内蒙古小东沟钼矿成矿地质条件分析

小东沟钼矿为中型斑岩型钼矿,矿区及其外围已发现多个钼或钼多金属矿点.文章根据小东沟钼矿的赋矿地质条件和物化探异常特征,阐述了该矿床钼矿的成矿地质条件,及钼矿与外围铅锌矿之间成因上的联系,提出本区钼矿的成矿母岩为边墙岩体,矿化富集部位为小岩株前缘的周边及顶部,铅锌矿矿质来源主要为于家北沟组地层,其成矿与后期岩浆热液活动关系密切.同时,由物探成果和钻探资料推测在边墙岩体周边还存在有类似小东沟岩体的隐伏含矿小岩体,为该区今后的工作提出了新的找矿思路.     

吉林省九台市李家屯东沟钼矿床地质特征及找矿标志

本文阐述了吉林省九台市李家屯东沟钼矿的区域地质背景、矿床地质特征及矿石结构构造等。总结了成矿条件和找矿标志,为寻找同类型的矿床及地质研究方面提供参考。     

东沟坝多金属矿床喷流沉积成矿特征的稀土元素地球化学示踪

为了进一步研究东沟坝矿床的喷流沉积成矿特征,对东沟坝矿床矿石及围岩的稀土元素进行了ICP-MS测定。东沟坝矿床矿石普遍显示明显的Eu正异常和弱的Ce负异常,说明成矿热液为温度较高(250℃及其以上)、相对还原的流体。Eu正异常和弱Ce负异常同时在矿石中发育,说明矿石沉淀时较高温度的热流体与少量的海水发生了对流混合。根据矿石与围岩的稀土配分模式的相似性及矿石铅、硫同位素组成特征,推断成矿金属元素主要来自赋矿围岩。根据矿石中大量发育重晶石和矿石普遍具有的LREE富集、明显的Eu正异常和弱Ce负异常的事实,推断同生成矿流体中大量SO4^2-的出现与岩浆脱气作用有关。     

陕南东沟坝金银矿床地质特征

陕南东沟坝金银矿床位于秦岭东西向构造带南缘、摩天岭褶皱带东端、“勉略宁三角地区”之中部。金银矿体产于中、上元古界浅海相火山岩——细碧角斑岩中。区内地质构造复杂,岩浆活动强烈,各类矿产重叠共生(图1)。东沟坝金银矿床是在评价东沟坝铅锌矿床程中发现的。为在火山岩地区寻找金银矿,现将矿床作一介绍。不妥之处,请批评指正。一、矿床地质特征矿区出露一套海相火山岩层。按其岩浆作用特点及成岩条件,可分为二个喷发旋回、五个沉积韵律、八个岩相岩性层,总厚度642m,归属于中、上元古界碧口群(AnZbk)中岩     

内蒙古小东沟斑岩型钼矿床的成矿时代及成矿物质来源

小东沟斑岩型钼矿床位于大兴安岭南段,距北部的西拉木伦河大断裂仅25 km。对小东沟岩体进行了Sr-Nd同位素和铅同位素分析,87Sr/86Sr(t)为0.705 0~0.705 5,εNd(t)为-2.4~-2.8;对主要钼矿体的6件辉钼矿样品进行了铼-锇同位素分析,所获同位素等时线年龄为(138.1±2.8)M a,表明小东沟钼矿床形成于早白垩世。铅同位素分析结果表明小东沟斑岩型钼矿床的成岩成矿物质具有不同来源,成岩物质来自俯冲洋壳衍生的新生地壳物质,而成矿物质来自地幔分异的产物(流体),属于壳源岩浆+幔源流体的组合。结合区域构造演化历史,对小东沟斑岩型钼矿的成因做出如下解释:在早白垩世,大兴安岭开始隆升,岩石圈拆沉,软流圈(层)物质上涌、基性岩浆的底侵以及地幔流体的加入,引起下地壳岩石的熔融,随后更多的地幔含矿流体进入到岩浆房。岩浆携带来自地幔的含矿流体,沿着区域性的EW、NE向深大断裂上侵定位,并在此过程中演化形成富硅、富钾质的花岗岩,最后沿近NS向的断裂侵位到二叠纪地层中,沉淀形成矿床。     

