Porphyry copper deposits: strike–slip faulting and throttling cupolas     

《International Geology Review》2012,54(1):43-65

Porphyry copper deposits sometimes form during the solidification of stocks of relatively oxidized magma of intermediate composition. Most workers have assumed ore-forming systems have special chemical attributes, but none has been found that is useful to guide exploration efforts. Stocks can form where strike–slip movements generate pull-apart pathways into which intrusions can rise from batholithic magma chambers. Upwelling of buoyant, bubble-bearing magma along the sides of a stock brings magmatic fluid to shallow depths where large bubbles can separate and pool under the cupola separating solidified igneous rock from mobile magma. Where rapid seismogenic movement on the bounding strike–slip fault ruptures the solidified, but hot and ductile carapace, downward propagating extension fractures can drain an accumulation of magmatic fluid. Decompression and cooling of fluid that jets upward into extension fractures causes mineral precipitation. Where strike–slip movements cause pull-aparts to dilate with sufficient recurrences – from decades to perhaps a century or so, throttling of the fluid accumulation acts as a safety valve that prevents explosive detonation of the system. Concurrently, the upward infiltration of magmatic fluid from the cupola is strongly focused into the pull-apart and generates the characteristic concentric alteration zones that guide exploration drilling. We conclude that porphyry copper ore deposits form where strike–slip movements are concurrent with the early stages of deep-seated bubbling (?6 km) along the walls of a rapidly cooling stock of magma. Supergiant deposits form where the bubbling front extends into the top of a parent batholith.  相似文献   

Microthermometric and O‐ and H‐isotope characteristics of the mineralizing fluid in the Akgüney copper–lead–zinc deposit,NE Turkey     

《International Geology Review》2012,54(5):375-387

We use updated rotations within the Pacific-Antarctica-Africa-North America plate circuit to calculate Pacific-North America plate reconstructions for times since chron 13 (33 Ma). The direction of motion of the Pacific plate relative to stable North America was fairly steady between chrons 13 and 4, and then changed and moved in a more northerly direction from chron 4 to the present (8 Ma to the present). No Pliocene changes in Pacific-North America plate motion are resolvable in these data, suggesting that Pliocene changes in deformation style along the boundary were not driven by changes in plate motion. However, the chron 4 change in Pacific-North America plate motion appears to correlate very closely to a change in direction of extension documented between the Sierra Nevada and the Colorado Plateau. Our best solution for the displacement with respect to stable North America of a point on the Pacific plate that is now near the Mendocino triple junction is that from 30 to 12 Ma the point was displaced along an azimuth of ～N60°W at rate of ～33 mm/yr; from 12 Ma to about 8 Ma the azimuth of displacement was about the same as previously, but the rate was faster (～52 mm/yr); and since 8 Ma the point was displaced along an azimuth of N37°W at a rate of ～52 mm/yr.

We compare plate-circuit reconstructions of the edge of the Pacific plate to continental deformation reconstructions of North American tectonic elements across the Basin and Range province and elsewhere in order to evaluate the relationship of this deformation to the plate motions. The oceanic displacements correspond remarkably well to the continental reconstructions where deformations of the latter have been quantified along a path across the Colorado Plateau and central California. They also supply strong constraints for the deformation budgets of regions to the north and south, in Cascadia and northern Mexico, respectively.

We examine slab-window formation and evolution in a detailed re-analysis of the spreading geometry of the post-Farallon microplates, from 28 to 19 Ma. Development of the slab window seems linked to early Miocene volcanism and deformation in the Mojave Desert, although detailed correlations await clarification of early Miocene reconstructions of the Tehachapi Mountains. We then trace the post-20 Ma motion of the Mendocino slab window edge beneath the Sierran-Great Valley block and find that it drifted steadily north, then stalled just north of Sutter Buttes at ～4 Ma.  相似文献   

甘肃北山地区白山堂铜矿地质特征及成矿流体研究   总被引：2，自引：0，他引：2  

陕亮  郑有业  许荣科  张雨莲  曹亮 《华南地质与矿产》2012,28(2):149-159

北山地区是我国重点成矿区带,蕴含很大的矿产资源潜力。以往工作发现斑岩型铜矿是北山地区重要的成矿类型,白山堂铜矿是其代表性斑岩型铜矿,但该矿至今一直未开展成矿流体的相关研究。本文进一步研究矿床地质特征,系统开展了矿床流体包裹体研究,发现其流体包裹体形态简单、多为气液两相,中低温(成矿期含矿石英脉均一温度230℃～260℃及160℃～170℃,共生黄铜矿爆裂温度约301℃)、低盐度[w(NaCleq)]为11%～15%,均值11.32%及3.4%～7.7%,均值4.8%)、中等密度(约0.95～1.00 g/cm3)、中低压力(约5×103～101×103 kPa)等物理化学特征,综合认为流体具有中低温热液脉型矿化特征,结合地质特征及近矿外围一系列环绕石板泉二长花岗岩分布的中低温热液脉型-矽卡岩型-斑岩型Cu、Fe、Pb和Zn等矿化分带模式,认为白山堂铜矿为中低温热液脉型矿化类型,代表岩浆热液系统演化到晚期阶段的产物,并认为环绕石板泉二长花岗岩周缘的系列斑岩型-矽卡岩型-热液脉型矿化存在某种联系。  相似文献   

