatures of 750–830°C, and recorded three metamorphic stages at kyanite (M1), sillimanite (M2) and cordierite-spinel grade (M3). Monazite and zircon crystals were dated by microbeam techniques either as grain separates or in thin sections. U–Th–Pb ages are linked to specific conditions of mineral growth on the basis of zoning patterns, trace element signatures, index mineral inclusions (melt inclusions, sillimanite and K-feldspar) in dated domains and textural relationships with co-existing minerals. The results show that inherited domains (500–400Ma) are preserved in monazite even at granulite-facies conditions. Few monazites or zircon yield ages related to the M1-stage (~30–29Ma), possibly corresponding to prograde melting by muscovite dehydration. During the early stage of isothermal decompression, inherited or prograde monazites in most samples were dissolved in the melt produced by biotite dehydration-melting. Most monazite grains crystallized from melt toward the end of decompression (M3-stage, 21–19Ma) and are chemically related to garnet breakdown reactions. Another peak of monazite growth occurred at final melt crystallization (~15Ma), and these monazite grains are unzoned and are homogeneous in composition. In a regional context, our pressure–temperature–time data constrains peak high-pressure metamorphism within the GHC to ~30–29Ma in Dinggye Himalaya. Our results are in line with a melt-assisted exhumation of the GHC rocks.
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影响因子：
3.5
作者：
D. Rubatto;I. Williams;I. Buick
通讯作者：
D. Rubatto;I. Williams;I. Buick
DOI：
--
发表时间：
2006-10
期刊：
Polar geoscience
影响因子：
--
作者：
T. Hokada;Y. Motoyoshi
通讯作者：
T. Hokada;Y. Motoyoshi
DOI：
10.1144/sp412.3
发表时间：
2015-09
期刊：
--
影响因子：
--
作者：
C. Montomoli;R. Carosi;S. Iaccarino
通讯作者：
C. Montomoli;R. Carosi;S. Iaccarino
影响因子：
5.3
作者：
P. Leloup;G. Mahéo;N. Arnaud;E. Kali;E. Boutonnet;Dunyi Liu;Xiaohan Liu;Haibing Li
通讯作者：
P. Leloup;G. Mahéo;N. Arnaud;E. Kali;E. Boutonnet;Dunyi Liu;Xiaohan Liu;Haibing Li
影响因子：
5.3
作者：
STEIGER, RH;JAGER, E
通讯作者：
JAGER, E