Granite Stock Research Articles

Porphyry Cu-Mo mineralization at Anabama Hill, Delamerian Orogen, South Australia: Fertility assessment implicated from epidote and chlorite chemistry

Abstract Porphyry-style hydrothermal alteration has long been recognized in the Delamerian Orogen, Southeastern Australia. However, the fertility of porphyry prospects in this belt, including the Anabama Hill, remains elusive, due to intermittent exploration activities and sparse exposure. Recent significant discoveries of porphyry-epithermal Cu-Au deposits in the adjacent Stavely Arc have led to renewed exploration interest. Reinvestigation of the Anabama Hill drill cores highlights that K-feldspar-rich and epidote-chlorite-dominated alterations are superimposed by extensive quartz-pyrite ± chalcopyrite ± molybdenite veins with white mica-quartz selvedges, related to early-middle Ordovician granitic stocks. Granodiorite and diorite hosts have diagnostic geochemical characteristics, including high Sr/Y, V/Sc ratios, and listric-shaped REE trends, implying amphibole-leading fractionation due to high water contents in primitive melts. LA-ICP-MS analyses show that characteristic element compositions, e.g., high Fe, Sr, Pb, U and Bi and low Mg and REEs in the Anabama Hill epidote, and high Mn, Zn, Zr and U and low Ca, Ba and Pb in the chlorite, suggest the two minerals resulting from propylitic alteration rather than metamorphism. Compared to well-mineralized porphyry deposits, the epidote shows high Bi, Cu, Sr, Ti, Zr and U, and the chlorite is high in Ti/Sr and Al/Si ratios, implying that they are most likely deposit-proximal or near a heat center. This is supported by intermediate to high temperatures of 200—420°C calculated by chlorite geothermometer. Propylitic epidote and chlorite outside pyrite halos typically define geochemical shoulders by anomalous As-Sb and Mn-Zn highs, 1—1.5 km away from the mineralized centers. Given most of the epidote and chlorite intergrown with sulfides, their close proximity to a likely mineralized center accounts for low to moderate concentrations of distal pathfinder elements and subdued performances on the As-Sb and Mn-Zn fertility plots. Combined with bulk-rock results, proximal-fertility indicators recorded in epidote and chlorite provide encouraging implications for porphyry exploration in the Delamerian belt.

Genesis of Yongping copper deposit in the Qin-Hang Metallogenic Belt, SE China: Insights from sulfide geochemistry and sulfur isotopic data

Yongping copper deposit is a large-scale polymetallic mine that contains 1.6 Mt of proven Cu metal reserves with an average grade of 0.74 % and contributes significantly to China’s production of copper. This deposit is situated in the eastern part of the Qin-Hang Metallogenic Belt (Jiangxi province, SE China) at the contact zone between the Yangtze Cu–Mo metallogenic belt and the Jiangxi W–Sn–REE metallogenic belt. The thick stratiform and lenticular-shaped orebodies are hosted in the Carboniferous Yejiawan Formation, consisting of sandstone, limestone, mudstone, and chert-rich clastic rocks. Dominant metal-bearing minerals are chalcopyrite and pyrite with a minor amount of sphalerite, tetrahedrite, galena, molybdenite, pyrrhotite, magnetite, hematite, and scheelite. Although intensive research has been done on its geological setting, geochemical characteristics, and geodynamic evolution over the past thirty years, the origin and depositional environments have remained controversial. In the current research, in situ trace element geochemistry and sulfur isotope analyses, coupled with microscopic investigation, were conducted on sulfide minerals using the LA-ICP-MS technique. The results display that Yongping pyrite rich in Co, As, Ni, Zn, Cu, and Te and deplete in other trace elements. Sphalerite rich in Fe, Mn, Cu, and Cd, followed by In, Co and Ga. The calculation results of formula T(°C) = (Fe/Zn + 0.2953)/(0.0013) reveal that sphalerite was formed in medium–high temperature conditions (262 °C–377 °C). The δ34SV-CDT values of studied sulfides (pyrite, chalcopyrite, sphalerite, and tetrahedrite) varied from −1.52 ‰ to 5.13 ‰ with an average of 2.36 ‰, which are highly consistent with those recorded from porphyritic biotite granite stock of Shizitou (from 2.20 ‰ to 4.5 ‰), suggesting a dominantly magmatic origin. Collectively, trace element compositions of analyzed sphalerite and pyrite from the Yongping area exhibit characteristics of typical skarn deposits. Combined with previous studies, we can conclude that the Yongping Cu deposit is a skarn deposit that was most likely formed by contact metasomatism after the intrusion of the Jurassic Huoshaogang-Shizitou granitic stock into the Carboniferous Yejiawan Formation.

The significance of Paleoarchean granitoids from the Saglek Block, Labrador, Canada

