陕西省略阳县徐家沟铜矿床成矿地质特征及控矿因素

徐家沟铜矿床位于勉(县)-略(阳)-阳(平关)铜多金属矿化集中区中部的铜厂矿田西北部,矿体产于中上元古界郭家沟组中的片理化细碧岩带內,已圈定铜矿体13条,多为盲矿体.矿石主要自然类型为黄铁矿化-磁黄铁矿化-片理化细碧岩型,属于火山沉积-构造、岩浆改造型铜矿床.郭家沟组中的细碧岩为铜的主要矿源岩,细碧岩中的近东西向构造片理化带为矿质富集提供了富集通道和空间.铜厂闪长岩体为成矿提供了动力、热源和主要硫源,成矿受上述地层岩性、构造、岩浆岩因素联合控制.     

Combined Sr isotope and trace element analysis of melt inclusions at sub-ng levels using micro-milling, TIMS and ICPMS

This paper describes a technique, which allows precise and accurate Sr isotope measurement combined with trace element analysis of individual melt inclusions, of sample sizes  1 ng of Sr. The technique involves sampling by micro-milling, chemical dissolution, micro Sr column chemistry, TIMS, and ICPMS analyses. A 10% aliquot of each sample solution is used for trace element analysis by double focusing magnetic sector field ICPMS, while Sr is chemically separated from the remaining 90% and used for ⁸⁷Sr/⁸⁶Sr determinations by TIMS.During the development of the technique outlined above, we documented in detail the potential sources of blank contributions and their magnitude. The average size and Sr isotope composition of our laboratory total procedural blank during this study was 5.4 pg ± 0.3 pg Sr (n = 21) with an ⁸⁷Sr/⁸⁶Sr of 0.7111 ± 0.0002 (2SE, n = 3). The total procedural Rb blank was 1.9 ± 0.7 pg (n = 21). The total procedural blank was found to have minimal effect (< 150 ppm shift) on the ⁸⁷Sr/⁸⁶Sr of sample material containing down to  250 pg Sr. Applying a blank correction allows ‘in house’ standards of this size to be corrected back to within 175 ppm of their accepted values. By applying blank corrections we can confidently measure the Sr isotope composition on sample sizes down to  25 pg Sr to an accuracy better than 400 ppm.The utility of the technique is illustrated by application to a suite of melt inclusions from NW Iceland and their host olivines. It is shown that the effect of a small amount of entrainment of the host olivine during sampling of 50 μm melt inclusions has a negligible effect on the measured Sr isotope and trace element composition. Furthermore, where melt inclusions are < 50 μm it is possible to obtain Sr isotope and trace element data on multiple melt inclusions hosted in a single olivine. This provides similar information to that of the single melt inclusions.     

Light hydrocarbons geochemistry of surface sediment from petroliferous region of the Mehsana block,North Cambay Basin

A study was carried out to test the usefulness of surface geochemical methods as regional evaluation tools in petroliferous region of the Mehsana block, North Cambay Basin. A suite of 135 soil samples collected from the depth of 2.5 m, were analyzed for adsorbed light gaseous hydrocarbons and carbon isotopes (δ¹³C_methane and δ¹³C_ethane). The light gaseous hydrocarbon analysis show that the concentration ranges 402 ppb, 135 ppb, 70 ppb, 9 ppb and 18 ppb of C₁, C₂, C₃, iC₄ and nC₄, respectively. The value of carbon isotopic ranges of methane −29.5 to −43.0‰ (PDB) and ethane −19.1 to −20.9‰ (PDB). This data, when mapped, indicates patterns coinciding with major known oil and/or gas field of Sobhasan/Linch in this study area. The existence of un-altered petroliferous microseeps of catagenetic origin is observed in the study area. A regional study, such as the one described here, can provide important exploration facts concerning the regional hydrocarbon potential in a block. This method has been confirmed and can be applied successfully in frontier basins.     

