The Mechanism of Structural Control of Ore Formation and Geochemical Characteristics in the Massive Sulfide Deposits of the Wushan Copper Ore Field,Jiangxi

The ore-controlling mechanism of the bedding fault system in the massive sulfide deposits of the Wushancopper orefield may be generalized as the control of ore deposition by optimum surface in an ore-formingstructural trap. The mechanism has three major features: (1) timing of mineralization; (2) positioning of hostformation; and (3) dependence of ore-controlling structure on properties of rocks. The 'optimum surface' is adivisional structural plane which marks obvious difference in physical, chemical and mechanical properties andis favorable for mineralization. It is also a unity of structures. lithofacies and orebodies. The structural and geochemical characteristics of the ore deposits indicate the migration trend of the ma-jor characteristic clements in the ore-controlling fault belt: elements with a small radius (Si, Fe, Mg and Al)moved towards and concentrated at the center of the belt while large-radius ones (Ca, K and Na) were remotefrom the center.

Alkaline-lacustrine deposition and paleoenvironmental evolution in Permian Fengcheng Formation at the Mahu sag, Junggar Basin,NW China

Alkaline-lacustrine deposition and its evolution model in Permian Fengcheng Formation at the Mahu sag, Junggar Basin were investigated through core and thin-section observation, geochemical and elemental analysis, logging response and lithofacies identification. Six lithofacies are developed in the Fengcheng Formation. The Feng 2 Member(P1 f2) is dominated by lithofacies with alkaline minerals, while the upper part of the Feng 1 Member(P1 f1) and the lower part of the Feng 3 Member(P1 f3) are primarily organic-rich mudstones that are interbedded with dolomite and dolomitic rock. Paleoenvironment evolution of Fengcheng Formation can be divided into 5 stages, which was controlled by volcanic activity and paleoclimate. The first stage(the early phase of P1 f1) was characterized by intensive volcanic activity and arid climate, developing pyroclastics and sedimentary volcaniclastic rocks. The secondary stage(the later phase of P1 f1) had weak volcanic activity and humid climate that contributed to the development of organic-rich mudstone, forming primary source rock in the Fengcheng Formation. The increasing arid climate at the third stage(the early phase of P1 f2) resulted in shrinking of lake basin and increasing of salinity, giving rise to dolomite and dolomitic rocks. The continuous aird climate, low lake level and high salinity at the fourth stage(the later phase of P1 f2) generated special alkaline minerals, e.g., trona, indicating the formation of alkaline-lacustrine. The humid climate made lake level rise and desalted lake water, therefore, the fifth stage(P1 f3) dominated by the deposition of terrigenous clastic rocks and dolomitic rocks.

Geological and Geochemical Characteristics and Genesis of the Shaxi Porphyry Copper (Gold) Deposits, Anhui Province

The Shaxi porphyry copper (gold) deposits are a typical example of porphyry copper deposits associated with diorite in eastern China. Quartz diorite, which hosts the deposits, has a Rb-Sr isochron age of 127.9 ± 1.6 Ma. Geochemically, the rock is rich in alkalis (especially sodium), light rare earth elements (LREE) and large-ion lithophile elements (LILE), and has a relatively low initial strontium isotopic ratio (Isr=0.7058); thus it is the product of differentiation of crust-mantle mixing source magma. The model of alteration and mineralization zoning is similar to the Hollister (1974) diorite model. The ore fluids have a relatively high salinity and contain significant amounts of CO2, Ca2+, Na+ and ***CI?. The homogenization temperatures of fluid inclusions for the main mineralization stage range from 280 to 420°C, the δ18O values of the ore fluids vary from 3.51 to 5.52 %, the δD values are in the range between ?82.4 and ?59.8 %, the δ34S values of sulphides vary from ?0.3 to 2.49 %, and the δ13C values of CO2 in inclusions range between ?2.66 and ?6.53 %. Isotope data indicate that the hydrothermal ore fluids and ore substances of the Shaxi porphyry copper (gold) deposits were mainly derived from magmatic systems.

