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Актуальность работы заключается в изучении особенностей химического состава берилла, являющегося важным источником бериллия и ювелирным камнем, геммологические свойства которого определяются концентрациями и формами вхождения примесных химических элементов. Целью исследования является определение содержаний примесных химических элементов в кристаллах берилла различной окраски, зависимостей между ними и связи с условиями образования. Объекты: кристаллы берилла различной окраски грейзеновых (Шерловая Гора, Спокойнинское) и пегматитовых (Орловское, Саханайское) месторождений Восточного Забайкалья. Методы: нейтронно-активационный и ICP MS. Результаты. Установлен широкий диапазон концентраций элементов-примесей в 31 кристалле берилла различного цвета сидерофиллит-кварцевых (Спокойнинское месторождеие вольфрама) и слюдисто-берилл-топаз-кварцевых (Шерловая Гора) грейзенов, а также редкометалльных (Орловское) и камерных (Саханайское) пегматитов. Кристаллы берилла слюдистоберилл-топаз-кварцевых (Шерловая Гора) грейзенов отличаются низкими содержаниями натрия и цезия по сравнению с таковыми из сидерофиллит-кварцевых грейзенов и пегматитов. Рубидий примерно в равной мере присутствует в кристаллах берилла всех изученных месторождений независимо от окраски. Впервые в них обнаружено золото, содержания которого имеют тенденцию к связи с кобальтом и цинком. Содержание мышьяка, изоморфное вхождение которого в берилл маловероятно, также проявляет корреляцию к связи с цинком и кобальтом. Наиболее высокие содержания железа установлены в желтых, голубых и желто-зеленых кристаллах, входя как в тетраэдрические (голубые), так и в октаэдрические позиции (зеленые, желтые и желто-зеленые). Содержание урана и тория выше в кристаллах берилла грейзенов (Шерловая Гора, Спокойнинское) по сравнению с пегматитами. Содержания их имеют тенденцию к взаимозависимости при преобладании тория над ураном. Уран имеет связи с железом, наибольшие концентрации которого присущи зональным кристаллам с перерывами в росте. Торий находится в основном в цирконе, что подтверждается положительной корреляцией его содержаний с гафнием. Относительно широкий спектр примесей в кристаллах берилла обусловлен различиями в условиях образования (грейзены и пегматиты) и геохимическими особенностями минераообразующих флюидных систем, отображенных в составе флюидных включений. The relevance of the work lies in the study of the features of the chemical composition of beryl, which is an important source of beryllium and gemstone, the gemological properties of which are determined by the concentrations and forms of occurrence of impurity chemical elements. The aim of the study is to determine the content of impurity chemical elements in beryl crystals of various colors, the relationships between them and the relationship with the conditions of formation. Objects of the research are crystals of beryl of different colors of greisen (Sherlovaya Gora, Spokoyninskoe) and pegmatite (Orlovskoe, Sachanayskoe) fields. Methods of the research are neutron activation and ICP MS. Results. The authors have established a wide range of concentrations of impurity elements in 31 beryl crystals of various colors, siderophyllite-quartz (Spokoininskoe deposit of tungsten) and mica-beryl-topaz-quartz (Sherlovaya Gora) greisens, as well as rare-metal (Orlovskoe) and chamber pegmatites (Sakhanayskoe). Beryl crystals of mica-beryl-topaz-quartz (Sherlovaya Gora) greisens are characterized by low sodium and cesium contents in comparison with those of siderophyllite-quartz greisens and pegmatites. Rubidium is approximately equally present in beryl crystals of all the studied deposits, regardless of color. For the first time, gold was found in them, the contents of which tend to be associated with cobalt and zinc. The content of arsenic, the isomorphic incorporation of which into beryl is unlikely, also shows a correlation to the bond with zinc and cobalt. The highest iron contents are found in yellow, blue and yellow-green crystals, entering both tetrahedral (blue) and octahedral positions (green, yellow, and yellow-green). The content of uranium and thorium is higher in the crystals of beryl greisens (Sherlovaya Gora, Spokoininskoe) in comparison with pegmatites. Their contents tend to be interdependent when thorium predominates over uranium. Uranium has bonds with iron, the highest concentrations of which are inherent in zonal crystals with breaks in growth. Thorium is associated mainly with zircon, which is confirmed by the positive correlation of its contents with hafnium. A relatively wide range of impurities in beryl crystals is due to differences in the conditions of formation (greisens and pegmatites) and the geochemical features of the mineral-forming fluid systems reflected in the composition of fluid inclusions.

U–Pb geochronology was applied to a combination of magmatic and hydrothermal minerals to help constrain the timing of emplacement of three units in the Mount Douglas Granite (MDG) and reveal their association with a complex mineralized hydrothermal system containing endogranitic Sn–W–Mo–Zn–Bi–U-bearing greisen/sheeted veins within the pluton. Magmatic monazite and zircon U–Pb ages obtained by LA–ICP–MS overlap at 368 Ma, recording a Late Devonian crystallization age for the MDG. Although discrimination, outside analytical error, of sequential pulses of magmatism is beyond the resolution of LA–ICP–MS U–Pb geochronology, geochemical variations of monazite accompanied by previous whole-rock geochemical analyses support a progressive fractional crystallization process starting from a parental magma (Dmd1), leading to the generation of Dmd2, and finally Dmd3 as the most fractionated unit. Hydrothermal uraninite, cassiterite, and monazite, collected from endogranitic greisen/sheeted veins, reveal evidence for syn-magmatic-related mineralization and a longer-lived post-magmatic hydrothermal system. The first stage is recorded by concordant uraninite dates at 367 ± 3 Ma and by an inverse isochron lower intercept of 362 ± 8 Ma for cassiterite. In contrast, hydrothermal monazite crystallized over a wider range of ages from 368 to 344 Ma, demonstrating post-magmatic hydrothermal activity within the MDG. These magmatic and hydrothermal ages combined with the geochemical signature of the MDG are similar to those documented for the nearby Mount Pleasant Sn–W–Mo–Bi–In granite-related deposit, which suggests that the two mineralizing systems occur at different levels of the same magmatic system.

Dissertação (mestrado) — Universidade de Brasília, Instituto de Geociências, Programa de Pós-Graduação em Geologia, 2021. O Brasil central hospeda suítes graníticas com idades paleo-mesoproterozóicas, localizadas principalmente nas regiões centro-norte e nordeste do Estado de Goiás. Estas suítes graníticas apresentam assinatura petrográfica e geoquímica similares a de magmatismo tipo-A, com um alto conteúdo de álcalis, Sn, W, F, Rb, Th, Y, Nb, Ga e ETR, sendo ainda responsáveis por formar juntas a tão famosa Província Estanífera de Goiás. O maciço granítico Pedra Branca é o principal corpo intrusivo mineralizado do sistema magmático rico em Sn (±W, ETR) da Província Estanífera de Goiás. A Faixa Placha é o principal local de concentração de minério do maciço granítico Pedra Branca. Os cristais de cassiterita são euédricos a subédricos, zonados, fraturados, contém inclusões de ilmenite, rutilo, tantalita e magnetita. O pleocroísmo varia de amarelo pálido a marrom escuro, onde nas cores mais fracas ápresenta-se um alto conteúdo de SnO2 e baixo FeOtotal. A cassiterita da Faixa Placha tem conteúdos de SnO2 entre 96-100% em peso, enquanto a soma dos elementos traços tem conteúdo inferior a 4% em peso. Os cristais de wolframita são relativamente raros e estão disseminados nos greisens, apresentando um conteúdo de WO3 entre 71.5 e 74.5% em peso e possuem inclusões ou exsoluções de nióbio- tantalatos. A wolframita é formada por uma solução sólida, cujos membros finais são representados por ferberite (FeWO4) and hübnerite (MnWO4). Os resultados de isótopos estáveis de oxigênio de quartzo (δ 18O = 9.4 -10.4‰) e cassiterita (δ 18O = 2.6 - 2.9 ‰) apresentam variações sutis em suas respectivas composições, indicando equilíbrio isotópico com um ambiente hidrotermal comum. No entanto, diferenças significativas nos valores de δ 18O entre quartzo-cassiterita revelam assinaturas de fracionamento isotópico mineral durante a ascenção do sistema hidrotermal. O interval geotermométrico calculado de 406 °C a 498 °C é interpretado como o intervalo de temperatura de cristalização do minério durante a evolução do sistema magmático/hidrotermal Pedra Branca. O estudo das inclusões fluidas mostrou que em temperature ambiente (25 °C), os cristais de quartzo e cassiterita hospedam inclusões de fluidos aquosos monofásicas e bifásicas, classificadas como pseudo-primárias e secundárias. Os dados microtermométricos revelaram um sistema de fluido aquoso com salinidade e densidade reduzidas, aprisionado sob temperatura baixa a moderada (100 °C – 270 °C). Durante o Neoproterozóico (0,75 – 0,50 Ga), a tectônica transpressiva ligada a Orogenia Brasiliana/Pan- Africana ocasionou diferentes níveis de deformação em todas as litologias. Falhas e fraturas de tração greisenizadas por minério ligado à Faixa Placha (exogreisen), bem como alguns corpos lenticulares de greisen ligados à Zona da Bacia (endogreisen) foram submetidos à deformação milonítica direcional. Os conjuntos de estruturas da Faixa Placha foram reativados em regime dúctil-rúptil, com geração local de dobras centimétricas e cortes de tensão, além de achatamento e fragmentação parcial sobre a assembléia mineral. Central Brazil hosts granitic suites with Paleo-Mesoproterozoic ages, located mainly in the north- central and northeastern regions of the State of Goiás. These granitic suites have a petrographic and geochemical signature similar to A-type magmatism, with a high content of alkalis, Sn , W, F, Rb, Th, Y, Nb, Ga and REE, being also responsible for forming together the famous Goiás Tin Province. The Pedra Branca granitic massif is the main mineralized intrusive body of the Sn-rich (±W, REE) magmatic system of the Goiás Tin Province. The Faixa Placha is the main ore concentration site in the Pedra Branca granitic massif. Cassiterite crystals are zoned, fractured, contain ilmenite, rutile, tantalite and magnetite inclusions. Pleochroism varies from pale yellow to dark brown, where in the weaker colors it presentes a high content of SnO2 and low FeOtotal. The cassiterite from the Placha shear fault has SnO2 contents between 96-100 wt.%, while the sum of trace elements has a content of less than 4 wt.%. Wolframite crystals are relatively rare and are widespread in greisens, have a WO3 content between 71.5 and 74.5 wt.% and have inclusions or exsolutions of niobium-tantalates. Wolframite is formed by a solid solution, whose final members are represented by ferberite (FeWO4) and hübnerite (MnWO4). The results of stable oxygen isotopes of quartz (δ 18O = 9.4 -10.4‰) and cassiterite (δ 18O = 2.6 - 2.9 ‰) show subtle variations in their respective compositions, indicating isotopic equilibrium with a common hydrothermal environment. However, significant differences in δ 18O values between quartz- cassiterite reveal mineral isotopic fractionation signatures during the rise of the hydrothermal system. The calculated geothermometric range from 406 °C to 498 °C is interpreted as the temperature range of ore crystallization during the evolution of the Pedra Branca magmatic/hydrothermal system. The study of fluid inclusions showed that at room temperature (25 °C), quartz and cassiterite crystals host monophasic and biphasic aqueous fluid inclusions, classified as pseudo-primary and secondary. Microthermometric data revealed an aqueous fluid system with reduced salinity and density, trapped at low to moderate temperature (100 °C – 270 °C). During the Neoproterozoic (0.75 – 0.50 Ga), the transpressive tectonics linked to the Brasiliano/Pan-African Orogeny caused different levels of deformation in all lithologies. Faults and tensile fractures greisenized by ore linked to the Placha Belt (exogreisen), as well as some lenticular greisen bodies linked to the Basin Zone (endogreisen) were subjected to directional mylonitic deformation. The sets of structures of the Placha Belt were reactivated in a ductile-brittle regime, with local generation of centimetric folds and stress shears, in addition to flattening and partial fragmentation over the mineral assemblage.

