ISLAND-ARC ELEMENTS AND ARC-RELATED OPHIOLITES
ISLAND-ARC ELEMENTS AND ARC-RELATED OPHIOLITES
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DOI：
10.1016/0040-1951(84)90176-8
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发表时间：
1984-01-01
期刊：
影响因子：
2.9
通讯作者：
LEITCH, EC
中科院分区：
文献类型：
--
作者：
LEITCH, EC
岛弧系统中的所有主要构造单元，弧前、岩浆弧、弧后盆地和残余弧，都是潜在的蛇绿岩来源，而那些据称是洋脊起源的蛇绿岩、席状岩墙杂岩、地幔远洋岩、热液变质作用和相关矿化作用的特征，也可以出现在弧环境中。年龄关系在解释弧相关的蛇颈龙中是至关重要的。大洋岩石圈的残余，确定了弧前的起始年龄，仅限于弧前，岩浆弧和残余弧元素，因为是蛇绿岩群众产生的开始俯冲。后者，显然常见于古代弧前地形，形成在新生的弧系统，其中的作用速度超过收敛速度的俯冲枢纽回来。扩展发生在下沉板之上，导致一些弧形的组成特征。在简单弧系统中，晚期蛇绿岩形成于活动弧后盆地或岩浆弧中。只有那些居住在岩浆弧内或非常靠近岩浆弧的蛇绿岩才显示出钙碱性或弧拉斑玄武岩岩浆的亲和力，或者被这些岩石侵入或覆盖。火山衍生的沉积物或远洋物质可能覆盖所有弧环境中的蛇绿岩，但远洋岩石通常在残余弧上方和弧后盆地底部（岩浆弧附近除外）的地层层序中占主导地位。在主要洋脊生成的蛇绿岩不太可能立即被含有大量火山成分的沉积物覆盖，而这种碎屑可能直接位于弧始、弧和弧后蛇绿岩上。一些弧源蛇绿岩保留在其原始构造位置，另一些则可以通过其内部特征、与其他构造单元的关系以及伴生岩石的性质来识别。
All major structural elements in island arc systems, fore-arc, magmatic arc, back-arc basins and remnant arcs, are potential ophiolite sources, and those features that allegedly characterise ophiolites of ocean-ridge origin, sheeted dyke complexes, mantling pelagic rocks, hydrothermal metamorphism and associated mineralization, can also arise within arc settings. Age relations are critical in the interpretation of arc-related ophiolites. Remnants of oceanic lithosphere, identified by a pre-arc initiation age, are restricted to fore-arc, magmatic arc and remnant arc elements, as are ophiolite masses generated at the inception of underthrusting. The latter, apparently common in ancient fore-arc terrains, form in nascent arc systems in which the rate of role back of the subduction hinge exceeds the rate of convergence. Spreading occurs above a foundering slab resulting in some arc-like compositional features. In simple arc systems later ophiolitic rocks have formed either in the active back-arc basin or the magmatic arc. Only those ophiolites that have resided within or very close behind magmatic arcs should show calcalkaline or arc tholeiite magmatic affinities, or be intruded or overlain by these rocks. Volcanic-derived sediment or pelagic material may mantle ophiolites from all arc settings, but pelagic rocks will generally dominate in stratigraphic sequences above remnant arcs and on back-arc basin floors except adjacent to the magmatic arc. Ophiolites generated at major ocean ridges are unlikely to be immediately overlain by sediment with a significant volcanic component whereas such detritus may lie directly on arc-inception, arc and back-arc ophiolites. Some arc-derived ophiolites are preserved in their original tectonic position, others can be identified from their internal features, their relationship to other tectonic elements, and the nature of associated rocks.