青海卡而却卡铜多金属矿床蚀变矿化类型及矽卡岩矿物学特征

卡而却卡铜多金属矿床是柴达木盆地南缘西段祁漫塔格地区颇具特色的一个破碎蚀变带热液脉状-矽卡岩型矿床。矿区内可见2类围岩蚀变：矽卡岩化和黄铁绢英岩化。前者由印支期似斑状黑云母二长花岗岩侵位引起,在岩体侵入接触面及外接触带围岩的不同岩性界面、构造破碎薄弱带形成含铜多金属矽卡岩透镜体,由透辉石、钙铁辉石、钙铁（铝）榴石、符山石、硅灰石、方柱石和阳起石等一套十分典型的钙矽卡岩矿物组成;后者在矿区西北部的似斑状黑云母二长花岗岩体中形成多条呈NWW向平行展布的黄铜矿化热液蚀变带,构成断裂破碎带控制的细（网）脉浸染状热液脉型矿化。研究认为：卡而却卡铜多金属矿床的形成与印支期侵位、具有浅成和高侵位特点的似斑状黑云母二长花岗岩关系密切,产出的矽卡岩型铜多金属矿与破碎蚀变带控制的细（网）脉浸染状热液脉型铜矿的成岩成矿年龄基本一致,其构造-岩浆活动背景相同,但属不同阶段、不同深度和不同部位发生成矿作用的产物,形成以接触带（或外接触带）矽卡岩型铜多金属矿为主体的、成矿母岩体内的构造断裂发育部位伴有热液脉状铜矿化的复合型矿床。     

豫西南栾川地区铅锌矿床碳、氧同位素地球化学

豫西南地区铅锌矿产勘查工作近年来进展迅速,尤其在栾川地区先后发现十余处铅锌银多金属矿脉群、上百条含矿断裂带,铅、锌、银资源前景广阔。对该区铅锌矿的科学研究丰富了华北陆块南缘区域成矿学认识,并促进了进一步找矿勘查工作。栾川地区铅锌矿产在燕山期斑岩体周围矽卡岩中和外围的断裂带(脉状)中。脉状铅锌矿脉石矿物碳酸盐C、O同位素的组成(赤土店矿床1δ3C为-3.66‰~-2.82‰,1δ8O为10.31‰~15.86‰;百炉沟矿床1δ3C为-3.00‰~1.80‰,1δ8O为9.40‰~17.70‰;冷水北沟矿床1δ3C为-4.90‰~-0.40‰,1δ8O为6.00‰~12.50‰)介于典型海相石灰岩(1δ3C为0±2‰,1δ8O为28‰~30‰)和岩浆岩(1δ3C为-3‰~-30‰,1δ8O为6‰~12‰;地幔1δ3C为-7‰~-5‰)之间,指示成矿流体、成矿物质的岩浆和地层双重作用、两种来源特点。综合分析认为,栾川地区铅锌矿有矽卡岩型和岩浆热液充填-交代型两种。     

湖南七里坪－半边街镁质矽卡岩硼矿床微量元素地球化学

湖南七里坪－半边街接触交代型硼矿，矿体产于中石炭统壶天群白云岩与燕山期花岗岩接触带的矽卡岩中，产状受岩体顶板形态的控制，多为似层状、透镜状、囊状等。一般离岩体较远的部位硼矿石的品位较富，但靠近岩体的部位矿体较厚大。据微量元素相关系数聚类谱系图分析，Ｂ元素在岩体中呈分散状态，在高温热液中易于聚集，在矽卡岩中富集成矿，在蚀变的白云岩中有轻微的富集。     

Preliminary mineralogical and petrological study of the Ortosa Au–Bi–Te ore deposit: a reduced gold skarn in the northern part of the Rio Narcea Gold Belt, Asturias, Spain

The Ortosa deposit (NW Spain) in the northern part of the Rio Narcea Gold Belt (RNGB) is located in the Cantabrian Zone of the Iberian Massif. This zone corresponds to the westernmost exposure of the European Hercynides. The deposit is hosted by marine shales, siltstones, calcareous siltstones and interbedded sandy limestones of the upper part of the Silurian Furada Formation. These rocks are intruded by a main stock and numerous sills and dikes consisting of a reduced, ilmenite-bearing quartz-monzodiorite (Ortosa intrusion). Skarn metasomatism and associated gold mineralization overprinted these sedimentary and igneous rocks, forming endo- and exoskarns.The earliest stage of alteration involved potassium metasomatism from which metasomatic biotite developed in the hornfels around the intrusion. In the endoskarn, the first metasomatic mineral to form is actinolite. Subsequently, quartz, pyroxene (Hd_30–45), and sulfides (mainly arsenopyrite and pyrrhotite) formed, followed by a second generation of amphibole (ferroactinolite and ferrohornblende). The exoskarn is a pyroxene-garnet skarn, which is often banded. The prograde minerals are pyroxene (Hd_10–30) and grossular garnet. The retrograde mineralogy consists of hedenbergite-rich pyroxene (Hd_50–87), amphibole (ferroactinolite–ferrohornblende), and the metallic minerals with minor fluorapatite, K-feldspar, albite, epidote–clinozoisite, vesuvianite and calcite. A final stage of retrograde alteration is characterized by calcite, quartz, and chlorite.Pyrrhotite and arsenopyrite are the more abundant metallic minerals, and löllingite, chalcopyrite, pyrite and sphalerite are present in smaller amounts. The gold occurs as native gold and maldonite, and is accompanied by hedleyite, native bismuth, and bismuthinite. These Au–Bi–Te mineral assemblages occupy cavities and fractures in the arsenopyrite or in the pyrrhotite.Estimated physiochemical conditions of formation based on the composition and stability fields of major calc-silicate and sulfide minerals indicate that the hedenbergite-rich pyroxene and the earliest sulfides (löllingite–pyrrhotite–arsenopyrite) crystallized at temperatures between 470 and 535°C at low log fS₂ between −10 and −6.5 and low log fO₂ of −22. The Ortosa skarns can be included in the reduced gold skarn subtype defined by Meinert (Mineralogical Association of Canada, Quebec city, Que., Canada, 1998, 26,359–414 ).     

