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901.
Lei CHEN Kezhang QIN Jinxiang LI Bo XIAO Guangming LI Junxing ZHAO Xin FAN 《Resource Geology》2012,62(1):42-62
The Nuri Cu‐W‐Mo deposit is located in the southern subzone of the Cenozoic Gangdese Cu‐Mo metallogenic belt. The intrusive rocks exposed in the Nuri ore district consist of quartz diorite, granodiorite, monzogranite, granite porphyry, quartz diorite porphyrite and granodiorite porphyry, all of which intrude in the Cretaceous strata of the Bima Group. Owing to the intense metasomatism and hydrothermal alteration, carbonate rocks of the Bima Group form stratiform skarn and hornfels. The mineralization at the Nuri deposit is dominated by skarn, quartz vein and porphyry type. Ore minerals are chalcopyrite, pyrite, molybdenite, scheelite, bornite and tetrahedrite, etc. The oxidized orebodies contain malachite and covellite on the surface. The mineralization of the Nuri deposit is divided into skarn stage, retrograde stage, oxide stage, quartz‐polymetallic sulfide stage and quartz‐carbonate stage. Detailed petrographic observation on the fluid inclusions in garnet, scheelite and quartz from the different stages shows that there are four types of primary fluid inclusions: two‐phase aqueous inclusions, daughter mineral‐bearing multiphase inclusions, CO2‐rich inclusions and single‐phase inclusions. The homogenization temperature of the fluid inclusions are 280°C–386°C (skarn stage), 200°C–340°C (oxide stage), 140°C–375°C (quartz‐polymetallic sulfide stage) and 160°C–280°C (quartz‐carbonate stage), showing a temperature decreasing trend from the skarn stage to the quartz‐carbonate stage. The salinity of the corresponding stages are 2.9%–49.7 wt% (NaCl) equiv., 2.1%–7.2 wt% (NaCl) equiv., 2.6%–55.8 wt% (NaCl) equiv. and 1.2%–15.3 wt% (NaCl) equiv., respectively. The analyses of CO2‐rich inclusions suggest that the ore‐forming pressures are 22.1 M Pa–50.4 M Pa, corresponding to the depth of 0.9 km–2.2 km. The Laser Raman spectrum of the inclusions shows the fluid compositions are dominated in H2O, with some CO2 and very little CH4, N2, etc. δD values of garnet are between ?114.4‰ and ?108.7‰ and δ18OH2O between 5.9‰ and 6.7‰; δD of scheelite range from ?103.2‰ to ?101.29‰ and δ18OH2O values between 2.17‰ and 4.09‰; δD of quartz between ?110.2‰ and ?92.5‰ and δ18OH2O between ?3.5‰ and 4.3‰. The results indicate that the fluid came from a deep magmatic hydrothermal system, and the proportion of meteoric water increased during the migration of original fluid. The δ34S values of sulfides, concentrated in a rage between ?0.32‰ to 2.5‰, show that the sulfur has a homogeneous source with characteristics of magmatic sulfur. The characters of fluid inclusions, combined with hydrogen‐oxygen and sulfur isotopes data, show that the ore‐forming fluids of the Nuri deposit formed by a relatively high temperature, high salinity fluid originated from magma, which mixed with low temperature, low salinity meteoric water during the evolution. The fluid flow through wall carbonate rocks resulted in the formation of layered skarn and generated CO2 or other gases. During the reaction, the ore‐forming fluid boiled and produced fractures when the pressure exceeded the overburden pressure. Themeteoric water mixed with the ore‐forming fluid along the fractures. The boiling changed the pressure and temperature, oxygen fugacity, physical and chemical conditions of the whole mineralization system. The escape of CO2 from the fluid by boiling resulted in scheelite precipitation. The fluid mixing and boiling reduced the solubility of metal sulfides and led the precipitation of chalcopyrite, molybdenite, pyrite and other sulfide. 相似文献
902.
Bo XIAO Kezhang QIN Guangming LI Jinxiang LI Daixiang XIA Lei CHEN Junxing ZHAO 《Resource Geology》2012,62(1):4-18
The Miocene Qulong porphyry Cu‐Mo deposit, which is located at the Gangdese orogenic belt of Southern Tibet, is the largest porphyry‐type deposit in China, with confirmed Cu ~10 Mt and Mo ~0.5 Mt. It is spatially and temporally associated with multiphase granitic intrusions, which is accompanied by large‐scale hydrothermal alteration and mineralization zones, including abundant hydrothermal anhydrite. In addition to hydrothermal anhydrite, magmatic anhydrite is present as inclusions in plagioclase, interstitial minerals between plagioclase and quartz, and phenocrysts in unaltered granodiorite porphyry, usually in association with clusters of sulfur‐rich apatite in the Qulong deposit. These observations indicate that the Qulong magma‐hydrothermal system was highly oxidized and sulfur‐rich. Three main types of fluid inclusions are observed in the quartz phenocrysts and veins in the porphyry: (i) liquid‐rich; (ii) polyphase high‐salinity; and (iii) vapor‐rich inclusions. Homogenization temperatures and salinities of all type inclusions decrease from the quartz phenocrysts in the porphyry to hydrothermal veins (A, B, D veins). Microthermometric study suggests copper‐bearing sulfides precipitated at about 320–400°C in A and B veins. Fluid boiling is assumed for the early stage of mineralization, and these fluids may have been trapped at about 35–60 Mpa at 460–510°C and 28–42 Mpa at 400–450°C, corresponding to trapping depths of 1.4–2.4 km and 1.1–1.7 km, respectively. 相似文献
903.