Late Pleistocene sea-level oscillations (MIS 10–2) recorded in shallow marine and coastal plain sediments of the southern Wanganui Basin, New Zealand

The northern Wanganui Basin, New Zealand, is one of the key global sites for understanding marine cyclic sedimentation during the Quaternary. This paper presents the first evidence of marine cyclic sedimentation from its central-southern parts. Sedimentological, micropalaeontological and palynological analyses on a 280-m-deep borehole encountered units dating back to MIS 10. The sequence includes four marine cycles spanning MIS 9–5, which are overlain by terrestrial fluvial aggradation surfaces dating from MIS 4–2. Each marine unit represents a progressively shallowing depositional environment from the mid-shelf to coastal plain. This is overlain by a terrestrial sequence of lowstand fluvial terraces. Localized fault movements appear to have influenced the sedimentary character of the sequence during MIS 7a and 5e producing basement highs which provided protection to the shoreline. The cyclothems described in this paper now extend the already extensive, previously described record from MIS 17–10 to produce a combined eustatic record of Quaternary sea level change within the basin to MIS 5. They also provide an excellent example of the sedimentary response of a coastal basin to a progressive loss of sedimentation accommodation space.     

安徽滁州琅琊山铜矿辉钼矿铼-锇同位素定年及其地质意义

首次运用铼-锇同位素方法对滁州琅琊山铜矿床中的辉钼矿进行定年。5件辉钼矿样品的模式年龄为(128.9±1.8)Ma～(130.3±1.9)Ma,187Re-187Os等时线年龄为(128.6±2.2)Ma,其加权平均方差(MSWD)为0.45,为滁州琅琊山铜矿床提供了准确的形成时限。分析结果表明,滁州琅琊山铜矿床是早白垩纪(燕山晚期)区域构造-岩浆活动的产物。琅琊山铜矿床辉钼矿中铼含量较高,推断成矿物质主要是壳幔混源,且主要是幔源。     

波长色散X射线荧光光谱法测定铜精矿中铜铅锌硫镁砷

采用偏硼酸锂和四硼酸锂混合熔剂熔融法制样,波长色散X射线荧光光谱法测定铜精矿中铜、铅、锌、硫、镁、砷,考察了熔剂、玻璃化试剂和预氧化条件对制样的影响。采用理论α系数和经验系数相结合的方法校正元素间的效应。测定铜精矿试样各组分的相对标准偏差(RSD,n=12)均小于3%,结果与化学分析法吻合。     

铜矿数字矿床模型专家系统的原理与技术实现

数字矿床模型是指将传统的地质学语言描述的矿床特征,转化成计算机可以识别的数字和符号,并加入人工智能的推理规则和知识,使之具备矿床自动推理和勘查辅助决策的功能。本项研究是在基于前人的工作基础上,结合国内外数字矿床模型的先进理论和经验进行了系统的实现。本文论述了铜矿床数字化的方法原理以及在系统实现时的关键性技术问题。系统知识库和规则库的建立是在多位铜矿专家的协助下完成的,专家对一系列先验概率等相关参数进行赋值,并用统计学方法下进行了处理。铜矿专家系统中知识库和规则库的保存和管理使用了数据库开发技术,采用数据挖掘作为知识发现的新手段。系统使用产生式规则,采用主观贝叶斯方法为推理的总体算法,搜索策略采用广度优先向前搜索的策略;在地质证据的输入方面不只提供与铜矿类型直接相关的证据,同时系统也提供了更为充分的地质证据,使推理的过程更加可靠和合理,同时地质词典功能的加入方便用户对相关地质术语进行查询和检索。系统不仅能实现单一成因的矿床进行推理,也能对复合矿床类型进行推理。     

Hydrothermal fluid geochemistry at the Chah-Firuzeh porphyry copper deposit,Iran: Evidence from fluid inclusions

