Ore and Alteration Types of the Gold and Copper Mineralization in the Lascogon Project, Surigao del Norte, Mindanao Island, Philippines

Two ore and three alteration types were identified in the Lascogon Project of Philex Gold Philippines, in Surigao del Norte, Mindanao Island, Philippines. The jasperoid ore is the host to the Carlin‐like gold mineralization in the Lascogon and Danao prospects. The ore occurs in a decalcified and silicified horizon, with minor chlorite and goethite, stibnite, pyrite and quartz crystals ranging from cryptocrystalline to botryoidal. The stringer–stockwork type Cu‐Au mineralization in the Suyoc prospect is hosted in argillized andesitic rocks of the Mabuhay Formation. The primary ore minerals are chalcopyrite with minor amounts of sphalerite. The alteration types identified are propylitic alteration, argillic alteration and silicification. The propylitized basaltic and andesitic flows of the Bacuag Formation bound the jasperoid mineralization in the Lascogon prospect. Stratigraphically, the relationship between propylitized basalts and stringer–stockwork Cu‐Au is not clear but a lateral change can be inferred from jasperoid in the center and stringer–stockwork towards the east.     

Geochemical Characteristics of Intrusive Rocks, Southeastern Mindanao, Philippines: Implication to Metallogenesis of Porphyry Copper-gold Deposits

This paper describes petrologic and geochemical characteristics of intrusive rocks associated with porphyry copper deposits in south-eastern Mindanao, the Philippines, where the Kingking deposit is located. Intrusive rocks at the Kingking deposit, are classified into biotite-bearing diorite porphyry, hornblende diorite porphyry and diorite porphyry. Intrusive rocks in other areas in south-eastern Mindanao, including Batoto, Bukal, Maragusan, Masara, Amacan and Sumlog, are hornblende diorite porphyry and hornblende quartz diorite. They are adakitic in Sr/Y-Y diagram, but not in La/Yb-Yb diagram due to relatively low REE contents. The magmas are oxidizing as suggested by the high X_Mg of mafic silicate phenocrysts and SO₃ contents of microphenocrystic apatite. An Oligocene-Miocene diorite intrusive complex formed by calc-alkaline, hydrous, oxidizing magma is considered to be associated with porphyry-type copper-gold mineralization.     

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.     

辽宁省本溪县杨家堡子金矿地质特征及成因浅析

本溪县杨家堡子金矿赋存于早古生代奥陶系马家沟组及寒武系凤山组内,矿体主要围岩为变质程度轻微的碎屑沉积岩及碳酸盐岩,矿体受断裂构造控制,金矿物及载金矿物——黄(褐)铁矿均呈稀疏浸染状分布,金成矿与燕山期二长花岗岩关系密切,具有"卡林型"金矿床地质特征。认为杨家堡子金矿是与早古生代寒武系、奥陶系地层、岩性、岩相(变质相)、断裂构造及燕山期岩浆活动有成因联系的金矿床,对矿体的矿物组合进行分析,初步确定矿化成因应属低温热液型金矿床。     

Origin of Bornite Pods in Intrusive Rocks at the Kingking Porphyry Copper-gold Deposit, Southeastern Mindanao, Philippines

At the Kingking porphyry copper-gold deposit, Compostela Valley, south-eastern Mindanao, Philippines, bornite pods occur in the brecciated parts in the biotite diorite porphyry, together with the volcanic rock and diorite fragments without associated stockworks of quartz veinlets. These pods are generally elongated in shape and measure several centimeters across their longest axes. They are composed of bornite and chalcopyrite with traces of calaverite. The δ³⁴S of bornite and subordinate chalcopyrite of bornite pods ranging from −2.2‰ to +0.1‰ are similar to the δ³⁴S of sulfides associated with quartz veinlets such as bornite and chalcopyrite ranging from −4.7‰ to ±0.0‰. This suggests that the ultimate source of sulfur is identical for bornite pods and sulfides associated with quartz veinlets. Bornite pods are associated with volcanic rock and dioritic fragments in the brecciated portion of the biotite diorite porphyry. It was observed that some dioritic fragments contain quartz veinlets, which may indicate an earlier episode of mineralization. Fragments of the earlier dioritic intrusive rocks and the volcanic rocks, together with the sulfides were incorporated into the biotite diorite porphyry magma. A molten sulfide is possible for the composition between bornite and intermediate solid solution at ∼800°C. The sulfides from the earlier dioritic intrusive rocks in the molten state were segregated and then eventually coalesce to form the bornite pods in the brecciated section of the biotite diorite porphyry.     

