Stratigraphic Correlation of the Malusok Volcanogenic Massive Sulfide Deposits, Southern Mindanao, Philippines

Abstract: Two adjacent volcanogenic massive sulfide (VMS) deposits, the Main Malusok and the Malusok Southeast, are delineated within Barangay Tabayo, Siocon, Zamboanga del Norte, Mindanao, Philippines. These deposits comprise massive to semi-massive sulfide lenses representing the down-dip equivalent of oxidized gossans. The massive sulfides have a primary mineral assemblage of pyrite-chalcopyrite-sphalerite with significant amounts of supergene copper in the form of chal-cocite. Owing to structural and metamorphic overprinting combined with intense alteration, primary textures are generally obliterated. Rock types are classified according to dominant mineral assemblages whereas the main lithologic units comprising the Malusok volcanic package are divided based on the position of each unit relative to the mineralized zone. The main lithologic units are designated as the hanging wall, the host, and the footwall sequences. In correlating the stratigraphy of the Main Malusok zone with that of the Malusok Southeast zone, a chlorite/epidote-rich interval located at the base of the hanging wall sequence serves as a distinct stratigraphic marker from which all lithologies are referred to. Comparisons between the stratigraphy of the two areas show that massive to semi-massive sulfide lenses are confined within a single stratigraphic interval representing the favorable horizon for the entire Malusok area. However, differences exist relative to style of mineralization and configuration of the altered interval between the Main Malusok and the Malusok Southeast VMS deposits. Based on characteristics exhibited by each individual deposit, it is inferred that the Main Malusok VMS deposit overlies a feeder zone whereas the Malusok Southeast sulfide lenses represent satellite deposits and transported blocks.     

Mass Change Calculations as Applied to the Search for Volcanogenic Massive Sulfide Deposits: An Example from Malusok, Siocon, Zamboanga del Norte, Mindanao, Philippines

Abstract. The Malusok volcanogenic massive sulfide (VMS) deposits comprise two adjacent ore bodies, the Main Malusok and the Malusok Southeast ore bodies, hosted within Cretaceous metamorphic rocks. Owing to the structural and metamor-phic overprinting combined with intense hydrothermal alteration, primary textures of the Malusok volcanic rocks have been obliterated. The stratigraphic correlation of the Main Malusok and the Malusok Southeast ore bodies show that both deposits are essentially confined within a single stratigraphic interval. The lithogeochemical analysis of the Malusok samples shows that constituent lithologies have precursor compositions ranging from sub-alkaline basalts to rhyodacites. Field and mass flux data suggest that the Main Malusok VMS deposits were derived as a consequence of axial hydrothermal activity. The Malusok Southeast ore bodies represent satellite deposits generated by off-axis hydrothermal activities from vents aligned along a NW-SE trend with the Main Malusok zone. This alignment represents an ancient fissure that served as a pathway for the upwelling metalliferous hydrothermal fluids. In searching for lateral extensions of these VMS deposits, this NW-SE alignment should serve as a possible exploration guide.     

Chemical Composition of Ores from the Takara Volcanogenic Massive Sulfide Deposit, Central Japan

Abstract. The Takara volcanogenic massive sulfide (VMS) deposit occurs in Miocene formation of the Misaka Mountain, the South Fossa Magna region, central Japan. The tectonic setting of the Misaka Mountain is reconstructed to be a part of the paleo Izu-Ogasawara arc which collided with the Honshu arc and to form accreted body in the present position. The Takara deposit, therefore, is considered to have formed in the paleo Izu-Ogasawara arc.
The ores from the Takara deposit are classified into pyrite-type ore, chalcopyrite-type ore, and sphalerite-type ore on the basis of chemical composition and their mineral assemblages. Some pyrite-type ores are characterized by their high Au content. The Au content is hardly recognized in the chalcopyrite-type and sphalerite-type ores.
The ores from the Takara deposit have intermediate bulk chemical composition between those from the Besshi-type deposits and the Kuroko-type deposits that are two representative VMS deposits. However, the bulk chemical composition is closer to that from the Kuroko-type deposits. And moreover, chemical composition of tetrahedrite-tennantite series minerals (tetrahedrite) is similar to that from the Kuroko-type deposits. The bulk chemical composition (Cu, Zn, Co, Pb, and As contents) of ores is affected by the chemical composition of volcanic rocks associated with VMS deposits.     

