Mineralium Deposita最新文献

The relative roles of magmatic versus hydrothermal processes in Nb-Ta-Li mineralization within highly evolved granites remain debated. The Hailuoling pluton comprises a magmatic-hydrothermal sequence from monzogranite (139.1 ± 1.2 Ma) through albite granite (137.0 ± 1.3 Ma) and pegmatite to greisen (137.0 ± 1.6 Ma), as dated by U-Pb geochronology on cassiterite/columbite. During the magmatic stage, columbite-group minerals evolve compositionally from columbite-(Fe) through columbite-(Mn) to tantalite-(Mn) and microlite, while siderophyllite exhibits progressively increasing Li, F contents and Ta/(Nb + Ta) ratios. Geochemical and mineralogical evidence suggests that the Nb-Ta mineralization [(Nb + Ta) = 200–300 ppm] in the albite granite mostly results from fractional crystallization of the monzogranite. The magmatic-hydrothermal transition stage features tantalite-(Fe) overgrowths on primary columbite-(Mn) and tantalite-(Mn), suggesting a metasomatic Nb-Ta mineralization episode triggered by hydrosaline melt separation from the fractionated albite granite/pegmatite system. The composition and mineral relics in greisen indicate fluid-rock interaction between the precursor monzogranite and acidic, Li-F-Fe-rich fluids exsolved from the evolving granitic melt. This process drives greisenization associated with elevated Li mineralization (Li ≈ 1500 pm) and minor Nb-Ta enrichment, which is marked by hydrothermal precipitation of Li-rich siderophyllite, W-bearing cassiterite, wolframite, and columbite-group minerals with decreased Ta/(Nb + Ta) and Mn/(Fe + Mn) ratios. This study concludes that fractional crystallization dominates the economic Nb-Ta mineralization and the initial Li enrichment in the Hailuoling deposit, while hydrosaline melt segregation and subsequent fluid exsolution contribute to subordinate metasomatic Nb-Ta enrichment and major Li mineralization.

This study reevaluates the previously proposed hypogene hypothesis and redefines the origin of smithsonite mineralization in the Angouran deposit, Iran (4.7 Mt of sulfide ore at 27.7% Zn; 14.6 Mt of carbonate ore at 22% Zn). Geological mapping and petrological observations reveal a distinct vertical mineralized zoning: a lower primary sulfide zone containing minor amounts of smithsonite, an intermediate transition zone characterized by smithsonite and newly formed sulfides, and an upper oxidation zone comprising smithsonite and Fe–Mn oxides, which is widely recognized as supergene origin under atmospheric oxygen fugacity conditions. This zoning pattern is analogous to classic supergene weathering profiles observed in porphyry Cu deposits. Morphological and sulfur isotopic analyses (³⁴S-depleted signatures) confirm that the newly formed sulfides within the transition zone are of supergene origin, primarily induced by bacterial sulfate reduction processes and partly formed by the direct replacement of primary sphalerite immediately below the paleo-water table. Smithsonite from all three zones exhibits similar C–O isotopic compositions that fall between those of the host marble and travertines, further supporting a consistent supergene origin. Reaction path modeling demonstrates that smithsonite cannot be generated by the direct replacement of sphalerite by CO₂-rich spring water unless under atmospheric oxygen fugacity conditions. The development of the vertical zoning with distinct mineral assemblages is primarily controlled by the position of the paleo-water table. Near it, rapid fluctuations in oxygen fugacity and sulfur fugacity occur, allowing sulfides formed under reducing conditions to coexist with smithsonite precipitated in relatively oxidative environments. The occurrence of supergene sulfides provides valuable insights into the origin of nonsulfide Zn–Pb mineralization and aid in locating deeply buried primary sulfide orebodies.

