ISLAND-ARC AND CONTINENT-BUILDING MAGMATISM - A REVIEW OF PETROGENIC MODELS BASED ON EXPERIMENTAL PETROLOGY AND GEOCHEMISTRY
ISLAND-ARC AND CONTINENT-BUILDING MAGMATISM - A REVIEW OF PETROGENIC MODELS BASED ON EXPERIMENTAL PETROLOGY AND GEOCHEMISTRY
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DOI：
10.1016/0040-1951(80)90121-3
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发表时间：
1980-01-01
期刊：
影响因子：
2.9
通讯作者：
GREEN, TH
中科院分区：
文献类型：
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作者：
GREEN, TH
岛弧和大陆边缘环境火成岩套的详细地球化学和岩石学研究揭示了这些地区岩浆活动的复杂性。曾经被统称为造山钙碱性套的岩石，现在被认为是在拉斑岩、钙碱性套和碱性套之间形成的连续体。尽管岩石类型的多样性激发了不同的、重叠的起源假设，但实验和地球化学数据的应用确实限制了对会聚板块区域单个岩浆套的成因假设的适当选择。此外，一些起源假设可以联系起来，给出岛弧和大陆地壳生长的综合模式，某些地球化学参数在追踪这种渐进发展方面是独特的。钛钛石、钛斜殖石和榍石等小相对关键地球化学参数有重要影响。在汇聚板块区域岩浆生成的综合模式中，水起着关键作用。在第一阶段，由于俯冲物质中相的脱水，水的释放控制了地幔中大规模的熔融过程，形成了岛弧套中早期和最“原始”的拉斑岩浆（c.f. Ringwood, 1974），其中橄榄石起着主要的分分作用。这些岩浆在板块碰撞过程中形成了经过改良的加厚的地壳。一旦这种增厚地壳发育，随后的钙碱性岩浆作用就会变得更加复杂，涉及许多可能的来源或过程，包括(a)俯冲带榴辉岩的硅熔体，(b)“受污染”的橄榄岩的熔体，以及(c)增厚地壳中相对较浅的含水，通常以角闪岩为主的分选。关键微量元素丰度可以限制这些来源或过程的参与。岛弧进一步的岩浆活动与较深和较低程度的熔融有关，其中云母碎裂起重要作用，并遗留有硬玉斜辉石。作为残余地幔阶段。这就产生了向碱性岩组过渡的高钾钙碱性岩。最后，在地壳厚度超过35公里的“成熟”岛弧和大陆边缘，由地幔或俯冲带衍生的岩浆从俯冲带和/或地壳底层不断进入的水，导致地壳部分熔融。形成的岩浆主要是硅质和深成岩或火成岩。越来越多的实验、地球化学和矿物学证据表明，在演化的岛弧或大陆边缘环境中，“成熟”的沉积物质参与了深度熔融和火山岩浆和深部岩浆的形成。稀土元素为这些岩石的成因提供了有用的额外约束，就像它们对岛弧套中的其他岩石一样。
Detailed geochemical and petrological studies of igneous rock suites in island arc and continental marginal environments have revealed the complexity of magmatism in these regions. Rocks once collectively termed the orogenic calc-alkaline suite are now recognized as forming a continuum between tholeiitic, calc-alkaline and alkaline suites.Although this diversity of rock types has inspired varied and overlapping hypotheses of origin, the application of experimental and geochemical data do limit the appropriate choice of a genetic hypothesis for individual magma suites in convergent plate regions. Also a number of hypotheses of origin may be linked to give an integrated model of the growth of island arcs and continental crust and certain geochemical parameters are distinctive in tracingthisprogressive development. Minor phases such as titanochondrodite, titanoclinohumite and sphene have a critical bearing on key geochemical parameters.Water plays a key role in the integrated model for generation of magmas in convergent plate regions. In the first stage, release of water through dehydration of phases in subducted material controls large-scale melting processes in the mantle, forming the early and most “primitive” tholeiitic magmas in the island arc suite (c.f. Ringwood, 1974), where olivine plays a dominating fractionating role. These magmas form a modified and thickened crust in plate collision regimes. Once this thickened crust has developed, subsequent calc-alkaline magmatism becomes more complex, involving a number of possible sources or processes, including (a) silicic melt from eclogite in the subduction zone, (b) melts from “contaminated” peridotite and (c) relatively shallow level, hydrous, often amphibole-dominated fractionation in the thickened crust. Key trace element abundances can constrain the involvement of these sources or processes. Further magmatic activity in island arcs is related to deeper and low degrees melting, with mica breakdown making an important contribution and jadeitic clinopyroxene remaining.as a residual mantle phase. This produces high-K calc-alkaline rocks transitional into the alkaline suite. Finally, in both “mature” island arcs and continental margins where crustal thicknesses exceed 35 km, continued access of water from the subduction zone and/or underplating of the crust by mantle- or subduction zone-derived magmas, causes partial melting of the crust. The resultant magmas are dominantly silicic and plutonic or ignimbritic.An increasing amount of experimental, geochemical and mineralogical evidence indicates a prominent role for “mature” sedimentary material being involved in melting at depth and the generation of volcanic and plutonic magmas in evolved island arc or continental marginal environments. REE provide useful additional constraints on the genesis of these rocks, as they do for other rocks in the island arc suite.