内蒙古红花尔基白钨矿矿床赋矿花岗岩Sr-Nd-Pb-Hf同位素特征

对内蒙古红花尔基白钨矿矿床的赋矿花岗岩进行了全岩Sr、Nd同位素、钾长石Pb同位素以及LA-MC-ICPMS锆石Hf同位素特征研究。结果表明,从肉红色二长花岗岩、灰白色二长花岗岩到石英二长岩,它们的(~(87)Sr/~(86)Sr)_i值依次降低,均值分别为0.70525、0.70517和0.70482,_(εNd)(t)值则依次增加,均值分别为+2.2、+2.3和+3.1。2种二长花岗岩的钾长石Pb同位素值较均一,其中~(206)Pb/~(204)Pzb为18.258~18.276,~(207)Pb/~(204)Pb为15.507~15.512;~(208)Pb/~(204)Pb为37.994~38.018。3种花岗岩的锆石Hf同位素特征显示~(εHf)(t)值分别为+5.2~+10.4(均值+8.1)、+3.1~+9.8(均值+7.5)、+5.8~+14.4(均值+9.2)。赋矿花岗岩的Sr-Nd-Pb-Hf同位素特征指示其源岩物质很可能是以新元古代起源于亏损地幔的下地壳物质为主,石英二长岩可能是岩浆混合了少量地幔物质形成的包体。区域构造分析表明,红花尔基白钨矿矿床赋矿花岗岩岩浆源区的形成可能与新元古代古亚洲洋演化过程中俯冲大洋板块与上地幔的相互作用有关;早侏罗世,蒙古—鄂霍次克洋盆在本区闭合后,板块碰撞隆起的挤压环境触发了源岩物质的部分熔融,从而形成了赋矿花岗岩。     

Fluid Inclusions and C-H-O Isotope Characteristics of the Xianggou-Sigou Tungsten Deposit,Shanyang County,South Qinling北大核心CSCD

The Xianggou-Sigou tungsten deposit is located in Shanyang County, Shaanxi Province, which is one of the newly discovered gold-tungsten deposits in south Qinling. Previous studies have summarized the geological characteristics of the deposit and studied scheelite chronology in detail, but there is no related research on the fluid metallogenic characteristics of tungsten ores in the deposit. In this work, scheelite and symbiotic calcite in the main mineralization stage were selected, and fluid inclusion thermometry, C-H-0 isotope and laser Raman composition tests were carried out. Studies on fluid inclusions show that the homogenization temperature of fluid inclusions is concentrated in 115. 5 X.-273. 6 X. and the salinity is (0. 33-22. 01)% NaCleqv in the main ore-forming period of the deposit. The mineralization temperature is about 150 °C determined by isotope mineral pairs. The main component of fluid inclusions is H20. The values of «5CV-PDB of calcite, 5 Ov-smow an<^ ^DV-SMOW are-0. 80%c ~ 1. 4%c, 2. 09%o ~ 9. 56%c, and-88. 40%e ~ 107. 90%c, respectively. Comprehensive analysis shows that the ore-forming fluid of the deposit is low-temperature magmatic hydrothermal fluid system with obvious mixing of atmospheric water, and the estimated metallogenic depth is about 2 km. The cooling and mixing of the fluid with atmospheric water may be the main mechanism leading to the mineral precipitation. The tungsten ore body in the mining area is mainly produced in the calcite quartz vein type, which is a common feature of the top of the magmatic hydrothermal tungsten ores. The deep part of the mining area is inferred to possess great prospecting potential. © 2022 Editorial Board of Geology and Exploration. All rights reserved.     

江西武山铜矿区新发现钨矿（化）体特征和其成因——来自矿相学、白钨矿原位U-Pb年代学和元素地球化学的约束

钨和铜有明显不同的地球化学性质,但钨、铜在矿床中可以共伴生,原因还不清楚。长江中下游成矿带发育典型的斑岩-矽卡岩-层状铜（钨）多金属成矿系统,其中层状铜（钨）矿体成矿时代数据相对较少。作者以该带九瑞矿集区武山铜矿区新发现的钨矿（化）体为研究对象,开展了矿相学、白钨矿原位U-Pb年代学和元素地球化学的研究。研究发现,武山矿床具有层状、矽卡岩型、斑岩型3类铜矿体均有白钨矿矿化,矿床整体由浅至深存在Cu→Cu-W的分带规律。3类矿石中的白钨矿产状类似,充填在粗粒黄铁矿晶体间隙,或呈浸染状分布,被黄铜矿、闪锌矿等交代,产于退化蚀变阶段;其中斑岩中还存在少量晚世代白钨矿,与石英、黄铁矿共生,形成细脉并穿切花岗闪长斑岩,为石英-硫化物阶段产物。通过对退化蚀变阶段白钨矿进行测年和地球化学研究,作者获得了层状矿体含钨黄铜矿矿石中的白钨矿原位LA-ICP-MS U-Pb同位素年龄为（140.6±1.5）Ma,代表层状铜钨矿体成矿时代,在误差范围内与前人获得的斑岩、矽卡岩型矿体的成矿时代基本一致。层状矿体中白钨矿的稀土元素特征和Sr/Mo值符合岩浆热液矿床特征,相比矽卡岩型、花岗岩型白钨矿,层状矿体中白钨矿具有明显较低Mo含量,反映了形成于相对低氧逸度条件;另外,层状矿体中白钨矿具有正Eu异常和与围岩相近的高Y/Ho值的特征,推测其是流体充分交代了含碳围岩地层导致流体性质的明显改变,并且有利于白钨矿和黄铁矿的沉淀,可从深部黄龙组层间部位形成钨品位更富的黄铁矿矿石得到佐证。文章从白钨矿角度证实层状矿体是斑岩-矽卡岩成矿系统的重要组成部分,提出在九瑞矿集区已知铜矿床的深部,尤其是燕山期中酸性侵入岩与含碳质碳酸盐岩的接触带及黄龙组层位,是寻找富钨矿体的新找矿方向。白钨矿的U-Pb同位素定年为长江中下游成矿带层状矿体的成矿时代提供了新的可靠依据。     