接触交代夕卡岩型矿床中石榴子石和辉石成分特点及其与矿化的关系

本文对中国十四个接触交代钙夕卡岩矿床和钙-镁夕卡岩矿床中的三百多个样品的石榴子石和辉石成分进行了电子探针分析。不同矿床类型的石榴子石和辉石成分代表着钙夕卡岩矿床的十个矿种(Fe、Fe-Cu、Pb-Zn、W、Sn、Sn-Mo-Bi-W、、W-Bi-Cu-Mo、Cu-Zn、Cu-Sn、W-Zn-Cu)和钙-镁夕卡岩矿床的三个矿种(Fe-Cu、Mo、Pb-Zn)。石榴子石和辉石成分变化范围大,大多数石榴子石是含锰铝榴石+铁铝榴石+镁铝榴石小于15％(摩尔百分数)的钙铝榴石-钙铁榴石固溶体;大多数辉石是含小于5％的锰钙辉石的透辉石-钙铁辉石固溶体。有些Pb-Zn钙-镁夕卡岩矿床中的辉石显示出Mn含量有所增加。只有Sn和W钙夕卡岩矿床及Pb-Zn钙-镁夕卡岩矿床含(Sps+Alm+Pyr)总量大于15％的石榴子石。石榴子石和辉石成分与夕卡岩矿床金属矿化类型之间有某些联系。     

Geology of gold-bearing skarn deposits in the middle and lower Yangtze River Valley and adjacent regions

The middle and lower Yangtze River Valley and adjacent regions are the most important metallogenic belt of gold (and copper)-bearing skarn deposits in China. The total gold reserves in this belt have been estimated at more than 600 t. The gold-bearing skarns are mainly distributed in the southeastern Hubei, Tongling and northern Anhui regions. Favorable tectonic settings are depressions and fold zones of the platforms, i.e., mobile belts. These skarns are hosted by platformal limestone, dolomitic limestone and dolomite of the Triassic, Carboniferous-Permian and Middle to Lower Cambrian formations. The related intrusions are Yenshanian (180 to 113 Ma) calc-alkaline quartz monzodiorite, granodiorite, quartz monzonite, monzogabbro, and their hybabyssal facies. The intrusions have high Fe₂O₃/FeO (>0.5) and intermediate initial ⁸⁷Sr/⁸⁶Sr ratios (0.7046 to 0.7087). Their REE distribution patterns are LREE-enriched and exhibit smooth, right-dipping curves. These suggest that the source materials mainly came from upper mantle, with contamination by sialic crustal components. The auriferous skarns are both calcic and magnesian, but calcic skarns are most common. The constituent minerals of the calcic skarns are diopside, garnet, wollastonite, vesuvianite and scapolite, whereas magnesian skarns are dominated by forsterite, spinel, diopside, phlogopite, chondrodite and clinohumite, with abundant superimposed serpentine, clinochlore and brucite. The compositions of coexisting pyroxenes and garnets are diopside and andradite, indicating the high oxygen fugacity and low acidity conditions. Gold is closely associated with Cu (Pb, Zn) sulfides and exists mainly in the form of native gold and electrum. Arsenides, tellurides, bismuthides and selenides are present in many ore deposits. Therefore, Cu, As, Bi, Te, Ag, Pb, Zn, Se and Co are the major metals present in the deposits and are important geochemical ore-searching indicators. In some Au (Fe, Cu) magnesian skarns, magnesiomagnetite, magnesioferrite and ludwigite are locally abundant. The metasomatic zoning in many gold skarn deposits is very distinct consisting of an outward sequence of: Fe (Cu)→Cu (Mo)→Cu (Au)→Au (Cu)→Au (Pb, Zn). The geologic characteristics of Au (Cu) skarn deposits that formed in the mobile platformal setting of China have distinct differences compared to Au skarns formed in orogenic belts at convergent plate margins in British Columbia and the western USA.     

