Variations in Chemical Composition of Clay Minerals and Magnetic Susceptibility of Hydrothermally Altered Rocks in the Hishikari Epithermal Gold Deposit, SW Kyushu, Japan     

Hiroyasu Murakami 《Resource Geology》2008,58(1):1-24

Hydrothermal alteration, involving chiefly chlorite and illite, is extensively distributed within host rocks of the Pleistocene Hishikari Lower Andesites (HLA) and the Cretaceous Shimanto Supergroup (SSG) in the underground mining area of the Hishikari epithermal gold deposit, Kagoshima, Japan. Approximately 60% of the mineable auriferous quartz‐adularia veins in the Honko vein system occur in sedimentary rocks of the SSG, whereas all the veins of the Yamada vein system occur in volcanic rocks of the HLA. Variations in the abundance and chemical composition of hydrothermal minerals and magnetic susceptibility of the hydrothermally altered rocks of the HLA and SSG were analyzed. In volcanic rocks of the HLA, hydrothermal minerals such as quartz, chlorite, adularia, illite, and pyrite replaced primary minerals. The amount of hydrothermal minerals in the volcanic rocks including chlorite, adularia, illite, and pyrite as well as the altered and/or replaced pyroxenes and plagioclase phenocrysts increases toward the veins in the Honko vein system. The vein‐centered variation in mineral assemblage is pronounced within up to 25 m from the veins in the peripheral area of the Honko vein system, whereas it is not as apparent in the Yamada vein system. The hydrothermal minerals in sandstone of the SSG occur mainly as seams less than a few millimeters thick and are sporadically observed in halos along the veins and/or the seams. The alteration halos in sandstone of the SSG are restricted to within 1 m of the veins. In the peripheral area of the Honko vein system, chlorite in volcanic rocks is characterized by increasing in Al in its tetrahedral layer and the Fe/Fe + Mg ratio toward the veins, while illite in volcanic rocks has relatively low K and a restricted range of Fe/Fe + Mg ratios. Temperature estimates derived from chlorite geothermometry rise toward the veins within the volcanic rocks. The magnetic susceptibility of tuff breccia of the HLA varies from 21 to less than 0.01 × 10^?3 SI within a span of 40 m from the veins and has significant variation relative to that of andesite (27–0.06 × 10^?3 SI). The variation peripheral to the Honko vein system correlates with an increase in the abundance of hematite pseudomorphs after magnetite, the percentage of adularia and chlorite with high Fe/Fe + Mg ratios, and the degree of plagioclase alteration with decreasing distance to the veins. In contrast, sedimentary rocks of the SSG maintain a consistent magnetic susceptibility across the alteration zone, within a narrow range from 0.3 to 0.2 × 10^?3 SI. Magnetic susceptibility of volcanic rocks of the HLA, especially tuff breccia, could serve as an effective exploration tool for identifying altered volcanic rocks.  相似文献   

桃山大布铀矿床绿泥石特征及其形成环境   总被引：1，自引：0，他引：1  

于秋莲  张展适  陈载林 《铀矿地质》2014,(6):340-344

花岗岩型铀矿中,绿泥石化作为热液蚀变的重要类型之一,其种类多样,据此可以推断其形成环境。笔者在岩石薄片观察的基础上,通过对绿泥石进行电子探针成分分析,认为桃山大布铀矿床的绿泥石主要为铁绿泥石、蠕绿泥石,其形成于中低温酸性热液作用环境。  相似文献   

川南玄武岩气孔中硅铁灰石杏仁体的特征与研究     

张良钜  刘靖娜  曾伟来  李东升  黎琪  曾南石  阮青锋 《岩石矿物学杂志》2014,33(5):917-923

川南普格杏仁状玄武岩气孔中产出硅铁灰石、绿泥石、石英、方解石、沥青等5种不同成分类型的杏仁体。硅铁灰石杏仁体呈圆形或椭圆形,其直径多为5～8 mm,由杏仁体壁至中心,依次分别产出石英→铁镁绿泥石→硅铁灰石。硅铁灰石晶体呈铁黑色、薄板状,由5个平行双面单形组成。微区X射线衍射分析结果显示,硅铁灰石属三斜晶系,空间群为P1 。化学成分分析表明,硅铁灰石氧化物含量(ω_B/%)为SiO₂ 53.55%、CaO 18.84%、Fe₂O₃ 13.65%、FeO 9.68%、MgO 1.44%、H₂O⁺1.74%,FeO/Fe₂O₃=0.71;铁镁绿泥石氧化物含量(ω_B/%)为SiO₂ 33.17%、Al₂O₃ 13.03%、Fe₂O₃ 8.45%、FeO 13.06%、MgO 18.82%、H₂O⁺12.12%、CaO 0.87%,FeO/Fe₂O₃=1.55。硅铁灰石杏仁体的矿物组合变化表明,玄武岩晚期的成矿热液由富Mg、Fe向富Si、Ca演化,硅铁灰石是由偏酸性、弱还原环境向偏碱性、弱氧化环境转化时所形成的过渡性产物。  相似文献   