The Saglek Block in the Nain Province of northeast Canada is part of the North Atlantic Craton. It comprises Archean gneisses that record magmatic and metamorphic ages between ca. 3.9 and 2.5 Ga. In this study, a grey banded gneiss from Maidmonts Island records an age of 3.72 Ga, which is equated with Uivak I gneisses reported from across the Saglek Block, and contains 3.8 Ga xenocrysts. These rocks were deformed and metamorphosed prior to the intrusion of augen gneiss protoliths on both Maidmonts and Mentzel islands that record U-Pb zircon ages of 3.33 Ga. These rocks are composed of ferroan calc-alkaline granite and granodiorite and were likely generated by partial melting of pre-existing quartzo-feldspathic crust, as attested by the presence of ca. 3.8 Ga xenocrysts. Such augen gneiss was previously classified as ca. 3.6 Ga ‘Uivak II gneiss’, a term we argue should now be abandoned. The final magmatic events recorded on Maidmonts and Mentzel islands took place in the Neoproterozoic with the emplacement of granitic stocks at ca. 2.72 Ga, and sills and dykes at ca. 2.57 Ga. This sequence of magmatic events from the Eoarchean to Neoarchean is very similar to that recorded in the Itsaq Gneiss Complex of southwest Greenland, where, based on the Hf signature, it has been suggested that a change in tectonic environment resulted from the initiation of subduction at ca. 3.2 Ga. Although Lu-Hf and Sm-Nd isotopic signatures from the ca. 3.33 Ga gneisses have been interpreted in the literature as due to partial melting of Hadean mafic crust, alternatively, they can be generated by partial melting of Eoarchean continental crust in a continental arc setting. We argue this is more consistent with the non-TTG geochemistry of the augen gneisses.

The Spatial and Temporal Evolution of the Sadisdorf Li-Sn-(W-Cu) Magmatic-Hydrothermal Greisen and Vein System, Eastern Erzgebirge, Germany

Abstract The Sadisdorf Li-Sn-(W-Cu) prospect in eastern Germany is characterized by vein- and greisen-style mineralization hosted in and around a small granite stock that intruded into a shallow crustal environment. The nature and origin of this mineral system are evaluated in this contribution by a combination of petrography and fluid inclusion studies, complemented by Raman spectroscopy and whole-rock geochemical analyses. The early magmatic-hydrothermal evolution is characterized by a single-phase low-salinity (7.0 ± 4 wt % NaCl equiv), high-temperature (>340°C), CO2-CH4–bearing aqueous fluid, which caused greisen alteration and mineralization within the apical portions of the microgranite porphyry. The bimodal distribution of brine and vapor fluid inclusions, and the formation of a magmatic-hydrothermal breccia associated with the proximal vein mineralization are interpreted to mark the transition from lithostatic to hydrostatic pressure. The vein- and stockwork-style mineralization (main stage) displays lateral zonation, with quartz-cassiterite-wolframite-molybdenite mineral assemblages grading outward into base-metal sulfide-dominated assemblages with increasing distance from the intrusion. Late fluorite-bearing veinlets represent the waning stage in the evolution of the mineral system. The similarity in the homogenization temperature (250°–418°C) of fluid inclusions in quartz, cassiterite, and sphalerite across the Sadisdorf deposit suggests that cooling was not a significant factor in the mineral zonation. Instead, fluid-rock interaction along the fluid path is considered to have controlled this zonation. In contrast to quartz-, cassiterite- and sphalerite-hosted fluid inclusions, which have a salinity of 0.0 to 10.0 wt % NaCl equiv, the fluid inclusions in late fluorite veins that overprint all previous assemblages have a salinity of 0.0 to 3.0 wt % NaCl equiv and homogenize at temperatures of 120° to 270°C, thus indicating cooling with or without admixture of meteoric fluids during the waning stage of the mineral system. The Sadisdorf deposit shares similar characteristics with other deposits in the Erzgebirge region, including a shallow level of emplacement, similar mineralization/alteration styles, and a hydrothermal evolution that includes early-boiling, fluid-rock interaction, and late cooling. In contrast to most systems in the region, both proximal and distal mineralization are well preserved at Sadisdorf. The recognition of such spatial zoning may be a useful criterion for targeting greisen-related Li and Sn resources.

Mechanism of beryllium mineralization in a granite-pegmatite system: Constraints from ore geology and beryl mineralogy of the large Arskartor Be-Nb-Mo deposit, southern Chinese Altai

The Arskartor Be-Nb-Mo deposit is the second largest Be deposit in the Chinese Altai, NW China, which hosts over 11,000 tons of BeO resource. The muscovite-albite granite and rare-metal pegmatite in the ore district are spatially and temporally coexisted and both are beryllium mineralized. The muscovite-albite granitic stock can be divided into a barren zone and a Be-mineralized zone. The pegmatite shows an well-developed internal zone including the layered muscovite-quartz-albite zone, (lower) beryl-muscovite-quartz zone, quartz core, (hanging) beryl-muscovite-quartz zone, and muscovite-quartz-microcline zone. Beryl is the dominant Be-bearing mineral and mainly occurs in the Be-mineralized granite, the layered muscovite-quartz-albite and the beryl-muscovite-quartz zones of the pegmatite. Subhedral to euhedral beryl in the Be-mineralized granite is interstitial to or intergrown with rock-forming minerals. In contrast, beryl crystals in the pegmatite are coarser in grain size and more euhedral in shape, and mainly coexist with coarse “booked” muscovite and blocky quartz. Concentrations of Li, Cs and Na/Li ratios of beryl are 184–760 ppm, 218–1996 ppm, and 2.13–21.3, respectively. The progressive variations of incompatible elements compositions and Na/Li ratios are consistent with the fractional crystallization mechanism of the granite-pegmatite system. Paragenesis and internal structure of beryl suggest nonequilibrium crystallization of a relatively incompatible elements and fluxes-enriched late granitic melt, generated the coarse-grained Be-mineralized granite. With the progressive enrichment of incompatible and fluxing elements and decreasing temperature, liquidus overcooling was achieved and generated the aplite and immediate zoned pegmatite that hosts abundant beryl. Moreover, the differentiating pegmatitic melt with varying amounts of aqueous fluids at different melt fractions, likely resulted in heterogeneous distribution of beryllium and subsequent variable amounts of beryl crystallization in different internal zones. The exsolution of aqueous fluids from the residual pegmatitic melt resulted in Mo-mineralization and related hydrothermal alteration. Consequently, both protracted fractional crystallization and subsolidus processes contributed the formation of the Arskartor granite-pegmatite system with Be-polymetallic mineralization.