西藏努日白钨矿床微量和稀土元素地球化学特征——对成矿流体与矿床成因的指示

对努日矿床白钨矿中稀土元素、微量元素的地球化学特征研究表明:白钨矿亏损V、Cs、Hf、Ta等元素,并具有异常低的Rb/Sr、Zr/Hf、Nb/Ta的比值,以及Hf/Sm、Nb/La、Th/La值也都远远小于1,指示原始富钨成矿流体来源于深部壳源岩浆结晶分异,并总体以富CL热液为主;采自不同位置的白钨矿样品其稀土元素组成基本一致,其球粒陨石配分曲线表现为明显轻稀土富集的右倾模式,具有明显的Ce正异常(δCe=1.066~1.107)和弱Eu负异常(δEu=0.768~0.910),表明白钨矿与流体之间稀土元素发生了不太明显的分异;白钨矿与夕卡岩化有密切关系的黑云母花岗岩的REE球粒陨石标准化配分曲线均为明显的右倾模式,ΣREE、δCe、δEu值基本一致,暗示岩体对努日白钨矿成矿物质的贡献。努日矿床初始热液流体为一中高温、中低盐度的流体,其沿着构造裂隙运移过程中,与比马组地层发生接触交代反应,体系中CO2和Ca含量的增加,流体的初始平衡体系被破坏,最终导致大量Ca2+与WO42-结合形成了巨量的白钨矿。     

电感耦合等离子体质谱法对白钨矿中稀土元素的准确测定——以云南麻栗坡南秧田白钨矿床的成因探讨为例

通过建立的高分辨电感耦合等离子体质谱测定稀土元素( REEs)的分析方法,准确测定出麻栗坡南秧田白钨矿床两类不同矿体的围岩和矿石中稀土元素的含量,方法的灵敏度高,检出限低,精密度和准确度均非常满意.通过对稀土元素地球化学特征的研究,表明存在两种不同成因的白钨矿,一为与围岩同时沉积形成的白钨矿,在变质作用条件下形成了矽卡岩型白钨矿;二为后期热液携带来的具有较高稀土含量的石英脉型白钨矿.前者具有轻稀土元素富集、重稀土亏损、中等程度的Eu、Ce负异常等特征,与沉积环境关系密切,推测是海底火山喷发(喷流)沉积变质作用的产物;后者具有较低的稀土总量∑REEs以及显著的Eu正异常特征,表现出较高的稀土分馏特性,为后期热液作用形成,并对先期矿体有叠加改造作用,使矿化更加富集.     

低温酸性条件下白钨矿的不一致溶解动力学

在75℃和pH=1.04～2.46时采用间歇型实验方法测定了天然白钨矿在HCl溶液中的溶解速率,揭示了溶解反应的动力学机理。结果表明,Ca的释放速率随反应时间保持稳定,并随pH降低而增大。W的释放行为则更为复杂,在反应初期与Ca呈一致溶解,之后由于钨酸表面层(中间产物)的形成,W的释放量和释放速率明显下降。这说明白钨矿的溶解作用由早期的表面化学反应转变为化学反应-扩散控制过程,从而导致W、Ca呈不一致溶解。pH越小,不一致溶解出现的时间越早。酸性溶液中白钨矿的溶解速率方程为v=k[H+]n,以W和Ca计算的速率常数k分别为0.65×10-5mol/m2s和1.04×10-5mol/m2s,反应级数n则分别为1.20和1.26。结合他人研究结果,白钨矿的溶解反应相对于H+可能为一级反应。     

白钨矿床的地质特征及在吉林省的找矿方向

独立的白钨矿矿床和以白钨矿为主要组分的白钨矿矿床是一类重要的矿床。本文研究了这类矿床的实例,总结了这类矿床的成矿特征,提出了吉林省这类矿床的找矿方向。     

吉林省珲春杨金沟白钨矿区地质特征及找矿方向

杨金沟矿区白钨矿体产于下古生界五道沟群地层与印支期二长花岗岩内外接触带中。矿化类型为花岗岩中的白钨矿—石英脉和斜长角闪片岩、云母石英片岩、红柱石片岩中的白钨矿—石英脉。矿体受南北向、北西向断裂及裂隙构造控制,矿床成因为岩浆热液—层控与岩浆热液复合型。     