Geochemical Characteristics and Genesis of the Metallogenic Rocks in the Chagande'ersi Molybdenum Deposit in Wulatehouqi,Inner Mongolia

Geochemical characteristics of the Chagande＇ersi molybdenum deposit in Inner Mongolia and its genesis were analyzed in this study using rock mineralography and rock geochemical testing. The mineralized country rocks of the Chagande＇ersi molybdenum deposit consist mainly of medium- to fine-grained monzogranite, medium-to fine-grained rich-K granite, with minor fine-grained K- feldspar granite veins and quartz veins. The rocks are characterized by high silica, rich alkali, high potassium, which are favorable factors for molybdenum mineralization. The rocks have the Rittmann index ranging from 1.329 to 1.961, an average Na20＋K20 value of 7.41, and AI2Oa/（CaO＋Na20＋K^O） 〉1, suggesting that the rocks belong to the high-K calc-alkaline peraluminous granite. The typical rock samples are enriched in Rb, Th, K and light rare earth elements, depleted in Sr, Ba, Nb, P and Ti, and these features are similar to that of the melt granite resulting from collision of plate margins. The JEu of the rocks falls the zone between the crust granite and crust-mantle granite, and are close to that of the crust granite; （La/LU）N indicates the formation environment of granite is a continental margin setting. The Nb/Ta ratios are close to that of the average crust （10）; the Zr/Hf ratios of monzogranite are partly below the mean mantle （34-60）, while the Zr/Hf ratio of K-feldspar granite are close to the mean value in the crust. Comprehensive analyses show that the granite in this area formed during the transition period between tectonic collision and post-collision. During the plate collision and orogeny, the crust and mantle material were mixed physically, remelting into lava and then crystal fractionation, finally gave rise to the formation of the rock body in this area. This has close spatial and temporal relation with the molybdenum mineralization.

Geological characteristics and genesis of subbottom pinnoite deposit of Da Qaidam salt lake in Qaidam Basin

Da Qaidam salt lake is known for its both liquid and solid boron resource.Data from previous investigation of the Da Qaidam salt lake provided a comparable framework for this study that focused on investigating the section beneath the bottom of the perennial salt lake,including the timing,

Ore-forming fluid characteristics and genesis of vein-type lead-zinc mineralization of Xiaohongshilazi deposit,Jilin Province, China

The Xiaohongshilazi mineral deposit in Jilin Province,China,is located in the accretion zone in the northern margin of the North China Block. The deposit contains two types of ore bodies: layered Pb-Zn ore bodies in volcanic rock and vein-hosted Pb-Zn ore bodies controlled by fractures. The vein Pb-Zn ore bodies are strictly controlled by tectonic fracture zones trending in S-N direction,which comprise sulfide veins or sulfidebearing quartz veins distributed along faults or structural fissures. The ores mainly appear mesh-vein and vein structures,and also show solid-solution separation and metasomatic textures. The metal minerals are mainly sphalerite,galena,and pyrite,etc. Wall-rock alteration includes mainly sericitization,chloritization,silicification and carbonatization,etc. Microscope observations and Raman spectroscopy analyses indicate that the oreforming fluid of the vein Pb-Zn ore bodies was mainly magmatic water with low temperature,low salinity,and a shallow depth of metallogenesis( ~ 1.5 km). Sulfur and lead isotope analyses indicate that the sulfide source is mainly formation sulfur or biogenic sulfur,which is similar to the sulfur source of hydrothermal deposit( negative( δ^(34) S values),while the main Pb source was the upper crust with some mantle input. This article argues that the vein Pb-Zn ore body of the Xiaohongshilazi deposit is a low-to medium-temperature hydrothermal vein type related to the formation of a shallow magma chamber.

Preliminary Study of the Characteristics and Genesis of Arsenate Minerals in the Oxidized Zone of the Debao Skarn-Type Cu-Sn Ore Deposit in Guangxi

Through the study of the oxidized zone of the Debao skarn-type Cu-Sn deposit in Guangxi, the authorshave found 14 arsenate minerals, most of which are for the first time reported in China. They are mainly Cuarsenate minerals with subordinate Cu-Pb arsenate minerals and minor Fe-Pb-Ba varieties. Based on their paragenesis these minerals may be divided into the following series: (1) the clinoclasite-olivenite-cornwallite- cornubite- debaoite- copper silicarsenate association, (2) the scorodite- carminite- beudan-tite-bayldonite- duftite association, and (3) the scorodite-Ba-bearing pharmacosiderite- dussertite association. Arsenate minerals are formed generally in the oxidized zone of the sulfide-type deposits which lie in thewarm, humid and rainy torrid-subtropical zone with pH=6-8 and contain large amounts of arsenopyrite andcarbonate rocks.