Geochronology and Geochemistry of Volcanic and Intrusive Rocks from the Beizhan Iron Deposit, Western Xinjiang, NW China: Petrogenesis and Tectonic Implications

The Awulale Iron Metallogenic Belt (AIMB) located in Central Tianshan is a significant iron ore belt in China. The Beizhan area exhibits extensive volcanic and intrusive rocks that formed during or close to the iron mineralization period. The iron ores in Beizhan are found in Early Carboniferous rhyolite and dacite tuff. The rhyolite is enriched in LILEs and LREEs, depleted in HFSEs, and shows high positive εNd(t) values (+3.0–+4.0). Late Carboniferous intrusive rocks include a granite stock and diabase and diorite dykes. The zircon grains from the granite yield a weighted mean 206Pb/238U age of 311.8 ± 2.6 Ma. The geochemical features of the granite are similar to those of rhyolite, but with pronounced negative anomalies of Eu, Sr, P, and Ti and higher positive εNd(t) values (+4.9–+5.1). The zircons in the diorite dyke yield a weighted mean 206Pb/238U age of 299.2 ± 1.4 Ma. Both the diabase and diorite dykes show an enrichment of LREEs and depletion of HFSEs with high positive εNd(t) values (+3.3–+7.3 and +2.3–+2.6, respectively), although the Eu, Th, and Sr anomalies are more negative in the diorite compared to the diabase. The rhyolite displays high positive εNd(t) values and young Nd model ages (TDM2 = 760–838 Ma) and has Nb/Ta ratios (11.3–12.8) close to that of the continental crust, indicating that it originated from the partial melting of the juvenile lower crust. The granite has similar geochemical characteristics (TDM2 = 656–673 Ma and Nb/Ta ratio = 8.7–10.9) and is also believed to have originated mainly from the partial melting of the juvenile lower crust. The diabase and diorite dykes have low (Tb/Yb)N ratios (<2) and high Ba/Th (31.8–353.2 and 185.3–251.3, respectively) and Sr/Th (113.8–312.9 and 144.7–163.1) ratios, and exhibit a pronounced depletion of HREEs and Y and negative Th anomalies, suggesting that they originated from a spinel-garnet lherzolite mantle source. The Early Carboniferous rhyolite erupted in a continental arc setting, whereas the Late Carboniferous granites, diabase dykes, and diorite dykes formed in an extensional setting associated with the upwelling of the asthenosphere. Therefore, the magmatism and Fe mineralization in the AIMB are correlated with an extensional setting associated with oceanic slab breakoff.

Tin Mineralization in the Triassic Chacaltaya District (Cordillera Real, Bolivia) Traced by In Situ Chemical and δ18O-δ11B Compositions of Tourmaline

Abstract We present a petrographic and geochemical study of tourmaline from the Triassic Chacaltaya Sn-polymetallic district in the Cordillera Real of Bolivia. Tourmaline is associated with greisens, breccias, and veins, which occur around the Triassic Chacaltaya peraluminous granitic stock hosted by Silurian metasedimentary rocks. Three main petrographic types of hydrothermal tourmaline have been identified: pre-ore greisen-related (Tur-1), syn-ore breccia-related (Tur-2), and syn-ore vein-related (Tur-3). The three types of tourmaline belong to the alkali group and have Fe-rich compositions mostly close to the schorl end member. Overlapping Fe/(Fe + Mg) ratios suggest broadly similar compositions of the hydrothermal fluids during the deposition of tourmaline. The most notable differences in minor and trace element contents include relative enrichment in Zn and Li in Tur-1 and relative enrichment in Ca, Sc, V, Cr, Sr, Sn, Y, Cs, Be, and Zr in Tur-3, with Tur-2 showing intermediate compositions between those of Tur-1 and Tur-3. The progressive enrichment in Sn from Tur-1 (avg = 14 ppm) through Tur-2 (avg = 311 ppm) and Tur-3 (avg = 476 ppm) indicates an increase of Sn concentrations in the hydrothermal system coinciding with cassiterite deposition in breccias and veins. The transition from high Li and Zn contents in Tur-1 to elevated Ca, Sr, V, and Cr contents in Tur-3 is interpreted as reflecting interaction between a hydrothermal fluid of magmatic origin and the metasedimentary country rocks. Strong and relatively steady positive Eu anomalies in all tourmaline types suggest dominantly reduced hydrothermal conditions. In situ δ18O and δ11B analyses of greisen-related Tur-1 reveal crystallization in isotopic equilibrium with magmatic water derived from a peraluminous S-type granite. In contrast, higher δ18O values of breccia-related Tur-2 and vein-related Tur-3 indicate crystallization in isotopic equilibrium with a fluid of metamorphic origin or a magmatic fluid that variably interacted with the metasedimentary host rocks. Geochemical modeling reproduces interactions between a fluid of magmatic origin and the host metasedimentary rocks at moderate water/rock ratios between 0.1 and 0.5. We conclude that cassiterite mineralization in the Chacaltaya district was formed primarily through interaction between B-Sn–rich magmatic fluids and the metasedimentary country rocks.