Towards a Higher Comparability of Geothermometric Data obtained by Raman Spectroscopy of Carbonaceous Material. Part I: Evaluation of Biasing Factors   总被引：1，自引：0，他引：1  

Nils K. Lünsdorf  Istvan Dunkl  Burkhard C. Schmidt  Gerd Rantitsch  Hilmar von Eynatten 《Geostandards and Geoanalytical Research》2014,38(1):73-94

Raman spectroscopy of carbonaceous material (RSCM) is frequently used to determine metamorphic peak temperatures from the structural order of carbonaceous material enclosed in metasediments. This method provides a quick, robust and relatively cheap geothermometer. However, the comparability of the RSCM parameter is low as there are at least three major sources of biasing factors. These sources are the spectral curve‐fitting procedure, the sample characteristics itself and the experimental design including the used Raman system. To assess the impacts of the biasing factors on RSCM, a series of experiments was performed. The experiments showed that curve‐fitting is strongly influenced by individual operator‐bias and the degrees of freedom in the model, implying the need for a standardised curve‐fitting procedure. Due to the diversity of components (optics, light detection device, gratings, etc.) and their combinations within the Raman systems, different Raman instruments generally give differing results. Consequently, to estimate comparable metamorphic temperatures from RSCM data, every Raman instrument needs its own calibration. This demands a reference material series that covers the entire temperature calibration range. Although sample heterogeneity will still induce some variation, a reference material series combined with standardised curve‐fitting procedures will significantly increase the overall comparability of RSCM data from different laboratories.  相似文献   

不同粘土矿物对赖氨酸的吸附行为对比研究          下载免费PDF全文

开炜  蔡元峰  蔡进功  季峻峰 《高校地质学报》2018,24(5):671

以皂石、高岭石、绿泥石和伊利石为原材料,分别与赖氨酸进行反应,研究赖氨酸在上述粘土矿物上的吸附行为, 并运用粉末X-射线衍射技术（XRD）、傅里叶变换红外吸收光谱术（FTIR）和热重（TG）等分析方法,表征反应前后粘土 矿物的变化。实验结果表明,不同粘土矿物对赖氨酸的吸附等温线均符合Freundlich等温方程,且不同粘土矿物对赖氨酸的 饱和吸附量大小顺序为：皂石>蒙脱石>绿泥石>高岭石>伊利石;XRD结果表明皂石对赖氨酸的吸附发生在矿物层间,而绿 泥石、高岭石和伊利石对赖氨酸的吸附主要在矿物表面进行;FTIR和TG结果表明赖氨酸主要取代粘土矿物层间吸附水,以 氢键的形式与Si-O-Si(IVAl)键合。实验结果将有助于进一步探明环境中粘土矿物对有机质的吸附机理。  相似文献   

致密砂岩储层自生矿物特征及其对储集性能的影响——以鄂尔多斯盆地陇东地区长3油组为例   总被引：1，自引：1，他引：0  

张航  廖明光  姚泾利  廖纪佳 《沉积与特提斯地质》2017,37(3):22-31

鄂尔多斯盆地陇东地区长3油组是近年来该区油藏评价新层系,分析砂岩中自生矿物特征对储层致密化机理研究有重要的意义。长3油组主要发育岩屑长石砂岩和长石岩屑砂岩,平均孔隙度为13.35%,渗透率为4.90×10-3μm2,为低孔低渗透致密储层,目前砂岩处于中成岩阶段A期。通过铸体薄片、扫描电镜、阴极发光、电子探针、X射线衍射等技术和手段,研究自生矿物的含量、类型、分布及成岩共生序列等特征。研究结果表明,早期绿泥石包膜有利于原生孔隙的保存,后期孔隙式充填降低了岩石孔隙度和渗透率;伊利石易堵塞孔隙喉道,导致储层物性变差;高岭石沉淀往往与长石溶解伴生,局部溶蚀作用强烈;晚期含铁碳酸盐胶结作用发育,镜下溶蚀现象少见,对储层的发育有破坏作用;石英次生加大边和自生晶粒占据了大量孔隙空间,同时石英也增强了岩石的抗压能力,对孔渗影响不大。总体上,长3油组自生矿物胶结对储集物性起负面效应,是砂岩储层致密化的主要因素之一。  相似文献   

