Petrogenetic relationships between jadeitite and associated high-pressure and low-temperature metamorphic rocks in worldwide jadeitite localities: a review
Petrogenetic relationships between jadeitite and associated high-pressure and low-temperature metamorphic rocks in worldwide jadeitite localities: a review
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DOI：
10.1127/0935-1221/2012/0024-2193
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发表时间：
2012-03-01
影响因子：
2.1
通讯作者：
Harlow, George E.
中科院分区：
文献类型：
--
作者：
Tsujimori, Tatsuki;Harlow, George E.
含硬玉的蛇纹岩-基性混杂岩分布于加勒比海(危地马拉、古巴和多米尼加共和国)、环太平洋(日本、美国西部和巴布亚新几内亚)、阿尔卑斯-喜马拉雅(意大利、伊朗、希腊和缅甸)和加里东(俄罗斯和哈萨克斯坦)造山带，并始终含有高压低温(HP-LT)变质岩。在美国科罗拉多高原的金伯利岩筒中也有翡翠岩捕虏体。在日本、俄罗斯和哈萨克斯坦的早古生代，翡翠岩的产状最早，这表明俯冲带热构造自早古生代以来为翡翠岩的形成演化了必要的高压/温度条件；最年轻的产状是科罗拉多高原的捕虏体。主要产状以侵入地幔楔体的流体沉淀物(P型)为主，斜长花岗岩、变质辉长岩和榴辉岩交代(R型)的产状较少，两种类型可能在同一产状或系统内。翡翠岩层形成的P-T条件可以扩展到以前争论的蓝片岩相条件的范围之外。部分硬玉岩形成于绿帘角闪岩中，另一些形成于榴辉岩相条件下。已有的翡翠岩及其伴生的HP-LT岩石年代学数据表明，在某些地区，翡翠岩建造与HP-LT变质作用之间存在着时间上的差异。同一混杂岩杂岩中较老的翡翠岩和较新的HP-LT岩石之间的密切联系意味着俯冲通道和含翡翠混杂岩的不同历史。含硬玉的蛇纹岩混杂岩可在地幔楔体停留相当长的时间，因此经历了多次流体渗透事件。由于构造侵蚀，俯冲通道有时会合并上覆的蛇纹状地幔楔形物质。随着时间的推移，含有翡翠岩脉的破碎地幔楔体与较年轻的蓝片岩、折返榴辉岩和各种超俯冲带岩性碎片混合在一起。因此，硬玉岩的再结晶和再沉淀沿板块-地幔楔形界面重新激活。所有这些可能的情景及其组合在翡翠岩中产生了复杂的岩石学记录。随着研究的深入，硬玉-HP-LT变质岩-蛇纹岩的岩石组合有可能对俯冲通道和上覆地幔楔体有更好的认识。
Jadeitite-bearing serpentinite-matrix melange is distributed in the Caribbean (Guatemala, Cuba, and Dominican Republic), circum-Pacific (Japan, Western USA, and Papua New Guinea), Alpine-Himalayan (Italy, Iran, Greece, and Myanmar), and Caledonian (Russia and Kazakhstan) orogenic belts, and always contains high-pressure, low-temperature (HP-LT) metamorphic rocks. There are also jadeitite xenoliths in kimberlitic pipes in the Colorado Plateau (USA). The oldest occurrences of jadeitite are Early Paleozoic in Japan, Russia, and Kazakhstan, suggesting subduction-zone thermal structures evolved the necessary high pressure/temperature conditions for jadeitite formation since Early Paleozoic; the youngest occurrence is a xenolith from the Colorado Plateau. Major occurrences consist principally of fluid precipitates (P-type) that infiltrated the mantle wedge; fewer occurrences document metasomatic replacement (R-type) of plagiogranite, metagabbro and eclogite, and both types may be possible in the same occurrence or system. The P-T conditions for jadeitite formation can be extended beyond the previously argued limits of blueschist-facies conditions. Some jadeitite formed at epidote amphibolite and others at eclogite facies conditions. Available geochronological data of both jadeitite and associated HP-LT rock show temporal discrepancies between jadeitite formation and HP-LT metamorphism at some localities. The close association between older jadeitite and younger HP-LT rock in a single melange complex implies different histories for the subduction channel and jadeitite-bearing melange. Jadeitite-bearing serpentinite melange can stay at the mantle wedge for a considerable time and, as a result, experience multiple fluid-infiltration events. The subduction channel can occasionally incorporate overlying serpentinized mantle wedge material due to tectonic erosion. With time, the disrupted mantle wedge containing jadeitite veins is mixed with younger blueschists, exhumed eclogites and various fragments of suprasubduction-zone lithologies. Consequently, recrystallization and re-precipitation of jadeitite are reactivated along a slab-mantle wedge interface. All these possible scenarios and their combinations yield a complicated petrological record in jadeitite. With further investigation, the rock association of jadeitite-HP-LT metamorphic rocks-serpentinite has the potential to yield a greater understanding of subduction channels and overlying mantle wedge.