Graphite, Sheelite and Cassiterite Mineralized Skarns of Frag Al Ma, Sidi Bou Othmane District, Jebilet, Morocco

Sidi Bou Othmane region in the Central Jebilet is formed by a Devonian schistose series. The polyphase Hercynian deformation in this area is characterised by penetrative, subvertical, synmetamorphic schistosity (S1), accompanied by folding. Syntectonic granitic intrusions, hidden in the Sidi Bou Othmane region, is marked by a contact of metamorphism, which responsible for the replacement phenomena observed essentially in the limestones of the region which are transformed into graphitic Sn-W exoskarns. Syn-tectonic, skarnification is polyphase : (i) prograde stage (T= 500- 750°C) : with graphite, garnets, idocrase, pyroxene, wollastonite, quartz, scheelite and molybdenite, crossed by a network of successive veins (garnet, idocrase, wollastonite, quartz and calcite; (ii) retrograde stage (T= 400-500°C): with garnet, idocrase, pyroxene wollastonite, quartz, calcite, epidote scheelite and cassiterite; (iii) hydrothermal alteration stage (T ≤400°C) : with sericite and clay accompanied by abundant scheelite and cassiterite, favoured by the high oxidation rate. Therefore, they would have formed in a reduced environment, in relation to large batholiths or stocks of quartz diorites and/or granites in syn, late- to post-orogenic to anorogenic contexts, in the absence of any cogenetic volcanism. The economic mineralisation of graphite was formed mainly during prograde stage, under reducing conditions. It was formed by devolatilization of a bituminous origin linked to the reef limestones and organic matter, trapped in the shales according to the following reaction:

Nb-Ta-Ti oxidy v topazových granitech cíno-wolframového rudního ložiska Ehrenfriedersdorf (Krušné hory, Německo)

Nb-Ta-Ti-bearing oxide minerals represent the most common hosts of Nb and Ta in high-F, high-P2O5, Li-mica granites from the Sauberg granite stock in the Krušné hory/Erzgebirge Mts. batholith (Figure 1). The stock hosts the Ehrenfriedersdorf ore deposit, representing the most significant Sn-W ore deposit in this area. This ore deposit was mined from the 13th century until the year 1990. Since July 2019, the Ehrenfriedersdorf mining landscape makes a significant part of the UNESCO world heritage site, the Montanregion ore mountains. Fine- to medium-grained granites of the Sauberg granite stock are composed by quartz, albite (An 0.1–0.5), K-feldspar (Or97–99, Ab1–3), Li-mica and topaz. Both feldspars are partly enriched in phosphorus (up to 0.52 wt. % P2O5). Apatite, zircon and monazite are accessory phases. The Nb-Ta-Ti-bearing oxide minerals – Nb-Ta-rich rutile, Fe-columbite, W-ixiolite occur in accessory amounts in ore-bearing structures together with cassiterite and wolframite. The main ore-bearing structures are represented by mineralised vein structures and metasomatic stringer zones, which are the most significant. The latter are characterised by numerous parallel to sub-parallel E-W striking en-echelon sets of ore veins. The Sauberg granite stock hosting the Nb-Ta mineralization is mostly formed by highly fractionated, highly peraluminous S-type granites (ASI = 1.2–1.4) with Nb/Ta ratio = 1.8–5.5 and depletion in CaO, MgO, Ba, Sr and high-field-strength elements. (Table 1, 2). The Nb-Ta-bearing rutile is the most common Nb and Ta carrier and occurs mostly as subhedral inclusions in Li-mica flakes. It has very low Mn/(Mn Fe) ratio (0.0–0.01) and low Ta/(Ta Nb) ratio (0.04–0.25) (Table 3). Columbite-group minerals are represented by columbite-(Fe) with a Mn/(Mn Fe) ratio varying from 0.11 to 0.14 and with relatively low Ta/(Ta Nb) values (0.08–0.26) (Table 4). The rare, W-ixiolite was observed as needle-like subhedral crystals and/or as inclusions in needle-like aggregates of wolframite. The W-ixiolite is Fe-rich with relatively low Mn/(Mn Fe) and Ta/(Ta Nb) values of 0.11–0.13 and 0.07–0.25, respectively (Table 5).

Mineral Chemistry of the Eagle Lake Granite Porphyry, Southwestern New Brunswick, Canada: Implications for Cu-Mo-Au Mineralization

Abstract The oxidized I-type Eagle Lake Granite stock in southwestern New Brunswick, Canada, is texturally divided into porphyritic and equigranular phases. The porphyritic granite consists of phenocrysts (i.e., plagioclase, K-feldspar, quartz, and biotite) and microcrystalline groundmass with minor magnetite–ilmenite, titanite, apatite, and zircon. The equigranular phase has a similar primary mineral assemblage to the porphyritic phase. Their common magnetite-ilmenite-titanite assemblage reflects co-crystallization (magnetite series) from a magma imparting some redox control. However, these granite phases show minor potassic to propylitic alteration mineral assemblages with very minor sulfides, suggesting localized fluid–rock reaction. The composition of plagioclase varies between albite and oligoclase, and K-feldspar is orthoclase commonly displaying considerable turbidity. The An% versus Al/(Ca+Na+K) data indicate that these feldspars are slightly aluminous, reflecting cryptic alteration. Biotite is rich in Fe, plotting near the boundary of primary and re-equilibrated biotite; these biotites formed at temperatures ranging from 670 to 725 °C, based on Ti-in-biotite thermometry. Secondary biotite grains are also locally evident, formed from magmatic-hydrothermal fluids. Secondary fine-grained biotite associated with fine-grained magnetite-pyrite indicates potassic alteration and related Cu±Mo±Au mineralization. Some of these various biotites are partially altered to chlorite at ∼301–361 °C. Like biotite, apatite occurs as both igneous and hydrothermal phases. Based on the concentration of F (4.21–2.90 wt.%), all these apatites are fluorapatites with content of light rare earth elements about 7000 ppm and Eu/Eu* = 0.16.