Stable Isotopic Information on Calcareous Pelitic Rocks in the Tizapa Volcanogenic Massive Sulfide Deposit Area, the United Mexican States

Abstract: Tizapa volcanogenic massive sulfide (VMS) deposit is hosted in greenschist facies metamorphic rocks; footwall is green schist of felsic to mafic metavolcanic rocks and hanging wall is graphite schist of metasedmentary pelitic rock. Pb-Pb dating of ore samples indicates 103. 4Ma to 156. 3Ma for the age of mineralization (JICA/MMAJ, 1991).     

Geology and Geochemistry of Highly Metamorphosed Footwall Alteration Zones in the Hongtoushan Volcanogenic Massive Sulfide Deposit,Liaoning Province,China

The Hongtoushan Archean Cu–Zn volcanogenic massive sulfide (VMS) deposit, which was metamorphosed (3.0–2.8 Ga) to upper amphibolite facies at temperatures between 600 and 650°C, occurs in the Hunbei granite–greenstone terrane, Liaoning Province of NE China. Stratiform cordierite–anthophyllite gneiss (CAG) that occurs hundreds of meters below the ore horizon in the Hongtoushan district corresponds to the metamorphosed semi‐conformable alteration zone of the VMS hydrothermal system, whereas the CAG that contains abundant deformed sulfide‐bearing quartz veins immediately below the main ore layer represents the metamorphosed discordant alteration zone. Whole‐rock geochemistry indicates that stratiform CAG was derived ultimately from five lithologies (basalt, basaltic andesite, andesite, dacite, and rhyolite), while discordant CAG derived from a single lithology (rhyolite). Amphibolite and biotite‐rich gneiss are identified as a metamorphosed least‐altered precursor for these CAGs. Mass change calculation indicates that, compared to the least‐altered rocks, stratiform CAG is enriched in Fe and Mg, and depleted in Na, K, Ca, Cu, Pb and Zn, while discordant CAG is enriched in Fe, Mg, Si, Na, Pb, Cu and Zn, and depleted in K. HREE and HFSE (Zr, Ti, Nb and Ta) behaved inertly during submarine alteration, whereas Rb, Sr, Ba and LREE (especially Eu) were leached off. Both stratiform and discordant CAGs are depleted in ¹⁸O, with values up to 7‰ lower than their corresponding least‐altered precursors. Addition of Fe, Mg, and depletion of Ca, K, Sr, and ¹⁸O, indicate that hydrothermal alteration for both types of CAGs was characterized by chloritization prior to metamorphism. Stratiform CAG could be used to evaluate the mineralization potential of VMS in metamorphic terranes, while discordant CAG containing sulfide‐bearing quartz veins could be a good indication for overlying stratiform massive sulfide ores as well as an exploration target itself.     

块状硫化物矿床研究进展评述

最近十余年来,海底块状硫化物矿床的研究在如下方面有新的进展：矿床类型,矿化和蚀变特征,矿石结构－构造和变形－变质,矿床模式和成矿机制,金属和硫的来源,成矿流体的性质和来源,以及现代海盆地中的成矿作用等。     

华南型块状硫化物矿床中的胶黄铁矿及其退火作用

华南型块状硫化物矿床中胶黄铁矿的退火过程从早到晚可分成三个阶段:原始晶化变胶体阶段、不等粒变晶生长阶段和颗粒界面调整阶段。不同阶段的矿石各具特征性的结构,反映了燕山期侵入活动对于先存胶黄铁矿的不同程度热效应。     

Double Convective Hydrothermal System beneath Massive Sulfide Orebody in Gacun Deposit,Southwestern China

The Gacun Kuroko-type deposit, Southwestern China, is hosted in rhyolitic rocks associated with the underlying mafic rocks occurred in the ～1000 m deep fault-hounded basin within the intra-arc rifting zone which formed on the Triassic Yidun island-arc. Two vertically separated alteration systems are recognized: one is conformable or semiconformable alteration zone developed in ～150 m thick mafic unit 1-1.5 km below the massive sulfde orehody; the other is discordant alteration pipe directly surrounded around stockwork ore within rhyolitic unit. The lower conformable alteration zone extending for several kilometers along strike is characterized by silicification and epidotization which result in the development of quartz vein and quartz-epidote vein systems in mafic lava flows and replacement of primary minerals and groundmass in spilitized mafic volcanics and dikes by quartz, epidote-group minerals and sodic plagiocluse. Sulfides often occur in the vein system and altered mafic volcanics. Quartz solubi     