内蒙古克什克腾旗黄岗山锡铜矿激电测量方法应用分析     

李国庭  王海涛  孔红杰  郭忠义 《山东地质》2012,(8):44-47

内蒙古克什克腾旗黄岗山锡铜矿区北部及中部为第四纪冰川遗迹,在植被极其发育的地表之下为冰渍物、残坡积物等组成的碎石层,厚度多大于3m,因此开展地表地质工作有一定的难度。为提高找矿效果,开展了1：1万激电测量工作。通过对激电异常的查证分析,在DJH-1号激电异常南西侧边界,燕山早期似斑状中细粒黑云母二长花岗岩与两侧石英闪长岩、花岗斑岩的内、外接触带附近发现有多期次岩浆侵入,矿化蚀变强烈,目前共圈定锡矿体10个、铜矿体8个;圈定的矿体和发现的激电异常具有较好的对应性,为进一步开展地质勘查工作提供了重要的依据。  相似文献   

柴北缘绿梁山一带与造山作用相关的铜铅锌矿床成矿规律及找矿启示   总被引：2，自引：0，他引：2  

许荣科  郑有业  周宾  吴亮  祝海洋  张宇  马超  吕登 《西北地质》2012,45(1):192-201

在研究柴北缘绿梁山铜矿、双口山铅锌矿矿床地质特征基础上,指出上述矿床围岩为遭受了强烈褶皱构造变形及低绿片岩相变质的蛇绿混杂岩构造块体,矿体呈脉状或似层状产出于韧性剪切带内的强带内,分别与加里东期和晚华力西期—印支期的两次碰撞造山作用相联系,并很可能与区域上对应时期的造山带型金矿床的形成同步。暗示绿梁山铜矿区和双口山铅锌矿区外围是寻找潜在的造山带型金矿床的重要靶区,而在绿梁山铜矿区新发现的VHMS型铜矿化和双口山SEDEX型铅锌矿化指示位置,是寻找遭受后期改造的青龙滩式铜矿化和锡铁山式铅锌矿化的重要靶区。  相似文献   

青海德尔尼铜矿床成因最新研究进展   总被引：3，自引：0，他引：3  

董富权  钱壮志  王建中  仲佳鑫  孙涛  徐刚  段俊 《西北地质》2012,(3):93-102

德尔尼铜矿床位于青海省玛沁县积石山中段德尔尼山南坡,是一个以铜为主,钴、锌等多元素可以综合利用的大型矿床。矿床成因存在较大分歧,因此,笔者运用宏观观察、矿相学研究及电子探针测试分析相结合的方法,重点对该矿床金属矿物矿相学、矿石矿物组合及矿床成因进行了系统研究,首次在德尔尼铜矿床中发现重晶石和石膏。石英-碳酸盐-重晶石-石膏为海底热液矿床的典型低温矿物组合。通过构造成矿环境、成矿物质来源研究,结合草莓状结构、矿体顶部的硅质岩、重晶石和石膏的发现等,种种迹象表明该矿床为海底热液喷流沉积矿床。  相似文献   

东昆仑德尔尼铜矿喷流岩——铁硅质岩的发现及其成矿意义   总被引：1，自引：0，他引：1  

宋忠宝  栗亚芝  陈向阳  陈博  任有祥  张雨莲  张晓飞 《地质通报》2012,31(7):1170-1177

德尔尼地区的"炭质(砂)板岩"是一个使用了30多年的岩石名称,前人把这类岩石当作与成矿并无任何关系的一种沉积岩。本次工作发现并证实这类岩石进一步可分为2种:一种为陆源碎屑岩,即正常沉积岩——炭质(砂)板岩,与成矿无直接关系;另一种为海底喷流作用形成的一种喷流岩——铁硅质岩。由此推断德尔尼大型铜(钴)矿床,是一个以海底喷流-沉积成矿为主体的后期有叠加成矿的多期成矿作用形成的矿床。这在德尔尼地区寻找该类矿床有重要的理论意义和指导意义。  相似文献   