Genesis of Gold-Silver Deposits in Qingchengzi Ore Field

The gold-silver complex ore field of Qingchengzi is located in Liaohe group of Liaodong rift. The gold-silver ore bodies mainly lie in Dashiqiao group and Gaixian group. which provides ore-forming materials for the mineralization. For taking place multi-period and multi-stage magmatic activities, the ore-forming materials in the formation had had dyna- mothermal metamorphism for a long time and enriched and formed ore bodies after magmatism in Indo-Chinese and Yan- shan epoch. The ore bodies are controlled by stratigraphic formation and stored in the interformational faults and schistosity belts. Silicalite is the most important indicator for searching them. Although the Pb-Zn and the gold-silver deposits are the same series of mineralized products, their positions are different, resulting from the differences of elements nature and mineralized conditions. The gold silver deposits belong to strata-bound and hysterogeneticmesothermal-epithermal de- posit.

江汉盆地潜江凹陷北部潜江组盐湖重力流沉积特征与模式

江汉盆地潜江凹陷潜江组盐湖沉积中首次发现大范围的重力流沉积,关于其沉积特征、成因机制、主控因素和有利岩相尚有待深入研究。本研究通过对潜江凹陷北部20口取心井的精细观察,结合测录井、薄片、矿物成分和粒度分析,识别出10种重力流相关的岩相。研究区重力流沉积可分为4种成因相类型,包括风暴重力流沉积、滑动-滑塌沉积、碎屑流沉积和浊流沉积。根据岩相组合类型,将重力流沉积划分为近端、中端和远端沉积。地震、风暴和洪水为重力流沉积的诱发因素,潜4^(0)沉积期气候干旱,潭口地区的次级断裂带活动,引发斜坡带沉积物的滑动滑塌。潜4^(0中)沉积期为盐湖淡化期,洪水引发长距离搬运的超密度流体。碎屑流成因的纯净块状粉砂岩、细砂岩和浊流成因的平行层理砂岩为有利储集体。平行层理粉砂岩、块状粉砂岩和泥岩的组合是在流体转化过程中形成的优势岩相组合。

浙江青田县山口矿区叶蜡石矿蚀变分带特征及矿床成因

在分析总结浙江青田县山口矿区叶蜡石矿床特征和蚀变分带特征的基础上,对矿床成因进行研究,结果表明,山口矿区自上而下分为4个相带,即石英相带、叶蜡石石英相带、绢云母石英相带、黄铁矿石英相带,叶蜡石矿主要分布在叶蜡石石英相带,呈似层状,控矿因素为火山构造洼地、火山碎屑岩、潜火山岩等,矿床类型为火山气成-热液交代蚀变型矿床。

肯尼亚沃伊矿区高岭土矿床地质特征及成因探讨

本文在对肯尼亚沃伊矿区高岭土矿进行专项地质调查和综合研究的基础上,分析了高岭土矿床的地质特征和矿床成因,总结了找矿标志。研究认为:肯尼亚沃伊矿区高岭土矿床赋存于前寒武纪长英质变粒岩中,是优质的高岭土矿石,可满足各类工业应用要求;该矿床为风化残积型高岭土矿床;区内高岭土一般为白色高岭土,白色的黏土矿物为本区高岭土找矿直接标志,富含有长石的基岩为高岭土矿的间接找矿标志。研究结果为肯尼亚高岭土的找矿工作提供参考。

福建闽清前洋铁矿地质特征及成因分析

通过对前洋铁矿区域地质背景、矿区地质特征和矿床地质特征进行研究,分析了矿床成因。结果表明:铁矿体赋存于晚侏罗世南园组第二段火山岩中,壳幔混合源岩浆为铁矿成矿提供了物质来源,成矿母岩为中性次火山岩,次火山岩浆热液为成矿提供了巨大的动能和热能,断裂构造为矿床形成提供容矿空间及导矿通道。矿床成因属玢岩型铁矿床。