Geology and Hydrothermal Alteration of the Duobuza Gold‐Rich Porphyry Copper District in the Bangongco Metallogenetic Belt,Northwestern Tibet

The Duobuza gold‐rich porphyry copper district is located in the Bangongco metallogenetic belt in the Bangongco‐Nujiang suture zone south of the Qiangtang terrane. Two main gold‐rich porphyry copper deposits (Duobuza and Bolong) and an occurrence (135 Line) were discovered in the district. The porphyry‐type mineralization is associated with three Early Cretaceous ore‐bearing granodiorite porphyries at Duobuza, 135 Line and Bolong, and is hosted by volcanic and sedimentary rocks of the Middle Jurassic Yanshiping Formation and intermediate‐acidic volcanic rocks of the Early Cretaceous Meiriqie Group. Simultaneous emplacement and isometric distribution of three ore‐forming porphyries is explained as multi‐centered mineralization generated from the same magma chamber. Intense hydrothermal alteration occurs in the porphyries and at the contact zone with wall rocks. Four main hypogene alteration zones are distinguished at Duobuza. Early‐stage alteration is dominated by potassic alteration with extensive secondary biotite, K‐feldspar and magnetite. The alteration zone includes dense magnetite and quartz‐magnetite veinlets, in which Cu‐Fe‐bearing sulfides are present. Propylitic alteration occurs in the host basic volcanic rocks. Extensive chloritization‐silicification with quartz‐chalcopyrite or quartz‐molybdenite veinlets superimposes on the potassic alteration. Final‐stage argillic alteration overlaps on all the earlier alteration. This alteration stage is characterized by destruction of feldspar to form illite, dickite and kaolinite, with accompanying veinlets of quartz + chalcopyrite + pyrite and quartz + pyrite assemblages. Cu coexists with Au, which indicates their simultaneous precipitation. Mass balance calculations show that ore‐forming elements are strongly enriched during the above‐mentioned three alteration stages.     

安徽枞县拨茅山-牛头山铜矿床地质特征及找矿方向

拨茅山—牛头山铜矿床的的赋矿岩石为中生代的火成岩系。侵入岩一潜火山岩一火山岩构成完整的侵入—喷发系列。该矿床可分为火山气液—沉积铜矿床和斑岩型铜矿床两种类型。在成矿前期，陆相火山岩在湖底发生火山喷气、火山热泉以及火山热水沉积。潜火山岩的侵入，伴有长期热液循环活动，在张性断裂为主的赋矿空间生成与斑岩有关的各类型矿床。     

Recognition of two contrasting structural-and mineralogical-gold mineral systems in the Youjiang basin,China-Vietnam:Orogenic gold in the south and Carlin-type in the north

The gold deposits in the Youjiang basin,totaling 25 Moz gold,have traditionally been thought to be of Carlintype,particularly those with extensional structural geometries in the northern basin dominated by platform sedimentary sequences.However,the structural geometries,mineralization styles and alteration types for the Jinya,Gaolong and Nakuang gold deposits in the south-central part of the basin are remarkably similar to those of unequivocal orogenic gold deposits.Structural studies show that gold mineralization in the three gold deposits was controlled by tight "locked-up"anticlines with NW—SE-to E-W-trending and/or concomitant thrusts and/or shear zones,which resulted from NE-SW-to N-S-trending compression or transpression following the Early Triassic closure of the Paleo-Tethyan Ocean.Alteration zones in these deposits are dominated by silicification(quartz),sericitization,sulfidation and carbonation.Zoned pyrites in these deposits comprise Au-poor cores and invisible Au-bearing rims with minor external free gold.Euhedral to subhedral auriferous arsenopyrites also contribute to the gold budget.These features indicate that the three gold deposits are sediment-hosted orogenic gold deposits that contrast markedly with the Carlin-type gold deposits in the northern part of the Youjiang basin in terms of structural geometry and timing,mineralization style and nature of associated alteration.Although additional reliable ages using robust methodologies are still required,the older isotopic ages of the gold deposits in the south-central Youjiang basin are also consistent with earlier formation during transpression that predated extension during orogenic collapse,the period of formation of the Carlin-type gold deposits in the northern Youjiang basin.     

