Volcanoes of the Diamante cross-chain: evidence for a mid-crustal felsic magma body beneath the Southern Izu–Bonin–Mariana arc
Volcanoes of the Diamante cross-chain: evidence for a mid-crustal felsic magma body beneath the Southern Izu–Bonin–Mariana arc
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钻石跨链火山：南伊豆-小博宁-马里亚纳弧下方中地壳长英质岩浆体的证据
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发表时间：
2013
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通讯作者：
I. Pujana
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作者：
R. Stern;Y. Tamura;O. Ishizuka;Hiroshi Shukano;S. Bloomer;R. Embley;M. Leybourne;H. Kawabata;A. Nunokawa;A. Nichols;E. Kohut;I. Pujana
南马里亚纳弧的三座海底Diamante交叉链火山标志着一个沿弧（南北）延伸的岩浆愈合带，该带允许基性幔源玄武岩或来自增厚弧壳中部的长英质岩浆喷发。最大的火山是东钻石火山，有一个发育良好的火山口（5×10公里），是由近0.5 Ma开始的激烈的长英质海底喷发形成的。其中一次或多次喷发还形成了一个巨大的海底沙丘区，向火山西北方向延伸30公里。长英质火成岩活动至少持续到距今约2万年前，英安岩圆顶重新出现，其中一些热到足以为马里亚纳弧已知的唯一的黑烟热液系统提供动力。相比之下，西部的两座火山没有发生长英质喷发，这意味着中地壳长英质带并不位于马里亚纳海槽弧后盆地较薄的地壳之下。钻石交叉链熔岩定义了一个中等的K套；基性熔岩斑晶组合显示富钙长石斜长石与富铁橄榄石呈弧形组合。一个玄武安山岩和三个英安岩的岩浆温度分别为1100°c和800°c，是典型的冷、湿、俯冲相关的长英质岩浆。长英质岩浆形成于低磷地壳条件下。迪亚曼特交叉链是至少七座或八座马里亚纳弧火山的最南端，在一个长约115公里的弧段中，以长英质火山喷发为特征。这是“Anatahan Felsic省”，它可能形成于一个由分馏形成的中地壳块状岩体之上，或者在1200°c的幔源岩浆加热后被重新熔化。弧上和弧上的变化表明，长英质火山喷发和穹窿侵位发生在地壳中玄武岩被基性岩浆侵入重新活化的时候，而南北伸展则促进了通向地表的导管的发育。补充资料：详细的Hyperdolphin ROV潜水轨迹，Cook 7疏浚位置，40Ar/39Ar分析数据，分析方法，整个岩石样品的主要和选定微量元素分析，矿物成分数据可在http://www.geolsoc.org.uk/SUP18611上获得
Abstract Three submarine Diamante cross-chain volcanoes in the southern Mariana arc mark a magma-healed zone of along-arc (north–south) extension that allows either mafic mantle-derived basalts or felsic magmas from the middle of thickened arc crust to erupt. The largest volcano is East Diamante, with a well-developed (5×10 km) caldera that formed via violent felsic submarine eruptions beginning nearly 0.5 Ma. One or more of these eruptions also formed a giant submarine dune field extending 30 km to the NW of the volcano. Felsic igneous activity continues at least as recently as c. 20 000 years ago, with emplacement of resurgent dacite domes, some hot enough to power the only black smoker hydrothermal system known in the Mariana arc. In contrast, felsic eruptions do not occur on the two volcanoes to the west, implying that the mid-crustal felsic zone does not underlie the thinner crust of the Mariana Trough back-arc basin. Diamante cross-chain lavas define a medium K suite; mafic lava phenocryst assemblages show arc-like associations of anorthite-rich plagioclase with Fe-rich olivine. Magmatic temperatures for a basaltic andesite and three dacites are c. 1100 °C and c. 800 °C, respectively, typical for cool, wet, subduction-related felsic magmas. Felsic magmas formed under low-P crustal conditions. The Diamante cross-chain is the southernmost of at least seven and perhaps eight Mariana arc volcanoes in a c. 115 km long arc segment characterized by felsic eruptions. This is the ‘Anatahan Felsic Province’, which may have formed above a mid-crustal tonalite body that formed by fractionation or was re-melted when heated by c. 1200 °C mafic, mantle-derived magmas. Across- and along-arc variations suggest that felsic eruptions and dome emplacement occurred when midcrustal tonalite was remobilized by intrusions of mafic magma, while north–south extension facilitated the development of conduits to the surface. Supplementary material: Detailed Hyperdolphin ROV dive tracks, Cook 7 dredge locations, 40Ar/39Ar analytical data, analytical methods, major and selected trace element analyses of whole rock samples, and compositional data for minerals are available at http://www.geolsoc.org.uk/SUP18611