山西交城狐偃山碱性偏碱性杂岩体岩石学与地球化学特征研究.pdf

太原理工大学 硕士学位论文 山西交城狐偃山碱性偏碱性杂岩体岩石学与地球化学特征研究 姓名：康健 申请学位级别：硕士 专业：矿产普查与勘探 指导教师：周安朝 20100401 太原理工大学硕士研究生学位论文 1 山西交城狐偃山碱性偏碱性 杂岩体岩石学与地球化学特征研究 摘 要 山西狐偃山碱性偏碱性杂岩体出露于吕梁山东翼中段，由于其典型的 碱性岩岩石类型一直受到地学界的关注本文在野外地质工作的基础上， 通过对狐偃山碱性偏碱性杂岩体各岩带的野外地质特征、岩石学、矿物学 特征的研究，并结合其微量元素、稀土元素、同位素等地球化学特征的分 析，探讨了碱性岩源区特征和原生岩浆形成机制与演化机理及一些深部动 力学等问题，对探索华北克拉通中西部的破坏具有重要意义 狐偃山岩体属中- 基性碱性偏碱性杂岩体， 来源深、 侵位浅 是多阶段、 多期次岩浆作用的产物狐偃山碱性偏碱性杂岩体岩石组合为等粒近等粒 二长岩- 斑状似斑状二长岩- 斑状含石英二长岩- 石英正长斑岩- 霓辉二长斑 岩- 正长斑岩组合，狐偃山碱性偏碱性杂岩体形成于 1 0 7 . 0 6 - 1 5 9 . 5 4 1 M a 前， 相当于晚中生代晚侏罗世- 早白垩世。

狐偃山碱性偏碱性杂岩体岩石的结构构造除少数最早的等粒近等粒状 （中粒）二长岩外，均为斑状结构明显的岩石，更晚期的斑岩类显示出流 动构造，岩体岩石组合属二长岩—正长岩组合狐偃山碱性偏碱性杂岩体 的矿物组成主要为正长石、斜长石、辉石、角闪石、石英从燕山早期侵 入的等粒近等粒二长岩到燕山晚期侵入的正长斑岩总的演化趋势为：正长 石含量由少到多；斜长石含量由多到少，斜长石牌号由大到小；石英含量 由少到多又到少，在石英正长岩中含量最高；辉石含量变化不大，在 10% 左右，角闪石含量比较少，一般不足 3%以上演化规律在岩石学方面的体 太原理工大学硕士研究生学位论文 2 现为：由二长岩类演化为正长岩；岩石由偏碱性岩演化为碱性岩 狐偃山碱性杂岩体全碱含量高，均属于钾质的碱性- 偏碱性系列岩石， 过铝质、 贫钙、 镁、 较富铁 岩石中N a2O 与 S i O2呈正相关关系， A l2O3、 T F e2O3、 M g O 、C a O 、P2O5与 S i O2呈负相关关系球粒陨石标准化的稀土分布为 L R E E 富集的右倾型， （L a / Y b ）N值较高， 为 8 . 2 2 ～9 . 0 1 ； δE u 在 1 . 0 8 - 1 . 3 1 之间， E u 均为正异常。

在微量元素标准化蛛网图上，以显著的P b 、H f 、S r 、B a 、 C s 、T h 、U正异常和 C r 、N i . C o负异常为特征具有低的 8 7 S r / 8 6 S r值 （0 . 7 0 5 6 4 3 ～0 . 7 0 6 1 1 3 ） ，εN d （T ）值小于 0 山西狐偃山碱性偏碱性杂岩体来源于局部熔融作用对岩浆形成起主导 作用的富集地幔，它是岩浆多期次脉动式侵入后冷凝形成的，岩石圈地幔 岩为尖晶石二辉橄榄岩关于不同时期形成的岩石类型不同，是因为在不 同的侵入阶段，尖晶石二辉橄榄岩的熔融程度不同岩浆作用时期与华北 克拉通解体时限一致充分说明对狐偃山碱性偏碱性杂岩体的研究不仅可 以揭示华北板块内部岩石圈地幔的组成特征，而且能为进一步探索华北克 拉通解体的动力学机制提供重要信息 关键词 碱性杂岩体，地球化学，岩浆作用，山西交城狐偃山 太原理工大学硕士研究生学位论文 1 A STUDY OF HUYANSHAN ALKALINE COMPLEX CHARICTERISTIC OF PETROLOGY AND GEOCHEMISTRY IN JIAOCHENG COUNTY, SHANXI PROVINCE, CHINA ABSTRACT The Hanshan alkaline complex outcrops in the middle part on the eastern wing of the Lü liang Mountain, Shanxi Province. Due to its typical alkaline rocktype, the Huyanshan complex has been attracted much attention from geological field. In this paper, based on field geological work, the author has detailedly and systematically studied the field geological and mineral characteristic and combinded with the analysis of microelement and lanthanon and isotope and discussed the scientific problems such as sources, mechanisms of genesis, deep dynamic processes and tectonic- magmatism evolutions. It is very significant to explore the destruction of the central and western North China Craton. The Huyanshan alkaline complex belongs to intermediate- basic rocks, deep- sourced and hypabyssal alkaline complex rocks. It was formed through muti- petrogenesis stages and epochs, and included incursionand facies. It is potassic alkaline, attributed to the alkaline- parlkaline series by alkali ratio. The rock assemblage of ring complex is consists of equal granularity monzonite - quartz monzonite- quartz syenite- aegirine augite monzonite- syenite series. The alkaline complex was formed between 155～102Ma b.p.,corresponding to the late Jurassic to early cretaceous of late Mesozoic on geological era. It is outgrowth of the Yanshan movement. The Huyanshan alkaline complex belongs to monzonite- syenite series.Its mineral includes potassium feldspar anorthose augite and less hornblende and 太原理工大学硕士研究生学位论文 2 quartz. The evolution tendency is that potassium feldspar become from many to few, （— ） 2V from big to small, anorthose from many to few, quartz from few to many to few and last disappear.The hornblende is less than 3%.The tendency incarnate from monzonite to syenite. The Huyanshan alkaline complex mineral formation and evolution embody from eary to late no reverse tendency. The Huyanshan alkaline complex has the chemical characteristics of SiO2- low alkali- rich, K2O- rich, Fe- rich, Mg- lean, and CaO- medium, Al2O3- medium. 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. All above show that the complex was derived from enriched mantle in inner continent and the magma formation was mainly controlled by partial melting process.Different types rocks was formed in different intusive phase because mantle rock has different extent in melting process. The Huyanshan alkaline complex 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 Huyanshan complex has close connection with its geotectonic setting.The study to Huyanshan alkaline complex can reveal the formation of Hua Bei mantle rock,what’ s important,it extends more significant message and methord to the dynamic mechanism of the destruction of the central and western North China Craton. KEY WORDS alkaline complex, magmatism, Huanshan in Jiaocheng County 太原理工大学硕士研究生学位论文 1 第一章 绪 论 1 . 1 碱性岩概述 碱性岩历来就是岩石学。