新疆乌恰县沙热拉重晶石矿地质特征及矿床成因浅析

本文主要通过对沙热拉重晶石矿床地质特征和矿石特征的分析研究,探讨了重晶石矿床成因,总结了找矿标志。沙热拉重晶石矿床赋存于中泥盆统托格买提组,属低温热液脉型矿床。地层、构造控矿作用明显,中泥盆统托格买提组地层,断裂、破碎带等可作为找矿标志,对今后区域上同类矿床的找矿工作具有一定的指导意义。

白云石晶体结构和地球化学特征对沉积环境响应:以扬子地台晚埃迪卡拉纪灯影组白云岩为例

受沉积环境的影响,在白云石形成过程中,其晶体结构与地球化学记录着相应的环境信息。本文以扬子地台晚埃迪卡拉纪灯影组杨坝剖面为例,通过系统采样研究了白云石的晶体结构和地球化学特征,明晰了基于岩石学和地球化学特征的灯影组沉积环境演化,归纳出了白云石晶体结构、地球化学特征与形成环境的耦合关系。结果表明:(1)杨坝剖面灯影组主要发育叠层石、核形石、泡沫棉石及凝块石等4种微生物白云岩和少量的晶粒、颗粒及角砾白云岩,垂向发育多期的微生物白云岩叠置韵律层,主要为局限台地潮坪相颗粒滩相。(2)地球化学分析表明,灯影组沉积演化过程为:一段主要为干旱气候、较高盐度的较浅水体,发育泥、粉晶白云岩沉积;二段下部水体加深、潮湿、低盐度,微生物白云岩最为发育;二段中上部水体总体相对较浅,湿度降低,盐度略增高;四段时水体先加深后迅速变浅,湿度逐渐降低,盐度亦逐渐增大。(3)研究区白云石晶体结构特征突显出典型的高Mg/Ca环境下流体参与形成,在干旱、高盐度的环境下,a/c值负偏,潮湿、低盐度的环境会导致晶胞参数a/c值正偏。有序度分布表明,随有序度的增加,a/c值逐渐靠近理想白云石。该结果不仅阐明准同生白云石晶体结构与形成环境关联,还揭示元古宇灯影组古海水环境特征。

川南五峰组-龙马溪组页岩岩相特征及沉积作用

【目的】川南地区上奥陶统和下志留统黑色页岩是页岩气勘探的主要目标,探究此套页岩的岩相划分、沉积环境以及沉积过程,可为页岩气勘探开发提供理论依据。【方法】通过岩心、光学显微镜以及扫描电镜的观察与分析,根据矿物组成及含量、沉积构造特征,并综合考虑生物作用及成岩作用对岩相进行划分;利用氧化—还原指标(U/Th、V/Cr、V/(V+Ni)、Ni/Co)、海平面变化指标(Ce^(*))、水体滞留程度指标(Mo/TOC)、古气候指标(Sr/Cu)、古盐度指标(Sr/Ba)以及古生产力指标(Cu、生源Ba)对古环境进行分析,并基于岩心和薄片观察、X射线荧光扫描以及矿物X衍射全岩分析对沉积过程进行识别。【结果】五峰组—龙马溪组页岩识别出六种岩相:生物硅质页岩、黏土质页岩、(长英质—钙质)粉砂页岩、钙质粉砂页岩、钙质页岩以及长英质粉砂页岩。沉积环境自下而上经历五个阶段的变化。五峰组—龙马溪组页岩主要是在低能条件下悬浮沉积形成,也在五峰组中部和龙马溪组下部发育上升流沉积,五峰组顶部发育少量风暴流沉积,在龙马溪组上部也见有重力滑塌、碎屑流、和浊流沉积。【结论】沉积环境的频繁变化以及沉积过程的多样性控制了岩相的类型与特征,进一步导致不同岩相的有机质含量、孔隙度、含气量等储层品质因素存在显著差异,后续仍需在页岩岩相与储层品质等方面加强研究,为页岩气的勘探与开发提供理论依据。