The Tin Islands of Indonesia (Riau Archipelago, Bangka and Belitung) constitute the southernmost part of the SE Asian tin province. U–Pb ages of cassiterite from three granite-related tin deposits (Pemali, Selumar and Tikus) and four placer tin deposits (Penyusuk, Sadab Perlang, Gunung Mudal Sincong and Riding Panjang) on Bangka and Belitung Islands were determined by in situ LA-ICPMS U–Pb dating. Cassiterite from the Pemali, Selumar and Tikus deposits has ²³⁸U/²⁰⁶Pb lower intercept U–Pb ages (2 s) of 217.2 ± 2.9 Ma, 223.7 ± 1.6 Ma and 212.5 ± 3.3 Ma, respectively. Alluvial cassiterite from the placer tin deposits of Penyusuk, Sadab Perlang, Gunung Mudal Sincong and Riding Panjang gave U–Pb ages (2 s) of 225.4 ± 3.6 Ma, 216.9 ± 4.2 Ma, 230.1 ± 2.5 Ma and 222.7 ± 1.4 Ma, respectively. These dates define the age of 230—210 Ma for tin mineralization in the Tin Islands, in alignment with the metallogenic ages of tin deposits in the Main Range belt of Malaysia and Thailand.

Granitic pegmatites are a significant source of critical metals including tin, tantalum, and most notably lithium. To meet future demand, a comprehensive exploration model is required to assist in the discovery of new hard rock deposits. Whereas recent work has largely focused on understanding the source and mineralization processes of pegmatites, the structural controls on the distribution and size of individual deposits remains poorly understood and understudied. In this contribution, we present a structural study on the Zulu pegmatite field in Zimbabwe, which provides a good example of the influence of shear zones, host rock rheology, and lithological competency contrasts on the orientation, size, and distribution of pegmatite bodies within a pegmatite field. At Zulu, we observe both structural and petrographic evidence for two types of pegmatite emplacement within an active shear zone during D₂ strike-slip dominated deformation. An early generation (Type 1) was emplaced syn-kinematic to D₂ within dilational jogs subparallel to the shear fabric, and continued ductile shearing also drove significant recrystallization which affected the primary magmatic phases and therefore influenced the preserved mineralogy. A later generation (Type 2) was emplaced syn-to-late-kinematic to D₂ along tension gashes and subordinate fracture sets oblique to the shear fabric, which served to truncate the cooling history and preserve a primarily magmatic mineralogy within this pegmatite group. By comparing Zulu to other large pegmatite deposits, we conclude that geologic structures are critical to source-to-sink connectivity in lithium pegmatite systems, and affect the mineralization potential of individual deposits by driving recrystallization. Assessing the structural history and relative timing of emplacement within a pegmatite field, in conjunction with detailed (micro)textural observations from within pegmatite bodies, is essential to understanding pegmatite emplacement geometries. A more systematic approach in constraining these relationships will therefore aid in generating new exploration targets in both greenfield and brownfield settings.

Carbonatites are important sources of rare metals (e.g., REE, Nb), but are not generally considered prospective for Mo mineralization. Numerous quartz-carbonate-rich vein-type Mo-(REE) deposits and prospects of enigmatic origin extend over 200 km along an E-W belt at the southern margin of the North China Craton (S-NCC). These veins commonly contain carbonates, quartz, sulfates, K-feldspar, sulfides, REE minerals, with minor aegirine-augite and pyrochlore occurring locally. This mineral assemblage is diagnostic of carbonatite-related hydrothermal systems. These veins also show alkali metasomatism, elevated REE contents, sulfate-bearing high-salinity fluid inclusions, and mantle-like isotopic compositions consistent with a carbonatite origin. Two Mo-(REE) mineralization events at ~ 238 Ma and ~ 220 to ~ 210 Ma are recognized based on monazite U-Th-Pb and molybdenite Re-Os isotopic dates acquired from representative deposits across the belt. Combined with previous geochronological data, we propose that these deposits define a Triassic carbonatite-related vein-type Mo-(REE) metallogenic belt in the S-NCC which formed during the syn-collisional to post-collisional period of the Qinling-Dabie Orogenic Belt. The carbonatite-related Mo mineralization formed via a synergistic interplay of three key mechanisms: (1) mantle metasomatism by Mo-rich crustal materials (subducted sediments/delaminated crust) generating fertile metallogenic mantle sources; (2) Mo dissolution and transport in mantle-derived volatile-rich carbonatitic melts and related hypersaline fluids; and (3) Mo enrichment/saturation through fractional crystallization of Mo-deficient phases (carbonates, K-feldspar, sulfates) combined with temperature and redox controlled precipitation processes.

