Zoned quartz phenocrysts in supercooled melt inclusions in granulites from continental collision orogens
Zoned quartz phenocrysts in supercooled melt inclusions in granulites from continental collision orogens
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大陆碰撞造山带过冷熔体包裹体中的分区石英斑晶
DOI：
10.1111/iar.12374
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发表时间：
2020
期刊：
影响因子：
1.5
通讯作者：
Kazuyuki Shiraishi
中科院分区：
文献类型：
--
作者：
27.Yoshikuni Hiroi;Tomokazu Hokada;Masahiro Kayama;Akira Miyake;Tatsuro Adachi;Bernard Prame;Keerthi Perera;Madhusoodhan Satish-Kumar;Yasuhito Osanai;Yoichi Motoyoshi;David J. Ellis;Kazuyuki Shiraishi
来自大陆碰撞造山带的麻粒岩石榴石中的长英石包裹体（FI）是过冷长英质熔融包裹体。这些不仅代表非平衡结构，例如石英和其他矿物的树枝状和球晶晶体，而且斑状结构是浅成岩和火山岩的结构。本文介绍了来自斯里兰卡中部高地杂岩、东南极洲吕佐夫-霍尔姆杂岩、加拿大东南部格伦维尔省和印度南部喀拉拉邦孔兹岩带的各种麻粒岩中具有代表性的带状石英斑晶 FI。石英斑晶表现出简单而明确的阴极发光 (CL) 分区，具有自形明亮核心和深色边缘和过度生长。除脉状石英外，自形石英从未在固相线以下变质岩中发育，并且具有在熔融相中生长的特征。 FI 内石英斑晶周围的基质石英在 CL 中总是较暗，而石榴石外部的基质石英和石榴石中的单晶包裹体石英通常比石英斑晶的核心更亮。紫色 CL 发射强度与石英的 Ti 含量之间的密切关系表明不同的生长温度与推断的结晶顺序相一致。石英斑晶中CL生长带的保存和精细的非平衡结构意味着一些麻粒岩的冷却速率比目前推测的要快1到2个数量级。
Felsite inclusions (FIs) in granulite garnets from continental collision orogens are supercooled felsic melt inclusions. Not only do these represent non‐equilibrium textures, such as dendritic and spherulitic crystals of quartz and other minerals, but the porphyritic texture is that of hypabyssal and volcanic rocks. This paper presents representative zoned quartz phenocryst‐bearing FIs in various granulites from the Highland Complex in central Sri Lanka, the Lützow‐Holm Complex in East Antarctica, the Grenville Province in southeastern Canada, and the Kerala Khondalite Belt in southern India. Quartz phenocrysts show simple and definite cathodoluminescence (CL) zoning with euhedral bright cores and dark rims and overgrowths. Euhedral quartz never develops in subsolidus metamorphic rocks except for vein quartz, and is characteristic of growth in a melt phase. Groundmass quartz surrounding quartz phenocrysts within the FIs is always dark in CL, whereas matrix quartz outside garnet and single‐grain inclusion quartz in garnet are usually brighter than the cores of quartz phenocrysts. The close relationship between violet CL emission intensity and Ti content of quartz indicates different growth temperatures in harmony with the inferred crystallization sequence. The preservation of CL growth zoning in quartz phenocrysts and fine non‐equilibrium textures imply that the cooling rates of some granulites are 1 to 2 orders of magnitude faster than so far presumed.