The geological structure of the border zone of the Southern and Middle Urals (Kunashak area), as well as the composition and conditions for the formation of granitoid complexes developed here, whose age varies from Devonian to Triassic, is briefly considered. Thermobarometric studies of quartz of medium-grained biotite granites showed that in the age range ― Poletaev (D 3 ), Shalkar (P 1 ), Sultayev (P 1 ), and Yugokonev (P 1 −T 2 ) complexes ― water pressure during the formation of melt inclusions was 2.2–2.7, 2.5–3.0, 3.9–4.4 and 3.6–4.5 kbar, and the crystallization temperature of rocks ― 800–840, 900–940, 840–900 and 940–980°С. This indicates a consistent increase in the crystallization depth of the granite massifs in this series from the hypabyssal-subsurface to the hypabyssal-abyssal facies. At the same time, in the melt-fluid inclusions, a decrease in fluid volume is noted ― 14.2–16.8, 8.1–14.3, 6.2–7.9 and 4.3–6.8 vol.%, Water concentrations ― 3.7–4.8, 2.1–3.9, 1.8–2.3 and 1.3–1.9 wt.% as well as chlorine ― 0.04–0.08, 0.03–0.07, 0.03–0.06 and 0.02–0.05 wt.%. It is shown that the granitoids of the Sultayev and Yugokonev complexes are very promising for tantalum, niobium, tungsten, molybdenum and beryllium. Of the greatest interest in rare-metal mineralization are the leucocratic aplitic and greisen granites of the final phases of the formation of intrusions. The level of erosional slice of various structural and formation zones of the Kunashak area relative to each other has been established.

The geology, mineralogy, and geochemistry of the Spetsugli high-germanium coal deposit in the Pavlovsk coalfield were studied. The deposit is characterized by the complex polyelemental composition of the ores and can be evaluated as a complex rare metal-coal deposit. The metal-bearing coals of the deposit are characterized by abnormally high, tens or even hundreds of times greater than the mean contents for brown coals of the world, for Ge, Sb, Hg, W, Li, Be, Cs, and As. Somewhat less anomalous are the levels of accumulation of U, Mo, Y, Rb, medium and heavy lanthanides, Zn, and Ga. Detailed mineralogical and geochemical characteristics of the germanium mineralization and associated anomalous concentrations of W, Sb, Hg, As Li, Be, Cs, U, Mo, Y, Rb, and HREE are described in the paper. The variations in concentrations were studied in vertical profiles and laterally. Complex mineralogical-geochemical and geological-structural analysis of the composition and structural features of the Spetsugli Ge-coal deposit allow us to revise the accepted hydrothermal model of the Ge mineralization formation in coals and substantiate the previously proposed hypergenic model for deposits of this type. The new data are in good agreement with the hydrogenic hypergenic model of the formation of complex Ge coal deposits where the source of metals is the basement rocks or the coal-bearing depression margins. The formation of the Ge and associated mineralization in the Spetsugli deposit was controlled by the weathering crust formation on hydrothermally altered rare metal granites of the Voznesenk Complex, broken through by the Late Permian dikes. The isotopic ages of the granites (448.2 Ma) and dikes (263.6 Ma) were determined and also the rhyolitic tuffs (25.1 Ma) which overlie the Eocene-Oligocene coal- bearing sediments in the basin. The isotopic age of the granites (448.2 Ma), dikes (263.6 Ma), and rhyolite tuffs overlapping the carbonaceous deposits (25.1 Ma) was determined. The rare metal mineralization is related to the basement protrusion in the centre of the deposit, forming a concentric-zone halo of Ge and associated elements around it. The basement protrusion granites were hydrothermally altered to form quartz-albite-microcline metasomatites and greisen containing the W-Mo and Hg-Sb-As mineralization. The metasomatically altered granites and dikes were transformed into a kaolin weathering crust as a result of late hypergenic alterations, with destruction of primary endogenous mineralization and removal of major elements to the surrounding paleopeatlands. Both types of endogenous mineralization in granites and dikes have anomalous accumulation of W, Mo, Sb, Hg, As, Li, Rb, Cs, Be, U, Y, lanthanides, Zn and Ga in the germanium-bearing coals during the Eocene- Oligocene time.

Ambient seismic noise tomography is a novel, low-impact method for investigating the earth's structure. Although most passive seismic studies focus on structures on crustal scales, there are only a few examples of this technique being applied in a mineral exploration context. In this study, we performed an ambient seismic experiment to ascertain the relationship between the shallow shear wave velocity and mineralized zones in the Erzgebirge in Germany, one of the most important metal provinces in Europe. Late Variscan mineralized greisen and veins occurring in the Geyer-Ehrenfriedersdorf mining district of the Central Erzgebirge were mined from medieval times until the end of the 19th century. These occurrences represent a significant resource for commodities of high economic importance, such as tin, tungsten, zinc, indium, bismuth and lithium. Based on ambient noise data from a dense “LARGE-N” network comprising 400 low-power, short-period seismic stations, we applied an innovative tomographic inversion technique based on Bayesian statistics (transdimensional, hierarchical Monte Carlo search with Markov Chains using a Metropolis/Hastings sampler) to derive a three-dimensional shear wave velocity model. An auxiliary 3D airborne time-domain electromagnetic dataset is used to provide additional insight into the subsurface architecture of the area. The velocity model shows distinct anomalies down to approximately 500 m depth that correspond to known geological features of the study area, such as (a) gneiss intercalations in the mica schist-dominated host rock, imaged by a SW–NE striking low-velocity zone with a moderately steep northerly dip, and (b) a NW-trending strike-slip fault, imaged as a subvertical linear zone cross-cutting and offsetting this low-velocity domain. Similar to the velocity data, the electromagnetic data exhibit north-dipping (high-conductivity) structures in the mica schists, corresponding to the strike and dip of the predominant metamorphic fabric. An unsupervised classification performed on the bivariate 3D dataset yielded nine spatially coherent classes, one of which shows a high correspondence with drilled greisen occurrences in the roof zone of a granite pluton. The relatively high mean shear velocity and resistivity values of this class could be explained by changes in density and composition during greisen formation, as observed in other areas of the Erzgebirge. Our study demonstrates the great potential of the cost-efficient and low-impact ambient noise technology for mineral exploration, especially when combined with other independent geophysical datasets.

El objetivo del presente trabajo de final de grado, es el estudio de la mineralogía, texturas y química mineral de las mineralizaciones peribatolíticas, tipo greisen, de W-Sn-(Nb) localizadas en Escacena del Campo, Huelva. Las muestras estudiadas, fueron recolectadas durante los trabajos de campo realizados en el depósito mineral, de reciente descubrimiento, tras varios años de trabajo en el sector. Tanto el wolframio como el estaño y el niobio, son elementos que se encuentran dentro de la lista de materias primas críticas, establecido por la Unión Europea, en el documento “Resiliencia de las materias primas fundamentales: trazando el camino hacia un mayor grado de seguridad y sostenibilidad”, en septiembre de 2020, en la que se publica la lista de materias primas fundamentales para la UE en 2020, así como los desafíos que plantea un suministro seguro y sostenible de las mismas y las acciones dirigidas a incrementar la resiliencia y la autonomía estratégica abierta de la UE. Geológicamente hablando, la zona de interés, se encuentra dentro de la Faja Pirítica Ibérica (FPI), localizada dentro del dominio Surportugués del macizo Ibérico. En la FPI se encuentra una de las mayores concentraciones de mineralizaciones de sulfuros masivos del mundo, sin embargo, las mineralizaciones hidrotermales tardivariscas, nunca han merecido mucha atención por parte de la industria minera en este sector, siendo este estudio, unos de los pocos que detallan la mineralogía, con interés económico, asociado a esta tipología de depósitos minerales en el área seleccionada. La mineralización, consiste en filones de cuarzo con wolframita, casiterita y en los que es posible observar una muscovitización típica de la alteración hidrotermal tipo greisen. Tras un estudio detallado de la mineralogía y la química mineral, se ha podido descubrir que la wolframita, posee anomalías en Nb (del orden de 300 ppm) que aportan un gran valor añadido a la ya interesante mineralización de wolframio y estaño.

