内蒙古东升庙、甲生盘中元古代SEDEX矿床同生断裂活动及其控矿特征

东升庙Zn -Pb -Cu矿床和甲生盘Zn -Pb矿床具有鲜明的层控特征, 前者产在中元古界狼山群二组中, 后者则局限在中元古界渣尔泰山群阿古鲁沟组第二岩段内.二者产出层位相当, 根据(1) 含矿地层有岩相(性) 的突变; (2) 含矿岩段地层厚度顺走向和倾向变化性大、厚度突变现象明显, 并存在层间砾岩和滑塌角砾岩, 角砾成分为大小不一的白云石大理岩块、碳质千枚岩、石英团块、凝灰岩块、变粒岩块、变质火山岩碎块、黑云母片岩碎块; (3) 矿体总体呈层产出, 但有一些Zn -Pb -Cu矿体突然变薄, 甚至消失, 形成鱼头状矿体, 且发育角砾状矿石, 角砾成分与层间砾岩的相同, 且还含Pb -Zn矿石或Py矿石角砾; (4) 火山岩或凝灰岩夹层顺同生断裂带分布, 确认其唯一容矿岩组形成过程中有明显的同生断裂活动.同生断裂系统是含矿热水和火山熔浆进入沉积盆地的通道, 是两大矿床形成的有利因素, 但其活动频率、规模与持续时间的差异, 也造成不同的矿床规模和矿体分布.东升庙矿床同生断裂活动时限相对长、矿床规模大、矿种多.甲生盘矿床同生断裂活动时间短, 矿床规模为大型.      

山西高家山铝土矿稀土元素地球化学特征及意义

山西沁源县高家山铝土矿床是山西省地质调查院于2013年发现的大型铝土矿床。本文通过对高家山铝土矿的研究,分析并研究铝土矿样品的稀土元素含量和地球化学特征,探讨稀土元素对于本区铝土矿成因和环境的指示意义。研究表明:该区铝土矿体的ΣREE总量较大,轻稀土元素相对富集,具有明显的Eu负异常;利用稀土元素图解大致反映出底板碳酸盐岩是本区铝土矿床的主要物质来源,铝土矿形成于被动大陆边缘地带海相或海陆过渡相环境。ΣREE与Al2O3含量相关性不大。本区矿床稀土元素含量达到或超过综合利用标准,具有巨大的潜在经济价值。     

Large tufa mounds,Searles Lake,California

Mounds that have formed around spring vents occur in a variety of environmental settings, many at sites generally difficult or inaccessible for sampling. In contrast, over 500 tufa mounds occur in the dry bed of Searles Lake, California. The mounds range from minor features to 45 m in height; most are 5 to 12 m high. These mounds, composed of calcite and aragonite, formed associated with spring vents in the Pleistocene lake bottom. Thus, analyses of these mounds in Searles Lake provide a model with regard to the origin and architecture of tufa mounds. The mounds consist of four distinctive tufa facies. The initial deposits consist of porous tufa, including the innermost (porous 1) and the outermost (porous 2) deposits, followed by nodular tufa, then columnar tufa, and laminated crusts. There are two simple sequences of tufa deposition. The first sequence is from porous 1 to nodular to laminated crusts and, finally, to porous 2. A second sequence consists of: porous 1 to columnar to laminated crusts and, lastly, to porous 2. Facies changes are a response to changes in environmental conditions from deep water (porous 1 facies) to an essentially dry lake phase (during and after the formation of laminated crusts facies), to deep water (porous 2 facies) and, at the present time, totally dry. The primary constituents that comprise the tufa deposits include thin laminae, pisoids, spherulites, peloids and stromatolite‐like crusts. On the microscopic scale, these constituents dominantly make up nano‐spheres, micro‐rods and rod‐like crystals, as well as other calcified bodies. These constituents are interpreted to be the calcified remains of bacterial bodies. These findings suggest that microbial participation in the construct of other mounds should be a major concern of investigation, both for terrestrial and extraterrestrial spring‐fed mounds.     