The Chah-Firuzeh porphyry copper deposit is located in 35 km north of Shahre Babak (Kerman province). It is associated with granodioriteic intrusive of Miocene age which intruded Eocene volcanosedimentary rocks. Copper mineralization was accompanied by both potassic and phyllic alteration. Field observations and petrographic studies demonstrate that the emplacement of Chah-Firuzeh pluton took place in several intrusive pulses, each with associated hydrothermal ore fluid formation that was also associated with hydrostatic pressure increasing respect to that of lithostatic pressure (and fracturing development-relative boiling) by circulated fluid. Copper is concentrated as a very early hydrothermal mineralized phase in the evolution of the hydrothermal system. Early hydrothermal alteration produced a potassic assemblage (orthoclase–biotite) in the central deep part of the stock. Alteration ore fluids could be classify into two groups of liquid-reach, containing solid phases, high temperature (390 to 500 °C) high salinity (more than 60 wt.% NaCl equiv.) and gas-rich, high temperature (311 to 570 °C), no solid phase and with low salinities. These magmatic source fluids illustrate sever boiling process and also are the responsible for the both potassic alteration, quartz group I and II veins and chalcopyrite deposition. Propylitic alteration occurred by the liquid-rich, low temperature (241 to 390 °C) and Ca-rich fluid with meteoric origin. Continuous decreasing temperature let the meteoric water diffusion into the system, mixed with magmatic fluids and descending the salinities down to the 1 wt.% NaCl equiv. and leaching the Cu from vein groups II and III by sever thermodynamic anarchies from potassic to the phyllic alteration zones. Phyllic alteration and copper leaching resulted from the inflow of oxidized and acidic meteoric waters with decreasing temperature of the system followed by the incursion of this fluid into and its convection in upper part of the system. A late episode of boiling occurred in the apical the phyllic zone, and was associated with significant copper deposition. Based on the field observation on sharp alteration and related mineralization, it is possible to conclude that all these procedures have been controlled by local faults that could be active even before the pluton injection. These faults and the new form ones (which have been formed after injection), could crash the hosted rocks, and act as physical dams to restrict and limit the mineralization in special strikes and zones within the Cah-Firuzeh ore deposit.     

龙门山泥盆纪腕足化石锶同位素组成特征及其古环境意义

生物成因的海相碳酸盐岩中Sr同位素组成与演化是目前研究古海平面变化、造山运动以及古气候变化的主要工具,在海相地层定年及全球等时对比研究中发挥着重要作用。对四川龙门山泥盆纪剖面腕足化石Sr同位素组成进行了研究。保存鉴定结果显示：腕足化石壳体结构保存完整;阴极射线照射下壳体不发光或部分壳体呈微弱橙黄色;大多数壳体微量元素Mn〈250μg／g、Sr〉400μg／g。表明腕足化石保存完好,后期成岩作用影响微弱。锶同位素结果显示：龙门山泥盆纪sr同位素演化同全球泥盆纪Sr同位素演化基本一致,表明龙门山泥盆纪Sr同位素演化受全球性变化影响。早泥盆世较高Sr同位素比值（甘溪组0．708437）可能是受加里东造山运动的影响,大量古陆的出露,风化作用的加强所致。其后的缓慢下降可能受海平面上升古陆面积缩小的影响。中泥盆世Sr同位素组成低值平台显示着幔源Sr和陆源Sr（风化作用较弱）输入量之间的平衡。随后的Sr同位素组成的上升可能是受中泥盆世开始温度上升的影响,致使风化作用的加强所致。     

龙王(石童)A型花岗岩地球化学特征及其地球动力学意义

龙王花岗岩岩体产于华北克拉通南缘,岩石类型主要为黑云母钾长花岗岩,局部见有霓辉石花岗岩。岩体高硅(SiO2=72.17%～76.82%)、富碱(K2O+Na2O=8.28%～10.22%,K2O/Na2O>1),碱性指数AI(agpaitic index)=0.84～0.95,分异指数DI=95～97,铝指数ASI(aluminium saturation index)=0.96～1.13。含铁指数高(FeO/(FeO+Mg)=0.90～0.99),岩石为准铝质至弱过铝质、碱性—碱钙性、铁质A型花岗岩。岩石富集大离子亲石元素,稀土元素含量很高(854～1572μg/g);高场强元素(Nb、Ta、Zr、Hf)的富集程度明显低于大离子亲石元素,因此在微量元素蛛网图上呈相对亏损特征;岩石显著亏损Ba、Sr、Ti、Pb;εNd(t)=-4.5～-7.2,Nd模式年龄为2.3～2.5Ga。εHf(t)=-1.11～-5.26,模式年龄tHf1=2.1～2.3Ga,tHf2=2.4～2.6Ga。黑云母钾长花岗岩中的锆石主要为无色透明柱状晶体,CL图像多数显示清晰的岩浆成因的韵律环带结构,锆石LA-ICPMSU-Pb年龄为...