REE geochemistry data from the Fanshan alunite deposit indicated that its ore-forming materials came chiefly from the country rocks, with δCe>0 for alunite ores. According to the differences in δEu,the alunite or...REE geochemistry data from the Fanshan alunite deposit indicated that its ore-forming materials came chiefly from the country rocks, with δCe>0 for alunite ores. According to the differences in δEu,the alunite ores were divided into three types: weak negative Eu anomaly, weak positive Eu anomaly and remarkable positive Eu anomaly. The phenomena of Ce-enrichment in the ores indicated that the Fanshan alunite deposit was formed in an oxidizing environment. Variations in fO2 are corresponding to those in δEu: Eu anomaly varies from negative to positive with increasing fO2 . And two other important factors may impact the occurrence of Eu anomalies: the contents of alkaline feldspar and the protolith structure in the mineralization period.展开更多
Lithocaps are composed of silicic and advanced argillic altered rocks,and represent an important target for porphyry-epithermal Cu-Au exploration.Previous studies showed that integrating alunite spectral and compositi...Lithocaps are composed of silicic and advanced argillic altered rocks,and represent an important target for porphyry-epithermal Cu-Au exploration.Previous studies showed that integrating alunite spectral and composition with lithocap whole-rock geochemistry can effectively aid exploration for concealed Cu-Au mineralization.The Zijinshan Cu-Au and Dafanshan alunite deposits are located in the Coastal Volcanic Belt in SE China,where alunite is an indicator of hypogene mineralization and alteration.Detailed mineralogical studies of alunite from these two deposits were performed with short-wavelength infrared spectroscopy(SWIR),whole-rock geochemistry and laser ablation inductively coupled plasma mass spectrometry(LA-ICP-MS).For Zijinshan,wavelength variation of the SWIR alunite absorption peak at 1480 nm is proportional to the whole-rock Na/(Na+K)molar ratio of alunitebearing samples.Different percentage of alunite and mineral assemblages in the lithocap samples would both affect the wavelength of the SWIR alunite absorption peak at1480 nm.We suggest that the alunite Ba-Bi contents and the whole-rock Nb/La value(of alunite-bearing rocks)are reliable vectoring tools for detecting magmatic-hydrothermal mineralization center in the district.Comparing the alunite SWIR spectral and mineral geochemical features and whole-rock geochemistry of alunite-bearing rocks between the Zijinshan and Dafanshan deposits,Au–Ag mineralization may be concealed at depth in northwestern Dafanshan.展开更多
紫金山金铜矿是我国大陆首例高硫化型浅成低温热液型矿床。矿床上金下铜，金矿主要赋存在潜水面以上，与强硅化有关；铜矿主要赋存于潜水面之下，与明矾石化有关。明矾石有四种产出状态，分别为蚀变岩型、与铜硫化物共生型、后期脉状、...紫金山金铜矿是我国大陆首例高硫化型浅成低温热液型矿床。矿床上金下铜，金矿主要赋存在潜水面以上，与强硅化有关；铜矿主要赋存于潜水面之下，与明矾石化有关。明矾石有四种产出状态，分别为蚀变岩型、与铜硫化物共生型、后期脉状、粉末状。不同产出状态的明矾石具有不同的拉曼光谱特征和荧光散射背景。明矾石流体包裹体激光拉曼谱图显示：（1）从蚀变岩型、与铜硫矿化物共生型到后期脉状明矾石均具有明矾石特征性的谱带，只是受荧光散射影响逐渐减弱；粉末状明矾石具有与前三者不同的谱带特性，各谱带强度均较弱，荧光散射较强烈。（2）100～700 cm -1区间谱带可作为明矾石分子结构中阳离子类质同象置换的“指纹谱带”。蚀变岩型明矾石，161和234 cm -1峰变化明显，具有较广泛的N a对K的类质同象置换；与铜硫化物共生的明矾石，381和484 cm -1峰变化明显，指示Cu和Ga等阳离子对Al离子的类质同象置换；后期脉状明矾石，161，234，484，508 cm -1峰值均比较稳定，Na对K和Si对Al的类质同象置换较少；潜水面附近的粉末状明矾石因荧光散射强烈，各个谱带强度均较弱。（3）明矾石的激光拉曼光谱和红外光谱配合使用，可为明矾石矿物研究提供完整的分子振动光谱特征，为明矾石的成因提供结构信息。在岩相学、矿相学、矿床地质、矿床地球化学、区域地质特征研究的基础上，通过明矾石的激光拉曼光谱（结合荧光散射背景）可进一步为紫金山金铜矿这个典型的高硫化型浅成低温热液矿床的形成机制提供演化进程信息。展开更多