河南省栾川县罗村钼矿成矿特征及找矿

通过对河南省栾川县罗村钼矿区域地质背景、矿床地质特征与南泥湖、三道庄及东沟超大型钼矿的综合对比、分析、研究,总结归纳了矿区NWW构造形迹、小岩体与钼矿成矿关系、围岩对成矿的控制作用、围岩蚀变与成矿的关系、地球化学异常与钼矿床的关系等成矿特征.根据罗村钼矿的成矿特征,初步指出今后的找矿方向.     

鸡西市东沟石墨矿地质特征及成因

鸡西市东沟石墨矿经过勘探达到中型矿床规模。本文概述了该矿床的矿区地质特征,含矿层位、含矿变质岩、矿体规模,矿石类型,矿物及化学成分等。最后参照邻近同一类型的柳毛石墨矿的碳同位素研究成果,以及矿石的碳钒铀组合特征,论述了碳质来源为有机成因。     

青龙县二拨子东沟金矿及其周边成矿地质特征和找矿远景

简要介绍了二拨子东沟金矿及其周边金矿点的地质特征，从区域构造、岩浆作用及成矿热液作用等方面分析了该区的成矿地质条件，简要论述了矿床成因，并对区内金矿的找矿远景做出初步评价。     

吉南、辽东一带的侯家屯组

<正> 辽宁省新宾县、桓仁县、涛原县及吉林省柳河县、通化市一带的侯家屯组原称小东沟组,时代历有争议。王钰等(1954)将出露在本溪附近的中生代地层划分为三个部分:下部大明山统、中部大峪统、上部林家统。大明山统自上而下又分为尖山沟层、小岭火山岩层和小东沟层,并在小东沟剖面中采得Pagiophyllum cf.gracile Sze,Ephemeropsis trisetalis Eichwald等,时代为早白垩世。1959年,顾知微将大明山统改置为中上侏罗统,称小东沟     

陕西东沟坝金银多金属矿床形成条件成矿机制及成矿模式探讨

本文综合了东沟坝矿床地质特征,结合硫、氢、氧、碳稳定同位素,硫、氧、二氧化碳逸度及包体测温,天然热发光,热电系数等测定结果,分析了成矿物理化学条件和环境;计算了单阶段铅同位素模式年龄(858—1042Ma,相当于青白口纪);划分了成矿阶段,建立了成矿模式,总结了找矿标志及找矿方向。矿床成因类型属火山沉积—受变质矿床。     

Geochronology of the Xiaodonggou Porphyry Mo Deposit in Northern Margin of North China Craton

The Xiaodonggou porphyry Mo deposit is located in the Mesozoic calc-alkaline Xiaodonggou granitoid within a Palaeozoic fold zone of northern China. The mineralization mainly occurred in an area of 0.54 km² at the south-eastern part of the Xiaodonggou granitoid. The mineralization includes disseminated molybdenite, pyrite, chalcopyrite, magnetite and pyrrhotite and stockwork quartz-sulfide veins. A molybdenite-rich inner core is surrounded by a concentric zone of the sulfide mineral assemblage of pyrite, galena and sphalerite. Intense potassic alteration is overprinted by sericitization and silicification in the mineralized zone. SHRIMP U-Pb data of zircon indicate that the granitoid crystallized at 142 ± 2 Ma (2σ). Re–Os age dating for six molybdenite samples from underground galleries of the deposit constrains the age of porphyry-style Mo mineralization to be 138.1 ± 2.8 Ma (2σ). These data suggest that porphyry-style mineralization was associated with the Xiaodonggou granitoid intrusion and support an Early Cretaceous porphyry-type metallogenic epoch along the northern margin of North China Craton.     