Quartz veins and silver-containing crushing zones in the exocontact of Solur granite stock (Kularsky district, Yakutia)

The purpose of the work is a investigation of quartz varieties present in quartz veins and crushing zones in order to establish the formation conditions and the possibilities of using quartz varieties to study the distribution of mineralization during exploration. The work was stimulated by the discovery of gold and gold-silver mineralization in adjacent areas and the possibility of using some new methods for studying quartz. Research methods. Samples for the study were taken during the mineralogical mapping of the studied area in the course of work to assess the prospects for its ore potential. The characterization of quartz from veins and crushing zones was carried out on the basis of its field descriptions and laboratory microscopic study, as well as measurements of X-ray luminescence (RL) of vein quartz in the region of 350–550 nm. Fluid inclusions in quartz and sulfur isotope composition in sulfides from quartz veins were also studied. Results and conclusions. The granite stock, surrounded by a zone of contact hornfels with cordierite and andalusite, lies among terrigenous sedimentary rocks that have undergone metagenesis (anhimetamorphism). Veins of glassy coarse-grained quartz and recrystallized (granular) quartz are located directly in the granites, partially recrystallized gray quartz – among the contact cornea, and veins of deformed milky-white quartz - in terrigenous sedimentary rocks outside the contact halo. As the transition from veins located among granites to veins located outside the granite massif, the intensity of quartz RL decreases sharply. The nature of the RL indicates the probable presence in the crystal lattice of quartz from veins in granites of their own defects – vacancies of oxygen or silicon, and in gray and milkywhite quartz – cation-compensated [AlO4 /M+]-centers. Sulfide mineralization in quartz veins is mainly represented by arsenopyrite with an isotopic composition of sulfur close to the meteorite standard. In addition to quartz veins, later crushing zones with hydrothermal injection breccias are also common in the area. In breccia cement and in breccia-intersecting veins, early non-split hypidiomorphic quartz and later split comb-shaped and chalcedony quartz are present. In micro-cryptogrаined chalcedony quartz with grain size up to 0.05 mm contaminated with inclusions of finely crushed rock particles and kaolinite grains, the inclusions of the pyrargyrite – one of the main silver-containing minerals on a number of gold-silver deposits of the region – were found. Based on the known vertical zonality of epithermal gold-silver deposits with the confinement of kaolinite-containing ores and chalcedony quartz to the upper horizons of the deposits, and due to the presence of micro-cryptograined chalcedony quartz containing kaolinite and pyrargyrite in the considered crushing zones, it can be suggested that these crushing zones may be confined to the upper parts of the silver mineralization development zone.

Indosinian magmatism and mineralization in the Banjiaoyuan tin deposit, middle Nanling Range, South China: Constraints from zircon and cassiterite U-Pb ages, geochemistry and Sr-Nd-Hf isotopic compositions

Indosinian W-Sn metallogeny associated with granites in South China has been reported in recent years by many researchers. However, the refined genetic relations between these deposits and the related granites remain unclear in most areas, and the tectonic setting of Indosinian magmatism and W-Sn mineralization are still widely controversial. The Banjiaoyuan tin deposit is located in the east vicinity of Yangmingshan pluton in the middle Nanling Range, South China. The granitic stocks in this deposit comprise two intrusive episodes, i.e., the first episode of medium-coarse-grained porphyritic tourmaline-biotite monzogranite (G1), and the second episode of micron-fine-grained tourmaline-muscovite monzogranite (G2). LA-ICP-MS zircon U-Pb dating gives weighted ages of 226.9 ± 1.6 Ma to 223.8 ± 1.9 Ma for G1, and 224.3 ± 2.0 Ma for G2, respectively. LA-MC-ICP-MS cassiterite U-Pb dating yields Tera-Wasserburg concordia age of 216.7 ± 2.4 Ma for tin mineralization. These ages indicate that both the granitic magmatism and related mineralization were initiated in the late Indosinian period. All the granites have high SiO2, Al2O3, P2O5 contents, and low TFeO, CaO, MgO, TiO2 contents, indicating that the granites are highly differentiated S-type granites, and furthermore, the high DI and Rb, K, U, Hf, Sm, low SI and Ba, Sr, Ti, TREE further show that the granites have undergone high extent of differentiation and evolution. High Rb/Nb and K/Nb ratios, low Nb/Ta and Zr/Hf ratios, widely varying CaO/Na2O ratios, low and uniform εNd(t) values, and dominantly negative and relatively dispersed εHf(t) values jointly indicate that the granites were derived from a heterogeneous mixture of calcium-poor mudstone and calcium-rich psammite (or metamorphic igneous rocks) in the crust. The known Indosinian W-Sn deposits in South China are more closely related to S-type granites than to I-type granites, suggesting that their ore-forming materials are mainly derived from the crust. In addition, individual positive εHf(t) values indicate that a small amount of newborn crustal components were involved in the formation of granitic magma. Compared with G1, G2 differs distinctly in petrological, chemical and isotopic characteristics, especially it is more richer in F content and contains magmatic cassiterite and wolframite crystals, suggesting that G2 have undergone higher extent of differentiation and evolution, and are much more closely related to the Sn-W mineralization than G1. The late Indosinian granites in this deposit were formed in post-collisional extensional tectonic environment, while the early Indosinian granites intruded in the Yangmingshan area were formed in syn-collision compression environment. Based on the statistics, the metallogenic ages of Indosinian W-Sn deposits in South China are between 212 and 230 Ma, and the petrogenetic ages of related granites are between 211 and 230 Ma, both age groups belong to the late Indosinian period, representing a regional large-scale granitic magma intrusion and mineralization event that initiated in post-collisional extensional tectonic environment.

