Apatite fingerprints on the magmatic-hydrothermal evolution of the Daheishan giant porphyry Mo deposit, NE China

Porphyry deposits are the main source for global Cu and Mo production. The generation of hydrous silicate magmas and subsequent separation of volatile-rich magmatic fluids with hydrothermal alteration are significant processes leading to the formation of porphyry deposits. However, a specific understanding of these processes has been limited by a lack of direct mineralogical records in the evolving magmatic-hydrothermal system. In this paper, we present an integrated textural and geochemical investigation on apatite from the giant Daheishan porphyry Mo deposit in NE China, illustrating that apatite can be a potential recorder of the magmatic-hydrothermal evolution of porphyry systems. Apatite from the ore-forming porphyry displays distinctive core-rim textures, with melt inclusions in the resorption cores (Type-A1) and co-existing of melt and fluid inclusions in the euhedral rims (Type-A2), indicating a magmatic-hydrothermal origin of apatite. This is also supported by both chemical and isotopic compositions obtained by in situ analyses using laser ablation−inductively coupled plasma−mass spectrometry (LA-ICP-MS) and LA-multi collector-ICP-MS. The late Type-A2 apatite is relatively enriched in incompatible elements, such as rare earth elements (REE) and Th, but slightly depleted in fluid-mobile elements such as Na and S, compared to the early Type-A1 apatite. Relatively homogeneous (87Sr/86Sr)i ratios (0.70436−0.70504) of the Type-A1 and Type-A2 apatites indicate that they were formed in a relatively closed system without detectable contamination. Meanwhile, some apatite in the wall rock (biotite granodiorite) shows characteristics of secondary altered textures, resulting from the intensive alteration by hydrothermal fluids exsolved from the porphyry system. Apatite trapped in mineral phenocrysts of the wall rock is usually unaltered (Type-B1 apatite), with clear oscillatory growth zones in cathodoluminescence (CL) images. In contrast, the intergranular apatite is commonly altered (Type-B2 apatite), with chaotic zoning in CL images, abundant micro-fractures and secondary fluid inclusions. Compositionally, the Type-B2 apatite shows notable tetrad REE patterns, relatively lower light-REE and S contents, and elevated 147Sm/144Nd ratios compared to the Type-B1 apatite. LA-ICP-MS U-Pb dating yields a lower intercept age of 171.4 ± 2.3 Ma for Type-B2, which is consistent with the age of 171.5 ± 2.4 Ma for Type-A2, but is notably younger than the Type-B1 apatite (175.5 ± 1.3 Ma). It is suggested that the Type-B2 apatite has been significantly reset by hydrothermal fluids exsolved from the porphyry system. Therefore, we conclude that the textures and geochemistry of apatite in porphyry systems can be used as a potential proxy for recording fluid exsolution and hydrothermal alteration processes.

Рудно-метасоматическая зональность молибден-порфировой системы Аксу (Северо-Восток Азии)

The article presents the data from a comprehensive study of the Aksu Mo-porphyry system metasomatites (Korkodon-Nayakhan magmatic activation zone). The halo of metasomatic changes around the porphyry system, associated with the tectonic-block structure of the territory, is shown to be asymmetric. The core of the system is brought to the surface and located in a halo of kalifeldspar- muscovite metasomatites; the northwestern block is elevated and characterized by high-temperature epidote-biotite and epidote-pyroxene propylites, while in the southeastern block there is a consistent transition from kalifeldspar-sericite metasomatites to fragments of argillisite ones. The established zoning is confirmed by geochemical associations and mineralization types from the northwest to the southeast: in the northwest, Au-Bi (As, Cu) at the Solnechnoye ore occurrence; in the center, Mo (Cu, Au) at the Aksu deposit; in the southeast, Ag-Pb-Zn (Cu, Bi, As, Au) at the Vysokoye ore occurrence.