We present isotopic data bearing on the origin of the vent-distal, Lovisa stratiform Zn-Pb sulfide deposit, Bergslagen, Sweden. The age of deposition is constrained by secondary ionisation mass spectrometry (SIMS) U–Pb zircon dating of pumiceous mass flow deposits interbedded with mineralised, fine-grained volcaniclastic strata. Two mass flow deposits in the stratigraphic footwall yield ages of 1892 ± 2 Ma and 1892 ± 5 Ma respectively, whereas a mass flow deposit in the stratigraphic hanging wall yields an age of 1891 ± 3 Ma, constraining the mineralisation to c. 1892 Ma. Positively correlated δ⁶⁶Zn (-0.299 to + 0.219‰), δ³⁴S (-0.2 to + 4.7‰) and Zn/Cd (122 to 659) in sphalerite suggest mass-dependent, kinetic fractionation during sulfide deposition. Upwards decrease in these parameters and Zn/Pb relative to stratigraphic younging suggest that the hydrothermal system matured over time, whereby later fluid batches reached the depositional site less fractionated. Thermochemical sulfate reduction and cooling of single hydrothermal fluid batches are suggested as sulfide precipitation mechanisms while bacteriogenic sulfate reduction is deemed less likely based on by absence of highly negative δ¹¹⁴Cd (-0.212 to -0.069‰), and δ³⁴S values. Sphalerite and galena Pb isotope compositions indicate leaching of c. 1.91–1.89 Ga felsic volcanic rocks as a principal metal source followed by subsequent, syn-metamorphic addition of radiogenic Pb. Limited syn-metamorphic isotopic homogenisation is suggested by retained systematic variations in different sulfide beds.

The Luobusa massif within the Yarlung Zangbo Suture Zone (YZSZ) in SW Tibet hosts distinct chromitite types: low-grade, intermediate-grade, and high-grade (massive) ores, each reflecting unique mantle processes and formation conditions. Variations in Cr# and Mg# values in chromian spinels suggest a dynamic magmatic environment influenced by melt-peridotite interactions, gravitational settling, and metasomatic processes, with boninitic melts characteristic of forearc settings playing a significant role in chromitite formation. Isotopic analyses, including δ²⁶Mg, δ⁵⁶Fe, and PGE alloys, suggest high P-T conditions during chromitite genesis, indicating multiple phases of magmatic differentiation and metasomatism. The Re-depletion (T_RD) ages of 1.0–2.2 Ga for the YZSZ peridotites indicate the presence of ancient subcontinental lithospheric mantle, representing the earliest component in the mantle history of the region. These ancient mantle domains were subsequently modified through interaction with convective mantle sources, likely during the breakup of Gondwana. The chromitites, with an age of ~ 340 Ma, align with subduction-related tectonics and mark an early Paleozoic subduction episode. The peridotites, with formation ages spanning 305–376 Ma, reflect a protracted and non-linear mantle evolution influenced by mantle heterogeneity, episodic melt infiltration, and metasomatic alteration. The transition from MORB- to arc-type basaltic magmatism further suggests subduction initiation and slab rollback during this time. However, the Luobusa peridotites appear to have formed during a distinct, younger tectonic episode, possibly linked to an earlier phase of subduction or mantle plume activity. This is supported by the published Sm–Nd isochron age of 177 ± 31 Ma for Luobusa gabbro, pointing to a Mesozoic magmatic event. Re–Os isotopic data from both YZSZ and Luobusa peridotites reveal interactions between S-saturated basaltic melts and the lithospheric mantle, emphasizing the importance of melt-rock interaction and metasomatism during Neo-Tethyan subduction. Collectively, these observations support a multi-stage tectonic model for the evolution of the Neo-Tethys, involving early subduction, plume-related processes, and the recycling of ancient lithospheric materials.