云南二叠纪白马寨铜镍硫化物矿床的成因:地壳混染与矿化的关系

云南金平白马寨-营盘街-带的奥陶纪变砂岩和板岩中出露大量小型约260Ma的镁铁-超镁铁质岩体,其中白马寨地区三个岩体具明显铜-镍硫化物矿化：三号岩体有一个中型铜镍硫化物矿床,一号和二号岩体可见微弱矿化。一号岩体的Ni／Cu值为0．7～2．2,二号岩体的Ni／Cu值为1．4～4．0,与三号岩体的比值（Ni／Cu=-0．5～6．7）相近,说明他们的母岩浆成分接近,为富Mg的镁铁质或苦橄质岩浆。三个岩体遭受不同程度的地壳混染,表现为强烈的Nb（Ta）异常,很低的Nb／La值（O．5～O．7）和很负的￡。。（f）值（一5．1～一9．O）。根据全岩的Th／Yb和Nb／Th值估算,一号岩体的地壳混染程度为5％～20％,二号岩体的地壳混染程度为5％～10％,而三号岩体的地壳混染程度高达35％。三个岩体的地壳混染程度与岩体中硫化物的含量呈正相关关系,表明地壳混染是导致白马寨岩体硫化物饱和的主要因素。     

运用正交函数拟合预测新疆阿舍勒地区块状硫化物矿床

新疆阿舍勒块状硫化物铜锌矿床,是一个正在勘探的大型富铜矿床,矿体呈厚大透镜状,具层控特征,矿体和围岩之间密度差较大。地面重力方法,理应是最有效的勘探方法,但是,由于阿舍勒矿区地质构造过分复杂,地下不同深度的多种密度体叠合在一起,往往掩盖了矿体所产生的重力异常。为了解决这个疑难问题,通过研究,选择适当的正交函数去进行拟合,实现目标信息分离,将成矿层位的重力异常从实测重力异常值中分离出来,勾绘出了矿区线状构造成矿带的轮廓,揭示了矿区构造;指出找矿方向,圈出１１个重力异常,根据矿区矿石的最低密度大于围岩最高密度的实事,可以说：“凡有矿的地方必然显示出重力异常”。故使用本方法处理重力资料,在阿舍勒这类矿区,可具直接找矿效果。     

现代海底热液活动与块状硫化物矿床成因研究进展

现代海底热液活动的发现及对其分布特征和成矿机理的研究是近年来海洋地质学和矿床地质学的一大进展。对现代海底金属硫化物成矿作用的研究大大推动和促进了对古代块状硫化物矿床成因的认识。有关研究成果综合分析表明：(1)深部热液对流循环系统是块状硫化物成矿的核心，对流循环模式有简单的热液对流模式和双扩散对流模式。(2)块状硫化物矿床集中分布在大洋中张裂性活动板块边界，与大地构造活动紧密联系。(3)成矿流体与成矿物质均有多源性，在强调海水循环淋滤的同时，通过应用新的方法技术，岩浆来源物质(流体及成矿金属等)对一些块状硫化物矿床成矿的直接贡献得到初步确认。(4)在高温热液活动区及金属硫化物沉积中发现大量生命活动和生物群体，意义重大。     

闽中裂谷块状硫化物型铅锌矿床的地质特征及找矿意义

中-新元古代闽中地区铅锌多金属矿床形成的古构造环境、主要矿床地质特征及矿床成因研究是了解华夏古陆前寒武纪构造成矿演化及进一步找矿的关键。地层层序及岩相学研究表明闽中地区马面山群东岩组并不是一次火山旋回的产物,而是经历了至少3期双峰式火山作用。地球化学研究表明赋矿地层东岩组的原岩属海相细碧-石英角斑质火山岩系,形成于中-新元古代的大陆裂谷环境。典型矿床地质研究表明闽中地区在新元古代形成海底火山喷流沉积块状硫化物铅锌矿床（或矿胚层）,燕山晚期受到了强烈的构造及岩浆热液的叠加改造,并形成一定规模的矿床。在此基础上初步探讨了中-新元古代古裂谷环境与块状硫化物矿床形成的成因联系。根据闽中地区铅锌矿床的主要特征、找矿方法的分析,总结了该类矿床的找矿标志,并对该区的找矿前景进行了初步分析。     