氟碳铈矿U-Pb定年技术研究

本文以稀土矿床中的常见副矿物氟碳铈矿为研究对象,通过优化实验条件和仪器参数,分别采用激光剥蚀多接收电感耦合等离子体质谱法(LA-MC-ICP-MS)和同位素稀释热电离质谱法(ID-TIMS)对氟碳铈矿样品SAM进行U-Pb定年技术研究,并将此两种方法得到的结果进行对比。LA-MC-ICP-MS得到的U-Pb年龄为(409±18)Ma(N=27,MSWD=4.5),ID-TIMS得到的206Pb/238U U-Pb年龄为(407.8±3.3)Ma(N=3,MSWD=0.029),两种方法得到的U-Pb年龄结果在误差范围内一致。通过比较两种方法的实验流程和结果,总结了各自的优缺点,为氟碳铈矿U-Pb定年方法选择提供了参考依据。     

K-Ar Ages of Granitic Magmatism and Related Pegmatite Formation at the Umanotani-Shiroyama Mine, Shimane Prefecture, SW Japan and Their Bearings on Cooling History

Abstract. The Umanotani-Shiroyama pegmatite deposits, the largest producer of K-feldspar and quartz in Japan, are of typical granitic pegmatite. Ilmenite-series biotite granite and granite porphyry, hosting the ore deposits, and biotites separated from these rocks yielded K-Ar ages ranging from 89.0 to 81.4 Ma and 95.2 to 93.7 Ma, respectively. Muscovite and K-feldspar separated from the ore zone yielded K-Ar ages with the range of 96.2 to 93.1 Ma and 87.3 to 80.7 Ma, respectively. Muscovites from quartz-muscovite veins in the ore zone and in the granite porphyry yielded K-Ar ages of 90.4 and 76.3 Ma, respectively. K-feldspar is much younger in age than coexisting muscovite. It is noted that the K-Ar ages of biotite separates and the whole-rock ages are identical to those of muscovite and K-feldspar in the ore zone, respectively. These time relations, as well as field occurrence, indicate that the formation of the pegmatite deposits at the Umanotani-Shiroyama mine is closely related in space and time to a series of granitic magmatism of ilmenite-series nature. Using closure temperatures of the K-Ar system for biotite and K-feldspar (microcline), cooling rate of the pegmatite deposits is estimated to be about 82C/m.y. at the beginning, but slowed down to about 15C/m.y. in the later period.     

四川昌台农都柯金银矿矿床地质特征及成矿远景

农都柯火山岩浅成低温热液型金银矿床系在三江地区义敦岛弧带被首次发现,经初步评价达到中型规模。矿床赋存于流纹质火山碎屑岩中,受北北西向剪切带控制,矿体呈透镜状或似层状,基本顺层产出。围岩蚀变强烈,以硅化为主,次为绢云母化和重晶石化。矿石由黄铁矿、闪锌矿、自然金、辉锑铅矿、砷黝铜矿、辉锑矿、辉锑银铅矿、雄黄、雌黄等组成,为典型的低温热液矿物组合。主矿化温度发生在200℃以下,矿化元素除Ag、Au外,As、Sb、Hg也达到或接近工业品位。通过地球物理、地球化学方法的测量,成矿远景较好。     

华南花岗岩型铀矿床成矿机理研究进展

本文介绍了华南花岗岩型铀矿床地质特征,系统总结了前人对其成矿热液来源、物质来源,铀的迁移沉淀机制、碱交代及花岗岩与成矿的关系等方面的研究成果。指出铀源体中的晶质铀矿及富铀矿物在深部相对还原的环境中被氧化而进入成矿热液中起主要作用的可能是大量幔源F和放射性衰变诱发产生的氧及碱交代溶蚀作用,热液中的大部分U6 主要被S2-和Fe2 等还原剂在浅部相对氧化的环境中还原成矿;给出了一种较简易的物质来源定量方法和铀成矿模式。     