福建马坑矽卡岩型铁(钼)矿床地质特征及辉钼矿Re-Os同位素年龄

福建马坑矿床为赋存于莒舟—大洋花岗岩外接触带黄龙组(C2h)灰岩和林地组(C1l)碎屑岩层间构造破碎带中的大型层控矽卡岩型铁(钼)矿床。笔者利用Re-Os同位素方法对矿体中7件辉钼矿样品进行了成矿时代研究,获得的模式年龄为(131.9±1.9)～(133.3±2.3)Ma,加权平均年龄为(133.0±0.8)Ma,表明马坑铁(钼)矿床的成矿作用发生于早白垩世;其与莒舟花岗岩体的岩浆活动和侵位年龄一致,表明为同一构造-岩浆-流体活动的产物。7件辉钼矿样品中,5件样品Re质量分数为(0.47～5.14)×10-6,另外2个分别为51.87×10-6和186.2×10-6,再考虑到莒舟—大洋岩体为弱过铝壳源型花岗岩,推断成矿物质主要为地壳来源,可能混有少量地幔物质。白垩纪马坑铁(钼)矿的成矿可能为华南岩石圈减薄的响应。     

青海省格尔木市那陵郭勒河西地区铁多金属矿工艺矿物学研究

青海省格尔木市那陵郭勒河西地区铁多金属矿规模大,具有铁铜金等多金属矿化,属于接触交代型铁多金属矿床。本文采用工艺矿物学研究方法,查明了矿石工艺矿物学特性。研究结果表明,矿石的组成矿物种类较为简单,金属硫化物主要是黄铜矿、磁黄铁矿、黄铁矿、闪锌矿;铁矿物主要是磁铁矿、赤铁矿。脉石矿物主要是石英、方解石、透闪石、透辉石;其次为石榴子石、白云母、蛇纹石。矿石中铁、铜锌矿物均具均匀细粒—微细粒嵌布特征;通过选矿可获得铜精矿、锌精矿、铁精矿。     

青海省兴海县赛什塘铜矿床矽卡岩矿物学特征及地质意义

赛什塘铜矿位于东昆仑造山带东端的鄂拉山地区,是中国西部重要的矽卡岩型铜矿之一。矽卡岩形成于印支期石英闪长岩与中—下三叠统地层Tb2 1-2岩性段的接触带,矿体主要呈似层状、透镜状产于外接触带矽卡岩中。Tb2 1-2岩性段由中性火山岩、大理岩及变质粉砂岩构成,其中变安山质凝灰岩及安山岩与铜矿化有着密切的空间关系。岩相学研究表明,含铜矽卡岩的形成经历了矽卡岩阶段、退化蚀变阶段、石英-硫化物阶段及石英-碳酸盐阶段。矽卡岩阶段形成石榴子石、辉石及硅灰石,退化蚀变阶段则形成绿帘石、角闪石及磁铁矿,石英-硫化物阶段大量金属硫化物发生沉淀。电子探针分析表明,石榴子石与辉石矿物组分分别为Gro0.00~91.00And7.02~100.00(Pyr+Alm+Spe)0.00~4.27与Di12.80~98.08Hd2.41~79.80(Jo+Jd+Opx)0.00~13.47,表明其属于典型的钙矽卡岩类。空间上,靠近石英闪长岩与安山岩接触带处,钙铝榴石和绿帘石更富集,而向大理岩的一侧以钙铁榴石为主,并常见硅灰石及含Mn的钙铁辉石。矿物学特征及矿物成分的变化显示:从矽卡岩阶段到石英-硫化物阶段,流体性质呈幕式的变化,成矿流体至少经历了2次氧化还原性质的转变,这种变化可能与成矿流体中大气降水的不断加入有关。赛什塘铜矿属于矽卡岩型矿床,以石英闪长岩为主的岩浆活动携带了大量的热量及流体,侵入到中—下三叠统地层中,与围岩地层发生物质交换的同时,引起了大理岩、变质粉砂岩与中性火山岩之间的双交代作用,是导致矽卡岩和矿体形成的重要机制。     

矽卡岩矿床的研究现状

本文评述了矽卡岩矿床类型划分、矽卡岩形成的物理化学条件、成矿流体以及矿物成分与矿化关系的某些进展。镁矽卡岩形成于各种深度,而钙矽卡岩则形成于较浅和较低温的环境;限制矽卡岩形成的主要参数是ＣＯ＿２、深度以及岩浆期后诸元素的活度（如Ｍｇ￣（２＋）、Ｃａ￣（２＋）…）、ｐＨ和Ｅ＿ｈ值。当前已应用非平衡热力学去研究矽卡岩成岩成矿过程。接触交代带中存在两种流体,一种来自岩浆,另一种是天水循环来源;同位素资料提供水／岩反应的信息,而Ｓ、Ｐｂ、Ｓｒ等同位素资料提供矿质来源的标志。矽卡岩矿物如辉石、石榴石的化学成分与矿化关系密切,可以指示矿化类型。文中总结了矽卡岩型金矿特点,其蹄、铋矿物及退化蚀变是重要的找矿标志。含矿流体及成矿动力学是今后研究的重要方向。