Hydrothermal alteration characteristics of the Chating Cu-Au deposit in Xuancheng City, Anhui Province, China: Significance of sericite alteration for Cu-Au exploration
Hydrothermal alteration characteristics of the Chating Cu-Au deposit in Xuancheng City, Anhui Province, China: Significance of sericite alteration for Cu-Au exploration
复制标题
安徽省宣城市茶亭铜金矿热液蚀变特征：绢云母蚀变对铜金找矿的意义
DOI：
10.1016/j.oregeorev.2020.103844
复制
发表时间：
2020-12
影响因子：
3.3
通讯作者：
Xie Zujun
中科院分区：
文献类型：
--
作者：
Zhou Yan;Li Longming;Yang Kai;Xing Guangfu;Xiao Wenjiao;Zhang Hongliang;Xiu Liancun;Yao Zhongyou;Xie Zujun
安徽省宣城市茶亭铜金存款矿床是一个以强烈热液蚀变的斑岩型矿床。利用短波红外反射光谱法对两个剖面的岩心蚀变进行了系统分析。共鉴定出绢云母、蒙皂石、高岭石、地开石、蒙脱石、绿帘石、石膏、碳酸盐、氧化铁、皂石、绿帘石等11种蚀变矿物，并根据吸收峰深度计算了各矿物在不同深度的相对丰度。其中氧化铁和石膏可能与表生作用有关，其它蚀变矿物为热液蚀变矿物。矿物组合及其空间分布特征表明，该铜金存款的蚀变模式主要受岩浆热液作用的水-岩相互作用控制，形成了典型的斑岩型热液成矿系统。皂石-蒙皂石-钾长石-硬石膏蚀变组合主要产于容矿石英闪长斑岩中，少量见于围岩灰岩和成矿后闪长斑岩中。石英二长斑岩中广泛发育绢云母-绢云母蚀变组合，蚀变强度从存款中心向外逐渐减弱。高岭石-方解石蚀变组合主要产于石英闪长斑岩顶部及周围灰岩中。热液的物理化学条件，如温度和pH值，控制了特定蚀变矿物的成分变化。最显著的特征是绢云母中八面体铝离子含量的细微变化，这可以通过绢云母Al-OH吸收峰位置的波长变化来确定。绢云母的主要成分是白云母，并含有微量的多硅白云母。Cu-Au品位与绢云母Al-OH吸收峰位置的波长呈负相关，因为高矿石品位与相对较短的Al-OH波长相关，对应于绢云母中的高Al/Si比（即朝向白云母）。这种相关性表明，矿石金属倾向于在蚀变体系的酸性环境中富集和沉淀。此外，Al-OH波长在存款中的横向变化表明，热液流体的酸度从存款中心向外逐渐降低，而绢云母Al-OH波长随深度的变化表明，流体pH值随深度的减小而增加。蚀变模式表明，成矿流体在成矿过程中可能从斑岩系统深部的西南向近地表的东北方向迁移。通过光谱蚀变填图，认为茶亭矿区至少经历了3个阶段的热液活动：早期钾质-矽卡岩热液蚀变阶段、中期绿柱石-绢云母中低温蚀变阶段和晚期高岭石-地开石浅成热液蚀变阶段。绢云母蚀变阶段与铜金矿化有时间上的联系，并导致茶亭主矿体的形成。由于目前的勘探重点仍集中在绢云母蚀变带，推测茶亭地区深部勘探潜力巨大。
The Chating Cu-Au deposit in Xuancheng City, Anhui Province, is characterized by porphyry-style mineralization with intensive hydrothermal alteration. Short-wave infrared reflectance spectroscopy was used to systematically analyze the alteration of drill cores from two cross sections. Eleven alteration minerals—sericite, smectite, kaolinite, dickite, chlorite, epidote, gypsum, carbonate, iron oxide, saponite, and prehnite—were identified, and the relative abundances of individual minerals at various depths were calculated by depth of absorption peak. In these minerals, iron oxides and gypsum are probably related to supergene process and other alteration minerals are hydrothermal alteration minerals. The mineral assemblages and their spatial distributions indicate that the alteration patterns in this Cu-Au deposit were controlled mainly by water–rock interaction of the magmatic–hydrothermal process, resulting in a typical porphyry-style hydrothermal mineralization system. A saponite–smectite–K-feldspar–anhydrite (gypsum) alteration assemblage is located mainly in the host quartz diorite porphyry, and is minor in the wall rocks of limestone and a post-mineralization diorite porphyry. A sericite–chlorite alteration assemblage was widely developed in the quartz diorite porphyry, and the intensity of alteration decreases gradually outward from the center to the margins of the deposit. A kaolinite–calcite alteration assemblage is mainly located on the top of the quartz diorite porphyry and in the surrounding limestone. The physiochemical conditions of the hydrothermal fluid, such as temperature and pH, control the compositional variations of specific alteration minerals. The most remarkable feature is a subtle change in octahedral Al cation content of sericite, as identified by the change in wavelength of sericite Al-OH absorption peak position. Muscovite is the main component of sericite, with a trace amount of phengite. The Cu-Au grades are negatively correlated with the wavelength of sericite Al-OH absorption peak position, because high ore grades are associated with relatively shorter Al-OH wavelengths, corresponding to a high Al/Si ratio in sericite (i.e. towards muscovite). This correlation suggests that the ore metal tends to be enriched and precipitated in an acidic environment of the alteration system. In addition, a lateral variation across the deposit in Al-OH wavelength indicates that the acidity of the hydrothermal fluids decreases gradually from the center of the deposit outward to the wall rocks, whereas the variation of sericite Al-OH wavelength with depth suggests an increase in fluid pH with decreasing depth. The alteration patterns imply that during mineralization the ore-forming fluids probably migrated from the southwest in the deep part of the porphyry system towards the northeast near the surface. Based on the spectral alteration mapping, it is concluded that there were at least three stages of hydrothermal activity in the Chating mining district: an early potassic–skarn hydrothermal alteration stage, an intermediate propylitic–sericite medium-low temperature alteration stage, and a late kaolinite–dickite epithermal stage. The sericite alteration stage is temporally related to Cu-Au mineralization, leading to the formation of the main orebody at Chating. As the current exploration is still focused in the sericite alteration zone, it is inferred that deep exploration has great potential in the Chating district.
登录
查看更多内容
影响因子：
5.8
作者：
W. Herrmann;Michael Blake;Mark Doyle;D. Huston;J. Kamprad;Nick Merry;S. Pontual
通讯作者：
W. Herrmann;Michael Blake;Mark Doyle;D. Huston;J. Kamprad;Nick Merry;S. Pontual
影响因子：
5
作者：
W. Giggenbach
通讯作者：
W. Giggenbach
影响因子：
2.9
作者：
B. Velde
通讯作者：
B. Velde
DOI：
10.5382/segnews.2000-40.fea
发表时间：
2000
期刊：
SEG Discovery
影响因子：
--
作者：
James R. Lang;Tim Baker;Craig J. R. Hart;James K. Mortensen
通讯作者：
James R. Lang;Tim Baker;Craig J. R. Hart;James K. Mortensen
影响因子：
--
作者：
CLARK, RN;ROUSH, TL
通讯作者：
ROUSH, TL