【作者】 胡建勇；

【导师】 周安朝；

【作者基本信息】 太原理工大学 ， 矿产普查与勘探， 2007， 硕士

【摘要】 山西临县紫金山碱性杂岩体出露于吕梁山中段西翼，由于其典型的碱性岩岩石类型一直受到地学界的关注。论文对该杂岩体进行了详细系统地构造地质学、岩石学、岩石地球化学、同位素地球化学研究，并结合离石断裂带活动特征及其两侧沉积学的研究，探讨了碱性岩源区特征、成因机制、深部动力学及构造岩浆演化等问题。山西临县紫金山碱性杂岩体位于临县北西紫金山、大度山、尖山凹一带，大地构造位置处于稳定陆块——鄂尔多斯地块东部边缘晋西挠褶带内，靠近大型断裂——离石断裂带。紫金山碱性杂岩体形成于154～91Ma前，相当于晚中生代晚侏罗世-早白垩世，属于燕山运动的产物。紫金山岩体是一个多阶段、多期次形成的，侵入、喷出相均有的杂岩体；中心式侵入环状杂岩体为二长岩-霓辉正长岩-霞石正长岩-角砾岩（响岩）组合。紫金山碱性杂岩体的矿物组合比较接近，但矿物相对含量变化很大。主要矿物为钾长石，石英、斜长石仅见于早期侵入的二长岩中；霞石自中期的含霞霓辉正长岩出现，逐渐增多；霓辉石和黑云母随岩浆作用进展逐渐增多。临县紫金山碱性杂岩体具有低SiO₂，富碱、K₂O、Fe、贫Mg、中等CaO、Al₂O₃的岩石化学特征，属于中-基性高钾碱系列；岩石中Al₂O₃、Na₂O与SiO₂呈正相关关系，TFe₂O₃、MgO、CaO、P₂O₅与SiO₂呈负相关关系。球粒陨石标准化的稀土分布为LREE富集的右倾型，（La／Yb）_N=5.06～163.08；δEu在0.93～1.10之间，Eu异常不明显。在原始地幔标准化蛛网图上，富集大离子亲石元素（LILE，Cs、Rb、Ba、Th、U等），亏损高场强元素（HFSE，Nb、Ta、Ti等）。具有低的⁸⁷Sr／⁹⁶Sr值（0.704686～0.705198），低εNd（T）值，氧同位素δ¹⁸O=6.38～14.0SNOW‰。因此本文认为山西临县紫金山碱性杂岩体具有深源特征，形成于大陆板内富集地幔。而且在岩浆作用过程中结晶分异作用不明显，部分熔融起主导作用。碱性杂岩体由富集地幔多次批式部分熔融而成，部分熔融比例比较小。岩石类型变化的原因是岩浆混合作用、熔融程度以及岩浆所含挥发分有关。岩浆开始起源于上涌的软流圈边部或岩石圈上地幔，岩浆脉动式侵位形成环状中心侵入体。山西临县紫金山碱性杂岩体位于华北地块内部山西地块和鄂尔多斯地块交接部位，演化历程与两地块差异升降密切相关，其构造-岩浆活动更可能是太平洋板块碰撞华北板块的远程效应和深部软流圈活动的共同结果，其构造-岩浆演化对应于燕山运动。岩浆岩的侵位机制与区域构造环境密切相关，属于板内构造体系。与离石断裂带的活化和吕梁隆起有着密切关系。更多还原

【Abstract】 The Zijinshan alkaline complex outcrops on the western wing of in the middle part of the Luliang Mountain, Shanxi Province. Due to its typical alkaline rocktype, the Zijinshan complex has been attracted much attention from geological field. In this paper, the author has detailedly and systematically studied on the complex by the method of structuralgeology, lithology, petrochemistry, isotope geochemistry, combined with the investigation of Lishi fault actions feature and sedimentological alteration on its both sides, and discussed the scientific problems such as sources, mechanisms of genesis, deep dynamic processes and tectonic- magmatism evolutions.The Zijinshan alkaline complex is located to the northwest of Linxian Couty. Its tectonic location is in the Jinxi（Western Shanxi） flexural fold belt, which is in the east margin of Ordos block, and near the Lishi faults zone. Thealkaline complex was formed between 154～91 Ma b.p., corresponds to from thelate Jurassic to early cretaceous of late Mesozoic on geological era. It is outgrowth of the Yanshanian movement.The Zijinshan alkaline complex belong to intermediate-basic rocks, deep-sourced and hypabyssal alkaline complex rocks. It was formed through muti-petrogenesis stages and epochs, and included incursionand and eruptive facies. It is potassic alkaline, attributed to the alkaline-parlkaline series by alkali ratio. The rock assemblage of ring complex is consists of monzonite- aegirine augite syenite- nepheline syenite- breccia（phonolite） series. The mineral association of different type rocks are similar, but their relative content vary greatly. Their main minerals are potassium feldspar. Quartz and anorthose only appear in early intrusive monzonite; Nepheline appear from nepheline-bearing aegirine augite syenite in the medium period of incursion and their content increase progressively. Aegirine-augite and biotite increase with the phases of magmatism, too.The Zijinshan complex has the chemical characteristics of SiO₂-low alkali-rich, K₂O-rich, Fe-rich, Mg-lean, and CaO-medium, Al₂O₃-medium. There is positive correlation between the content of SiO₂ and Al₂O₃ with Na₂O, and there is negative correlation between the content of SiO2 and TFe₂O₃, MgO, with CaO. Their chondrite normalized REE patterns are characterized by high content of rare earth elements, no negative Eu anomalies and rich in LREE. In the primitive mantle-normalized trace element spider diagram, they are enriched in large ion lithophile elements（LILE） such as Cs, Rb, Ba and Th, and depleted in high field strength elements（HFSE） such as Nb, Ta and Ti. Meanwhile,according to isotope geochemistry, they have low value of～（87）Sr/～（86）Sr（ 0.704686～0.705198 ） and low value of eNd （ T ） ,δ¹⁸O6.38～14.0SNOW‰. All aboveshow that the complex was derived from enriched mantle in inner continent and the magma formation was mainly controlled by partial melting process.The Zijinshan complex is located in the transition zone between the Shanxi block and Ordos block in Northchina block. Its formation and evolution were closely related to differential uplift and depressed of two block. The tectonic-magmatism might be caused not only by recorded far-field effects produced by different inter-plate convergences, but also by reflected changes in deep-seated thermal tectonic regimes. The explore evolution model of the Zijinshan complex has close connection with its geotectonic setting, the activation of Lishi faults and the uplift of Luliang Mountain.更多还原