论梅仙块状硫化物矿床的特征及成矿地质环境

梅仙铅锌矿床产于双峰式火山岩系内,火山岩的岩石化学,稀土和微量元素特征的研究表明其形成于大陆裂谷环境中,闽中裂谷带的发生,发展和演化控制着梅仙矿床的成矿过程。梅仙铅锌矿床特征的研究揭示其是裂谷火山活动有关的块状硫化物矿床,并经后期热液叠加改造。     

Geology, Geochemistry and U-Pb SHRIMP Age of the Tacloban Ophiolite Complex, Leyte Island (Central Philippines): Implications for the Existence and Extent of the Proto-Philippine Sea Plate

Abstract. The oceanic basement of the Central Philippines is exposed in ophiolitic massifs the age and origin of which remain debated. The Tacloban Ophiolite Complex (TOC) outcrops as a NW-SE trending massif in the northeastern portion of Leyte Island, Central Philippines. It is unconformably overlain by sedimentary sequences dated to Late Miocene-Pliocene and Pleistocene volcaniclastic deposits on its eastern and western flanks, respectively. Field, petrographic and trace element data suggest a subduction-related origin for this ophiolite. Sensitive High Resolution Ion Microprobe (SHRIMP) U-Pb dating of zircons from a gabbro yielded Early Cretaceous magmatic age for the TOC, which is very much older than a previously reported whole rock K-Ar derived Eocene age. The Early Cretaceous age of the TOC limits its possible progenitor to the proto-Philippine Sea Plate. Correlation with other Cretaceous ophiolites in Central Philippines reveals the possible extent of the proto-Philippine Sea Plate remnants now exposed onland.     

Jusa and Barsuchi Log Volcanogenic Massive Sulfide Deposits from the Southern Urals of Russia: Devonian Analogs of the Kuroko Deposits of NE Honshu, Japan

Chemical analysis of 60 samples from the Jusa and Barsuchi Log volcanogenic massive sulfide (VMS) deposits by inductively coupled plasma–mass spectrometry shows that, on average, the Jusa deposit is more enriched in the chalcophilic elements than the Barsuchi Log deposit, whereas the Barsuchi Log deposit is more enriched in the lithogenous elements and Te. In addition, the yellow ores in these deposits are more enriched on average in Cu, As and Mo and the black ores more enriched in Zn, Ga, Cd, Sb, Ba , Hg and Pb relative to each other. Both these deposits are similar in composition to the Kuroko deposits of NE Honshu and may be considered to be analogs of these deposits. The Kuroko deposits, however, contain much higher concentrations of As, Ag, Sb, Ba, Hg and lower contents of Te on average than the Jusa and Barsuchi Log deposits. Based on the higher contents of Te in the Barsuchi Log deposit compared to the Jusa deposit, as well as on textural considerations, it is concluded that the Barsuchi Log deposit is intermediate between the Urals- and Kuroko-type deposits, whereas the Jusa deposit is more analogous to the Kuroko-type deposits. Based on the compositional data presented here, the Jusa and Barsuchi Log deposits may be described as Zn-Pb-Cu-Ba deposits rather than as Zn-Cu-Ba deposits, as the Baimak-type deposits of the west Magnitogrosk zone have previously been described.     

加拿大拜韦尔特半岛金-铜矿集区成矿地质背景与矿床特征

拜韦尔特半岛矿产资源主要包括铜、金和石棉,区域地层和构造是控制矿床形成、发展和叠加改造的主要因素。这些矿产资源主要赋存在拜韦尔特海洋带达利吉带圣母玛利亚亚带的早奥陶世潜次火山岩中,包括起源于超俯冲作用带的蛇绿岩套和火山岩盖层。其蛇绿岩套超镁铁堆积岩的热液蚀变岩中产出石棉,火山成因的块状硫化物型(VMS型)铜±金矿产在基性和双峰式火山岩中,金矿产在基性和超基性的热液蚀变岩中。而蛇绿岩套火山岩盖层中则产出与条带状含铁建造(BIF)有关的后生金矿,石英脉型或相关的交代型矿床则大多赋存在蚀变和变形的基性岩中。拜韦尔特半岛的构造样式和几何结构非常复杂。     

