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首页> 外文期刊>The island arc >Geochemistry and origin of Archean volcanic rocks from the Upper Keewatin assemblage (ca 2.7 ga), lake of the woods greenstone belt, Western Wabigoon Subprovince, Superior Province, Canada
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Geochemistry and origin of Archean volcanic rocks from the Upper Keewatin assemblage (ca 2.7 ga), lake of the woods greenstone belt, Western Wabigoon Subprovince, Superior Province, Canada

机译：加拿大上级省西瓦比贡省上层森林绿岩带湖（上盖瓦汀组合）（ca 2.7 ga）中的太古代火山岩的地球化学和成因

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摘要

Volcanic rocks from the Upper Keewatin assemblage (ca 2720 Ma) were geochemically classified into five groups; komatiites, tholeiitic rocks having near-flat primitive mantle-normalized abundance patterns, Nb-enriched basalts and andesites (NEBA) plus normal calc-alkaline (NCA) rocks, adakites and shoshonites. The adakites having [La/Yb](N) > 30 and < 30 were probably derived from felsic magmas formed by partial melting of a subducted slab at relatively greater and smaller depths, respectively. Ascending adakite magmas, by interaction with the overlying mantle wedge, decreased in Al2O3 / Y ratio and selectively lost high-field strength elements, thereby forming mantle sources for both NEBA + NCA and shoshonite magmas. Under the influence of a mantle plume, the source of komatiites, the NEBA + NCA magmas were generated from that part of the mantle wedge metasomatized by adakite magmas having [La / Yb](N) < 30, and tholeiitic magmas from unmetasomatized part of the same mantle wedge. Magmas of both adakites having [La / Yb](N) > 30 and shoshonites were generated in a normal Archean Arc system setting.
机译：上基瓦廷组合（约2720 Ma）的火山岩在地球化学上分为五类：科马提岩，具有接近平坦的原始地幔归一化富集模式的生硬质岩石，富Nb的玄武岩和安山岩（NEBA）以及普通的钙碱性（NCA）岩石，陶粒岩和长寿岩。 [La / Yb]（N）> 30和<30的达卡石可能分别来自于俯冲板块在相对较大和较小深度处部分熔融而形成的长英质岩浆。通过与上覆的地幔楔相互作用，上升的akakite岩浆Al2O3 / Y比降低，并有选择地失去高场强元素，从而形成NEBA + NCA和shoshonite岩浆的地幔源。在地幔柱羽的影响下，科马提岩的来源，NEBA + NCA岩浆是由被[La / Yb]（N）<30的Adakite岩浆交代的地幔楔的一部分，以及来自未变质岩浆部分的生胶质岩浆产生的。相同的地幔楔。 [La / Yb]（N）> 30的两种akakite和shoshonite的岩浆都是在正常的太古宙弧系统中生成的。

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