The Baogutu gold deposit in west Junggar, NW China: An epizonal intrusion-related gold deposit

The Baogutu gold deposit (∼4 Mt ore @ 5.5 g/t Au) in West Junggar, is hosted by Early Carboniferous volcano-sedimentary rocks and Late Carboniferous dioritic dikes. Both the dikes and gold mineralization are controlled by NE-trending faults. Two diorite dikes in direct spatial association with gold-bearing quartz veins have LA–ICP–MS zircon U–Pb ages of 316 ± 5 Ma and 314 ± 3 Ma, respectively. The emplacement ages of the dikes are a little older than reported gold mineralization ages (312–311 Ma), which is consistent with their crosscutting relationships. Gold mineralization occurs in quartz veins and stockworks in altered tuff, tuffaceous siltstone, silty mudstone, and dikes. Three gold-bearing vein stages have been identified: (I) pyrite–quartz veins in the deep part of the system; (II) stibnite–quartz veins and (III) native arsenic–quartz veins at shallower-level. Fluid inclusion study shows that the pyrite–quartz veins of stage I formed at temperatures between 345 and 265 °C from fluids with salinities of 5.1–9.1 wt% NaCl equiv, whereas the native arsenic–quartz veins of stage III formed at ∼200 °C from fluids with salinities of 1.4–3.9 wt% NaCl equiv. The ore-forming pressure is estimated to be ∼50–62 MPa, corresponding to mineralization depth of ∼3.3–4.0 km. Oxygen and hydrogen isotope compositions of the fluids (δ18OH2O = 7.9 to 11.2 ‰, δD = -88 to −96 ‰) indicate that the initial hydrothermal fluids have a magmatic source, with involvement of meteoric water in the late stage. The in-situ lead isotopic compositions of pyrite in stage I pyrite–quartz veins are similar to those of bulk sulfide minerals in the Baogutu porphyry Cu deposit, and close to the porphyry stocks, whereas the stibnite and native arsenic in stage II and III quartz veins have more radiogenic lead isotopic signatures due to water–rock exchange with the wall rocks. The Baogutu gold deposit shows affinities to epizonal gold deposits in intrusion-related gold systems (IRGS). The IRGS model suggests that, sheeted, disseminated and vein-type Au–As–Bi mineralization might be found hosted in dioritic to granitic stocks and proximal strata, and vein-type Au–As–Sb mineralization in distal faults.

Zircon U-Pb ages and Hf isotope characteristics of granitic rocks from the Shapinggou molybdenum deposit, Dabie Shan, China

The giant Shapinggou porphyry molybdenum deposit in Jinzhai county, Anhui province is located in eastern Dabie Shan, but its genesis, genetic type and tectonic setting are still debated. New zircon U − Pb age data presented in this contribution show that the granitic rocks at Shapinggou area have been episodically formed at ∼ 135 Ma, ∼127 Ma, ∼117 Ma and ∼ 113 Ma in Early Cretaceous, and can be classified into the early-stage (135–127 Ma) granodiorite and monzogranite plutons, and the late-stage (117–113 Ma) quartz-orthophyre stock and cryptoexplosive breccia pipes. Mo mineralization is closely associated with the late-stage shallow-seated granitic stock or pipes. Granitic rocks of both stages have high contents of SiO2, K2O + Na2O and Al2O3, low contents of TiO2, CaO and MgO, showing a metaluminous to peraluminous, high-K calc-alkaline to shoshonite affinity. They are generally featured by enrichments of LILE (Rb, U, Th) and LREE, and depletions of HFSE (Nb, Ta, Ti) and HREE, with high (La/Yb)N ratios. The early-stage granitic plutons show trace element geochemical signatures of partial melting of over-thickened continental crust (>50 km), whereas element geochemistry of the late-stage small-sized granitic intrusions suggests a shallow source depth (ca. 35 km) under post-collisional extension setting. The Hf isotope data indicate that the Shapinggou granitic rocks are originated from a crustal source predominated by the Kuanping Group mixed with other components such as the mantle. The southward subduction and partial melting of the southern North China Block (including Kuanping Group) beneath the Dabie Shan lead to the generation of the Shapinggou porphyry Mo system in the post-collisional extension setting. Hence the Shapinggou Mo system distinguishes for its crustal source and post-collisional tectonic setting from the porphyry Mo deposits of Climax- or Endako-types, and should belong to collision-type or Dabie-type porphyry Mo deposit.

