Ultrahigh-pressure garnet peridotites from the devolatilization of sea-floor hydrated ultramafic rocks
文献类型：期刊论文
| 作者 | Yang, J. -J .1; Powell, R.2 |
| 刊名 | JOURNAL OF METAMORPHIC GEOLOGY
 |
| 出版日期 | 2008-08-01 |
| 卷号 | 26期号:6页码:695-716 |
| 关键词 | garnet peridotites lizardite Northern Qaidam Mountains north-west China oceanic crust short-lived UHP metamorphism |
| ISSN号 | 0263-4929 |
| DOI | 10.1111/j.1525-1314.2008.00780.x |
| 文献子类 | Article |
| 英文摘要 | Garnet peridotites occur in quartzofeldspathic gneisses in the Northern Qaidam Mountains, western China. They are rich in Mg and Cr, with mineral compositions similar to those in mantle peridotites found in other orogenic belts and as xenoliths in kimberlite. Garnet-bearing lherzolites interlayered with dunite display oriented ilmenite and chromite lamellae in olivine and pyroxene lamellae in garnet that have been interpreted to indicate pressures in excess of 6 GPa. However, some garnet porphyroblasts include hornblende, chlorite and spinel + orthopyroxene symplectite after garnet; some clinopyroxene porphyroblasts include abundant actinolite/edenite, calcite and lizardite in the lherzolite; some olivine porphyroblasts (Fo(92)) include an earlier generation Mg-rich olivine (Fo(95-99)), F-rich clinohumite, pyroxene, chromite, anthophyllite/cummingtonite, Cl-rich lizardite, carbonates and a new type of brittle mica, here termed 'Ca-phlogopite', in the associated dunite. The pyrope content of garnet increases from core to rim, reaching the pyrope content (72 mol.%) of garnet typically found in the xenoliths in kimberlite. The simplest interpretation of these observations is that the rock association was formerly mantle peridotite emplaced into the oceanic crust that was subjected to serpentinization by seawater-derived fluids near the sea floor. Dehydration during subduction to 3.0-3.5 GPa and 700 degrees C transformed these serpentinites into garnet lherzolite and dunite, depending on their Al and Ca contents. Pseudosection modelling using THERMOCALC shows that dehydration of the serpentinites is progressive, and involved three stages for Al-rich and two stages for Al-poor serpentinites, corresponding to the breakdown of the key hydrous minerals. Static burial and exhumation make olivine a pressure vessel for the pre-subduction mineral inclusions during ultrahigh-pressure (UHP) metamorphism. The time span of the UHP event is constrained by the clear interface between the two generations of olivine to be very short, implying rapid subduction and exhumation. |
| WOS关键词 | UHP METAMORPHIC TERRANE ; CONTINENT COLLISION OROGENS ; NORTHERN TIBETAN PLATEAU ; SINKING INTRUSION MODEL ; NW CHINA ; PHASE-RELATIONS ; WESTERN CHINA ; TITANIAN CLINOHUMITE ; BEARING PERIDOTITES ; HYDROUS PERIDOTITES |
| WOS研究方向 | Geology |
| 语种 | 英语 |
| WOS记录号 | WOS:000257708200005 |
| 出版者 | WILEY-BLACKWELL |
| 源URL | [http://ir.iggcas.ac.cn/handle/132A11/69343]  |
| 专题 | 中国科学院地质与地球物理研究所 |
| 通讯作者 | Yang, J. -J . |
| 作者单位 | 1.Chinese Acad Sci, Inst Geol & Geophys, State Key Lab Lithospher Evolut, Beijing 100029, Peoples R China 2.Univ Melbourne, Sch Earth Sci, Melbourne, Vic 3010, Australia |
| 推荐引用方式 GB/T 7714 | Yang, J. -J .,Powell, R.. Ultrahigh-pressure garnet peridotites from the devolatilization of sea-floor hydrated ultramafic rocks[J]. JOURNAL OF METAMORPHIC GEOLOGY,2008,26(6):695-716. |
| APA | Yang, J. -J .,&Powell, R..(2008).Ultrahigh-pressure garnet peridotites from the devolatilization of sea-floor hydrated ultramafic rocks.JOURNAL OF METAMORPHIC GEOLOGY,26(6),695-716. |
| MLA | Yang, J. -J .,et al."Ultrahigh-pressure garnet peridotites from the devolatilization of sea-floor hydrated ultramafic rocks".JOURNAL OF METAMORPHIC GEOLOGY 26.6(2008):695-716. |
入库方式： OAI收割
来源：地质与地球物理研究所
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