Monazite and rutile occurring in hydrothermally altered W mineralizations, in the Echassières district of the French Massif Central (FMC), were dated by U-Pb isotopic systematics using in-situ Laser ablation-inductively coupled plasma–quadrupole mass spectrometry (LA-ICP-MS). The resulting dates record superimposed evidence for multiple percolation of mineralizing fluids in the same area. Cross-referencing these ages with cross-cutting relationships and published geochronological data reveals a long history of more than 50 Ma of W mineralization in the district. These data, integrated in the context of the Variscan belt evolution and compared to other major W provinces in the world, point to an original geodynamic-metallogenic scenario. The formation, probably during the Devonian, of a quartz-vein stockwork (1st generation of wolframite, called wolframite “a”, &gt, 360 Ma) of porphyry magmatic arc affinity is analogous to the Sn-W belts of the Andes and the Nanling range in China. This stockwork was affected by Barrovian metamorphism, induced by tectonic accretion and crustal thickening, during the middle Carboniferous (360 to 350 Ma). Intrusion of a concealed post-collisional peraluminous Visean granite, at 333 Ma, was closely followed by precipitation of a second generation of wolframite (termed “b”), from greisen fluids in the stockwork and host schist. This W-fertile magmatic episode has been widely recorded in the Variscan belt of central Europe, e.g. in the Erzgebirge, but with a time lag of 10–15 Ma. During orogenic collapse, a third magmatic episode was characterized by the intrusion of numerous rare-metal granites (RMG), which crystallized at ~310 Ma in the FMC and in Iberia. One of these, the Beauvoir granite in the Echassières district, led to the formation of the wolframite “c” generation during greisen alteration.

Актуальность. Определение современными методами условий формирования редкометального оруденения на примере типовых месторождений Кукульбейского рудного района, в совокупности с изотопно-геохронологическими исследованиями являются ключевыми аспектами в решении одной из важнейших фундаментальных проблем рудной геологии и геохимии – выяснение условий, источников, механизмов и последовательности формирования рудных концентраций металлов в различных геологических обстановках. Цель: получение новых данных о физико-химических условиях формирования редкометального оруденения, а также установление возраста оруденения. Объекты: Букукинское, Белухинское и Антоновогорское месторождения. Методы. Флюидные включения были изучены в прозрачно-полированных пластинках методами крио-термометрии и Рамановской спектроскопии. Крио-термометрические исследования выполнялись в микротермокамере THMSG-600 фирмы Linkam. Образцы последовательно охлаждались до температуры –190 °С и нагревались до полной гомогенизации вещества включений. В процессе наблюдения замерялись температуры эвтектики, плавления льда и гомогенизации. Температуры плавления льда для двухфазных и температуры плавления кристалликов соли для трехфазных флюидных включений позволили установить концентрацию солей в пересчете на NaCl-эквивалент. Состав газовой и минеральной фаз флюидных включений изучался методом Рамановской спектроскопии – спектрометр Ramanor U-1000 и детектор Horiba DU420E-OE-323 фирмы Jobin Yvon, лазер Millennia Pro фирмы Spectra-Physics; Confocal Raman Microscope alpha 300R фирмы WITec. 40Ar/39Ar метод изотопно-геохронологического датирования по методике ступенчатого прогрева применялся для установления абсолютного возраста оруденения. Результаты. Рудные минеральные ассоциации рассматриваемых месторождений сформировались при участии хлоридных высокотемпературных флюидов, насыщенных углекислотой. Повсеместно рудоносные флюиды содержат восстановленные газы, из которых превалирует метан, а сероводород, азот и водород находятся в подчиненном количестве. В рамках кристаллизации отдельных минеральных ассоциаций прослеживается эволюция рудоносного флюида: снижение температуры и концентрации растворов. Катионный состав растворов также изменился от существенно натрового до существенно калиевого. Для объектов исследования получены умеренные оценки глубин: 6–8 км для Букукинского, 4,5–6 км для Белухинского и 3–3,5 км для Антоновогорского месторождения. Возраст редкометального оруденения составляет на Антоновогорском месторождении – 146,7±1,7 млн лет (мусковит из кварц-мусковитовых грейзенов с вольфрамитом); на Букукинском месторождении – 135±2,8 млн лет (серицит из кварц-вольфрамитовых жил); на Белухинском месторождении – 155,6±1,8млн лет (серицит из кварц-вольфрамитовых жил). Выводы. Редкометальная минерализация Кукульбейского рудного района, на примере типовых месторождений, формировалась из высокотемпературных гидротермальных насыщенных восстановленными газами (метан, сероводород, азот и водород) углекислотно-водно-хлоридных растворов магматического происхождения. По глубине становления рассматриваемые рудоносные системы можно отнести к гипабиссальным от 8 до 3 км. Проведенные изотопно-геохронологические исследования показали, что в пределах Кукульбейского рудного района формирования вольфрамового оруденения происходило в позднеюрское-раннемеловое время, основная часть которого связана со становлением магматических пород кукульбейского комплекса, не исключено что позднеюрское оруденение связано со становлением магматических пород шахтаминского комплекса.

Skarn-hosted deposits can be important high-grade resources for a variety of metals, but Sn skarns are still of subordinate importance for global mining because of their complex mineralogy and evolution. As part of recent exploration efforts, the economic potential of the Sn–Zn–In mineralization at the Hammerlein skarn-hosted deposit is currently being re-evaluated. The temporal and spatial evolution of the ore-forming hydrothermal system is still debated. We analyzed fluid inclusion assemblages (FIA) in ore and gangue minerals using conventional and infrared microthermometry and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). We further estimated alteration temperatures with chlorite thermometry and compared the fluid inclusion (FI) record at Hammerlein with a mineralized greisen sample of the nearby Eibenstock granite. Cassiterite in skarn forms the major mineralization at Hammerlein during stage I and hosts FIs showing homogenization temperatures of up to 500 °C and salinities between 30 and 47 wt% NaCl eq. Cassiterite from schists and the additional greisen sample from the Eibenstock granite of the later stage II show lower homogenization temperatures (350–400 °C) and considerably lower salinities varying from 1.9 to 6 wt% NaCl eq. Despite the different homogenization temperatures and salinities, the chemical compositions of FIs hosted in both generations of cassiterite show that both (cassiterite in skarn and in schist and greisen) are similar, which points to a common source. The gangue minerals mainly contain low-temperature FIA (max. 330 °C and 2–9 wt% NaCl eq.) and are interpreted to form during further cooling of the system in stage III. Intergrown chlorite has compositions indicating similar temperatures of around 260 °C and is thus also related to stage III. FIA in sphalerite homogenize around 200 °C with salinities between 2 and 6.7 wt% NaCl eq. and show decreasing trace element contents despite having the same salinity range as the gangue minerals, indicating dilution of the ore-fluid during stage IV as a possible precipitation mechanism. Stage I inclusions are solely hosted in cassiterite from skarn, which shows the importance of fluid inclusion analyses in ore minerals, and record remarkable high mineralization temperatures, exceeding the typically temperature range reported in other studies by at least 100 °C. Our results suggest that this main ore stage is related to the early expulsion of a high-salinity brine phase from an underlying magmatic intrusion at depths greater than 3 km, which likely is a relatively short-lived event within the evolution of the hydrothermal system.

Scheelite has been analyzed from the Shizhuyuan and the Xianglushan world-class W deposits from the Nanling W–Sn region and Jiangnan W belt, respectively. The Shizhuyuan deposit consists of proximal skarn and greisen W–Sn–Mo–Bi and distal Pb–Zn–Ag veins. The Xianglushan deposit, contains layer-like sulfide–scheelite and skarn W orebodies on granite cupolas overprinted by W greisen veins. Scheelite in skarn ores from the Shizhuyuan contains higher concentrations of Mo than those in the sulfide–scheelite and skarn ores from the Xianglushan deposit, reflecting differences between oxidizing and reducing magmatic-hydrothermal fluids. Under oxidizing conditions, W is accompanied by Mo partitions into exsolved fluids to form W–Mo garnet skarns, whereas under reducing conditions, little Mo is carried by exsolved fluids to form W pyroxene skarns. Trace element patterns of scheelite from both deposits show negative Ba, Sr, Zr, and Ti, and positive Ta anomalies. Rare earth element (REE)patterns of scheelite within skarns from the Shizhuyuan deposit have negatively inclined and flat M-type tetrad patterns, and scheelite from the greisens displays flat and positively inclined M-type tetrad patterns. We infer that the fluids formed scheelite within the W skarns and greisens inherited parental magma trace element and REE characteristics (depleted Ba, Sr, Zr, and Ti, enriched Ta, negative Eu anomalies, and tetrad effects). Whereas, scheelite from sulfide–scheelite veins and skarns of the Xianglushan deposit also has W- and MW-type tetrad REE patterns. The W-type tetrad REE patterns are complementary to REE patterns from the Renjiashan granite, and the MW-type tetrad REE patterns occur during a single evolutionary stage within a complex hydrothermal environment. Sulfide mineralization can form after or before W skarns (the former like Shizhuyuan deposit and the latter like Xianglushan deposit). The formation conditions of the latter included reducing conditions and sulfide firstly supersaturated in the melt, resulting in sulfide drops which carried W aggregated on the cupolas. W skarns and greisens in both deposits underwent generally successive processes related to water supersaturation in the melt. Following a temperature decrease and crystallization, bubbles carried material changing from Si and metal to Si oxide complexes.

The Zhuxi W deposit in Jiangxi, South China, with a resource of 2.86 Mt W and an average grade of 0.54% WO3, is the largest W deposit in the world. The deposit occurs at the contact between a late Mesozoic granitic intrusion and Carboniferous – Permian carbonate rocks and Neoproterozoic metamorphic rocks. The ores are divided into three types: skarn ore (dominant), sulfide ore and greisen ore. Based on occurrences and petrographic relationships, scheelite (the dominant ore mineral) is classified into three types, i.e. type I (greisen), type II (skarn, specifically in the retrograde stage), and type III (hydrothermal sulfides). Type I and type II are time equivalent but spatially separated, whereas type III is later. The different types of scheelite have distinctly different REE and trace element compositions. Type I scheelite is characterized by an average ΣREE of 67.9 ppm, LREE/HREE ratio of 24.4, δEu of 8.5, Mo of 0.1 ppm and Sr of 1058 ppm, whereas type II scheelite features an average ΣREE of 48.1 ppm, LREE/HREE ratio of 10.6, δEu of 0.67, Mo of 1892 ppm and Sr of 90.1 ppm. Type III scheelite has an average ΣREE of 53.9 ppm, LREE/HREE ratio of 4.8, δEu of 17.5, Mo of 92.9 ppm and Sr of 37.1 ppm. The extremely high concentrations of Sr and highly positive Eu anomalies in type I scheelite are likely related to release of these elements from plagioclase in the granite during greisenization, whereas the extremely low concentrations of Mo may be related to the reducing and high-temperature nature of the magmatic fluid – Mo probably was mainly in the Mo4+ state and could not replace W6+ in the scheelite lattice. In contrast, the negative Eu anomalies and high Mo concentrations in type II scheelite suggest that the mineralizing environment in the retrograde alteration stage was relatively oxidizing, causing Eu to exist mainly as Eu3+, which is difficult to replace Ca2+ in scheelite, and Mo mainly as Mo6+, which is easy to replace W6+ in scheelite. In the sulfide mineralization stage, the fluid became relatively reducing again, and Eu2+ could easily replace Ca2+ in scheelite causing positive Eu anomalies, whereas Mo mainly exists as Mo4+ and precipitated as molybdenite, and so has limited substitution for W6+ in scheelite. The REE and trace element compositions of the dominant W mineral (type II scheelite), characterized by high concentrations of Mo, high LREE/HREE ratios and negative Eu anomalies, indicate that the ore-forming materials were mainly derived from the granitic intrusions. The variation of REE and trace elements in scheelite in time and space reflects a complex magmatic-hydrothermal mineralization process involving various fluid-rock reactions within the intrusion and in the country rocks. The formation of the Zhuxi W deposit is linked with a large fertile granitic intrusion, which delivered a large amount of W to the site of mineralization through convection within the magma chamber, and W precipitation in the skarn was largely caused by an abrupt drop in temperature and increase in pH of the ore-forming fluid.