蚀变岩帽在地表一般表现为陡倾的正地形,是高温、高氧逸度流体对围岩进行酸性淋滤,形成的一系列高级泥化和泥化等蚀变矿物组合。这种蚀变是浅成低温热液蚀变系统的一部分,其深部可能具有寻找斑岩型矿化的潜力。浙东南陆相火山岩地区普...蚀变岩帽在地表一般表现为陡倾的正地形,是高温、高氧逸度流体对围岩进行酸性淋滤,形成的一系列高级泥化和泥化等蚀变矿物组合。这种蚀变是浅成低温热液蚀变系统的一部分,其深部可能具有寻找斑岩型矿化的潜力。浙东南陆相火山岩地区普遍发育此种蚀变岩帽,但该类型蚀变常被前人定义为"次生石英岩"。本文选择其中典型的后坑蚀变岩帽,通过大比例尺蚀变填图、岩心编录,利用短波红外(ASD)、电子探针(EPMA)、扫描电镜(SEM)、能谱仪(EDS)等分析技术手段,发现蚀变岩帽具有垂直方向和水平方向的蚀变矿物分带。垂直方向由深到浅依次发育刚玉-绢云母,绢云母-叶蜡石,明矾石-高岭石-地开石具分带特征;水平方向上从核部到边部依次发育多孔状石英-金红石、高级泥化带(明矾石-叶蜡石-高岭石-地开石-水铝石-Aluminum Phosphate and sulphates矿物)、泥化带(高岭石-伊利石-蒙脱石)。并得出以下几点认识:①后坑蚀变岩帽中明矾石短波红外特征吸收峰在1480~1491nm之间,以岩浆-热液成因的钾明矾石为主,含少量钠明矾石;②叶蜡石短波红外特征吸收峰在2167nm左右,分为两种成因:早期高级泥化阶段的绢云母经后期热液退变质蚀变而成以及早期高岭石经后期热液进变质作用形成;③蚀变岩帽根部的刚玉被后期热液蚀变形成绢云母,刚玉-绢云母蚀变带之下可能是黄铁绢英岩化带;④早期水铝石被后期热液蚀变形成地开石,代表了热液的多期次性;通过对比后坑蚀变岩帽与其他斑岩-浅成低温热液矿床(如Horse-Ivaal和Vuda等矿床)的蚀变矿物分带后,发现后坑蚀变岩帽蚀变矿物分带与这些典型矿床相似。本文认为后坑蚀变岩帽属于该成矿系统上部的浅成低温热液蚀变部分,其深部具有寻找斑岩矿床的潜力,同时提出浙东南其他发育在陆相火山岩中的蚀变岩帽也属于该蚀变系统,具有寻找斑岩型铜金矿床的较大潜力。展开更多
Laser micro area analysis 40 Ar 39 Ar isochron dating for pure alunite is first reported. Micro area 40 Ar 39 Ar isochron dating results revealed that the metallogenetic epoch of Fanshan superlarge alunite deposit is ...Laser micro area analysis 40 Ar 39 Ar isochron dating for pure alunite is first reported. Micro area 40 Ar 39 Ar isochron dating results revealed that the metallogenetic epoch of Fanshan superlarge alunite deposit is 74.50 Ma, and this age is 10-20 Ma later than that of regional volcanic activity. Moreover, the potential application of micro area analysis 40 Ar 39 Ar isochron dating method in metallogenetic epoch studies for nonmetal deposits is also discussed.展开更多
基金This research project was financially supported jointly by the Key Research Project (No. KZCX3-SW-125) of CAS and the National Natural Science Foundation of China (No. 40172037).
文摘REE geochemistry data from the Fanshan alunite deposit indicated that its ore-forming materials came chiefly from the country rocks, with δCe>0 for alunite ores. According to the differences in δEu,the alunite ores were divided into three types: weak negative Eu anomaly, weak positive Eu anomaly and remarkable positive Eu anomaly. The phenomena of Ce-enrichment in the ores indicated that the Fanshan alunite deposit was formed in an oxidizing environment. Variations in fO2 are corresponding to those in δEu: Eu anomaly varies from negative to positive with increasing fO2 . And two other important factors may impact the occurrence of Eu anomalies: the contents of alkaline feldspar and the protolith structure in the mineralization period.
基金financially supported by the National Natural Science Foundation of China(Grant No.41925011)the National Key Research and Development Program of China(Grant No.2022YFC2903601)。
文摘Lithocaps are composed of silicic and advanced argillic altered rocks,and represent an important target for porphyry-epithermal Cu-Au exploration.Previous studies showed that integrating alunite spectral and composition with lithocap whole-rock geochemistry can effectively aid exploration for concealed Cu-Au mineralization.The Zijinshan Cu-Au and Dafanshan alunite deposits are located in the Coastal Volcanic Belt in SE China,where alunite is an indicator of hypogene mineralization and alteration.Detailed mineralogical studies of alunite from these two deposits were performed with short-wavelength infrared spectroscopy(SWIR),whole-rock geochemistry and laser ablation inductively coupled plasma mass spectrometry(LA-ICP-MS).For Zijinshan,wavelength variation of the SWIR alunite absorption peak at 1480 nm is proportional to the whole-rock Na/(Na+K)molar ratio of alunitebearing samples.Different percentage of alunite and mineral assemblages in the lithocap samples would both affect the wavelength of the SWIR alunite absorption peak at1480 nm.We suggest that the alunite Ba-Bi contents and the whole-rock Nb/La value(of alunite-bearing rocks)are reliable vectoring tools for detecting magmatic-hydrothermal mineralization center in the district.Comparing the alunite SWIR spectral and mineral geochemical features and whole-rock geochemistry of alunite-bearing rocks between the Zijinshan and Dafanshan deposits,Au–Ag mineralization may be concealed at depth in northwestern Dafanshan.