Late Tertiary Gold-Bearing Volcanic Belt in the Sierras Pampeanas of San Luis,Argentina

In the Sierras Pampeanas of San Luis, Argentina, Late Tertiary volcanic rocks extend along a 80-km NW-SE-trending belt, between La Carolina and Sierra del Morro. Several gold deposits, among which those in the western end of the belt are better known, are genetically related to the volcanic rocks, formed during a volcanic episode that occurred between 9.5 Ma and 1.9 Ma. Located 600 km from the Peru-Chile trench, the volcanic belt represents the easternmost and youngest mineralized magmatic manifestation associated with the shallowing of the Nazca plate in the flat-slab Andean segment extending from 28° to 33° S Lat.

The volcanic complex includes lavas and volcaniclastic rocks. Small-volume lavas were emplaced as domes, flows, and dikes. Pyroclastic deposits are associated with them in certain areas, such as at La Carolina, Cerro Tiporco, and Sierra del Morro. At La Carolina, phreatomagmatic breccias and base-surge deposits define a maar-diatreme volcanic setting. At Cerro Tiporco and Sierra del Morro, the volcaniclastic units are related to the formation of calderas. Mesosilicic magmas (SiO₂ = 59% to 68%) belong to normal to high-K calc-alkaline and shoshonitic magma types. At both local and regional scales, K enrichment accompanies progressively decreasing age. Although the volcanic rocks differ from the typical Andean series, some geochemical features, such as Ta and Ti depletion, high large-ion-lithophile-element (LILE) contents, and arc-like Ba/La and La/Ta ratios, indicate an arc signature.

In the La Carolina zone, the most important mineralization is the La Carolina volcanic-hosted, low-sulfidation, epithermal gold deposit. Here, several gold and base-metal-bearing epithermal veins cut basement rocks. In the Canada Honda district, the most important mineral deposits are the Diente Verde gold-rich porphyry copper deposit and low-sulfidation epithermal gold and base-metal veins hosted by both basement and coeval volcanics.

There is no strong evidence of gold-bearing mineral deposits on the eastern side of the volcanic belt. However, there are hydrothermal alteration zones at Cerros del Rosario and El Morro as well as traces of gold at the Santa Isabel calcareous onyx deposit and inside the Sierra del Morro caldera. In addition, favorable volcanic structures, such as the calderas at Tiporco, Cerro Lomita, and El Morro, make the eastern side of the belt an interesting target for mineral exploration.     

Tectonogeochemical features and metallogenic prognosis in the Xiaolongtan copper mining district, Binchuan, Yunnan Province, China

The Xiaolongtan copper mining district is an important area in Dali, West Yunnan, where porphyry copper deposits occur, and copper orebodies are controlled by fault or contact zone structures between porphyry massifs and country rocks. Based on detailed field investigation and deep-going analysis, the authors systematically studied the tectonogeochemical features of this mining district, proposed the principle and foundation of metallogenic prognosis, and delineated the most potential mineralization target area.     