The Li-Sn-W deposit Cinovec/Zinnwald in the eastern Erzgebirge (Czech Republic and Germany) represents one of the worldwide best known examples of complex rare-metal plutons with pervasive greisenization. Mica from altogether 38 samples representing all granite and greisen varieties from the present surface to the depth of 1596 m was analysed using electron microprobe (EMPA) and laser-ablation inductively-coupled plasma mass spectrometry (LA-ICP-MS) for major (including F, Rb) and trace (Li, Sc, Ga, Ge, Nb, In, Sn, Cs, Ta, Tl, W) elements, respectively. All primary micas at Cinovec are trioctahedral Li-Fe micas close to the annite–zinnwaldite–trilithionite series. Biotite from granites in the deeper part of the pluton (depth of 735–1596 m) contains 33.9–39.6 wt% SiO2, 19.6–23.8 wt% FeO, 0.5–0.7 wt% Rb2O, 0.9–1.8 wt% Li2O, 3.4–4.8 wt% F, 381–937 ppm Nb, 34–134 ppm Ta, 20–46 ppm W, and 93–617 ppm Sn. Zinnwaldite from granites in the upper part of the pluton (depth of 0–735 m) contains 41.2–48.5 wt% SiO2, 8.9–15.2 wt% FeO, 0.9–1.9 wt% MnO, 2.0–4.4 wt% Li2O, 0.8–1.9 wt% Rb2O, 7.0–8.6 wt% F, 43–464 ppm Nb, 101–213 ppm Sn, 6–80 ppm Ta, and 28–52 ppm W. Zinnwaldite from bodies of pervasive greisen and quartz-zinnwaldite veins is, compared to zinnwaldite from granites, relatively slightly enriched in Si, Mn and Ga, and depleted in Fe, F, Rb, Sn, W and Nb; Li and Ta contents are similar. Contents of Li, Rb and F, and the Fe/Mn and Nb/Ta values in mica closely positively correlate with those in the bulk rock, illustrating an upwards fractionation of parental melt. In contrast, the contents of high-field-strength elements in mica do not correspond to their contents in the bulk rock (melt): they were controlled by the order of crystallization of mica vs. accessory oxide minerals. Therefore, biotite generally contains distinctly higher Sn, Nb, Ta, and W than zinnwaldite. Dioctahedral micas of the muscovite–phengite series were found only as a late product of alteration of primary trioctahedral mica. Replacement of greisen-stage zinnwaldite by muscovite is chemically expressed in a strong depletion in Fe, F, and Li, and an enrichment in Sn. The share of trioctahedral mica in the bulk-rock budget of Sn decreases from 40–70% in biotite granite to less than 5% in greisen; in the case of Nb and Ta from 20–50% to less than 10%. The share of mica in the budget of W, mostly in the range of 2–15%, is stable through the whole pluton.

The Mocambo Granitic Massif is an A-type granite located in the northeastern part of Goias State, near the city of Monte Alegre de Goias. It belongs to the Pedra Branca Suite, which is itself part of the Goias Tin Province, a group of stanniferous granites that exhibit similar geochemical features, including to a greater or lesser degree of rare earth elements enrichment. The parent rock in the Mocambo Granitic Massif is a coarse porphyritic pink biotite granite. Thin section observations coupled with electron microprobe analyses reveal the presence of several REE-bearing minerals: allanite, fergusonite (Ce), fergusonite-(Y), zircon and apatite as accessory minerals, and xenotime-(Y), bastnasite-(Ce), thorite, monazite-(Ce) and hingganite-(Y) as secondary (hydrothermal) minerals. Fergusonite and hingganite are identified in this massif for the first time. This work investigates the forms of occurrence and enrichment of rare earth elements in the Mocambo Granitic Massif, in the parent rock, as well as in greisen, saprolite and soil, with emphasis placed on the rare earth elements adsorbed on clay minerals, and the entire process of transport and fractionation of these elements from the fresh rock until adsorption. The results show enrichment of rare earth elements (with the exception of Ce) in soils in comparison to rock, especially in the clay fraction. Moreover they suggest that these elements are mostly adsorbed on clay minerals, mostly kaolinite and illite, which are identified in the X-ray patterns. The surface oxidation of Ce3+ to Ce4+ on surfaces and the probable formation of Ce oxides cause this element to present a smaller quantity of exchangeable ions. The presence of cerianite grains in one superficial soil sample shows that Ce is mostly found in the Ce4+ state in the soil profile. The Mocambo Granitic Massif displays substantial enrichment in REEY, 555–1229 ppm for the parental granite and 569 ppm for the greisen, and the exchangeable REEY concentrations in the soils horizons, more than 600 ppm, in particular, representing a potential target for an ion-adsorption-type rare earth elements deposit.

The results of analysisof the patterns of the spatial relationship between hydrothermal gold ore formations and the zones of metasomatites and systems of deep faults within the Chortomlyk greenstone structure of the Middle Pridniprovie megablock in the Ukrainian Shield are given. As a result of studying the localization conditions of gold mineralization, it was established that the gold-bearing mineralization is confined to tectonically fractured zones and is localized among metasomatically altered rocks. The hydrothermal series of metasomatites in the Chortomlyk greenstone structure is represented by greisens, propylites, amphibole-carbonate metasomatites and listvenite-berezites. The mineralization of Au and Mo is associated with metasomatites of the greisen type. The study of spatial relationship between the fields of metasomatites and the gold mineralization and zones of deep faults revealed that the closest relationship is expressed with systems of faults with azimuths of 0° and 270°, 17° and 287°, 77° and 347°. The results of the studies allowed us to develop a newprospecting criterion, which, in turn allows us to state that the gold mineralization within the Chortomlyk greenstone structure is spatially confined to metasomatites related to the schistosity, fracture, millonitization, and cataclase zones with high content of sulphide mineralization. These zones are localized in nodes of intersecting faults of the first order of the system 77° and 347° with discontinuous violations of high orders of azimuths of 0° and 270°, 17°and 287°. The results of the research can be used to develop a set of predictive criteria and the allocation of promising sites of hydrothermal mineralization of gold within the Chortomlyk greenstone structure of the Middle Pridniprovie megablock in the Ukrainian shield.

The world-class Shizhuyuan W–Sn–Mo–Bi deposit is spatially related to the Qianlishan granite complex (QGC) in Hunan Province, China. However, the age and classification of the QGC are still debated, and a better understanding of the temporal genetic relationship between the QGC and the Shizhuyuan deposit is essential. Here, we present chemical compositions the intrusive phases of the QGC and the results of detailed zircon U–Pb dating and muscovite Ar–Ar dating of a mineralized greisen vein. Our new zircon laser ablation inductively coupled plasma mass spectrometry U–Pb age data constrain the emplacement of the QGC to 155–151.7 Ma. According to petrological, geochemical and geochronological data and the inferred redox conditions, the QGC can be classified into four phases: P1, porphyritic biotite granites; P2, porphyritic biotite granites; P3, equigranular biotite granite; and P4, granite porphyry dikes. All phases, and especially P1-P3, have elevated concentrations of ore-forming metals and heat-producing elements (U, Th, K; volume heat-producing rate of 5.89–14.03 μWm−3), supplying the metal and heat for the metalogic process of the Shizhuyuan deposit. The Ar–Ar muscovite age (154.0 ± 1.6 Ma) of the mineralized greisen vein in the Shizhuyuan deposit is consistent with the emplacement time of the QGC, suggesting their temporal genetic relationship.

The results of the study of rare-metal (Bi, Te, Se. Be, In) mineralization of skarn deposits (Sn, Zn) in the Pitkäranta Mining District, genetically related to the Salmi anorthosite-rapakivi granite batholiths of Early Riphean age are reported. Minerals and their chemical composition were identified on the base of optical microscopy as well as electron microanalysis. The diversity of rare-metal ore mineralization (native metals, oxides, and hydroxides, carbonates, tellurides, selenides, sulfides, sulphosalts, borates, and silicates) in Pitkäranta Mining District ores is indicative of considerable variations in the physicochemical conditions of their formation controlled by the discrete-pulse-like supply of fluids. Bismuth, wittichenite, and matildite are the most common rare-metal minerals. Sulfosalts of the bismuthinite-aikinite series are represented only by its end-members. The absence of solid solution exsolution structures in sulfobismuthides suggests that they crystallized from hydrothermal solutions at low temperatures. Be (&gt, 10 minerals) and In (roquesite) minerals occur mainly in aposkarn greisens. Roquesite in Pitkäranta Mining District ores formed upon greisen alteration of skarns with In released upon the alteration of In-bearing solid sphalerite (Cu1+ In3+) ↔ (Zn2+, Fe2+) and chalcopyrite In3+ ↔ Fe3+ and 2Fe3+ ↔ (Fe2+, Zn2+) Sn4+ solutions. Sphalerite with an average In concentration of 2001 ppm, is a major In-bearing mineral in the ores.