内蒙古克什克腾旗小东沟斑岩型钼矿床成岩成矿机制探讨

本文选取内蒙古克什克腾旗的小东沟斑岩型钼矿区作为研究区,它位于西拉沐伦钼矿带的西南部.对小东沟岩体进行了主微量元素、SHRIMP锆石U-Pb定年等地球化学方面的研究;对岩体中的钾长石和含矿矿物辉钼矿进行了普通铅同位素分析.小东沟岩体具有高硅富钾、REE含量低、Zr含量高、无负铕异常、高ε_(Nd)(t)、低Sr_i等特点,指示岩浆起源于加厚新生下地壳的熔融,同时具有高温、快速熔融、快速析离逃离源区的特点;小东沟岩体的SHRIMP锆石U-Pb定年结果为142±2Ma,对应140Ma左右主应力场由南北向转为东西向的构造体制大转折时期,这个时期大兴安岭处于伸展的构造环境下,底侵作用发育,地幔物质可以添加到下地壳熔融形成的岩浆中;对岩体钾长石和辉钼矿进行的普通铅同位素分析显示前者具有从造山带-地幔过渡的特征,后者则显示有地幔特征,说明成岩、成矿物质来自两个不同的源区,下地壳的岩浆和地幔含矿流体发生了混合.通过以上的分析,结合水-岩浆物理反应的实验结果,本文提出小东沟斑岩型钼矿床的成矿模式:大兴安岭地区在早白垩世伸展的构造背景下,地幔含矿流体加入受底侵作用加热的下地壳中使之熔融形成岩浆,随后更多的地幔含矿流体进入岩浆房,促使其迅速析离逃逸出源区,二者一起上升侵位.在岩浆温度较高时,地幔舍矿流体和岩浆大致以较稳定的液态不混溶的状态共存;当岩浆和流体侵位到较浅深度时,压力下降,温度降低,晶体增多,流体-岩浆体系变得不稳定,岩浆被流体分割成许多很小的岩浆团.流体中H~+、K~+和各种成矿元素的存在使之必然会和岩浆或冷却后形成的岩石发生蚀变反应,并晶出成矿矿物,形成现在我们看到的具有浸染状矿化现象的小东沟斑岩型钼矿床.     

内蒙古小东沟钼矿外围找矿前景分析

通过对小东沟钼矿的勘查和研究,类比外围物探异常和矿化特征,探讨了该地区钼矿和铅锌矿的成矿地质条件,提出小东沟钼矿外围综合利用物探成果进行找矿的思路及找矿前景。研究认为,该地区有望成为大型钼多金属矿床。     

Ages and geodynamic settings of Xilamulun Mo–Cu metallogenic belt in the northern part of the North China Craton

The Xilamulun belt along the northern part of the North China Craton is located in eastern segment of the Central Asian Orogenic Belt and has great economic potential for Mo–Cu mineralization. More than ten medium to large ore deposits have been discovered in this region in the recent years. The major types of mineralization type include porphyry (Chehugou Mo–Cu, Kulitou Mo–Cu, Xiaodonggou Mo and Jiguanshan Mo), quartz vein (Nianzigou Mo, Xinjing Mo), epithermal (Hongshanzi Mo–U) and alteration assemblage (Liulingou Mo). The timing of mineralization was previously thought to be Yanshanian (208–290 Ma), however, Indosinian (260–208 Ma) ages for intrusions and mineralization have been recognized in recent years. Based on geochronologic data and regional geological evidence, it is suggested that the mineralization in the Xilamulun belt was formed during multiple events. The mineralization processes are related to a post-collisional extension stage (~ 258–210 Ma) with the generation of the porphyry molybdenum–copper deposit, a tectonic stress transformation from NS to EW (~ 185–150 Ma) that gave rise to vein or porphyry molybdenum deposit, and a lithospheric thinning stage (~ 140–110 Ma) with porphyry molybdenum deposit.     

