Metamorphic P–T evolution of high‐pressure eclogites from garnet growth and reaction textures: Insights from the Kaghan Valley transect, northern Pakistan
Metamorphic P–T evolution of high‐pressure eclogites from garnet growth and reaction textures: Insights from the Kaghan Valley transect, northern Pakistan
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石榴石生长和反应结构的高压榴辉岩的变质 P-T 演化：来自巴基斯坦北部 Kaghan 谷横断面的见解
DOI：
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发表时间：
2013
期刊：
影响因子：
--
通讯作者：
K. Shin
中科院分区：
文献类型：
--
作者：
H. Rehman;H. Yamamoto;K. Shin
位于巴基斯坦北部Kaghan山谷样带的喜马拉雅变质带是印度板块岩石俯冲至亚洲板块下100公里深处并经历高压至超高压变质作用的关键区域。在卡汗河谷变质的基性岩单元（榴辉岩和角闪岩）中，至少可以识别出三个明显的变质事件：(1)进积；(2)峰;（三）逆行阶段。石榴石的化学组成、分带模式和包裹体，以及主要矿物组合（石榴石+斜辉石+石英+角闪洞+绿帘石）的变质反应表明，石榴石的核心部分是在渐进阶段发育的，而大部分中间部分是在高压阶段（P-T条件为2.3±0.4 GPa, 766±107℃）下发育或再结晶的。与角闪石相关的石榴石边缘部分和共长石的存在表明角闪岩-榴辉岩-角闪岩相（逆行）阶段，平均P-T条件为1.5±0.2 GPa和710±75°C。石榴石的分带表现为宽芯缺钙，薄中部富钙，绿泥石和角闪孔沿最外边缘发育，表明角闪岩相阶段，芯部发育渐进式，中部发育均质，边缘发育退行式。这些特征表明，大部分石榴石是在印亚碰撞前印度板块岩石圈俯冲期间形成的，而边缘部分是在碰撞后的快速挖掘过程中形成的。
The Himalayan Metamorphic Belt of the Kaghan Valley transect in northern Pakistan is a key area where rocks of the Indian Plate have been subducted to greater depths >100 km beneath the Asian Plate and experienced high‐ to ultrahigh‐pressure metamorphism. At least three distinct metamorphic events can be recognized in the metamorphosed mafic rock units (eclogites and amphibolitized eclogites) of the Kaghan Valley: (i) prograde; (ii) peak; and (iii) retrograde stages. Chemical composition, zoning pattern and inclusions in garnet, and metamorphic reactions among major mineral assemblage (garnet + clinopyroxene + quartz + amphibole + epidote) show that core portions of garnet grew under the prograde stage, whereas most of the middle portions were developed or recrystallized under the high‐pressure stage with P–T conditions at 2.3 ± 0.4 GPa and 766 ± 107°C. The rim portions of garnet in association with amphibole and presence of symplectites indicate amphibole‐eclogite to amphibolite‐facies (retrograde) stage with average P–T conditions at 1.5 ± 0.2 GPa and 710 ± 75°C. Zoning in garnet shows Ca‐poor wider cores, Ca‐rich thin middle portions, and chlorite and amphibole development along the outermost rims, suggesting prograde growth at cores and homogenous middle portions and retrogressive formation at rims during the amphibolite‐facies stage. These features suggest that most of the garnet grew during subduction of the Indian Plate lithosphere before the India–Asia collision, whereas rim portions developed during rapid exhumation in the post‐collision stage.
巴基斯坦喜马拉雅山的不同榴辉岩类型及其对折返过程的影响
DOI：
10.3126/hjs.v5i7.1345
发表时间：
2008
期刊：
Himalayan Journal of Sciences
影响因子：
--
作者：
O'Brien;Ahmed Khan
通讯作者：
Ahmed Khan
巴基斯坦喜马拉雅山不同榴辉岩类型的多阶段反应历史及其对折返过程的影响
影响因子：
3.5
作者：
O'Brien;Altenberger;Konrad-Schmolke;Ahmed Khan
通讯作者：
Ahmed Khan