铜资源现状与发展态势分析   总被引：4，自引：0，他引：4  

周平  唐金荣  施俊法  杨宗喜  金玺 《岩石矿物学杂志》2012,31(5):750-756

进入21世纪以来,全球矿业走出低谷,步入了新一轮矿业繁荣周期.铜作为一种重要矿种,在过去的十多年里,经历了空前的繁荣,铜矿勘查开发投入屡创新高,国际铜价在中国、印度等新兴经济体强劲需求的带动下,走向高位,甚至出现了过度金融化倾向,价格泡沫化严重.中国国内铜储量严重不足,对外依存度高达70％,外加国际铜价虚高,对中国贯彻落实“立足国内,充分利用国内国外两种资源市场”的战略方针提出了严峻挑战.文章较为系统地总结了全球铜资源的总体发展态势以及中国铜资源的基本现状和特点,并对未来十年中国铜资源的供需形势进行了预测,提出应立足国内,以地质找矿新机制为核心,加大后续勘探开发投入力度,将近十年来地质大调查查明的铜资源储量转换为铜储量,提升资源保证程度.同时,针对国际铜价出现的重大转变,应充分利用市场机制实现国家和铜产业利益的最大化.  相似文献   

安徽铜陵冬瓜山层控矽卡岩铜矿床形成过程——来自磁黄铁矿的证据   总被引：3，自引：0，他引：3  

杨爽  杜杨松  曹毅  张智宇  刘绍锋 《现代地质》2012,26(1):54-60

冬瓜山铜矿床是安徽铜陵地区代表性的层控矽卡岩型铜矿床之一,磁黄铁矿是冬瓜山铜矿床中广泛分布的矿石矿物。野外调研与矿相学观察显示,该矿床中的磁黄铁矿矿石具有沉积、热变质和热液交代结构构造。矿物学研究表明,不同矿石中的磁黄铁矿成分差异较大,其Fe含量变化于57.78%～60.67%之间,分属高温六方相和低温单斜相,主要由黄铁矿变质脱硫而成。冬瓜山铜矿的形成可能经历了早期沉积作用、中期热变质作用和晚期岩浆热液交代作用等复杂成矿过程。  相似文献   

S and Pb Isotopic Constraints on the Relationship between the Linong Granodiorite and the Yangla Copper Deposit,Yunnan, China     

YANG Xi′an  LIU Jiajun  HAN Siyu  WANG Huan  CHEN Siyao 《《地质学报》英文版》2012,86(6):1488-1499

The Yangla copper deposit, located in western Yunnan Province, China, is a typical giant, newly started mining copper deposit with an estimated Cu reserves of about 1,200,000 tons. The deposit is spatially and temporally associated with the Linong granodiorite, which is rich in SiO2 (SiO2=58.25 wt%–69.84 wt%) and alkalis (Na2O+K2O=5.98 wt%–8.34 wt%), indicating an association with shoshonitic series to high-K calc-alkaline series granites, and shows low contents of TiO2 (0.35 wt%–0.48 wt%), MgO (1.51 wt%–1.72 wt%), and Al2O3 (13.38 wt%–19.75 wt%). The δ34S values of sulfides of the main ore stage from copper ores vary range from ?4.2‰ to ?0.9‰, indicating a much greater contribution from the mantle to the ore-forming fluids. The δ34S values of the late ore stage is ?9.8‰, indicating enrichment of biogenic sulfur which may derive from the crustal hydrothermal fluid. The 208Pb/204Pb, 207Pb/204Pb and 206Pb/204Pb of sulfides of the main ore stage from copper ores range within 38.66–38.73, 15.71–15.74 and 18.35–19.04, respectively, implying that the Pb was derived from the mantle, with the crustal component, probably representing mixtures of mantle lead and crustal lead. Sulfide of the late ore stage in their Pb isotopic composition, 208Pb/204Pb= 38.69, 207Pb/204Pb=15.70, 206Pb/204Pb=18.35, implying that the Pb was derived from the crust. The Linong granodiorite is syn-collisional, produced by partial melting of thickened lower crust, which was triggered by the westward subduction of the Jinshajiang Oceanic plate. During a transition in geodynamic setting from collision-related compression to extension, gently dipping ductile shear zones (related to subduction) were transformed to brittle shear zones, consisting of a series of thrust faults in the Jinshajiang tectonic belt. The tensional thrust faults would have been a favorable environment for ore-forming fluids. The ascending magma provided a channel for the ore-forming fluid from the mantle wedge. After the magma arrived at the base of the early-stage Linong granodiorite, the platy granodiorite at the base of the body would have shielded the late-stage magma from the fluid. The magma would have cooled slowly, and some of the ore-forming fluid in the magma would have entered the gently dipping thrust faults near the Linong granodiorite, resulting in mineralization.  相似文献