西准噶尔博什库尔-成吉斯火山弧中早石炭世火山岩的地球化学特征及其构造意义  

Geochemistry Characteristics of the Early Carboniferous Volcanic Rocks in the Boshchekul-Chingiz Volcanic Arc,West Junggar and Its Tectonic Implication

作　　者：易善鑫[1] 李永军[1] 焦光磊[1] 孙羽[1] 杨高学[1] 王军年[2] 杨丰柱 

机构地区：[1]长安大学地球科学与资源学院、西部矿产资源与地质工程教育部重点实验室,西安710054 [2]新疆维吾尔自治区地质矿产勘查开发局第七地质大队,新疆乌苏833000

出　　处：《矿物岩石地球化学通报》2014年第4期431-438,共8页Bulletin of Mineralogy, Petrology and Geochemistry

基　　金：中国地质调查局地质矿产调查评价专项(1212011120516)

摘　　要：西准噶尔北部谢米斯台山西缘发育的下石炭统黑山头组主要为一套火山碎屑岩 中酸性火山熔岩组合.通过对黑山头组英安岩和安山岩进行岩石地球化学研究,不仅可以提高博什库尔 —成吉斯火山弧的研究程度,更有助于对西准噶尔北部岩浆活动及构造演化提供新认识.研究发现二者均具有较高的SiO2 （60.52％～71.58％）、全碱Na2O＋K2O（6.88％～10.31％）、Al2O3 （13.37％～16.31％）,较低的P2O5（0.03％～0.27％）和TiO2 （0.07％～1.89％）.英安岩属于碱性 亚碱性系列,安山岩属于钙碱性系列.岩石稀土元素总量较高（62.7×10-6～274×10-6）,富集轻稀土元素（（La/Yb）N=2.75～12.7）,具有明显的负铕异常（δEu=0.247～0.501）,富集大离子亲石元素（Rb,Ba,Th）,相对弱亏损高场强元素（Nb,Ta,Ti）,显示岛弧火山岩的地球化学特征.通过对其源区和构造环境分析发现,博什库尔 — 成吉斯火山弧形成于岛弧俯冲环境下,且在此过程中伴随有消减沉积物熔体的加入.The Lower Carboniferous Heishantou Formation in the west Xiemisitai Mountain, northwest of Junggar, consists pyroclastic rocks and neutral-acidic volcanic lava. Geochemical studies of the neutralacidic volcanic rocks in the Heishantou Formation improve understandings of the Boshchekul Chingiz volcanic arc and magmatic and tectonic evolutions of the northern West Junggar. The geochemical characteristics study showed that the dacites are Alka- line-subalkaline series and the andesites are Calcium alkaline. Their SiO2 contents are higher （60.52 %- 71.58%）, their P2O5 and TiO2contents are lower （0.03%-0.27% and 0. 07%- 1.89%, respectively）, their total alkaline （Na2O＋K2O） is about 6.88% 10.31% and their Al2O3 contents are about 13.37% 16.31%. They have high ∑REE of 62.7 × 10-6 4274 × 10-6, enrich LREE with （La/Yb）N =2.75-12.7, and have a significant Eu anomalies of c3Eu=0. 24740. 501, they also enrich LILE （Rb, Ba, Th） and slightly deplete HFSE （Nb, Ta, Ti）, showing the similarities to island-arc volcano rocks. It can be concluded that the Boshchekul-Chingiz volcanic arc was formed by the former subduction of the island-arc zone and mixed with melted subduction sediment during the formation.

关 键 词：地球化学 岛弧 黑山头组 博什库尔—成吉斯火山弧 西准噶尔 

分 类 号：P588.14[天文地球—岩石学]