White mica and tourmaline are the dominant hydrothermal alteration minerals at the world-class Panasqueira W–Sn–Cu deposit in Portugal. Thus, understanding the controls on their chemical composition helps to constrain ore formation processes at this deposit and determine their usefulness as pathfinder minerals for mineralization in general. We combine whole-rock geochemistry of altered and unaltered metasedimentary host rocks with in situ LA-ICP-MS measurements of tourmaline and white mica from the alteration halo. Principal component analysis (PCA) is used to better identify geochemical patterns and trends of hydrothermal alteration in the datasets. The hydrothermally altered metasediments are enriched in As, Sn, Cs, Li, W, F, Cu, Rb, Zn, Tl, and Pb relative to unaltered samples. In situ mineral analyses show that most of these elements preferentially partition into white mica over tourmaline (Li, Rb, Cs, Tl, W, and Sn), whereas Zn is enriched in tourmaline. White mica has distinct compositions in different settings within the deposit (greisen, vein selvages, wall rock alteration zone, late fault zone), indicating a compositional evolution with time. In contrast, tourmaline from different settings overlaps in composition, which is ascribed to a stronger dependence on host rock composition and also to the effects of chemical zoning and microinclusions affecting the LA-ICP-MS analyses. Hence, in this deposit, white mica is the better recorder of the fluid composition. The calculated trace-element contents of the Panasqueira mineralizing fluid based on the mica data and estimates of mica-fluid partition coefficients are in good agreement with previous fluid-inclusion analyses. A compilation of mica and tourmaline trace-element compositions from Panasqueira and other W–Sn deposits shows that white mica has good potential as a pathfinder mineral, with characteristically high Li, Cs, Rb, Sn, and W contents. The trace-element contents of hydrothermal tourmaline are more variable. Nevertheless, the compiled data suggest that high Sn and Li contents are distinctive for tourmaline from W–Sn deposits.

The Cuonadong Sn-W-Be polymetallic deposit is the first rare-metal deposit with an extraordinary metallogenic potential that has been discovered in the Tethyan Himalayan metallogenic belt. The deposit shows a wide range of different mineralization types, including greisen-, pegmatite-, skarn-, and hydrothermal vein-type mineralization. Of these mineralization types, the skarn-type has the largest inferred resources. In order to constrain the source and evolution of the ore-forming fluid, we conducted a detailed study of the skarn-hosted scheelite, including cathodoluminescence imaging, in-situ trace elemental analysis, and bulk Sr isotope analysis. In addition, bulk Sr isotope analysis of fluorite, phlogopite 40Ar-39Ar dating, and marble whole-rock geochemical analysis were also conducted. Phlogopite 40Ar-39Ar dating indicates that the skarn was formed at ca. 15 Ma, which is close to the formation age of the Cuonadong muscovite granite reported in previous studies. Cathodoluminescence images indicate that skarn-hosted scheelite can be subdivided into an older type 1 scheelite and a younger type 2 scheelite. Type 1 scheelite is characterized by a negative Eu anomaly, whereas type 2 scheelite shows a positive Eu anomaly. Considering the close temporal and spatial relationship between the Cuonadong Miocene leucogranite and the ore-bearing skarn, and their similar lanthanide tetrad effect as observed in the REE patterns, we propose that the negative Eu anomaly was inherited from the Cuonadong Miocene leucogranite, while the positive Eu anomaly resulted from the addition of Eu2+ to the ore-forming fluid during greisenization. Sr isotope data show that the fluorite (87Sr/86Sr)i value of 0.728885 is within the range of the Cuonadong Miocene leucogranite (87Sr/86Sr)i values, while scheelite (87Sr/86Sr)i values (0.709717-0.713480) are similar to those of the Cuonadong marble (0.709525-0.712146). Since scheelite is intergrown with fluorite, we propose that the hydrothermal fluid that exsolved from the Cuonadong Miocene leucogranite is responsible for formation of both fluorite and scheelite. Water-rock interaction between this magma-derived fluid and the marble is responsible for the loss of the scheelite magmatic Sr isotopic signature.

The original version of this paper was first published on February 2021, in the BSGF – Earth Sciences Bulletin, 192, 2.However, some remarks from one referee were not incorporated, and the Supplementary material was not available in the published version. For these reasons, we decided to publish this article again, with the necessary corrections and Supplement materials.We apologize for the inconvenience.; International audience; The W-Sn Panasqueira ore deposit is a magmatic-hydrothermal system, which includes a high grade quartz-vein type mineralization and underneath disseminated greisen-type mineralization located in the upper part of a two-mica granite. We investigate genetic and chronological relationships between greisenization of the Panasqueira granite and the formation of ore-bearing quartz veins by monitoring major and trace elements variations in quartz-muscovite assemblages composing the two-mica granite, greisen and ore-bearing quartz veins. Greisen is marked by an overall depletion in Mg, Ti, Ca, Na, Ba, Sr, REE and enrichment in Fe, Li, Rb, Cs, Sn, W that reflect the breakdown of feldspars and biotite and implication of W-Sn-bearing fluids during greisenization. Muscovite from greisen and mineralized quartz veins are enriched in granophile elements (F, Rb, Cs, Li, Sn, W and Zn) compared to magmatic muscovite from the two-mica granite. Trace elements contents in quartz depict evolutionary trends with progressive enrichment in Ge and B and depletion in Al, Ti and Li between magmatic and hydrothermal quartz that emphasize the progressive evolution and cooling of the magmatic-hydrothermal system of Panasqueira. Multivariate statistical approach applied on quartz and muscovite data demonstrates similarities in composition between quartz and muscovite from greisen with those composing ore-bearing quartz veins. These similarities suggest that greisenization and the formation of mineralized veins result from the same hydrothermal event and derived from the same source of hydrothermal fluids. Apatite from greisen and quartz vein yielded respectively U-Pb ages of 292 ± 10 Ma and 295 ± 5 Ma confirming that greisenization and the formation of mineralized veins occurred roughly at the same time. These ages also overlap with the cooling age of the Panasqueira granite (296 ± 4 Ma), indicating a temporal and genetic link between greisenization, W-Sn mineralization and the granite crystallization. Temperatures of the magmatic-hydrothermal system constrained by Ti-in quartz thermometry depicts a cooling trend from magmatic quartz of granite (700-600°C) to hydrothermal quartz of greisen (500-400°C) and veins (450-350°C). These results provide evidences that greisenization and the formation of W-Sn bearing quartz veins occurred at the magmatichydrothermal transition, during which orthomagmatic fluids rich in volatils, incompatible elements and metals (W and Sn) were exsolved at the final stage of solidification of the Panasqueira two-mica granite.

The Yanbei tin porphyry district with a total resource of about 250,000 t Sn is hosted in the Lower Cretaceous Mikengshan volcanic basin in the southeastern part of the Nanling Range. There are several tin deposits of greisen, stockwork and vein styles associated to the intrusive center of the 8 × 8 km large Mikengshan volcano-plutonic complex. LA-ICP-MS U-Pb dating of cassiterite yielded ages of 130.4 ± 4.0 Ma, 132.0 ± 1.5 Ma and 133.5 ± 1.7 Ma for the Yanbei deposit, 135.9 ± 1.5 Ma and 136.7 ± 1.4 Ma for the Taoxiba deposit, and 135.1 ± 4.0 Ma for the Kuangbei deposit. These data overlap within error and indicate that the three deposits belong to a same tin mineral system. Combined with the previous geochronological data, we propose a scenario for the porphyry tin mineral system in the Mikengshan basin. Dacitic to rhyolitic volcanic and subvolcanic rocks formed at ca. 140 Ma, and were shallowly intruded by highly evolved magmas which released magmatic-hydrothermal fluids to form veinlet-disseminated and greisen ore in the granitic rocks, and more distal stockwork and vein tin mineralization in the volcanic and subvolcanic envelope. The porphyry tin deposits in the Mikengshan volcanic basin are part of the 145–135 Ma tin metallogenic event in South China. The Early Cretaceous volcanic basins in the eastern part of the Nanling Range are promising targets for tin exploration.

International audience; The Echassières district of central France hosts diverse magmatic and magmatic-hydrothermal deposits of rare metals, mostly related to the well-known Beauvoir granite. Tungsten mineralization crops out at three distinct wolframite occurrences, the two most important of which are related to two distinct magmatic bodies, emplaced ca. 335 and 310 Ma (Monnier et al., 2019). The mineralization occurred at 335 Ma formed during a hydrothermal episode marked by precipitation of topaz replacing quartz in a stockwork system and as veinlets in the surrounding schist. Fluid inclusions in topaz and quartz display similar features, i.e., all have low salinity, contain significant amount of LiCl, display constant liquid/vapor ratios, and homogenized within a narrow temperature range (T h ≈ 380°C). No evidence for fluid pressure variations was observed, and temperature decrease is considered to be the main cause for wolframite deposition. The younger W mineralization is related to greisenizing fluids that altered the Beauvoir granite and generated several quartz (± topaz and apatite) veins. All greisen-related fluid inclusions display low salinity, however, T h are spread from ca. 190 to 400°C, and several populations exhibit heterogeneous liquid/vapor ratios while others consist of only vapor-rich fluid inclusions. Respectively, these populations are interpreted to have been trapped during boiling or flashing (vaporization) of the fluid. In contrast with the other regional veins, flashing was particularly intense in the Mazet veins, which host the bulk of the last wolframite generation. Consequently, it is proposed that flashing is the key factor that triggered W precipitation. This work highlights the role of two physical parameters, pressure and temperature, whose variations played a preponderant role on wolframite mineralization. It documents, in depth, an example of greisen fluid evolution, providing critical information on W behavior in orthomagmatic fluids, and on greisen-related rare-metal deposits.

