西准噶尔海山俯冲的地质效应:来自泥盆纪—石炭纪火山岩地球化学证据  

Geological effects of seamount subduction in West Junggar:insight from geochemical characteristics of Devonian-Carboniferous volcanic rocks

作　　者：杨高学[1,2] 李永军[1,2] 佟丽莉[1,2] 李甘雨[1] 吴乐[1] 

机构地区：[1]长安大学地球科学与资源学院,陕西西安710054 [2]国土资源部岩浆作用成矿与找矿重点实验室,陕西西安710054

出　　处：《地学前缘》2017年第6期60-67,共8页Earth Science Frontiers

基　　金：国家自然科学基金项目(41303027);陕西省青年科技新星计划项目(2016KJXX-71);中央高校基本科研业务费专项资金项目(310827153506;310827153407)

摘　　要：海山或火山岛链俯冲与洋壳俯冲具有明显不同的动力学和岩浆效应,主要表现在俯冲带的地貌、发生地震的频度和烈度及火山弧岩浆作用和资源效应。西准噶尔地区泥盆纪—石炭纪火山岩分布有限,多以夹层产出,岩性主要为玄武岩和安山岩,地球化学特征显示:钙碱性和碱性系列均有发育,具有E-MORB或OIB特征,较高的Nd/Sm及^(206)Pb/^(204)Pb比值,明显亏损Nb、Ta、Ti,具有岛弧岩浆特点。结合西准噶尔蛇绿混杂岩中不断识别出OIB特征玄武岩并认为其形成于大洋板内海山的地质事实,提出泥盆纪—石炭纪火山岩具有E-MORB和OIB特征很可能是受早期形成海山在俯冲带内部部分熔融的影响,即为海山俯冲的地质效应,而这种海山俯冲的地质效应可能在整个古亚洲洋的演化过程中都存在,然而需要后续进一步工作。海山俯冲模式的提出不仅丰富了西准噶尔火山岩成因理论,而且为研究西准噶尔构造岩浆事件提供了新思路。It is significantly different between seamounts or volcanic island chains and oceanic crust subduction in dynamics and magmas, including topography of subduction zone, frequency and intensity of earthquakes, magmatism and resource effects of volcanic arc. The West Junggar is characterized by few Devonian- Carboniferous volcanic rocks, mostly in sandwich output, and mainly in basalt and andesite. Geochemically, they show calc-alkaline and alkaline series, E-MORB or OIB feature, higher Nd/Sm and 206Pb/204Pb ratios, strongly depletion in Nb, Ta and Ti, indicating arc magmas trait. Combined with the oceanic island basalts （OIB） being identified constantly in West Junggar ophiolitic melange and formed at seamount in oceanic plate, we propose that the characteristics of E-MORB and OIB in Devonian-Carboniferous volcanic rocks were probably affected by partial melting of early seamount in subduction channel, that is geological effect of subducted seamount. This effect may be exist in entire evolution of the Paleo-Asian Ocean, and needs more works to do. The model of seamount subduction not only enriched the knowledge of volcanic rocks petrogenesis in West Junggar, but also gave a new idea for studying the tectono-magmatic events in West Junggar.

关 键 词：海山 火山岩 俯冲带 地质效应 西准噶尔 

分 类 号：P588.145[天文地球—岩石学] P595[天文地球—地质学]