藏东主要岩金矿床类型基本特点及其找矿前景

藏东地区是西南三江复合造山带有色金属，贵金属成矿带的重要组成部分，也是三江带中北段新生代强烈陆内变形区，具有金和金银金属矿产成矿的优越条件。已发现的众多岩金矿（化）点反映出藏东有多种岩金矿床成因类型，其中以斑岩型和破碎带充填交代型两种类型最为重要。前者以新生代浸源偏碱性斑岩为成矿母岩，矿（化）体赋存于斑岩，隐爆角砾岩内部，接触带及外接触蚀变带中，主矿化元素为金，银，铅，锌，少数还有铜，钨，后者的矿（化）体一般同存于多期活动的区域性大断裂侧次级断裂，派生断裂，层间破碎带及节理，劈理发育带内，主矿化元素亦为金及银，铅，锌，铜，个别有锑，汞等，成矿时代以新生代及白垩纪一新生代为主。文中还对藏东构造单元和新生代偏碱性岩带进行划分。对两种金矿床类型的一般矿化特征，矿源层，蚀变和化探异常与矿化关系。找矿标志及找矿方向作了简要论述。     

西秦岭地区金矿类型及其成矿作用

西秦岭地区是中国最重要的金矿矿集区之一,除产出少数夕卡岩型金矿床外,几乎所有的其他金矿床都可归并为造山型、卡林型和类卡林型3种类型。研究表明,西秦岭地区中生代花岗岩主要形成于中晚三叠世,而金矿成矿主要集中在晚三叠世,它们都是华北板块与华南板块碰撞导致的秦岭造山作用的产物。西秦岭地区造山型金矿床主要赋存在泥盆系和石炭系一套复杂的构造变形和区域变质的绿片岩相岩中,主要受北西西向脆韧性剪切带控制,成矿元素组合主要为Au-Ag。矿石中含有大量显微自然金、银金矿,明金可见。成矿流体主要为变质流体。由造山作用引起的强烈构造运动为成矿流体提供了运移通道,为矿质沉淀提供了有利的场所。虽然一些造山型金矿床与中酸性岩体相邻,但矿化与岩浆活动不具直接的成因关系。西秦岭地区卡林型金矿床主要产于轻微变质的寒武系至三叠系沉积岩中,明显受地层、岩性和构造控制。金矿床中的金以超显微金和存在于含砷黄铁矿与毒砂晶格中的固溶体金为主。成矿元素组合为Au-As-Hg-Sb-Ba。成矿流体由早期形成的地层水被后期大气降水补给活化形成,也有部分岩浆水或变质水的加入。在伸展背景下大气降水通过循环演化形成了较浅层次的流体系统,导致Au等成矿元素发生沉淀而形成浸染状矿石。西秦岭地区类卡林型金矿床主要产于浅变质沉积岩建造中,受脆韧性剪切带的控制,并形成于花岗岩岩体附近。与造山型、卡林型金矿床最大的不同之处在于,类卡林型金矿床的形成与同时期的岩浆活动有密切的成因关系。矿石中存在显微自然金,载金矿物主要为黄铁矿、含砷黄铁矿和碲化物。成矿热液主要是岩浆水与变质水、建造水的混合流体。与造山型金矿床类似,流体不混溶导致类卡林型金矿床的形成。     

西藏嘎拉勒铜金矿床地质特征及矽卡岩矿物学特征研究

嘎拉勒铜金矿床位于班公湖-怒江缝合带西段,是该带上新近发现的十分重要的矽卡岩(斑岩)型铜金矿床,其金资源量已达大型以上规模。矿区内出露地层有白垩系朗久组及捷嘎组,并发育大量燕山期中酸性侵入岩。矿体主要产于灰白色花岗闪长岩与白云岩或白云质大理岩的接触带矽卡岩内。矽卡岩主要呈层状、似层状、港湾状及不规则状等产出;矽卡岩矿物主要为橄榄石、蛇纹石、辉石、金云母、透闪石、绿帘石、水镁石等;靠近内接触带可见石榴子石;金属矿物主要有磁铁矿、自然金、黄铜矿、斑铜矿、辉铜矿、辉钼矿等。电子探针分析表明,矿区内矽卡岩矿物中的橄榄石主要为镁橄榄石,辉石主要为透辉石,云母主要为金云母,由此构成的矽卡岩矿物组合为典型的镁质矽卡岩;与之伴生的钙质矽卡岩矿物石榴子石主要为钙铁榴石。矿区中的矽卡岩在空间上具有较好的分带性,其表现为从内接触带至外接触带经历了镁橄榄石-透辉石相至金云母-透闪石相的渐变过渡演化,表明矿区矽卡岩具有从高温至低温的矿物组合演化序列;与矽卡岩分带相伴随的矿化分带,表现为深部的铜(钼)矿化过渡到浅部的铜金矿化。矿区最新勘查成果显示,在深部已发现少量斑岩型矿化,显示存在统一的矽卡岩-斑岩成矿系统的可能性,深部找矿潜力较大。     