Ore-magmatic systems of the copper-porphyry type of the Greater Caucasus

Статья посвящена выявлению особенностей геологического строения и минерагении Танадон-Сангутидон-Казбекского района проявлений медно-порфировых минерализаций Центральной части Большого Кавказа и оценке соответствия геологических обстановок оруденения современным моделям рудно-магматических систем медно-порфирового типа. Актуальность работы определяется необходимостью разработки научно-методической основы прогнозирования и поисков скрытого оруденения. Цель исследования.Выявить особенности геологии и минерагении Танадон-Сангутидон-Казбекского рудного района и установить соответствие обстановок оруденения современным моделям рудно-магматических систем медно-порфирового типа. Методы. Сравнительно-геологический и металлогенический анализ на основе современных геоинформационных технологий в среде программного комплекса ArcGIS. Результаты. Установлено, что рудно-магматические системы исследуемого района соответствуют геолого-структурной позиции медно-порфировых месторождений. Изученный район объединяет группу медно-порфировых рудно-магматических систем, связанных с малыми гранитоидными интрузиями теплинского плиоцен-плейстоценового комплекса. Здесь также отмечаются рудопроявления вольфрама, мышьяка, золота, сурьмы и др., составляющие единый генетический ряд, в котором медно-порфировое оруденение занимает вполне определенную позицию, – приурочено к порфировой фазе новейшего интрузивного магматизма. Сопоставление обстановок проявления позднекайнозойского оруденения и его характеристик в пределах изученных рудоносных площадей с основными элементами типовой модели медно-порфировой системы позволяет рассматривать Сангутидонский, Теплинский и Танадонский рудные узлы как выражение надстраивающих друг друга по вертикали частей единой рудно-магматической системы медно-порфирового ти­па. Продук­тивная на медно-порфировое оруденение новейшая гранит-гранодиоритовая формация Большого Кавка­за образовалась в условиях повторноорогенного режима активизации региона и наложена на его гетерогенный субстрат. Последний в пределах изучаемого района характеризуется двухэтажным стро­ением и состоит из нижне-среднеюрского вулканогенно-осадочного комплекса чехла и доюрского основания, в котором главную роль иг­рают докембрий – нижне-среднепалеозойские метаморфические тол­щи кристаллического фундамента Большого Кавказа, прорванные пале­озойскими гранитоидами Главного хребта. Состав поздненеогеновых гранитоидов находится в зависимости от состава субстрата, как на глубинных уровнях его анатектического плавления, так и на путях подъема образованных при этом магм. В этой связи повышенная основность гранитоидов полифазного теплинского комплекса, сформированных в гипабиссальных и субвулканических условиях, обусловлена более высокой по сравнению с соседними блоками степенью мафичности субстрата исследуемого района, включающего ряд базальтоидных или близких к ним по составу толщ The article is devoted to the identification of the features of the geological structure and mineralogy of the Tanadon-Sangutidon-Kazbek district of the manifestations of copper-porphyry mineralization in the Central part of the Greater Caucasus and the assessment of the correspondence of the geological conditions of mineralization to modern models of ore-magmatic systems of the copper-porphyry type. The relevanceis determined by the need to develop a scientific and methodological basis for forecasting and searching for hidden mineralization. Aim. To identify the features of the geology and mineralogy of the Tanadon-Sangutidon-Kazbek ore region and to establish the correspondence of the mineralization conditions to modern models of ore-magmatic systems of the copper-porphyry type. Methods.Comparative geological and metallogenic analysis based on modern geoinformation technologies in the environment of the ArcGIS software package. Results. It is established that the ore-magmatic systems of the studied area correspond to the geological and structural position of copper-porphyry deposits. The studied area unites a group of copper-porphyry ore-magmatic systems associated with small granitoid intrusions of the Teplinsky Pliocene-Pleistocene complex. There are also ore occurrences of tungsten, arsenic, gold, antimony, etc., which make up a single genetic series, in which copper-porphyry mineralization occupies a well - defined position-it is timed to the porphyry phase of the latest intrusive magmatism. The comparison of the conditions of the Late Cenozoic mineralization and its characteristics within the studied ore-bearing areas with the main elements of the typical model of the copper-porphyry system allows us to consider the Sangutidon, Teplinsky and Tanadon ore nodes as an expression of the parts of a single ore-magmatic system of the copper-porphyry type superstructuring each other vertically. The newest granite-granodiorite formation of the Greater Caucasus, which is productive for copper-porphyry mineralization, was formed under the conditions of a repeated-rhogenic regime of activation of the region and superimposed on its heterogeneous substrate. The latter within the studied area is characterized by a two-story structure and consists of the Lower-Middle Jurassic volcanogenic-sedimentary complex of the cover and the Pre - Jurassic base, in which the main role is played by the Precambrian-Lower-Middle Paleozoic metamorphic strata of the crystalline basement of the Greater Caucasus, broken by Paleozoic granitoids of the Main Ridge. The composition of Late Neogene granitoids depends on the composition of the substrate, both at the deep levels of its anatectic melting, and on the ascent paths of the magmas formed during this process. In this regard, the increased basicity of granitoids of the polyphase Teplinsky complex formed under hypabyssal and subvolcanic conditions is due to a higher degree of maficity of the substrate of the studied area, which includes a number of basaltoid or similar strata in composition, compared to neighboring blocks.