Geochemistry and Petrogenesis of the Wadhrai Granite Stock of the Malani Igneous Suite in Nagar Parkar Area, SE Pakistan

The Wadhrai granite stock is a part of the Nagar Parkar Igneous Complex, an extension of the Neoproterozoic Malani Igneous Suite of western Rajasthan. It is occupied by a petrographically uniform granite comprising perthite, plagioclase, quartz, with small quantities of biotite, opaque oxides, titanite, and secondary minerals. The rocks are sparingly porphyritic and contain dykes of microgranite, aplite, and rare pegmatite. In the south-central part, parallel sheets and swarms of mafic dykes, and in the western part very fine-grained felsic sheets intrude the body. The granite is metaluminous to peraluminous and characterized by high silica (73–76 wt%), and alkalis (7–9 wt%), and low CaO (0.15–1.4 wt%), MgO (0.15–0.38 wt%), Th (7–12 ppm), and U (1–2 ppm). On geochemical discriminant diagrams, it classifies mostly as A-type (with rather high Y/Nb (8.6 to 2.4, average 5.2) and low Nb/Ga and Ce (typical of A2-type), but sparingly as I-type. Chondrite-normalized patterns show enrichment in LREE over HREE, and small negative Eu anomalies, whereas mantle-normalized spidergrams display higher LILE over HFSE, distinct troughs for Nb, Sr, P, Ti, and spikes for La, Ce, Nd, Sm and Tb. The granite magma was possibly derived from a tonalite-granodiorite-dominated crustal source. Based on the above-mentioned geochemical evidence, it is interpreted that the source rocks of the magma of the Wadhrai granite likely developed initially in a continental margin subduction setting and underwent partial melting in a continental extensional environment.

Evolution of the Paleo-Tethys Ocean in Eastern Kunlun, North Tibetan Plateau: From continental rift-drift to final closure

The dynamic evolution of the Paleo-Tethys Ocean from continental rift-drift and seafloor spreading to initial subduction and final closure has been hotly debated. This paper tries to bring new constraints to this longstanding debate based on the compiled the latest data and investigations into Carboniferous-Triassic magmatism in the westernmost segment of the Eastern Kunlun orogenic belt, North Tibetan Plateau. New results indicate that the ca. 335 Ma appinite stocks were derived from the asthenosphere mantle wedge slightly modified by slab-derived materials. The ca. 244 Ma dioritic appinite stocks were sourced from the partial melting of hydrothermally altered upper oceanic crust following the closure of the Paleo-Tethys Ocean. The ca. 231 Ma adakitic granite stock originated from the partial melting of the thickened eclogitic lower crust in the syn -collisional setting, and the ca. 219–215 Ma granite batholith had a mafic source in the post-collisional setting. By integrating records available, new scenarios of the evolution of the Paleo-Tethys Ocean in Eastern Kunlun were established. The ca. 390–380 Ma continental rifting leading to the opening of the Paleo-Tethys Ocean is attributed to the post-collisional gravitational instability subsequent to the closure of the Proto-Tethys Ocean and the far-field extensional stress induced by the retreating subduction of the Paleo-Asian Oceanic lithosphere along the northern margin of Tarim-Qaidam. The Paleo-Tethys Oceanic lithosphere initially northward subducted at ca. 366–335 Ma. The closure of the Paleo-Tethys Ocean leading to the “soft” collision between the Eastern Kunlun and Bayanhar terranes occurred at ca. 235–225 Ma followed by the ca. 225–200 Ma post-collisional extension. • The ca. 390–380 Ma opening of the PTO due to gravitational instability and retreating subduction. • The initial northward subduction of PTO occurred at ca. 366–335 Ma. • The closure occurred at 235–225 Ma followed by 225–200 Ma post-collisional extension.

Mineralogical-geochemical features of zircon from the Kumir granitic stock, Gorny Altai

Data on U-Pb age and composition of zircon from the Kumir granitic stock (Gorny Altai) and related greisens are presented. The magmatic, metamictic and pneumatolytic-hydrothermal zircons exhibit specifc changes in main and trace elements with increasing content of high-feld strength elemetns (U, Nb, Sc, REE) and decreasing of Eu/Eu* and Ce/Ce* ratios. Depending on the composition and activity of volatiles in fuids and O fugacity, the REE contents and their ratios varied that is refected on tetrad effect of REE fractionation of М- and W- types.

The Ulandryk and related iron oxide-Cu-REE(-Au-U) prospects in the Russian Altai: A large emerging IOCG-type system in a Phanerozoic continental setting

The Ulandryk and related prospects in the Altaid orogenic belt (near the Russian-Mongolian border) comprise intense iron oxide (hematite), Cu, REE, and locally U mineralization and are estimated to contain in excess of 240 Mt iron oxide ores and 3.7 Mt copper. These prospects bear many signatures of the “classic” IOCG (-REE, U) deposits typical of Precambrian terranes but, in contrast, are situated in a Phanerozoic (Paleozoic) setting. They are related to the Early Devonian subvolcanic potassic granite stocks with transitional shoshonitic to A-type granite signatures suggesting a post-orogenic (post-collisional) setting, with some anorogenic (intracontinental to within-plate) affinity. The stocks have been intruded into a coeval local volcanic structure (a volcanic dome complicated by the central caldera) composed of Devonian trachyandesite, trachydacite, quartz latite, rhyolite, rhyolite-dacite, and dominant trachyrhyolite lavas, tuffs and subovolcanic porphyry intrusions.The granitic stocks are accompanied by magmatic and multi-staged hydrothermal breccias, zones of sodic (albite-quartz), potassic (quartz-K-feldspar), propylitic (quartz-albite-chlorite-amphibole) and dominant phyllic to carbonate-phyllic (quartz-sericite to quartz-sericite-carbonate) to possibly argillic (quartz-kaolinite) alteration, with intense development of hematite. Fluorite is also ubiquitous and locally abundant. The mineralization occurs in several wide (typically 60–100 m, up to 200 m) and extended (1.4–6 km) linear to arc-like paralleling steeply dipping zones of breccias surrounding the granite stocks, with the host rock and quartz fragments cemented by fine-grained quartz-hematite and coarser hematite (specularite) material. Copper-gold, REE, and locally U mineralization overprints hematite-rich zones. Wider quartz-sulfide stockworks with Cu-Au mineralization zones containing minor to trace hematite are also present. Quartz is generally abundant forming quartz-hematite veins, stockworks, and breccias (locally with crustiform texture), and zones of quartzite-like pervasive silicification (typically with sericite and clay minerals).Fluid inclusions in quartz contain daughter halite crystals and homogenize by halite dissolution after vapor bubble disappearance indicating a homogenous, high-salinity (35–45 wt%), Na-Ca-K-chloride, aqueous mineralizing fluid. The relatively low homogenization temperatures (∼200–260 °C) and generally subvolcanic-level pressure (∼0.2–0.5 kbar) conditions suggest a shallow level of mineralization possibly corresponding to an upper (to the uppermost) part of a vertically extended magmatic-hydrothermal system.