Sediment‐Hosted Gold Deposits in Southeast Asia

Sediment‐hosted gold (SHG) deposits are becoming more widely recognized in the Southeast Asian region. They are characterized by very fine‐grained gold, typically occurring in stratabound jasperoid replacement and structurally controlled orebodies in calcareous or carbonaceous sedimentary rocks, which are commonly distal to porphyry copper–gold deposits. Gold mineralization is associated with anomalous As‐Sb‐Hg‐Tl and is normally concentrated in the arsenic‐rich rims of pyrite and arsenopyrite grains (commonly refractory). The examples discussed in this paper are located in Southeast Asian countries, and all occur in island or continental arc terrains. SHG deposits have many features comparable to the Carlin deposits in Nevada; however, they differ in tectonic setting, their shallow level of emplacement, fluid composition, and probable metal source. As such, the Southeast Asian examples described in this compilation may be classified as “Carlin‐like” but not “Carlin‐type.” Furthermore, they appear to represent a subclass of low‐temperature epithermal deposits, with most occurrences showing late‐stage colloform quartz vein events. Indeed, they are better described as sediment‐hosted epithermal gold deposits. Several examples are multimillion ounce deposits, such as Sepon, Laos, with its endowment of more than 4 million ounces of gold. Mesel, Sulawesi, and Bau (Jugan and Tai Parit), Sarawak, also possessed multimillion ounce resources prior to mining. Two centuries of Chinese alluvial and eluvial mining at Buduk in northwest Kalimantan has produced a significant unrecorded amount of gold. Structurally controlled feeder zones frequently contain higher‐grade gold mineralization (e.g. Mesel), and constitute valid exploration targets. More recently discovered deposits, such as those in Myanmar (Gegalaw, Taungzaw, and Katsena) and the Philippines (Hijo and Las Cogon), remain to be thoroughly explored. Most of the deposits (Sepon, Mesel, Abong, Sihayo, Jugan, Tai Parit, Hijo, and Lascogon) can be directly linked spatially and genetically to gold–copper porphyry intrusive centers. It is postulated that localities with no obvious connection to known porphyry deposits (Buduk, Ban Bak, Kyaukpahto, Gegalaw, Taungzaw, and Katsena) may represent district‐scale exploration targets for porphyry copper–gold deposits. In terms of discovery techniques, of the 13 SHG deposits discussed here, several were sites of historical mining (Mesel, Bau, and Kyaukpahto). The majority, however, are virgin deposits discovered in the past 25 years by intuitive area selection followed by systematic regional geochemical exploration programs and routine geological inspections. At the project scale, electrical resistivity techniques, such as controlled‐source audio frequency magnetotellurics (CSAMT) and induced polarization (IP), have proven to be useful for mapping blind jasperoid bodies and associated feeder zones and silicified structures. Traditional field mapping and stream float sampling in tropical regions are also effective exploration tools. Deposits that have significant jasperoid development may have conspicuous positive topographic relief, depending on erosion level.     