FORECASTING GEOCHEMICAL PREREQUISITES FOR DETECTING THE PORPHYROUS SYSTEM IN THE KOMSOMOLSK REGION OF KHABAROVSK REGION

The information on the results of geological exploration work to identify the porphyry system in the Komsomolsk region of the Khabarovsk Territory is given. It is shown that copper-molybdenum-porphyry mineralization is associated with the type of porphyry deposits by a porphyry stock surrounded by fields of hydrothermal-metasomatic alteration. The possibilities of the object of the gold-rare metal type are substantiated.

Mineralogy of hydrothermal breccia cement of Humpa Leu East porphyry copper-gold prospect, Sumbawa Island, Indonesia

Indonesia is a country that has several world-class copper-gold deposits, particularly in eastern Sunda arc. The Hu’u complex has several prospects in the surface as lithocap of extensive epithermal style alteration, but some were detected associated with porphyry beneath the surface. The study focuses on hydrothermal breccia cement as a factor influencing the porphyry system in the Hu’u district. The methods used is mineralogical analysis with petrography and μ-XRF elemental mapping on hydrothermal breccia samples. The Hu’u district is interpreted as a paleo-volcano; a member of the Old Volcanics Rocks Formation. The Humpa Leu East lithology consists of pre-volcanics unit (lava and pyroclastics), diorite, andesite-μ-diorite, and tonalitic intrusion at the depth. Hydrothermal alteration evolved from tonalite body to outward, consist of potassic, inner propyllitic and overprinted by phyllic and advanced argillic. Several phases of hydrothermal activities occur in this system, including the hydrothermal breccia phase associated with complex fluids. The hydrothermal cement of Humpa Leu East porphyry at least have three phases of mineralogical assemblages and possibly influencing the mineralization. The mineralogical assemblage of hydrothermal cement in HLE consists of quartz-feldspar-plagioclase-biotite as a high-temperature phase; then followed by epidote-sericite-chlorites-anhydrite-carbonates in medium temperature; there are aluminum-rich clay minerals interpreted as gibbsite. Mineralization occurs in three phases including chalcopyrite-magnetite, bornite-chalcopyrite and chalcopyrite-sphalerite phases. The occurrences of chalcopyrite at all phases indicate the stability of intermediate sulfidation proses in Humpa Leu and as a possible factor to answer the abundant copper in the Hu’u hydrothermal fluid system

Rapid Formation of Porphyry and Skarn Copper-Gold Mineralization in a Postsubduction Environment: Re-Os and U-Pb Geochronology of the Ok Tedi Mine, Papua New Guinea