Discovery of Yaozhuang Stock and Deep Ore Prospecting Implication for the Western Mangling Orefield in North Qinling Terrane, Central China

In the western Mangling orefield, the molybdenum (Mo) polymetallic deposits are closely related to the ore-bearing porphyry stocks (individual outcrop size: <1 km2). In this study, we have discovered several granitic stocks at Yaozhuang. Systematic petrologic, zircon U-Pb-Hf isotope and whole-rock geochemical studies show that both the granitic stocks of porphyritic granite (157 ± 2 Ma) and the intruding monzogranite dike (153 ± 1 Ma) were emplaced in the Late Jurassic. These granitic stocks are characterized by high SiO2(66.83–75.63 wt%), high K2O (4.15–5.05 wt%), high Al2O3(12.90–16.93 wt%), and low MgO (0.06–0.73 wt%) and are metaluminous to weakly peraluminous, being highly fractionated I-A-type transition granites. The content of the total rare Earth element (ΣREE) of the porphyritic granite (139.6–161.7 ppm) is lower than that of the monzogranite (151.4–253.6 ppm). The porphyritic granite has weakly negative Eu anomalies (Eu/Eu* = 0.77–0.93), whereas the monzogranite has weakly positive Eu anomalies (Eu/Eu* = 0.97–1.21) and are more enriched in light rare Earth elements. Both of them are enriched in large ion lithophile elements (LILEs, e.g., K, Rb, and Ba) but depleted in high-field-strength elements (HFSEs, e.g., Nb, Ta, Ti, Zr, and Hf). The zircon εHf(t) values of all the samples range from −16.1 to −6.9, and the two-stage model ages (tDM2) are 1.78–2.16 Ga. The magma may have originated from partial melting of the lower crust (more than 40 km in depth) caused by mantle-derived magma underwelling. The plutons and stocks were emplaced into the intersection of the early EW-trending faults and the late (Yanshanian) NE-trending faults. The fertile magma with high water content (H2O > 4%) and high oxygen fugacity (Delta FMQ > 1.5) indicates that the Yaozhuang area has significant potential for porphyry Mo polymetallic ore discovery.

Robust monazite U-Pb and molybdenite Re-Os ages reveal the magmatic and metallogenic history of a highly evolved granitic system in the Xianghualing deposit, South China

Tin, tungsten, and rare metals are key strategic metals and are regarded as having potentially relationship with highly evolved granites. However, excessive U accumulation with magmatic evolution, complex melt-fluid interaction, and late hydrothermal alteration make it difficult to obtain accurate age information from the highly evolved granitic system. The Xianghualing deposit, located in southern Hunan Province, China, is a giant Sn-Nb-Ta-polymetallic deposit with various types of mineralization spatially associated with the Laiziling and Jianfengling highly evolved granite plutons, and is an ideal target to investigate the magmatic-hydrothermal process of highly evolved magmas and related Sn-Nb-Ta-polymetallic mineralization. Previous studies have reported a relatively wide range of intrusion ages and multi-stage mineralization ranging from Triassic to Cretaceous. However, the timing and genetic link between magma emplacement and Sn-Nb-Ta-polymetallic mineralization remain controversial. Here we employ multiple dating methods, including SHRIMP zircon U-Pb analysis, LA-ICP-MS zircon and monazite U-Pb analysis, and molybdenite Re-Os dating analysis with a view to obtain a precise geochronological framework of the Xianghualing deposit. The SHRIMP zircon U-Pb data from the Laiziling protolithonite granite yielded a weighted 206Pb/238U age of 156.4 ± 1.5 Ma, whereas the LA-ICP-MS monazite U-Pb age for the Laiziling albite granite and the greisenized granite show 207Pb-corrected lower intercept 206Pb/238U ages of 155.5 ± 0.7 and 155.3 ± 0.5 Ma, respectively, which represent the emplacement ages of the Laiziling granite stock. Compared with the scattered SHRIMP and LA-ICP-MS zircon U-Pb age, monazite from the albite granite and greisenized granite yields more precise age information. Our study shows that monazite can be used as a robust tool for dating highly evolved granites. Molybdenite from the Laiziling pegmatite yields a Re-Os isochron age of 157.8 ± 4.2 Ma, which is consistent with the emplacement age of the Laiziling pluton. This result, integrated with previously reported metallogenic age, suggests a temporal and genetic link between the Laiziling granite and Sn-Nb-Ta polymetallic mineralization. Although multi-stage Sn-W metallogenic events have been identified in Nanling Region, it is suggested that the Xianghualing Sn-Nb-Ta mineralization formed during the Late Jurassic within a short duration coeval with the regional large-scale W-Sn mineralization at 160–150 Ma.