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No. of bitstreams: 1 farias_v_me_rcla.pdf: 55576397 bytes, checksum: a3e16348f38a7592f5cb53e227afa347 (MD5) Previous issue date: 2020-05-06 Made available in DSpace on 2020-05-20T22:05:06Z (GMT). No. of bitstreams: 1 farias_v_me_rcla.pdf: 55576397 bytes, checksum: a3e16348f38a7592f5cb53e227afa347 (MD5) Previous issue date: 2020-05-06 Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) O plúton Saubinha (1.316 ± 16 Ma.) compõe uma das intrusões graníticas do maciço São Lourenço que em conjunto com outros maciços (Caripunas, Abunã e São Simão) representam as áreas de exposição de rochas graníticas, com ou sem depósitos de estanho associados, pertencentes a Suíte Intrusiva São Lourenço-Caripunas (1.32 – 1.30 Ga.). O núcleo de ocorrência dos depósitos primários de estanho ocorre na forma de um stock granítico alongado NW – SE. Constitui-se por biotita-álcali feldspato granitos, cartografados em duas unidades mapeáveis, 1:10.000, e em contatos, aparentemente, transicionais entre si. A Unidade A (UA) que integra tipos heterogranulares a equigranulares de granulação média e, subordinamente porfiríticos de matriz fina; e a Unidade B (UB), restrita a borda leste do plúton, com tipos equigranulares a porfiríticos de matriz fina. Adiciona-se ainda uma lente delgada e não contínua de granito miarolítico a sudeste do plúton e diques de microgranito e aplito que seccionam preferencialmente as rochas da UB. Geoquimicamente são granitos ferrosos, pós-colisionais, tipo A (subtipo A2), de caráter metaluminoso que permeia entre os campos peralcalino e peraluminoso com alcalinidade álcali-cálcica a cálcio-alcalina. Apresentam características de magmas oriundos de anatexia de protólitos quartzo-feldspáticos, de mais alta temperatura (~827,0ºC), pouco hidratados e que se posicionaram em níveis crustais rasos. A variação dos elementos maiores e traços por SiO2 sugere um trend evolutivo dos tipos porfiríticos (UB) para os heterogranulares (UA), o que aponta também para uma cristalização centrípeta do plúton, ou seja, mais acelerada nas bordas a mais tardia e lenta no centro. Ademais, apresentam valores elevados totais de ETR (Σ=558) e de terras raras leves sobre os pesados (La/Yb: 7,9), que em conjunto com a intensidade das anomalias negativas de Ba, Sr, Ti e Nb, e razões de K/Na, Rb/Sr; apontam características de biotita granitos precursores à mineralização e, portanto, sem vínculo genético com os depósitos polimetálicos, na forma de lentes de greisen e veios de quartzo subverticais, de Sn ± Cu, Pb e Zn descritos no Distrito Mineiro de São Lourenço-Macisa. Saubinha pluton (1.316 ± 16 Ma.) composes one of granitic intrusions of São Lourenço massif, which together with other massifs (Caripunas, Abunã and São Simão) represent the areas of exposure granitic rocks, with or without associated tin deposits, belonging to the evolution of São Lourenço-Caripunas Intrusive Suite (1.32 – 1.30 Ga.). The core of occurrence of primary tin deposits occurs as an NW – SE elongated granitic stock. It consists of biotite-alkali feldspar granites, mapped in two mappable units, in scale 1:10.000, and in apparently transitional contacts. Unit A (UA) that integrates heterogranular to equigranular medium grain types and subordinately porphyritic of fine matrix; and Unit B (UB), restricted to the eastern edge of the pluton, with equigranular to porphyritic fine grain types. In addition, a thin non-continuous lens of miarolitic granite to the southeast of the pluton and dykes of microgranite and aplite that preferentially crosscut the rocks of UB. Geochemically, they are ferrous granites, post-collisional, A-type (subtype A2), of a metaluminous character that permeates between the peralkaline to peraluminous fields with alkali-calcic to calcic-alkali alkalinity. The granites have characteristics of magmas originated from anatexy of quartz-feldspar protoliths, of higher temperature (~827,0ºC), poorly hydrated and positioned in shallow crustal levels. Variation of major and traces elements by SiO2 suggests an evolutionary trend from porphyritic types (UB) to the heterogranular types (UA), which also points to a centripetal crystallization for the pluton, that is, more accelerated in the edges and later and slower in the center of the Saubinha pluton. Also, the granites have high total values of REE (Σ=558) and of light earth elements over heavy earth elements (La/Yb: 7,9) which together with intensity of negative Ba, Sr, Ti e Nb anomalies, and K/Na, Rb/Sr ratios; indicate characteristics of biotite granites precursors to mineralization and, therefore, without genetic link with the polymetallic (Sn ± Cu, Pb and Zn) deposits, in the form of subvertical greisen lens and quartz veins, described in the São Lourenço-Macisa mining district. CNPQ: 131593/2018-8.

In this study, we present the first systematic dataset on natural variations of OH defect and trace element contents in quartz within igneous bodies. Samples were derived from bore holes of two plutonic bodies from the Krušné Hory/Erzgebirge (German–Czech border), representing typical A-type (Cínovec/Zinnwald granite cupola) and S-type (Podlesí Stock) granite intrusions. Fourier Transform Infrared spectroscopy of quartz was used to investigate the sample set with regard to its OH defect speciation and content. For Zinnwald quartz, IR absorption spectra reveal different lithologies due to changes of the OH defect inventory, enabling a subdivision of the granitic body: (1) hydrothermal greisen quartz of the uppermost part of the intrusion have low OH defect contents (average of 15 µg/g H2O); (2) zinnwaldite granite quartz vary strongly in defect content and show the highest content of the dataset (10–70 µg/g H2O); (3) quartz from an underlying biotite granite have slightly lower, but very uniform contents down to the bottom of the borehole at 1600 m (average 20 µg/g H2O). Infrared spectra of Podlesí quartz reveal a gradual increase in total defect water content with increasing depth over 350 m (30–55 µg/g H2O). Lithium contents in quartz samples from the uppermost part of the Zinnwald intrusion correlate with the occurrence of Li-specific OH defects, while cathodoluminescence (CL) images do not show specific differences. Our findings evidence the potential of OH defects in quartz as a tool to decipher differentiation trends in igneous bodies, and the application of their eroded material for provenance analyses. Electronic supplementary material The online version of this article (10.1007/s00269-020-01091-w) contains supplementary material, which is available to authorized users.

Aqueous fluid saturation during the internal evolution of phosphorus- and boron-rich pegmatites in NW Rwanda has been investigated using petrography, fluid inclusion microthermometry, and microanalysis of minerals and fluid inclusions (Raman microspectroscopy and LA-ICP-MS). The Gatumba dyke system (GDS) in Rwanda has been selected for this study because it hosts a multiphase cassiterite mineralisation, in wall, core and internal replacement zones, suggesting an advancing influence of magmatic-hydrothermal conditions during dyke solidification. As such, multiphase cassiterite precipitation is applied as a tracer for magmatic to hydrothermal crystallisation processes in granitic pegmatites. The GDS consists of a group of six major LCT (lithium-caesium-tantalum) family dykes, which all belong to the most differentiated rare-element pegmatites in the Gatumba-Gitarama field. Petrography identified a well-developed internal anatomy consisting of a border, wall, intermediate and a quartz core zone. In addition, replacement zones developed as cleavelandite after perthitic microcline units in the intermediate zone and as muscovite-quartz pockets in the intermediate and wall zones. The latter replacement zone display muscovitisation reactions with the formation of greisens. Texturally, the greisen pockets replace the secondary cleavelandite units. During internal differentiation, multiphase cassiterite mineralisation formed in 1) large microcline crystals of the wall zone (Cst1), 2) assemblage with quartz, F-poor montebrasite, and carbonate- and boron-enriched Mn-fluorapatite in the core zone (Cst2), and 3) the greisen replacement units in the wall and intermediate zones (Cst3). Fluid inclusion micro-analyses demonstrate that a saline aqueous H2O-NaCl-KCl-(CO2,N2) L1-type fluid (∼20 wt.% NaCl and ∼3 wt.% KCl) was saturated during onset of crystallisation of the wall and intermediate zones and precipitation of the disseminated, magmatic-hydrothermal Cst1 mineralisation in and around large perthitic K-feldspars. Isochore reconstructions of this L1 fluid indicate crystallisation conditions of 535–560 °C and 5.1–5.6 kbar for the GDS. Extensive microcline fractionation and subsequent replacement reactions of cleavelandite after microcline in the intermediate zone were induced by a Li-enriched and more Na-depleted H2O-NaCl-LiCl-(CO2,N2) L2-type fluid, which was present during solidification of the core zone and present during precipitation of Cst2 phase mineralisation (6–12 wt.% NaCl, 1–10 wt.% LiCl). Late-stage, hydrothermal Cst3 mineralisation in the greisen pockets precipitated from a Cs-enriched H2O-NaCl-(KCl, CO2,N2) L3-type fluid (∼15 wt.% NaCl) distinctly after the formation of the cleavelandite replacement units. Subsolidus Cst3 precipitation is dominantly driven by metasomatic, hydrolytic fluid-rock reactions. Combining textural, microthermometric and fluid compositional data with reported Sn melt-fluid partitioning and solubility data demonstrate that primary cassiterite (i.e. Cst1 and Cst2) in the wall and core zone of the GDS precipitated from the exsolved saline aqueous L1-and L2-fluid present at the interface of the highly-fractionated melt phase. Fast disequilibrium growth of (near)-anhydrous mineral assemblages likely caused the formation of flux-rich and, at least locally, water-saturated melt compositions at the crystallisation front of the large crystals. This study emphasises the importance of local magmatic-hydrothermal conditions and the presence of an immiscible aqueous fluid phase during the internal crystallisation and cassiterite mineralisation of rare-element pegmatites.

