摘要
准噶尔盆地陆西地区(即陆梁隆起西部地区)构造背景复杂,石炭系火山岩广泛发育,长期以来对盆地原型认识不清,导致油气勘探程度低。对英西凹陷火山岩锆石LA-ICP-MS年龄、地球化学与构造环境等系统研究发现,英西凹陷英2井火山岩锆石LA-ICP-MS谐和年龄为310.8±2.9Ma,主量元素具有高硅、高钾、低钛含量特征,Mg#含量中等,Al2O3含量较高(铝过饱和指数A/CNK均大于1),总体表明该套火山岩建造为形成于晚石炭世的中钾钙碱性—高钾钙碱性酸性岩火山岩系列,且具有准铝质特征。另外,稀土元素总量中等,有轻微铕负异常,轻稀土元素较富集,(La/Yb)N变化范围为3.75~7.22;重稀土元素分馏不明显,(Gd/Yb)N值介于1.43~1.73;原始地幔标准化蛛网图指示富集K、Rb、Ba、La等大离子亲石元素,亏损Nb、Ta、Ti等高场强元素,表明英西凹陷石炭系火山岩具有壳源和幔源混合成因特征,为大洋岛弧环境形成产物。结合西准噶尔造山带露头、盆内钻井综合研究表明,西准噶尔洋持续活动到晚石炭世,并发生北西—南东向的俯冲,西准噶尔地区晚石炭世是由北东向展布的有限的西准噶尔洋盆、增生杂岩带和链状岛弧带、弧间—弧后盆地等组成,英西凹陷位于弧后盆地区,为自生自储型、古生新储型油气藏的有利勘探区。
Objectives：Carboniferous volcanic rocks widely developed at the Western edge of Luliang Uplift in Junggar Basin, due to the complex tectonic background and unclear prototype basin leads to the low degree of oil and gas exploration for a long time. This research studied the residual ocean closure time, the basin prototype and boundary, the basin basement property of the carboniferous at the Western edge of Luliang Uplift in Junggar Basin. Methods： Based on the seismic data and regional tectonic features analysis, applying volcanic chronology, petrology, and geochemistry analysis, the zircon LA-ICP-MS U-Pb dating, geochemistry and tectonic environment of the volcanic rock in Yingxi Depression were systematically studied.
Results：LA-ICP-MS zircon U-Pb ages of the Volcanic rocks from Well Ying-2 in Yingxi depression were mainly 310.8± 2.9 Ma. Volcanic rocks have the uniform characteristics with high SiO2 （ 62 % - 63 % ）, K20 （ 5.98 % -7.14% ）, low TiO2 （0.50% -0.65% ） and Mg#（ 43.4 - 58.4）, highA/CNK （ 〉 1 ）, generally show that this volcanic construction belong to high-K calc-alkaline acidic rock series formed in Late Carboniferous, having the feature of quasi aluminum. Besides, EREE are relatively high, and the rock has slight negative Euanomalies. Trace element diagram standardized by primitive mantle are characterized that LILE （K, Rb, Ba, La） is relatively enriched, while HFSE （Nb,Ta,Ti）depleted. The Geochemical characteristics above indicate Carboniferous rock in the Yingxi depression have the characteristics of the crust and mantle mixed source, which demonstrates that the rocks were the products of oceanic island arc.
Conclusions： Luxi area was still in the subduction-related environment in Late Carboniferous, moreover the subduction direction maybe is north-west to south-east. In late carboniferous epoch, peripheral orogenic belts and basins covering area of west Junggar as a whole was controlled by the west Junggar ocean,joined by limited ocean basin ,subduction--accretionary complex,chain island arc beh and arc or back-arc basin, the Yingxidepressionisa back-arc basin,is to explore, which is a potential favorable zones for exploring self-generated and Paleozoic source oil andgas reservoir.
出处
《地质论评》
CAS
CSCD
北大核心
2018年第1期77-90,共14页
Geological Review
基金
国家科技重大专项"碎屑岩层系大中型油气田富集规律与勘探关键技术"(编号:2011ZX05002-002)
中石化胜利油田科技攻关项目"乌伦古坳陷成藏主控因素分析及区带评价"(编号:YKK1607)的成果
关键词
陆西地区
晚石炭世
火山岩
地球化学
准噶尔盆地
Luxi
Late Carboniferous
Volcanic rocks
Geochemistry
Petrogenesis
Junggar basin