金沙江造山带碰撞后地壳伸展背景——火山成因块状硫化物矿床的重要成矿环境

近年来对金沙江造山带区域地质、矿床地质和岩石地球化学新资料的研究和典型火山成因块状硫化物(VHMS)矿床的解剖,金沙江造山带的VHMS成矿作用主要发生于早二叠世晚期—晚二叠世海相弧火山岩和晚三叠世裂谷盆地海相火山岩中,构成西南三江地区一条重要的多金属块状硫化物成矿带。成矿带内晚三叠世碰撞后地壳伸展背景下形成的上叠裂谷盆地是其VHMS成矿作用的主体,盆地中火山活动从早期的双峰式火山岩演变为晚期的中酸性火山岩,岩石地球化学特征与孤火山岩有明显的区别,反映其形成于伸展背景。伸展盆地的早期阶段,在双峰火山岩组合的高钾流纹质火山岩系中产出鲁春式VHMS矿床,具有Zn-Cu-Pb-Ag金属组合特征,形成于深水环境;伸展盆地的晚期阶段,在中酸性火山岩系与上覆碳酸盐岩接触带中产出赵卡隆式VHMS矿床,具有Ag-Fe-Pb-Zn金属组合特征,形成于浅水环境;盆地的末期阶段,在滨浅海相磨拉石碎屑岩中产出里仁卡式石膏矿床。金沙江造山带碰撞后地壳伸展背景下VHMS成矿作用的研究,对于造山带中的找矿工作具有重要的指导意义。     

古老大陆岩石圈地幔再循环与蛇绿岩中铬铁矿床成因

不同地区、不同时代蛇绿岩中不同类型铬铁矿岩的Re-Os同位素研究表明,在铬铁矿石或围岩中均存在极度亏损的具有大陆岩石圈地幔属性的物质。新疆达拉布特古生代蛇绿岩带中萨尔托海富Al铬铁矿岩的Os同位素组成为0.1109～0.1256,对应的模式年龄为3.5～0.6Ga;西藏班公湖—怒江中生代蛇绿岩带中东巧富Cr铬铁矿石及围岩Os同位素组成介于0.1175～0.1261,对应的模式年龄为1.5～0.1Ga;雅鲁藏布江中生代蛇绿岩带中罗布莎富Cr铬铁矿岩的Os同位素变化范围为0.1038～0.1266,对应的模式年龄为3.37～0.28Ga,而该带中不含矿的泽当二辉橄榄岩的Os同位素组成为0.1256～0.1261,没有古老大陆岩石圈地幔属性的物质存在,与新特提斯洋地幔Os组成较为接近。推测在蛇绿岩形成过程中,古老大陆岩石圈地幔参与循环有利于形成铬铁矿床,明确提出"熔体与古老大陆岩石圈地幔反应成矿"的假说,指出蛇绿岩带中存在的古老微陆块可能是找矿的指示标志。     

Jusa and Barsuchi Log Volcanogenic Massive Sulfide Deposits from the Southern Urals of Russia: Tectonic Setting, Structure and Mode of Formation

The Jusa and Barsuchi Log volcanogenic massive sulfide (VMS) deposits formed along a paleo island arc in the east Magnitogrosk zone of the Southern Urals between ca 398 and 390 Ma. By analogy with the VMS deposits of the west Magnitogrosk zone, they are considered to be Baimak type deposits, which are Zn‐Cu‐Ba deposits containing Au, Ag and minor Pb. Detailed mapping and textural analysis of the two deposits shows that they formed as submarine hydrothermal mounds which were subsequently destroyed on the sea floor under the influence of ocean bottom currents and slumping. Both deposits display a ratio of the length to the maximum width of the deposit >15 and are characterized by ribbon‐like layers composed mainly of bedded ore and consisting principally of altered fine clastic ore facies. The Jusa deposit appears to have formed in two stages: deposition of colloform pyrite followed by deposition of copper–zinc–lead sulfides characterized by the close association of pyrite, chalcopyrite, sphalerite, galena, tennantite, arsenopyrite, marcasite, pyrrhotite, bornite, native gold and electrum and high concentrations of gold and silver. The low metamorphic grade of the east Magnitogorsk zone accounts for the exceptional degree of preservation of these deposits.