The Kay Tanda epithermal Au deposit in Lobo, Batangas is one of the Au deposits situated in the Batangas Mineral District in southern Luzon, Philippines. This study aims to document the geological, alteration, and mineralization characteristics and to determine the age of the mineralization, the mechanism of ore deposition, and the hydrothermal fluid characteristics of the Kay Tanda deposit. The geology of Kay Tanda consists of (i) the Talahib Volcanic Sequence, a Middle Miocene dacitic to andesitic volcaniclastic sequence that served as the host rock of the mineralization; (ii) the Balibago Diorite Complex, a cogenetic intrusive complex intruding the Talahib Volcanic Sequence; (iii) the Calatagan Formation, a Late Miocene to Early Pliocene volcanosedimentary formation unconformably overlying the Talahib Volcanic Sequence; (iv) the Dacite Porphyry Intrusives, which intruded the older lithological units; and (v) the Balibago Andesite, a Pliocene postmineralization volcaniclastic unit. K‐Ar dating on illite collected from the alteration haloes around quartz veins demonstrated that the age of mineralization is around 5.9 ± 0.2 to 5.5 ± 0.2 Ma (Late Miocene). Two main styles of mineralization are identified in Kay Tanda. The first style is an early‐stage extensive epithermal mineralization characterized by stratabound Au‐Ag‐bearing quartz stockworks hosted at the shallower levels of the Talahib Volcanic Sequence. The second style is a late‐stage base metal (Zn, Pb, and Cu) epithermal mineralization with local bonanza‐grade Au mineralization hosted in veins and hydrothermal breccias that are intersected at deeper levels of the Talahib Volcanic Sequence and at the shallower levels of the Balibago Intrusive Complex. Paragenetic studies on the mineralization in Kay Tanda defined six stages of mineralization; the first two belong to the first mineralization style, while the last four belong to the second mineralization style. Stage 1 is composed of quartz ± pyrophyllite ± dickite/kaolinite ± diaspore alteration, which is cut by quartz veins. Stage 2 is composed of Au‐Ag‐bearing quartz stockworks associated with pervasive illite ± quartz ± smectite ± kaolinite alteration. Stage 3 is composed of carbonate veins with minor base metal sulfides. Stage 4 is composed of quartz ± adularia ± calcite veins and hydrothermal breccias, hosting the main base metal and bonanza‐grade Au mineralization, and is associated with chlorite‐illite‐quartz alteration. Stage 5 is composed of epidote‐carbonate veins associated with epidote‐calcite‐chlorite alteration. Stage 6 is composed of anhydrite‐gypsum veins with minor base metal mineralization. The alteration assemblage of the deposit evolved from an acidic mineral assemblage caused by the condensation of magmatic volatiles from the Balibago Intrusive Complex into the groundwater to a slightly acidic mineral assemblage caused by the interaction of the host rocks and the circulating hydrothermal waters being heated up by the Dacite Porphyry Intrusives to a near‐neutral pH toward the later parts of the mineralization. Fluid inclusion microthermometry indicates that the temperature of the system started to increase during Stage 1 (T = 220–250°C) and remained at high temperatures (T = 250–290°C) toward Stage 6 due to the continuous intrusion of Dacite Porphyry Intrusives at depth. Salinity slightly decreased toward the later stages due to the contribution of more meteoric waters into the hydrothermal system. Boiling is considered the main mechanism of ore deposition based on the occurrence of rhombic adularia, the heterogeneous trapping of fluid inclusions of variable liquid–vapor ratios, the distribution of homogenization temperatures, and the gas ratios obtained from the quantitative fluid inclusion gas analysis of quartz. Ore mineral assemblage and sulfur fugacity determined from the FeS content of sphalerite at temperatures estimated by fluid inclusion microthermometry indicate that the base metal mineralization at Kay Tanda evolved from a high sulfidation to an intermediate sulfidation condition.

中文翻译：

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菲律宾八打雁省Lobo的Kay Tanda超热金矿床的地质，蚀变和矿化

八打雁Lobo的Kay Tanda超热金矿床是位于菲律宾吕宋岛南部八打雁矿区的金矿床之一。这项研究的目的是记录地质，蚀变和矿化特征，并确定凯坦达矿床的矿化年龄，矿床沉积机理和热液特征。凯·坦达（Kay Tanda）的地质结构包括：（i）塔拉希卜火山岩层序，它是中新世中新世至安山岩火山碎屑岩层序，是成矿作用的主岩；（ii）Balibago Diorite配合物，是侵入Talahib火山层序的同基因侵入配合物；（iii）Calatagan组，是中新世晚期至上新世早期的火山沉积岩层，不整合地覆盖在Talahib火山岩层之上；（iv）达克特斑岩侵入体，侵入较旧的岩性单元；（v）上新世后矿化火山碎屑单元巴里巴哥安山岩。从石英脉周围蚀变晕收集的伊利石上的K-Ar年代测定表明，成矿年龄约为5.9±0.2至5.5±0.2 Ma（中新世晚期）。凯坦达（Kay Tanda）确定了两种主要的矿化样式。第一种类型是早期广泛的超热矿化，其特征是在Talahib火山岩层的较浅层上托管有地层约束的含Au-Ag的石英储层。第二种是后期贱金属（Zn，Pb，（Cu）和Cu）的超热矿化，局部富矿化的Au矿化存在于脉和热液角砾岩中，这些脉和水热角砾岩在Talahib火山层序的较深层和Balibago侵入复合体的较浅层相交。凯坦达（Kay Tanda）关于成矿作用的共生研究定义了六个成矿阶段。前两个属于第一个矿化样式，而后四个属于第二个矿化样式。第1阶段由石英脉构成的石英±叶蜡石±闪锌矿/高岭石±辉绿岩蚀变。第2阶段由含金-银的石英库存与普遍的伊利石±石英±绿土±高岭石蚀变有关。第三阶段由碳酸盐矿脉和少量贱金属硫化物组成。第4阶段由石英±阿杜利亚±方解石脉和热液角砾岩组成，具有主要的贱金属和富矿级金矿化作用，并与绿泥石－伊利石－石英蚀变有关。第五阶段由与碳酸盐-方解石-绿泥石蚀变有关的碳酸盐-碳酸盐脉管组成。第6阶段由硬石膏矿脉和少量贱金属矿化组成。矿床的蚀变组合是由岩浆挥发物从巴厘巴哥侵入复合体凝结成地下水引起的酸性矿物组合演化成的，而主岩和循环水加热的热水相互作用则引起了酸性的矿物组合。在成矿后期，Dacite斑岩侵入体的pH值接近中性。流体包裹体热计量法表明，由于Dacite斑岩的不断侵入，系统温度在第1阶段（T = 220–250°C）期间开始升高，并在第6阶段一直处于高温（T = 250–290°C）。深度侵入。由于更多的流域水进入热液系统，盐分在后期逐渐降低。沸腾被认为是矿石的主要沉积机理，其基于菱形小孔的出现，液-汽比可变的流体夹杂物的非均质捕集，均质温度的分布以及石英定量流体夹杂物气体分析获得的气体比率。 。