黔西南水银洞金矿床矿体数学特征及其勘查意义

水银洞金矿床是黔西南地区著名的特大型微细浸染型金矿床.对矿石品位统计分布特征的分析表明,水银洞金矿床为多次成矿作用叠加的产物.通过矿石品位进行混合总体筛分获得两个单一总体,分别对应两次成矿作用,即沉积成岩期的金预富集和构造-热液期的叠加成矿,其中后者成矿强度大但不均匀,前者成矿强度小但较均匀.对矿体自相关特征的变异函数模拟结果表明,对该矿床进行勘探时可采用沿矿体走向和倾向方向布置的矩形勘探网,提出今后矿山和外围的勘探可以使用比目前网矩更宽的网距,即75 m×190 m网距来控制矿体,这将大大降低勘探成本.矿石品位的趋势面分析结果表明,随着标高的降低,即往深部方向矿石品位的平均值和变化系数均呈现明显的下降趋势,说明往深部矿化强度减小,而矿化变得较均匀.结合矿区目前的勘探情况和趋势面分析结果,认为灰家堡背斜的北翼是矿区及其外围进一步找矿的重点区域.     

中蒙俄跨境区域铜、金、铅、锌、铀成矿特征对比及意义

本次研究的中蒙俄跨境区在大地构造位置上位于中亚造山带东部,是多种矿产的成矿密集区。本区成矿区带包括2个Ⅰ级成矿域、2个Ⅱ级成矿省和9个Ⅲ级成矿带。区内金属矿床的分布主要受北东-北北东向及北西向两组断裂的控制。研究区重点金属矿产中,铜矿床以斑岩型为主;金矿床以岩浆热液型为主,也有部分作为伴生矿种产于斑岩型铜(金)矿床之中;铅、锌矿床以热液脉型为主;铀矿床以火山岩型为主。铜、金、铅、锌、铀成矿作用与燕山期岩浆及其热液活动关系最为密切。本研究区具有良好的成矿地质条件和巨大的找矿前景,是进一步开展铜、金、铅、锌、铀等金属矿产找矿工作的重点地区。     

新疆阿尔泰小土尔根铜矿区岩体地球化学及其地质意义

小土尔根是近年来诺尔特地区新发现的斑岩铜矿。矿区内发育花岗斑岩、花岗闪长斑岩、黑云母二长花岗岩,其中与成矿作用密切相关的岩体为花岗闪长斑岩。为了确定矿区侵入岩成因及其与铜矿化的内在关系,对矿区内发育的岩体开展了岩相学和地球化学研究。结果表明,所有岩石富硅和碱,铝含量中等,属高钾钙碱性和钾玄质系列岩石。所有样品富集Rb、Ba等大离子亲石元素和轻稀土元素,相对亏损Nb、Ta、Ti、P、Sr和重稀土元素,指示其为同源岩浆分异演化的产物,形成于陆缘弧环境。结合区域地质背景,推测这些岩体是俯冲洋壳发生部分熔融并交代上覆地幔楔后,在上升过程中经分离结晶作用后的产物。与典型的还原性斑岩型铜矿形成条件进行对比研究后,认为小土尔根地区有形成斑岩型矿床的潜力。     

新疆哈赞布拉克金铜矿成矿地质特征及成因探讨

哈赞布拉克金铜矿位于博罗科努金铜钼铅锌成矿带.矿化产于华力西中期中酸性侵入岩体内及与围岩接触带内,主要蚀变为围岩地层中的角岩化,闪长岩中的钾化、绢云母化、青盤岩化及含矿岩石中的硅化、碳酸盐化等,矿区发现Ⅰ、Ⅱ、Ⅲ号三个矿化带,以Ⅱ号矿化带规模最大,矿床为铜、金共生矿化,矿化成因类型为石英脉型、矽卡岩型、斑岩型,以石英脉型矿化为主,矿化主要受岩浆岩和构造控制,矿床为先期斑岩型矿化,伴矽卡岩型矿化,经后期热液改造叠加的石英脉型矿床.     