In greenstones of the east-central Yilgarn Craton, Western Australia, Li-Cs-Ta (LCT) pegmatites of the albite-spodumene type (resources > 300 Mt at 1.4% Li₂O) are spatially associated with high-T (650–450 °C) granite-pegmatite-related skarn and skarn-quartz vein Au-Ag deposits (production 580 t Au). U-Pb and Rb-Sr ages (2.65–2.62 Ga) link both the LCT pegmatites and gold deposits to a suite of peraluminous I-type biotite granites, magnetite-series in least-fractionated K-feldspar megacrystic members, and magnetite- or ilmenite-series in pegmatitic garnet-muscovite intrusions contaminated by melt interaction with continental crust. The granite-pegmatite complexes and the gold skarns formed at 11–15 km crustal depth (300–400 MPa) in a post-orogenic batholith environment at the margin of the 2.7 Ga Eastern Goldfields orogen. Gold occurs in both endo- and exoskarn, and in granite and pegmatite dikes. Calcite carbon isotopes, and initial ⁸⁷Sr/⁸⁶Sr ratios in scheelite relate the skarns to post-orogenic intrusions. Inner calcite, pyroxene, and outer biotite, cordierite, amphibole, and olivine impart a CO₂-Ca-Mg-K metasomatic signature to the hydrothermal system (e.g., Nevoria, Yilgarn Star, Copperhead). An exception is the Ghost Crab deposit, where anthophyllite, cummingtonite, and albite are major constituents in sodic gold ore replacing paragneiss in a zone of magnesian skarn. This deposit is proximal to the albite-spodumene pegmatites of the Mt Marion mine. The skarns in the Yilgarn Craton share the granite-pegmatite association, the gangue mineralogy, the Au-Bi-W geochemical signature, and low- to moderate salinity H₂O-CO₂ fluid inclusions with reduced tungsten skarns, and with world-class gold deposits in other Archean cratons (Kaapvaal, Slave, Superior, Dharwar).

Hard-rock lithium exploration faces challenges due to less advanced deposit and exploration models compared to commodities like copper. Additional obstacles arise from the glaciated and densely vegetated terrains typical of much of Europe, which present additional obstacles to access and geological mapping. Our research focuses on a belt of LCT (Li-Cs-Ta-rich) spodumene pegmatites on the eastern margin of the Caledonian S-type Leinster Batholith, southeast Ireland. We analyse regional stream-sediment geochemistry data and mineralogy of selected stream-sediment samples. Our goal is to identify signatures of the Leinster LCT pegmatites and draw conclusions for lithium exploration. Our analysis reveals high tantalum and tin in several catchments containing known Leinster spodumene pegmatites before and after lithological background correction. Mineralogical analysis reveals that anomalous Sn and Ta in these stream sediments can be attributed to the presence of columbite-tantalite, tapiolite, microlite, and cassiterite. Through SEM-BSE/-EDS analysis and LA-ICP-MS chemical mapping, we show that these minerals exhibit similar textural and chemical characteristics to their counterparts in spodumene pegmatite drill cores and surface boulders and in similar deposits elsewhere, demonstrating that they are useful indicator minerals for these deposits. We conclude that regional lithium pegmatite and rare-metal granite prospectivity can be assessed by examining Sn-Ta associations in stream sediment data. If regional geology, tectonic setting, and stream-sediment geochemistry indicate prospectivity, more detailed local studies can be conducted. By analysing the mineralogy of regional stream sediment samples, prospective areas can be narrowed down to individual catchments. Local geochemical surveys can then follow to pinpoint mineral sources.