天然气藏He的聚集存在一定的年代累积效应,借鉴相关地质模型,引入气藏特征参数,对外部壳源以及气藏原位产生的He进行量化,明确天然气藏中He累积量与时间的数学关系,进而建立了约束天然气藏形成时代的新方法——He定年模型。将该方法应用于四川盆地威远气田,估算威远震旦系天然气成藏定型的时间约为31Ma,对应渐新世,处于喜马拉雅运动中期。该结果与威远气田成藏过程的研究成果相吻合,表明天然气藏He的年代累积效应可以用于成藏时代的研究,所建立的He定年模型具有一定的实用性和应用潜力。 相似文献
904.
日照东部地区具有较好的地热成矿条件及地热找矿前景。研究地热资源的成因、分布规律,对寻找地热资源具有重要的指导意义。本文在介绍日照东部地区地热资源分布特征和赋存规律的基础上,结合地热勘查及施工的成功经验,针对日照东部地区特殊的地热地质条件,采用可控源音频大地电磁测深(CSAMT)、电磁测深(VES)等方法对典型地热勘查区断裂构造特征及富水性进行解译,并确定地热井位,通过钻探施工及岩矿测试研究地热水成因。结果表明:日照东部花岗岩地区地热资源主要分布在NE向、NNE向及NW向断裂交会带附近,为断裂控制的深循环对流型带状地热资源,热储分布主要受断裂控制;勘查定井宜选择在2条或多条断裂的交会处;可控源音频大地电磁测深对断裂深部发育特征及裂隙含水情况反映明显,可作为花岗岩地区地热勘查定井方法;氢氧同位素检测结果反映研究区内地热水为大气降水补给,补给区为周边山区就近补给,沿断裂入渗循环,吸收热量形成地热水,循环距离不大。 相似文献
905.
文章探讨了东濮凹陷上古生界砂岩优质储层形成的主控因素,为预测优质储层提供依据。文章以东濮凹陷庆古3井为主要研究对象,通过岩心观察、铸体薄片、XRD、核磁共振冻融法及三束离子抛光—场发射扫描电镜联用等综合分析,研究了东濮凹陷二叠系储层发育特征及控制因素。研究表明:东濮凹陷上古生界砂岩以岩屑长石和长石岩屑砂岩为主,孔隙度值介于0.2%~12.8%,渗透率值介于0.0016~5.7 mD,属于特低孔致密型储层。溶蚀残余粒间孔、粒内溶蚀孔、晶间孔是东濮凹陷主要发育的孔隙类型,储集空间都是次生成因,各层段几乎未见原生孔隙留存,裂缝相对不发育。次生孔隙主要由长石颗粒和岩屑(包括凝灰质)溶蚀形成,在石千峰组和下石盒子组储层中较为常见。优质储层受沉积相、岩性和成岩作用的控制,石千峰组砂岩属于内陆河流相沉积,砂体发育,是东濮凹陷上古生界最有利的储集层系,长石的溶蚀是石千峰组优质储层形成的主要控制因素。下石盒子组属于三角洲沉积,由于沉积时期火山作用,导致大量的凝灰质沉积,凝灰质蚀变形成的高岭石晶间孔是该层储层形成的重要机制。山西组主要三角洲沉积,也是主要成煤期,煤系酸性流体导致溶蚀,但强烈的石英次生加大使砂岩致密化。 相似文献
906.
907.
908.
本文在分析大地水准面精化的目的意义及其发展现状的前提下,阐述了确定(似)大地水准面的原理,并针对贵州山区重力资料缺乏的现实情况,探讨了确定和精化山区局部区域大地水准面的方法;尤其对在贵州山区局部区域范围运用CPS水准资料结合地球重力场模型EGM96,拟合区域大地水准面的方法进行了详细的分析和讨论.通过运用原理和方法对实... 相似文献
909.
910.
以航空LIDAR点云数据为基础,在无其他辅助数据的情况下,采用数字图像处理技术,实现基于航空LIDAR点云数据提取城市地区建筑物的目标. 相似文献