内蒙小东沟钼-铅锌矿地质特征及成因探讨

小东沟中型钼矿、小型铅锌(银)矿在空间上紧邻,地质特征、化探异常特征、硫同位素的综合研究,显示了成因上、产出位置上密切关系,初步建立了该区成矿模型及其相互指示意义,进而为下一步找矿工作提供了一种新思路。     

The 401–409 Ma Xiaodonggou granitic intrusion: implications for understanding the Devonian Tectonics of the Northwest China Altai orogen

Abstract

Palaeozoic granitoids in the Chinese Altai are important for understanding the evolution of the Central Asian Orogenic Belt (CAOB). The Xiaodonggou granitic intrusion, situated in the Chinese Altai (southern CAOB), is composed of two intrusive phases, medium-grained granite intruded by porphyritic granite. Zircon LA-ICP-MS U–Pb analyses of medium-grained granite and porphyritic granite yield ages of 409 ± 2 Ma and 400 ± 1 Ma, respectively, indicating that these formed in Early Devonian time. Medium-grained granite and porphyritic granite have similar geochemical features and Nd–Hf isotopic compositions. Arc-like geochemical characteristics (e.g. enrichment of LILEs and negative anomalies of Nb, Ta, Ti, and P) show that both phases are volcanic arc granites (VAGs). Geochemical and isotopic characteristics suggest that these magmas originated from melting older crust. Based on their near-zero or negative ε_Nd(t) values (?1.4to 0) and positive ε_Hf(t) values (+1.4 to +7.8), together with Nd model ages of 1.15–1.26 Ga and zircon Hf model ages of 0.90–1.30 Ga, we suggest that the Xiaodonggou granites were derived from a mixture of juvenile and old crustal components. Some other Devonian granitic intrusions were recently identi?ed in the Chinese Altai with ages between 416 and 375 Ma. These Devonian granites have similar geochemical characteristics and petrogenesis as Xiaodonggou granites. The formation of these Devonian granites was in response to subduction processes, suggesting that Chinese Altai was an active continental margin in Early Devonian time.     

内蒙古中东部半干旱荒漠草原景观区岩屑地球化学测量的方法技术及应用效果

内蒙古中东部半干旱荒漠草原景观区选择B层-5～+40目粗粒级段的风化岩屑样品可以有效地排除风成沙的干扰,突出成矿及指示元素的地球化学异常特征.文中介绍了该景观条件下开展岩屑地球化学测量的方法技术,分析了白音查干矿区、油房西矿区和小东沟矿区的化探异常特征和找矿成果.认为在半干旱荒漠草原景观区开展岩屑地球化学测量是行之有效的找矿方法,已取得了明显的化探异常圈定和地质找矿效果.     

冀北滦平盆地大店子组叶肢介生物地层特征与陆相侏罗系—白垩系界线

大店子组是滦平盆地大北沟组之上、西瓜园组之下的一个岩石地层单元,建组剖面在滦平火斗山乡大店子东沟。在滦平火斗山乡张家沟,该组自下而上可进一步划分为4个岩性段,产有丰富的叶肢介化石,统属于东方叶肢介群(Eosestheria Fauna)。加之狼鳍鱼Lycoptera和女星介Cypridea与之共生,构成典型的热河动物群(Jehol Fauna)。根据叶肢介化石组合序列、叶肢介动物群的发展阶段与可能的演化谱系,将大店子组自下而上连续划分为5个叶肢介带。在大北沟组与大店子组界线的上下,尼斯托叶肢介群(Nestoria Fauna)和东方叶肢介群(Eosestheria Fauna)相继发生了集群绝灭和集群新生的重大生物事件。老的动物群的集群绝灭和新的动物群的集群新生,预示着一个大的时代界线的存在。在大北沟组与大店子组界线上C/O同位素有一高异常值和明显的降温事件,这可能就是这一集群绝灭和集群新生重大生物事件的原因。这一降温事件与世界范围内侏罗纪—白垩纪之间的降温事件相吻合。据此,中国乃至东亚陆相侏罗系—白垩系界线应置于大北沟组与大店子组之间,并以东方叶肢介Eosestheria属的出现为特征,以古老东方叶肢介Eosestheria antiqua的首现为标志,为大北沟阶的结束与张家沟阶的开始。其界线候选层型初步定于滦平县火斗山乡张家沟下营-上营剖面第9层之底和滦平县火斗山乡小东沟剖面第10-2层之底。