中国卡林型金矿的分布规律及找矿前景

我国卡林型金矿床主要分布于扬子陆块西南缘的板内古生代-中生代沉降带和西北缘古生代-中生代造山带。具有分布局限、成矿集中的特点。金矿床往往形成成矿带,单个金矿床的规模大小不一,矿化受构造、围岩和深部流体控制。金矿床成矿域发育一套大面积分布的巨厚的古-中生代造山带建造,成矿期的岩浆活动和构造活动强烈。基于我国卡林型金矿的分布规律,找矿应优先考虑的有力部位有:1)地块边缘裂陷槽拉张与挤压交替的环境中沉积建造和不同性质大地构造接合部位或构造过渡带;2)在背斜构造倾伏端、背斜轴转折端、背斜翼部以及不同方向、不同序次的断裂破碎带交叉与复合部位;3)在富粘土质、粉砂质和有机质中发育的交叉断裂和可微渗透的纹层状细粒钙质和白云质粉砂岩,局部为较粗粒砂岩和透镜状砾状钙质生物碎屑岩夹层接触部位;4)在燕山期岩浆活动以及热点活动地区发育的古生界和中生界地层。     

Geology and volcanic stratigraphy of the Canatuan and Malusok volcanogenic massive sulfide deposits,southwestern Mindanao,Philippines

The Canatuan and Malusok massive sulfide deposits are located near Siocon, Zamboanga del Norte, in southwestern Mindanao, Philippines. The Canatuan–Malusok area is underlain by the Jurassic–Cretaceous Tungauan schists, which form much of the Zamboanga Peninsula. The volcanic strata at Canatuan and Malusok can be traced for >7 km along strike and is host to at least three discrete massive sulfide bodies: Canatuan, Malusok and SE Malusok. Basal basaltic andesite volcanic rocks are generally chemically uniform and show only moderate alteration. The massive sulfide deposits occur in overlying rhyolitic to rhyodacitic volcanic rocks that are altered to a schistose assemblage of quartz, sericite, chlorite and pyrite. The alteration is texturally destructive but graded clastic beds are locally observed. Despite tropical saprolitic weathering, four lithogeochemical subunits of the felsic package are identified. Stratigraphic interleaving, however, has made correlation of these units over any significant distance difficult. The sulfide lenses are overlain by a few metres of felsic schists which locally contain manganese-bearing silicates and oxides that serve as a stratigraphic marker. Hangingwall andesitic volcaniclastic rocks are discontinuously preserved, although where present, they consist of regularly bedded mafic volcanic sandstones. The lateral continuity of a manganese-bearing marker and flanking felsic volcaniclastic intervals indicate that locally the volcanic strata form a homoclinal sequence. The Canatuan Au–Ag–Cu–Zn deposit consists of a gossan overlying a massive sulfide lens. The sulfides and gossan are flat lying and hosted within felsic volcanic rocks. The gossan is gold–silver-rich, and was formed by a combination of oxidation and volume collapse of the original sulfide lens. The sulfide minerals present below the current water table, are auriferous massive pyrite with base metal sulfides, with some supergene chalcocite. The transition from gossan to sulfides is very sharp, occurring at the water table. Massive sulfide deposits at Malusok are hosted in the same felsic sequence as Canatuan and they have similar base and precious metal contents. Only limited gossan has been found at Malusok. The bimodal nature of the volcanic rocks at Canatuan, together with their low HFSE contents, near-flat REE patterns and tholeiitic affinities, suggest that they formed in an intra-oceanic arc setting above a depleted mantle source. Mafic and felsic volcanic rocks of similar composition have been recovered from the Tonga-Kermadec and Izu-Bonin-Marianas island-arc systems in the western Pacific. Mafic rocks at Canatuan show no evidence for LILE enrichment that characterizes melts derived from metasomatized mantle under more mature arcs, suggesting that they are the product of a nascent, rather than a mature arc. There is no evidence from the REE, or other incompatible trace elements, that continental crust or evolved arc crust was involved in the generation of the Canatuan-Malusok volcanic rocks. Although it has been proposed that the Zamboanga metamorphic complex comprises microcontinental fragments of Eurasian affinity, our data do not support an evolved crustal setting for the Canatuan-Malusok volcanic rocks, which we suggest were derived from an intra-oceanic arc and subsequently accreted to the eastern Mindanao terrane.Electronic Supplementary Material Supplementary material is available in the online version of this article at http://dx.doi.org/10.1007/s00126-003-0350-7Editorial handling: R.R. Large