Im Rahmen des Projektes ROHSA 3 wurden auf Basis vorhandener und neu verfügbar gemachter Daten Prognosen für Zinn, Wolfram sowie Fluss- und Schwerspat in einem 740 m² großen Gebiet im Mittelerzgebirge angefertigt. Die Karten zeigen höffige Gebieten, wobei für Zinn und Wolfram erstmals auch Mengen-Prognosen erstellt wurden. Geophysikalische, geochemische Daten sowie Lagerstättenindikatoren (z. B. Tektonik, Erz kontrollierende Lithologien) wurden durch die Software advangeo@ aufbereitet und mittels ihrer künstlich neuronalen Netze (KNN) verarbeitet. Durch höhere Datendichte, Einbeziehung dreidimensionaler geologischer Daten und Aufstellung quantitativer Modelle wurde ein deutlicher Erkenntnisfortschritt erzielt. Redaktionsschluss: 31.07.2020

A-type granite intrusions in the southern Shi–Hang magmatic zone, South China, contain several world-class W–Sn deposits. The Dayishan granite batholith is located in the north of the southern Shi–Hang magmatic zone, and contains potential Sn mineralization. The batholith contains three intrusive phases, which are the Guankou, Tangshipu, and Nibantian phases. The Guankou phase consists mainly of biotite–K-feldspar granite (G1). The Tangshipu phase consists of three secondary units, which are coarse-grained biotite monzogranite (G2) that cut monzogranite (G3) and fine-grained two-mica monzogranite (G4). The Nibantian phase consists of coarse-grained two-mica monzogranite (G5). Zircon U–Pb dating indicates that the G1 to G4 granites were emplaced at ca. 160 Ma and the G5 granites formed at ca. 144 Ma. All the granites are silica-rich (SiO2 = 69.24−77.02 wt.%), peraluminous (A/CNK = 1.08−1.50), and A2 sub-type granites. High eNd(t) (−6.9 to −5.2) and zircon eHf(t) (−6.2 to −1.9) values suggest that the parental magma was probably derived by partial melting of lower crust, which was induced by input of mantle-derived basaltic magmas. Oxygen fugacity determinations show that the G2 to G5 granitic magmas were reduced, but the G1 granitic magmas were relatively oxidized. From the G1 to G4 granites, Ba, Th, Nd, Zr, Hf, and rare earth element contents decrease, while Rb and Ta contents increase, indicative of extensive fractional crystallization of K-feldspar, plagioclase, and accessory minerals. This suggests that the G1 granites represent the least fractionated magmas, while the G2 to G4 granites are the highly fractionated products of the G1 granitic magma, with the G4 granites being the most fractionated. The G5 granites were formed during a later magmatic activity, though they show similar geochemical features with the G2 and G3 granites. Due to this continuous fractionation process, Sn was efficiently and progressively enriched in the G2 to G4 granites, as indicated by the good correlations between Sn contents and TiO2 contents, Eu/Eu*, Rb/Sr, Rb/Ba, K/Rb, Zr/Hf, Nb/Ta, and Y/Ho ratios, and TE1,3 values. Furthermore, the G2 to G4 granites crystallized at the magmatic–hydrothermal transition. These data indicate that the G2 to G4 granites underwent Sn mineralization, but the G4 granites are the best target for exploration. The G5 granites might also have Sn mineralization potential considering the similar geochemical features with G2 and G3 granites. Given the reduced nature of the magmas, the potential economic mineralization types are greisen and skarn.

To test the impact of cooling history and prolonged hydrothermal activity on the grade and total endowment of the tungsten deposits, we obtained new and detailed geochronology from the Yashan W-Mo and the Xiatongling W-Mo-Be deposits in the Wugongshan mining district in Jiangxi Province, South China. Both deposits contain stockwork and greisen ores within contact zones between granitic plutons and wall-rock metasandstone and mudstone and within the granitic plutons. New SHRIMP U–Pb zircon analyses yielded weighted mean 206Pb/238 U ages of 231.0 ± 5.0 Ma and 161.5 ± 1.8 Ma for the monzogranite and granite in the Yashan W-Mo deposit, and 154.7 ± 1.7 Ma for the granite in the Xiatongling W-Mo-Be deposit. Three molybdenite samples from stockwork ores in the Yashan deposit and four molybdenite samples from greisen and stockwork ores in the Xiatongling W-Mo-Be deposit yielded Re–Os isochron ages of 156.0 ± 2.8 Ma and 156.4 ± 8.7 Ma, respectively. Two muscovite samples from greisen W-Mo ores and W-bearing stockwork in the Yashan deposit gave 40Ar/39Ar plateau ages of 152.77 ± 0.78 Ma and 152.36 ± 0.78 Ma, and two muscovite samples from greisen W-Mo-Be ores and W-Mo-bearing muscovite-quartz stockwork ores in the Xiatongling deposit gave 40Ar/39 Ar plateau ages of 146.85 ± 0.8 Ma and 146.31 ± 0.75 Ma, respectively. The age data indicate that the ore-forming granitic magmas were emplaced earlier at the Yashan deposit than the Xiatongling deposit, but Mo mineralization was concurrent at both deposits, and the last hydrothermal ore-forming alteration started earlier again in the Yashan deposit. The U-Pb, Re-Os and Ar-Ar geochronological data indicate that both deposits had similar durations of magmatic-hydrothermal process: 9.1 ± 1.9 m.y. for the Yashan deposit and 8.6 ± 1.8 m.y. for the Xiatongling deposit, but with different cooling path rate. The Yashan deposit experienced a slow cooling rate (36.4 °C/m.y.) followed by a moderately rapid cooling rate (48.6 °C/m.y.), whereas the Xiatongling deposit had an early rapid cooling rate (74.1 °C/m.y.) followed by a slow cooling rate (29.7 °C/m.y.). Unlike porphyry Cu systems, the longevity of magmatic-hydrothermal process is not likely to be a key controlling factor for the total endowment and grade of W deposits. However, our analyses show that rapid cooling rates might facilitate formation of high grade stockwork and greisen W deposits.

Mineralization related to the post-collisional reorganization in Iberia occurs along strike-slip shear zones (Sn, Au, ± U), in extremely differentiated leucogranites and pegmatites (Sn, Nb, Ta, Be, Li), in skarns (W, ± Au, ± U), and in quartz-veins with greisen (W, Sn, ± Au, ± U). Episyenites/albitites with uraninite mineralization in strike-slip shear zones yield U–Pb ages of 304 ± 6 Ma (2σ) that are identical within error with the 40Ar/39Ar age of micas grown during fabric development (306 ± 3 Ma, 2σ), suggesting shearing and formation of episyenite/albitite and uraninite mineralization are directly related. Mineral chemistry of uraninite from episyenite and deformed muscovite-rich leucogranite host are indistinguishable and has immobile element signatures typical for uraninite that formed from a hydrothermal or metamorphic fluid. The mineral chemistry of uraninite hosted in the deformed muscovite-rich leucogranite, together with the large time span between granite emplacement (347.6 ± 1.9 Ma, U–Pb zircon) and uraninite (chemical age 300 ± 3 Ma) excludes a magmatic origin of uraninite. Mass balance indicates that leaching of rock-forming minerals (especially muscovite and monazite) of the muscovite-rich leucogranite during extensive metasomatism (e.g. albitite or episyenite formation) could provide most uraninite-hosted U. The precipitation of the uraninite-pyrite association with carbonaceous matter in episyenite/albitite was related to local reducing conditions and/or fluid unmixing processes, analogue to hydrothermal uraninite from retrograde scheelite skarn and W ± Au quartz veins in the Iberian Massif. Chemical ages of uraninite from episyenite and muscovite-rich deformed granite demonstrate that episyenitization is not a late-stage Variscan process, but a post-orogenic one. Metal mobilization is structurally controlled. Chemical dating of uraninite may provide a first-order age constraint in unravelling the post-Variscan tectonic history.

Deciphering the behavior of fluid flow at the magmatic-hydrothermal transition is crucial to understanding the physical processes leading to the formation of intrusion-related ore deposits and hence to predicting the locations of mineralized bodies. However, the hydrodynamics (direction and velocity) of the hydrothermal fluid flows related to this transitional stage remains poorly constrained. Here we present a coupled textural and chemical study performed on tourmaline growth bands to constrain fluid flow during the initiation of the hydrothermal system of the Panasqueira W–Sn–(Cu) deposit. This exceptional deposit consists of a dense network of flat wolframite and cassiterite-bearing quartz veins intensely developed above a well-known but hidden greisen cupola. The W–Sn mineralization is preceded by a tourmalinization stage occurring as metasomatic halos around veins and as selvages developed along the vein–wall-rocks contacts. Results emphasize the key role of the greisen cupola in fluid focusing and the role of fluid overpressure during vein opening. Velocity values highlight an efficient transport of metals in veins largely dominated by advective processes (10−4 to 10−3 m s−1), whereas fluid flow in the altered wall-rocks is slow and pervasive (10−6 to 10−5 m s−1), suggesting that element transport through the metasedimentary host rock was low and limited to the alteration haloes. LA-ICP-MS analyses of tourmaline growth bands reveal that fluids coming from the cupola are enriched in Na, K, Li, Sr and Sn, emphasizing the contribution of magmatic fluids during vein formation and the metasomatic alteration of the wall-rocks. More generally, this study demonstrates that the apical portions of granite bodies act as emanative centers of mineralizing fluids, and highlights the usefulness of mineral growth band analysis in the search for intrusion-related mineralization.

The Hämmerlein polymetallic deposit is hosted in skarn, schists, and gneisses that reached their metamorphic peak at ~ 340 Ma during the Variscan orogeny. The deposit is spatially closely associated with one of the most voluminous granites of the Erzgebirge, the Eibenstock granite which intruded the metamorphic units at ~ 320 Ma, and locally also developed greisen mineralization. Cassiterite is the main ore mineral in the Hämmerlein skarn and in greisen mineralizations associated with the Eibenstock granite. The age of skarn formation is bracketed by multi-mineral Rb-Sr isochron ages of the gneisses (~ 340 Ma) and the end of ductile deformation (> 330 Ma). The dated calc-silicate minerals of the skarn have elevated Sn contents, which implies that some Sn was present in the system during regional metamorphism, i.e., well before the emplacement of the Eibenstock granite. Tin in the > 330 Ma old skarn silicates possibly was mobilized from the metamorphic wall rocks. Retrogression of the skarn mineral assemblage may have released some Sn that formed cassiterite in an assemblage with chlorite and fluorite. The Sr isotope signatures of fluorite indicate that this late assemblage is not related to cooling of the metamorphic rocks, but to the emplacement of the Eibenstock granite, which introduced additional Sn into the skarn. Thus, mineralization in the Hämmerlein deposit includes Sn that was introduced during two different events from different sources.

