四川矿山梁子苦橄玢岩成因及其成矿意义

发布时间：2018-03-10 06:15

  本文选题：平川铁矿　切入点：苦橄玢岩岩床　出处：《中国地质大学(北京)》2017年硕士论文　论文类型：学位论文

【摘要】：作为与大规模玄武岩喷发和基性超基性岩侵入有关的磁铁矿床,平川铁矿也是攀西地区重要的铁矿床之一。但是,平川铁矿中苦橄玢岩成因并未引起人们的重视,所以苦橄玢岩的形成以及与平川铁矿的成因联系是我们本次研究的重点。本人选择四川盐源平川铁矿的主矿区矿山梁子铁矿为主要研究区域,运用地球化学及电子探针等方法,对矿山梁子铁矿床苦橄玢岩中的橄榄石进行深入研究。在岩相学镜下观察观察的基础上,通过对橄榄石、辉石等主要造岩矿物的电子探针成分分析,揭示苦橄玢岩原始岩浆的演化过程及其形成的物理化学条件。最终得出矿山梁子矿段苦橄玢岩中含有来源各异的橄榄石斑晶,根据其不同的镜下特征及地球化学数据分别定名为粗晶橄榄石、微晶橄榄石、包裹体橄榄石及“鬣刺”状橄榄石。不同类型橄榄石具有不同的成分特征及形成温度,微晶橄榄石的形成温度最高,为1335℃。粗晶橄榄石的初始结晶温度较低,为1295℃。包裹体橄榄石为1292℃,但橄榄石的结晶温度并未发生变化,说明了其相对稳定的特征。“鬣刺”状橄榄石的初始结晶温度相对较低,为1272℃,但随着橄榄石结晶的进行,温度持续降低,显示了其连续结晶的状态,说明了只有“鬣刺”状橄榄石才是苦橄玢岩原始岩浆结晶的产物。除包裹体橄榄石外,其他三类橄榄石边部的结晶温度相近,说明了其最终在固结成岩之前经过岩浆多期次混合形成我们现今所见的苦橄玢岩时的温度。运用CSD计算橄榄石斑晶的体积含量。剔除其他来源的橄榄石斑晶。即粗晶橄榄石、微晶橄榄石及包裹体橄榄石,另外保留“鬣刺”状橄榄石。剔除橄榄石后可以发现苦橄玢岩的SiO_2含量为48.41%,故苦橄玢岩的原始岩浆并非苦橄质岩浆。由于存在有不同类型橄榄石,苦橄玢岩的形成应该是一个开放环境。在这个开放的环境中,整体未固结的原始岩浆熔体会发生组分的带入或带出,这时含矿流体的加入导致了岩浆房的活化并从其他岩浆房中带入了其他岩浆房中结晶出来的橄榄石晶体。之后侵入至近地表后固结成岩,形成我们现今所见的苦橄玢岩。其作为平川铁矿的致矿侵入体,且作为铁矿的屏蔽层更加有利于成矿。
[Abstract]:As a magnetite deposit related to large-scale basalt eruption and basic ultrabasic intrusion, Pingchuan Iron Mine is also one of the important iron ore deposits in Panxi area. However, the genesis of picrite porphyrite in Pingchuan Iron Mine has not attracted much attention. Therefore, the formation of picrite porphyrite and its genetic relationship with Pingchuan Iron Mine are the key points of our research. I have chosen Liangzi Iron Mine, the main mine of Pingchuan Iron Mine in Yanyuan, Sichuan Province, as the main research area, using geochemical and electron probe methods. The olivine in picrite porphyrite of Liangzi iron deposit in mine is studied in depth. Based on the observation of lithofacies, the electron probe analysis of the main rock-forming minerals such as olivine and pyroxene is carried out. The evolution process and physical and chemical conditions of the primitive magma of picrite porphyrite are revealed. Finally, the porphyrite porphyrite from various sources is found in the picrite porphyrite of Liangzi Mine. According to their different microscopic characteristics and geochemical data, they are named as coarse olivine, microcrystalline olivine, inclusion olivine and "iguana" olivine, respectively. Different types of olivine have different composition characteristics and formation temperature. The formation temperature of microcrystalline olivine was 1335 鈩，

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