碳酸盐岩层系热历史恢复的有机质自由基古温标研究   总被引：2，自引：1，他引：1  

邱楠生  李慧莉  金之钧  朱映康 《地质学报》2006,80(3):390-397

古温标是恢复沉积盆地热演化历史的重要指标之一。目前,有众多的古温标用于碳酸盐岩层系热历史的恢复,既有沥青反射率(Rb)、牙形石色变指数(CAI)、镜状体反射率、有机质自由基浓度(N)、激光拉曼光谱等有机质古温标,也有矿物的裂变径迹热定年、岩石声发射、伊利石结晶度等矿物古温标,但他们都有不同的适用范围。本文针对有机质自由基浓度作为古温标在碳酸盐岩层系热历史恢复中的应用进行了探索研究。根据不同受热时间和加热温度下的热模拟试验,分析了型和型有机质的自由基浓度的热演化特征,得到了自由基浓度与时间-温度(TTI)的定量关系;由此建立了自由基浓度(N)与时间-温度(TTI)的定量模型并将之应用于塔里木盆地TZ12井的热历史研究。依据自由基浓度古温标模拟得到的TZ12井区奥陶纪时期的古地温梯度为3℃/100m左右,该结果与前人对该地区热史研究的结论及本研究中依据磷灰石裂变径迹模拟的结果相一致。对于经历了多期构造运动的下古生界碳酸盐岩层系的热史恢复,最好是多种古温标并用,多种方法综合运用,才能精确地恢复有机质的热演化史。  相似文献   

苗儿山中段向阳坪铀矿床绿泥石特征及其成岩成矿意义     

谭双  陈琪  万建军  高翔  吴昆明  欧阳平宁  张涛 《岩石矿物学杂志》2022,41(6):1097-1108

向阳坪铀矿床是近年在苗儿山地区发现的重要矿床,绿泥石化是向阳坪铀矿床重要的蚀变类型和找矿标志。本文对向阳坪矿床发现的铀-绿泥石型矿石的蚀变矿物学特征进行了系统地观察,结合电子探针原位微区分析,查明了绿泥石相关矿物的共生组合关系,获得了其化学定量分析结果,划分了绿泥石的种类及其形成条件,在此基础上探讨了绿泥石性质及其对铀成矿的启示。结果显示,向阳坪铀矿床绿泥石可分为黑云母蚀变型、裂隙充填型、铀矿物相关型和黏土矿物吸附铁镁质转变型4种。铁硅协变图解表明向阳坪矿床主体为铁镁绿泥石,部分为蠕绿泥石,含少量的密绿泥石。据经验公式计算所得绿泥石形成温度变化范围为190~265℃,平均239℃,属中低温热液蚀变,其形成机制包括溶蚀-结晶和溶蚀-迁移-结晶2种。绿泥石化为铀成矿过程提供了所需的环境,促进了铀的活化、迁移并最终沉淀成矿。  相似文献   

岩石变形对粘土矿物结晶生长影响的初步研究——以江西金山金矿为例          下载免费PDF全文

李晓峰华仁民  毛景文季峻峰 《岩石矿物学杂志》2003,22(3):265-272

作为流体作用过程中水—岩反应的产物，粘土矿物可以帮助人们认识水—岩反应的机制和流体活动的特征。本文以江西金山金矿为例，通过对热液蚀变粘土矿物伊利石和绿泥石结晶度、平均结晶大小和晶格应变的测定，讨论了岩石变形对伊利石和绿泥石结晶生长差异的影响。在岩石应变较弱、水／岩比较小的糜棱岩带，伊利石的平均结晶大小与结晶度成负相关，而在岩石应变较强、水／岩比较大的超糜棱岩带，绿泥石的平均结晶大小与结晶度成正相关。由应变较弱的蚀变糜棱岩带到应变较强的蚀变超糜棱岩带，伊利石的结晶度有变小的趋势，而绿泥石的结晶度则基本保持不变。认为在成矿流体作用过程中，粘土矿物的形成和特点不仅受水／岩比的影响，而且在岩石变形过程中，岩石的应变和恢复速率也影响粘土矿物的结晶大小；伊利石和绿泥石平均结晶大小与其结晶度之间的关系可以反映岩石变形的机制和行为。  相似文献