Magmatic and hydrothermal quartz populations related to the Late-Variscan Zinnwald/Cínovec Sn-W-Li greisen-type deposit in the Eastern Erzgebirge/Krušné Hory (German/Czech Republic) were studied in terms of trace element contents and growth structures visualized by cathodoluminescence. The sample suite represents different populations of hydrothermal greisen quartz and magmatic quartz of the granitic host collected at a 600-m long, lateral section crosscutting the northern part of the deposit at the 750-m level. The studied quartz populations are characterized by generally low concentrations and low variation of Al and Ti indicating relatively constant crystallization conditions (temperature, pressure and fluid chemistry) during ore precipitation. Magmatic and hydrothermal quartz are distinguished by their Al, Ti, Li and Ge concentrations and ratios. Magmatic quartz has commonly higher Al (>100 ppm) and Ti (>3 ppm) compared to hydrothermal quartz. The Ge/Al ratio in quartz increases systematically from high to low formation temperatures (664 to ~400 °C = temperature range including published data and our estimates) whereas Ti decreases. The Zinnwald albite granite (mineralization host), an albite-rich alkali granite, and massive quartz-zinnwaldite greisen contain both magmatic and hydrothermal quartz populations which are distinguishable by their Ge/Al weight ratio: magmatic quartz has a Ge/Al ratio of 0.008. Hydrothermal vein quartz related to the Sn-W mineralization (Flöze = flat veins and Morgengänge = steep veins) does not show systematic trace element variations along the sampling profile indicating that no significant chemical gradients (in lateral direction) in the ore forming fluid existed. The uptake of Li in the quartz lattice is limited by the incorporated Al although the Zinnwald/Cínovec magmatic-hydrothermal system was strongly enriched in Li. The calculated crystallization temperatures of quartz of the Sn-W mineralization applying the TitaniQ thermobarometer reveal crystallization temperatures ranging from 575 ± 48 °C (albite granite), 612 ± 12 °C (stockscheider), 610 ± 23 (massive greisen), 536 ± 77 °C (flat veins), to 516 ± 58 °C (steep veins) confirming in general early estimations based on fluid and melt inclusion studies. In economic terms, the hydrothermal quartz (flat and steep veins) with an average total trace element content of 128 ± 56 ppm has intermediate chemical quality and can serve as a by-product if colour sorting and other processing steps are applied. Rock-forming quartz of albite granite and massive greisen with an average total trace element content of 233 ± 127 ppm has medium quality and the disadvantage that quartz contains a high amount of contaminating mineral inclusion, which will be challenging to remove by processing.

The Xianglushan W deposit in northwestern Jiangxi Province, South China, is one of numerous large-size W deposits along the northern margin of the Jiangnan Massif. The deposit comprises lenticular and stratiform-like orebodies, mainly along the contact between argillaceous limestone of the Cambrian Yangliugang Formation and a biotite granite pluton. The mineralization is zoned from proximal W greisen within the cupolas of the biotite granite, through W skarn and sulfide-scheelite bands near the pluton, to distal quartz-sulfide ± scheelite veins. The granitic pluton and an aplitic dyke in the mining area contain zircon grains with U–Pb ages of 123.8 ± 0.8 Ma and 117.3 ± 1.7 Ma, respectively. Six molybdenite samples collected from skarn ores yielded a Re–Os weighted mean age of 125.5 ± 0.7 Ma, and muscovite separates from greisen ores yielded a 40Ar/39Ar plateau age of 122.8 ± 0.78 Ma. The molybdenite Re–Os and muscovite Ar–Ar ages are consistent with the zircon U–Pb age of the hosting granite. The Xianglushan deposit is formed by an Early Cretaceous W–dominated polymetallic ore-forming event in the Jiangnan porphyry–skarn W belt. Zircon from biotite granites in the Xianglushan deposit has negative eHf(t) values, generally from − 5.7 to − 3.1, with corresponding two-stage Hf model ages of 1363–1218 Ma, reflecting derivation of magmas from a crustal source. Molybdenite has Re contents from 12.12 to 22.77 ppm, indicative of a mixed crustal-mantle source, but with a dominantly crustal component. A compilation of precise ages for magmatism and mineralization in the Jiangnan porphyry–skarn W belt shows that there are two stages of mineralization at 150–135 Ma and 130–120 Ma, respectively. Integrated with published data, our results suggest that the Xianglushan W deposit formed in an extensional tectonic setting during the Early Cretaceous.

In South China, extensive multi-phase magmatism was accompanied by W-dominated, polymetallic mineralization. The Xingguo orefield of southern Jiangxi Province in the eastern part of the Nanling region is one of the most important W-dominated mineralized regions in South China. There are more than ten W deposits within or surrounding the Jiangbei complex, including the Huamei’ao quartz vein-type W deposit (WO3 67,400 tons at a grade of 1.344%), the Yanqian skarn-type W deposit (WO3 16,000 tons at a grade of 0.365%), and the Zhangjiadi quartz-vein- and greisen-type Mo-W deposit (Mo 31,806 tons at a grade of 0.1% and WO3 1746 tons at a grade of 0.353%). The orebodies all occur at the contact between the Jiangbei complex and the Sinian metasandstone or Carboniferous-Permian limestone. The Jiangbei complex consists of three lithologies: medium- to coarse-grained, biotite granite (Jγ1), medium- to fine-grained, biotite monzonitic granite (Jγ2), and fine-grained, biotite monzonitic granite (Jγ3), which have zircon U-Pb ages of 160.7 ± 1.1 Ma, 156.3 ± 0.9 Ma, and 153.3 ± 0.8 Ma, respectively. The associated Yanqian, Huamei’ao, Wangnipai, and Liujiazhuang deposits have molybdenite Re-Os ages of 159.2 ± 2.3 Ma, 157.1 ± 1.3 Ma, 157.7 ± 1.4 Ma, and 157.9 ± 1.6 Ma, respectively. A summary of available age dates of intrusions in the Xingguo orefield indicates that the granitic magmatism lasted for ∼8 m.y (ca. 160–153 Ma), whereas the W mineralization occurred in a relatively short period (159–155 Ma), corresponding in age to the episode of large-scale, Mesozoic (165–150 Ma) mineralization in South China. Low eNd(t) values (−10.2–−13.0) of the Jiangbei granitic rocks and low Re contents of the molybdenite suggest that the W-dominated ores and associated granites in the Xingguo orefield were derived mainly from crustal magmas. All three lithologies of the Jiangbei complex have similar geochemical characteristics, and are classified as high-K, calc-alkaline and peraluminous, S-type granites. The Zr/Hf, Nb/Ta, δEu, Rb/Sr, and LREE/HREE ratios all correlate positively with the W contents of the rocks and reach their highest level in the phase II granites. We propose a magmatic-metallogenic model in which W was concentrated by fractionation of crustally derived magmas of phase I and then deposited in skarn-, greisen-, and quartz vein-type ores by both magmatic and hydrothermal processes.

The Qingshan tungsten deposit is a quartz-vein type ore deposit in the Nanling region, South China, and consists of orebodies along the contact between Ordovician sandstone and the Mesozoic Keshuling granitic pluton. There are more than 54 ore-bearing quartz veins, controlled by NE- and NNE-trending faults. The principal ore minerals are wolframite and cassiterite with subordinate molybdenite, which formed dominantly during the early oxide and oxide-sulfide ore-forming stage together with extensive greisenization adjacent to the W-bearing quartz veins. The gangue minerals are mainly quartz and muscovite. Zircon grains from the Keshuling pluton have a U-Pb age of 231.9 ± 1.0 Ma (MSWD = 4.0). Molybdenite separates from the ore-bearing quartz veins have a well-defined 187Re/187Os isochron age of 228.7 ± 2.5 Ma (MSWD = 0.36), with model ages ranging from 227.6 ± 3.3 to 229.7 ± 3.2 Ma. Hydrothermal muscovite from the greisen between the granite and country rocks has a flat 40Ar/39Ar plateau age spectra, yielding a 40Ar/39Ar plateau age of 229.4 ± 1.4 Ma (MSWD = 0.34). The U-Pb, Re-Os and 40Ar/39Ar ages are nearly identical within analytical uncertainties, and these ages, together with the field relationships, provide tight constraints on the W(-Sn) mineralization at around 230 Ma. This multiple dating study reflects that the duration of the hydrothermal activity could be less than several million years. Our new results suggest that the Triassic large-scale W(-Sn) mineralization occurred throughout the Nanling region.

Recently, the mineral potential of the area surrounding the granitic batholiths in the Nanling Range was highlighted by the discovery of a series of tungsten and tin deposits or occurrences hosted in or near the Penggongmiao and Guidong batholiths in southern Hunan Province, South China. However, the lack of high-precision geochronological data from these deposits has hampered the understanding of their ore genesis and further W-Sn exploration progress. Based on detailed geological investigations, we obtained precise Secondary Ion Mass Spectroscopy (SIMS) zircon U-Pb and muscovite Ar-Ar ages from the greisen-dominated Liuyuan tin deposit and Zhuyuanli tungsten deposit, which are located on the western margin of the Guidong batholith. The results show that the 40Ar/39Ar plateau age of muscovite (153.10 ± 0.96 Ma) from the Liuyuan tin deposit is consistent with the 40Ar/39Ar plateau age of muscovite (151.64 ± 0.96 Ma) from the Zhuyuanli tungsten deposit within analytical error. These data indicate that the W-Sn mineralization in the region occurred during the Late Jurassic, which is significantly later than the emplacement of the Caledonian (Early Paleozoic) ore-hosting Guidong granite batholith, as evidenced by the SIMS zircon U-Pb age data from the Liuyuan greisen (438.1 ± 2.6 Ma) and the Zhuyuanli greisenized granite (433.8 ± 3.1 Ma). The remarkable differences in age between the Guidong batholith emplacement and formation of these two W-Sn ore deposits indicate that the regional tungsten and tin mineralization is temporally and genetically associated with possibly concealed Late Jurassic granite at depth rather than with the surrounding Caledonian granite batholith. The uniform W-Sn mineralization age (153–151 Ma) of the Liuyuan and Zhuyuanli deposits suggests that significant Late Jurassic W-Sn ore-forming potential exists along the western margin of the Guidong batholith.

Reconstruction of the redox conditions during formation of rocks and ore deposits often remains a challenging task, particularly if no reactions buffering the oxygen fugacity ƒO2 can be identified. This information is crucial for genetic models of numerous ore deposit types, and consequently there has been long-standing and in recent years increasing research activity addressing complexation and redox state of metals in fluids at high temperatures. In this study, we constrain ƒO2 during tin ore formation from the composition of primary fluid inclusions in the principal ore mineral cassiterite, SnO2. We show that the analysed cassiterite samples from worldwide locations (from hydrothermal veins, greisens, skarn deposits, and pegmatites) precipitated at ƒO2 between QFM (quartz-fayalite-magnetite) and above NNO (nickel-nickel oxide), with more oxidizing conditions up to MH (magnetite-hematite) for certain vein/greisen deposits. This, together with in situ Raman spectroscopic experiments, supports the hypothesis that Sn(IV) prevailed over Sn(II) in many if not most tin-ore forming hydrothermal fluids, which implies that redox reactions play a smaller role than assumed in previous formation models of hydrothermal tin deposits.