The Ok Tedi copper-gold mine in Western Province, Papua New Guinea, is situated in the western part of the Ok Tedi Complex where monzodiorite to quartz monzonite intrusions are associated with porphyry- and skarn-style copper-gold mineralization. The Pleistocene age of the intrusive rocks and mineralization provides an opportunity to study the longevity of the magmatic and hydrothermal evolution at Ok Tedi through U-Pb dating of zircon and high-precision Re-Os dating of molybdenite. Six main phases of intrusive rocks can be recognized within the mine area, with the sequence of intrusion indicated by contact relationships. Each has been dated by the SHRIMP U-Pb technique with correction for Th-U disequilibrium based on the U and Th content of each sample. In order of intrusion from oldest to youngest these include: Sydney Monzodiorite (1.368 ± 0.045 Ma), Warsaw Monzodiorite (1.269 ± 0.039 Ma), Kalgoorlie Monzodiorite (1.261 ± 0.050 Ma), Ningi Quartz Monzonite Porphyry (QMP)(1.229 ± 0.051 Ma), Bonn Quartz Monzonite (1.219 ± 0.040 Ma), and Fubilan QMP (1.213 ± 0.049 Ma). The intrusions are alkaline, high K to shoshonitic rocks with high Sr/Y ratios typical of Cu-fertile arc magmas. Chondrite-normalized REE patterns have minor or no negative Eu anomalies and downward sloping to listric-shaped HREE patterns typical of arc magmas in which high water contents supress plagioclase fractionation in favor of an evolution by hornblende ± garnet ± titanite fractionation. Cu-Au mineralization at Ok Tedi can be divided into four main stages based on crosscutting relationships: (1) skarn-endoskarn and associated vein-style mineralization in the Darai Limestone, Ieru siltstone, and Sydney Monzodiorite; (2) porphyry-style veins and breccias within the Ningi QMP and older intrusions, and at Siltstone Ridge: (3) porphyry-style veins and breccias in the Fubilan QMP and older intrusions: and (4) skarn-style mineralization in the lower part of the Darai Limestone along the Taranaki thrust. High-precision Re-Os dating of molybdenite has enabled a chronology to be established for the first three stages. Molybdenite from a quartz-mushketovite-epidote-carbonate-pyrite-chalcopyrite-molybdenite vein in clinopyroxene- and garnet-altered Sydney Monzodiorite has an age of 1.3206 ± 0.0020 Ma, and this dates the formation of the Gold Coast and Berlin skarns. Molybdenite from a quartz-pyrite-chalcopyrite-molybdenite vein in the sericite-altered Sydney Monzodiorite yields an age of 1.3166 ± 0.0043 Ma, and a quartz-pyrite-chalcopyrite-molybdenite vein with K-feldspar alteration selvages hosted in Ieru siltstone beneath the Gold Coast skarn has an age of 1.3031 ± 0.0015 Ma. Samples of molybdenite from quartz-sulfide veins from Siltstone Ridge have ages of 1.2116 ± 0.0029 and 1.2078 ± 0.0031 Ma. Molybdenite from a quartz-K-feldspar-pyrite-molybdenite vein, which overprints propylitic alteration in the Sydney Monzodiorite, has an age of 1.2120 ± 0.0024 Ma. These samples date porphyry-style mineralization in and around the Ningi QMP and at Siltstone Ridge. A sample of molybdenite from the matrix of hydrothermal intrusive breccia in the Fubilan QMP has an age of 1.2146 ± 0.0020 Ma, similar to the age of the adjacent Siltstone Ridge mineralization, and is interpreted to have been mechanically incorporated into the breccia during its formation. Several samples have been dated from the Fubilan porphyry system, including molybdenite from the matrix of a hydrothermal intrusive breccia (1.1648 ± 0.0020 Ma) and three samples from veins which postdate the breccias: a vuggy quartz-sulfide vein (1.1532 ± 0.0027 Ma), chalcopyrite-pyrite-molybdenite vein (1.1446 ± 0.0028 Ma), and duplicate analyses of a molybdenite-only vein (1.1326 ± 0.0034 and 1.1297 ± 0.0026 Ma) in agreement at 2σ. Molybdenite from a quartz-K-feldspar-biotite-magnetite-pyrite-chalcopyrite-molybdenite vein in endoskarn-altered Sydney Monzodiorite (beneath the Gold Coast skarn) has an age of 1.1459 ± 0.0012 Ma, and a similar vein without magnetite hosted in Warsaw Monzodiorite has an age of 1.1438 ± 0.0042 Ma, both within error of the chalcopyrite-pyrite-molybdenite vein in Fubilan QMP. Intrusive rocks in the Ok Tedi mine were emplaced over a period of approximately 200,000 years, with Cu-Au mineralization formed in discrete episodes of much shorter duration. The Gold Coast skarn and associated porphyry-style veins in Sydney Monzodiorite and Ieru siltstone formed in 14,000 to 21,000 years (n = 3), the Siltstone Ridge porphyry system in 2,000 to 12,000 years (n = 4), and the Fubilan porphyry system in 31,000 to 40,000 years (n = 6). The Taranaki skarn has not been dated in the mine area due to a lack of molybdenite, but geologic relationships indicate it is younger than the Fubilan QMP.

Re-Os Ages for the Kourki Porphyry Cu-Mo Deposits, North West Niger (West Africa): Geodynamic Implications

The study area is located at the southern end of the Gorouol greenstone belt, northwestern Niger. This region contains significant deposits of Copper and Molybdenum hosted in intrusive rocks metamorphosed in the green shale facies. This deposit was previously considered a porphyry system of Copper (Cu) and Molybdenum (Mo) without having been the subject of advanced research. The objective of this study is to confirm or refute this hypothesis and to date the mineralisation in an absolute manner in order to readjust the mineralising episode in the history of the West African Craton. The methodology used within the framework of this study is the isotopic dating by the Re-Os method carried out on the pyrites of the host rock. The results of this analysis give an age range between 2158 ± 50 Ma and 2110 ± 51 Ma for the Cu-Mo mineralisation. This age range represents the West African Craton scale to an episode of magmatic accretion. During this accretion, the subduction phenomena between the Crusts (Oceanic and Continental) would have been favourable for the formation of the Cu and Mo mineralisation of Kourki.