文摘紫金山金铜矿是我国大陆首例高硫化型浅成低温热液型矿床。矿床上金下铜，金矿主要赋存在潜水面以上，与强硅化有关；铜矿主要赋存于潜水面之下，与明矾石化有关。明矾石有四种产出状态，分别为蚀变岩型、与铜硫化物共生型、后期脉状、粉末状。不同产出状态的明矾石具有不同的拉曼光谱特征和荧光散射背景。明矾石流体包裹体激光拉曼谱图显示：（1）从蚀变岩型、与铜硫矿化物共生型到后期脉状明矾石均具有明矾石特征性的谱带，只是受荧光散射影响逐渐减弱；粉末状明矾石具有与前三者不同的谱带特性，各谱带强度均较弱，荧光散射较强烈。（2）100～700 cm -1区间谱带可作为明矾石分子结构中阳离子类质同象置换的“指纹谱带”。蚀变岩型明矾石，161和234 cm -1峰变化明显，具有较广泛的N a对K的类质同象置换；与铜硫化物共生的明矾石，381和484 cm -1峰变化明显，指示Cu和Ga等阳离子对Al离子的类质同象置换；后期脉状明矾石，161，234，484，508 cm -1峰值均比较稳定，Na对K和Si对Al的类质同象置换较少；潜水面附近的粉末状明矾石因荧光散射强烈，各个谱带强度均较弱。（3）明矾石的激光拉曼光谱和红外光谱配合使用，可为明矾石矿物研究提供完整的分子振动光谱特征，为明矾石的成因提供结构信息。在岩相学、矿相学、矿床地质、矿床地球化学、区域地质特征研究的基础上，通过明矾石的激光拉曼光谱（结合荧光散射背景）可进一步为紫金山金铜矿这个典型的高硫化型浅成低温热液矿床的形成机制提供演化进程信息。
文摘蚀变岩帽在地表一般表现为陡倾的正地形,是高温、高氧逸度流体对围岩进行酸性淋滤,形成的一系列高级泥化和泥化等蚀变矿物组合。这种蚀变是浅成低温热液蚀变系统的一部分,其深部可能具有寻找斑岩型矿化的潜力。浙东南陆相火山岩地区普遍发育此种蚀变岩帽,但该类型蚀变常被前人定义为"次生石英岩"。本文选择其中典型的后坑蚀变岩帽,通过大比例尺蚀变填图、岩心编录,利用短波红外(ASD)、电子探针(EPMA)、扫描电镜(SEM)、能谱仪(EDS)等分析技术手段,发现蚀变岩帽具有垂直方向和水平方向的蚀变矿物分带。垂直方向由深到浅依次发育刚玉-绢云母,绢云母-叶蜡石,明矾石-高岭石-地开石具分带特征;水平方向上从核部到边部依次发育多孔状石英-金红石、高级泥化带(明矾石-叶蜡石-高岭石-地开石-水铝石-Aluminum Phosphate and sulphates矿物)、泥化带(高岭石-伊利石-蒙脱石)。并得出以下几点认识:①后坑蚀变岩帽中明矾石短波红外特征吸收峰在1480~1491nm之间,以岩浆-热液成因的钾明矾石为主,含少量钠明矾石;②叶蜡石短波红外特征吸收峰在2167nm左右,分为两种成因:早期高级泥化阶段的绢云母经后期热液退变质蚀变而成以及早期高岭石经后期热液进变质作用形成;③蚀变岩帽根部的刚玉被后期热液蚀变形成绢云母,刚玉-绢云母蚀变带之下可能是黄铁绢英岩化带;④早期水铝石被后期热液蚀变形成地开石,代表了热液的多期次性;通过对比后坑蚀变岩帽与其他斑岩-浅成低温热液矿床(如Horse-Ivaal和Vuda等矿床)的蚀变矿物分带后,发现后坑蚀变岩帽蚀变矿物分带与这些典型矿床相似。本文认为后坑蚀变岩帽属于该成矿系统上部的浅成低温热液蚀变部分,其深部具有寻找斑岩矿床的潜力,同时提出浙东南其他发育在陆相火山岩中的蚀变岩帽也属于该蚀变系统,具有寻找斑岩型铜金矿床的较大潜力。
文摘Laser micro area analysis 40 Ar 39 Ar isochron dating for pure alunite is first reported. Micro area 40 Ar 39 Ar isochron dating results revealed that the metallogenetic epoch of Fanshan superlarge alunite deposit is 74.50 Ma, and this age is 10-20 Ma later than that of regional volcanic activity. Moreover, the potential application of micro area analysis 40 Ar 39 Ar isochron dating method in metallogenetic epoch studies for nonmetal deposits is also discussed.