李坝式金矿床成矿作用及矿床类型探讨

李坝式金矿床成矿作用过程分为成矿元素初始富集期和构造叠加热液改造成矿期，岩浆活动主号是通过改变矿床地质体物化条件而促进矿化体的形成，并有部分岩浆物质参与成矿。该矿床与国内外经典卡林型金矿床具有较大的可比性，但是由于缺乏低温矿物组合以及与岩浆活动的亲密性证据，该矿床应属广义上的卡林型金矿床。     

中国东北部陆缘内生金矿床成因类型、成矿时代及地球动力学背景

中国东北部陆缘是我国内生金矿床较为发育的地区之一,以成矿作用复杂、蕴藏丰富的金资源量倍受国内外地质学家关注。通过对该区内生金矿的地质和成矿年代的系统研究,初步将该区内生金矿床划分为中温热液金矿床、接触交代-热液金矿床、斑岩型/类斑岩型金铜矿床和浅成低温热液金矿床4种主要成因类型和3个重要成矿期（170～160 Ma、130～110 Ma和110～90 Ma）。结合同位素地球化学特征,进一步确定中温热液金矿床的成矿物质主要来自下地壳源,成矿作用与中生代燕山早期古太平洋板块俯冲作用引发的中国东部大陆边缘岩石圈减薄及拆沉的动力学过程密切相关;接触交代-热液金矿床的成矿物质来源于年轻地壳,成矿作用与古太平洋板块俯冲引起的岩石圈减薄拆沉的伸展构造背景下的岩浆接触交代作用更为密切;而斑岩型/类斑岩型金铜矿床和浅成低温热液金矿床的成矿物质来源为壳幔混合源,其成矿发生在古太平洋板块向亚洲大陆正北向俯冲转入Izanagi Farallon板块西向俯冲的构造转换期。     

大兴安岭北部主要金属矿床成矿系列和区域矿床成矿谱系

文章以大兴安岭北部内生金属矿床、海相火山岩型硫铁矿矿床和砂金矿床为研究对象,按照矿床成矿系列的学术思想将其划分为7个矿床成矿系列,即:多宝山地区与加里东期中酸性火山_侵入活动有关的铜、钼矿床成矿系列,呼玛地区与华力西期辉长岩和花岗岩有关的铁、钛、金矿床成矿系列,伊尔施_黑河地区与华力西期花岗岩和海相火山岩有关的铁、铜、锌、硫铁矿矿床成矿系列,牙克石地区与华力西期海相中基性火山岩有关的铁、锌、硫铁矿矿床成矿系列,得尔布干地区与印支期_燕山期中酸性火山_侵入活动有关的铅、锌、银、铜、钼、金矿床成矿系列,伊尔施_呼玛地区与燕山期中酸性火山_侵入活动有关的金、铁、锌、铜、钼、钨矿床成矿系列和黑龙江流域与第四纪冲积沉积作用有关的砂金矿床成矿系列。大兴安岭北部区域矿床成矿谱系表明,从奥陶纪到新生代该区不同构造单元经历了7个主要的构造演化及成矿时期,依次出现奥陶纪岛弧环境的斑岩型矿床、泥盆纪陆块边缘拉张环境的岩浆型和热液脉型矿床、泥盆纪—石炭纪俯冲_碰撞环境的海相火山岩型和矽卡岩型矿床、石炭纪弧后盆地环境的海相火山岩型矿床、晚三叠世—早白垩世俯冲_碰撞_后碰撞环境的斑岩型、热液脉型、浅成低温热液型和矽卡岩型矿床、早侏罗世—早白垩世俯冲环境的斑岩型、热液脉型、浅成低温热液型和矽卡岩型矿床和新生代地壳差异运动带砂金矿床。大兴安岭北部优势矿种为铜、钼、金、银、铅、锌,主攻矿床类型为斑岩型、热液脉型、低硫化浅成低温热液型、冲积型和海相火山岩型。