Coexistence of a Fluid Phase with Granitic Magma: Geochemical Characteristics of REE and Cu in Miyako Granite and in Scheelite-bearing Aplitic Veins at the Yamaguchi Cu-W Skarn Deposit, Iwate, Japan

Abstract: The North granitic body of the Miyako pluton is located in the Northern Kitakami belt, Northeast Japan. The formation of the scheelite–chalcopyrite–magnetite–bearing aplitic veins and scheelite–chalcopyrite–magnetite–bearing Yamaguchi skarn deposit was closely associated with the formation of the Miyako plutons. Petrographic facies of the North granitic body vary from quartz diorite in marginal zone (zone A), to tonalite and granodiorite (zone B), and to granite (zone C) in the central. The large numbers of aplitic veins distributed around the Yamaguchi mining area are divided into two groups: barren and scheelite–mag–netite–chalcopyrite–bearing aplitic veins. The latter cut massive clinopyroxene skarns of the Yamaguchi deposit, and are composed of plagioclase, K‐feldspar and titanite. Some plagioclase crystals have dusty cores with irregularly shaped K‐feldspar flakes, and clear rims of albite. Textures of plagioclase in the mineralized aplitic veins are different from the idiomorphic textures with sharp plagioclase crystal boundaries that occur in the North granitic body and barren aplitic veins. These textural data suggest that the mineralized aplitic veins were formed from hydrothermal fluid. Changes in the contents of major and minor (Rb, Sr, Sc, Co, Th, U) elements in the North Miyako granitic body are similar to those of zoned plutons formed by typical magmatic differentiation processes. On the other hand, concentrations of REE, especially middle to heavy REE, of granitic rocks in zone C and barren aplitic veins are significantly lower than those of granitic rocks in zones A and B. The hypothetical chondrite‐normalized REE patterns, calculated assuming fractional crystallization from zone B granitic melt, suggest that REE concentrations of the residual melt increased with the degree of fractional crystallization, and changed into a pattern with enriched LREE and strongly negative Eu anomaly. However, the REE patterns of granitic rocks in zone C are different from the hypothetical patterns. Moreover, the REE patterns of magnetite–scheelite–chalcopyrite aplitic veins are quite different from those of granitic rocks. The Cu contents of granitic rocks in the North Miyako body increase from zone A (5–26 ppm) to zone B (10–26 ppm), and then clearly decrease to zone C (5–7 ppm) and drastically increase to the barren aplitic veins (39–235 ppm). Concentrations of Cu in the mineralized aplitic veins are also higher than those of the granitic rocks in zone C. The decrease in REE and Cu contents of granitic rocks from zone B to zone C is not a result of simple magmatic fractional differentiation. Fluid inclusions in quartz from mineralized aplitic veins contain 3.3 wt% NaCl equivalent and 5.8 wt% CO₂. It was also demonstrated experimentally that the removal of MREE and HREE by fluid from melt enabled the formation of complexes of REE and ligands of OH^‐ and CO₃^2‐. Based on the possibility that the melt of the granitic rocks of zone C and the mineralized aplitic veins coexisted with CO₂‐bearing fluid, it is thought that REE were extracted from the melt to the CO₂‐bearing fluid, and that the REE in the mineralized aplitic veins were transported by the CO₂‐bearing fluid. It is likely that the low HREE and Cu contents of the granitic rocks in zone C could have been caused by the removal of those elements from the granitic melt by the fluid coexisting with the melt. The expelled materials could have been the sources of scheelite–magnetite–chalcopyrite–bearing aplitic veins and copper mineralization of the Yamaguchi Cu‐W skarn deposit.     

长江中下游成矿带庐枞矿集区新发现钨多金属矿床

庐枞矿集区是长江中下游成矿带内重要的铁铜矿集区,产出一系列典型的玢岩型铁矿床和斑岩型铜矿床。最近在庐枞矿集区北部东顾山地区,首次发现了钨多金属矿床,这是在长江中下游成矿带长江以北首次发现的钨矿化,为矽卡岩型。钨矿化主要呈浸染状或脉状产于东顾山岩体(黑云母花岗岩)与奥陶系(白云质灰岩)的接触带或大理岩层间破碎带中。矿石矿物主要为白钨矿及钼、铜、铅锌硫化物。钨矿化主要发育在华南地区,近年来在长江中下游成矿带的过渡带及以南的扬子地块如江南隆起等地发现多个新的大型钨矿床,但在长江以北地区一直未曾发现。庐枞矿集区北部东顾山钨矿床的发现,指明长江中下游成矿带燕山期除铁、铜大规模成矿作用以外,也有钨的成矿作用,指示该区具有良好的钨矿找矿前景。在长江中下游成矿带的其他矿集区要重视和加强钨矿化的成矿作用研究和找矿工作。