贵州开阳大坪磷矿地质特征及找矿预测

贵州开阳县为大型富磷产区,为进一步了解开阳磷矿特征并提供可靠的勘探方向,以期为矿产资源开发及矿山建设等提供基础依据,本文以开阳大坪磷矿床为研究对象,开展了地质特征、矿床成因、找矿预测等方面的相关研究。研究结果显示,区内磷矿石自然类型为致密状、条纹—条带状、碎屑状和团块状磷块岩。震旦系洋水组为研究区最主要的富磷层位,总体呈南厚北薄、西薄东厚特征,矿层整体厚度较大,品位高,连续性好,工业利用价值高。研究区矿层虽然埋深较大,但具有质优量大的资源优势。大坪磷矿床处于开阳地区成矿中心带的中部地段,向北、向东矿体未见尖灭,结合周边矿区的地质成果,综合分析认为,大坪磷矿区范围外,沿北东方向具有良好的找矿潜力,未来开采可能具有较大的经济价值。

福建银石坪铁矿床地质特征、矿床成因及找矿前景

银石坪矿床是近年来在福建龙岩马坑—大田汤泉铁矿整装勘查区内新发现的具有较大规模的铁矿床,研究程度较低。本文运用地质、地球物理和地球化学方法,系统总结了区内地层、构造、岩浆岩、磁异常、矿体和矿石特征,分析了地层、构造和岩浆岩与铁成矿关系,进而探讨矿床成因。研究表明,银石坪矿床主要矿体呈层状—似层状赋存于石炭系下统林地组,次要矿体往往呈脉状和透镜状;深部矿石为块状结构,地表矿石为蜂窝状、松散土状褐铁矿,并具有与矿化密切相关的硅化、褐铁矿化、磁铁矿化和绢云母化等围岩蚀变,矿床成因类型为沉积-改造型褐铁矿床。矿区磁异常地段、岩体与林地组接触带具有良好的找矿前景。该矿床的发现和评价将有助于闽西南大田铁铜多金属成矿区矿产资源勘查工作的接续和找矿工作的突破。

东昆仑屈库勒克东金锑矿床地质特征、控矿构造及成因

新疆屈库勒克东矿床是东昆仑造山带西段新近发现的一座大型金锑矿床,大规模金锑矿化及相关热液蚀变产于F_(5)断裂及相关构造破碎带内。矿体主要呈脉状赋存于上石炭统哈拉米兰河群浅变质碳质粉砂岩中,少量赋存于闪长质岩脉中。矿石矿物以黄铁矿、辉锑矿为主,其次为毒砂、黄铜矿、磁黄铁矿、自然金等,常见浸染状、脉状、细脉状、块状等矿石构造,矿化主要与硅化、绢云母化蚀变密切相关。构造几何学与运动学解析表明,控矿F_(5)断裂为近东西走向、陡倾向北(340°~20°),倾角55°~85°,具有自北向南逆冲的运动学属性,形成于区域三叠纪碰撞造山晚/后期环境。根据野外地质证据并结合前人研究成果,笔者提出F_(5)断裂严格控制了矿区金锑矿化带与高品位矿体的几何样式、空间展布和产出,其活动时代与金锑矿化也具有一致性,是金锑矿化的关键控矿因素;闪长质岩脉并非导致金锑矿化的直接因素,其在金锑富集与成矿过程中主要扮演了“催化剂”的角色。根据成矿地质特征、控矿构造及其对成矿的控制以及前人研究成果,笔者认为屈库勒克东金锑矿床很可能是断层控矿的造山型矿床。

山东省蓬莱市强沟金矿地质特征及成因研究

研究区位于郯庐大断裂东侧,属胶东半岛招平—莱州金成矿带,区内出露地层主要为胶东岩群,是区域主要的金矿源层。区内花岗闪长岩体发育,其金含量是标准花岗闪长岩体的7倍,岩体形成时,含大量金质的期后热液是胶东金矿床形成的主要物质来源,成矿地质条件较好。根据矿石的结构构造、矿物共生组合及其相互穿插关系判断,研究成矿作用可分为石英-粗粒黄铁矿阶段、金-石英-细粒黄铁矿阶段、绢云母-方解石阶段,前两个阶段为金主要富集阶段。强沟金矿床围岩蚀变较弱,矿石类型以石英脉型和蚀变岩型为主,矿床为岩浆期后中温热液充填交代型。花岗闪长岩体与胶东岩群接触带、NNE向断裂带中金石英脉是研究区内重要的找矿标志。