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Cytospora (Cytosporaceae, Diaporthales) is a fungal genus that usually inhabits plants as endophytes, saprobes, as well as pathogens. Species of this genus are characterized by possessing allantoid hyaline conidia and ascospores. Samples with typical Cytospora canker symptoms on Prunus davidiana, P. padus and Salix sp. were collected in Tibet and Xinjiang, China. Species were identified using both morphological and molecular approaches of combined loci of internal transcribed spacer region rDNA (ITS), the partial actin (act) region, RNA polymerase II second largest subunit (rpb2), the translation elongation factor 1-alpha (tef1) gene and the partial be-ta-tubulin (tub2) gene. Six isolates in the present study formed three distinct clades from previously known species. Cytospora hejingensis sp. nov. from Salix sp., C. jilongensis sp. nov. from P. davidiana and C. kunsensis from P. padus were proposed herein. The current study improves the understanding of species concept in Cytospora. [ABSTRACT FROM AUTHOR]

[Display omitted] • Mineralization at the Zhibula deposit can be divided into three stages. • Cobalt has two occurrences in Zhibula deposit. • Coeval Co, Te, Au, Ag and Cu mineralization occurred during the late retrograde stage. • The mineral occurrence of Zhibula deposit might be used as a general indicator of Co enrichment in skarn deposits. The Zhibula skarn deposit is a Cu polymetallic deposit, located in Eastern Gangdese, Tibet. In recent years, research on this deposit has mainly focused on lithology, geochemistry, ore-forming fluid and mineralization age, whereas there has been a relative lack of focus on the occurrence of Co, Te, Au and Ag. Three paragenetic stages were distinguished based on mineralogy and textural relationships: Stage I prograde skarn with formation of garnet, pyroxene, magnetite and wollastonite; Stage II early retrograde skarn comprising garnet, tremolite and epidote; late retrograde Stage III characterized by various sulfides with chlorite, quartz and calcite. Photomicrographs and backscattered electron images of thin sections confirm that Co, Te, Au and Ag mineralization are usually associated with chalcopyrite and bornite, which developed during the late retrograde skarn stage (III). The independent Co mineral siegenite was identified along with isomorphous substitution of Co in sulfides and oxides. Compared with chalcopyrite (mean Co content = 10.8 ± 5.32 ppm, 1σ, n = 43), both pyrite and magnetite typically contain obviously higher Co contents (2454 ± 1837 ppm (1σ, n = 14) and 228 ± 49 ppm (1σ, n = 19), respectively). The correlations between Co and other elements indicate that Co replaced Fe in pyrite via isomorphous substitution. The mineral assemblage of independent Co, Te, Au and Ag minerals (siegenite, hessite, calaverite, petzite) with bornite and chalcopyrite also indicates coeval Co, Te, Au, Ag and Cu mineralization during the late retrograde stage. Assuming a Cu-Co precipitation temperature of ∼ 300 °C (supported by previously published fluid inclusion microthermometric results), the mineral assemblage of siegenite and hessite with pyrite and galena reveals an ore-forming fluid logf Te2 of −14.9 to −8.3 and logf S2 of −11.4 to −10.5. The Zhibula deposit and the adjacent well-studied Qulong deposit have similar magmatic source characteristics and mantle-derived magma was likely involved in the formation of mineralization at Zhibula. Compared with previously published trace element data from other skarn deposits, chalcopyrite, pyrite and magnetite in the Zhibula skarn deposit have obviously higher Co contents (8 ∼ 20 ppm, 1500 ∼ 5000 ppm and 160 ∼ 300 ppm, respectively). Accordingly, we propose that trace element analysis of these minerals can be used as a general indicator of Co enrichment in skarn deposits. [ABSTRACT FROM AUTHOR]

[Display omitted] • Independent cobalt minerals. • Cobaltite, carrollite, linnaeite. • Isomorphic substitution. The Pusangguo cobalt-rich skarn deposit occurs in Gangdese, Tibet. In recent years, research on this deposit has detailed the geochronology, petrogenesis, fluid inclusions and skarn mineralogy, but there has been a lack of focus on the occurrence of cobalt. We present X-ray fluorescence, scanning electron microscopy and electron probe microanalyses that address this omission and help elucidate the genesis of cobalt-rich skarn deposits. Correlations between Co and other ore-forming elements (Cu, Pb, Zn and Ag) reveal that Co mineralization was synchronous with other metals. Photomicrographs and backscattered electron and X-ray maps of thin sections, confirm that cobalt mineralization is usually associated with chalcopyrite, sphalerite and other sulfides, which developed at the retrograde skarn stage with quartz, carbonate minerals, tremolite and other skarn-related minor phases. Three independent cobalt minerals are identified (cobaltite, carrollite, and linnaeite). The EPMA results further reveal two different occurrences of cobalt (independent cobalt minerals and isomorphous substitution Co in sulfides) in the Pusangguo deposit. Compared with chalcopyrite (mean Co content = 0.06 ± 0.06 wt.%, 1σ, n = 142) and galena (mean Co content = 0.02 ± 0.04 wt.%, 1σ, n = 82), both pyrite and sphalerite typically contain obviously higher Co contents (mean = 0.16 ± 0.17 wt.%, 1σ, n = 97 and 0.20 ± 0.10 wt.%, 1σ, n = 108, respectively). The correlations between Co and other elements indicate that Co + Ni replace Fe in pyrite via isomorphous substitution while Co + Fe replace Zn in sphalerite. These results further indicate that Co and Zn mineralization occurred at the same time. Combined with previously published Sr-Nd isotopic data on skarn minerals, the mineralization of Cu, Pb, Zn, Ag and Co were likely derived from, or share a common source with the intrusions at Pusangguo. [ABSTRACT FROM AUTHOR]

The formation of high-silica leucogranites and related detailed evolution of granitic crystal mush in southern Tibet bear significant information on the tectonic and magmatic evolution of the Asian–Indian continent–continent collisional zone. Here, we first report an integrated investigation of the Oligocene (ca. 30 Ma) leucogranites and main body granitoids exposed within the Gangdese Batholith in Gyaca County, southern Tibet. The Gyaca leucogranites can be divided into two groups in terms of field observation (gradational contacts vs. dykes), petrography and geochemistry (plagioclase fractionation vs. accumulation trends), and are characterized by their formation through different stages of evolution from (early) fractionation to (later) accumulation (up to 30%) of plagioclase for Group I and II leucogranites, respectively. Overall, the two groups of leucogranites are both characterized by high SiO2 (71.4–75.7 wt.%), Na2O/K2O (>1.0) and Sr/Y (58–629), and low Rb/Sr (0.02–0.27). The Gyaca main body granitoids resemble the published Gangdese granitoids and most of them also have high Na2O/K2O and they generally show varied SiO2 (64.4–76.1 wt.%) and other major and trace elements. The Gyaca leucogranites and main body granitoids have very similar Sr–Nd–Hf–O isotopic compositions, with initial 87Sr/86Sr ratios from 0.7054 to 0.7064, ɛNd(t) values from −3.40 to +0.65, zircon ɛHf(t) values from −3.0 to +5.2, and zircon δ18O values from 5.59‰ to 6.84‰. These leucogranites and main body granitoids are interpreted to have a same magma source and can be formed by water-present melting of garnet amphibolites from juvenile lower crust plus minor materials from felsic ancient crust beneath the southern Lhasa Terrane. The genetic association of the Oligocene Gyaca leucogranites and main body granitoids and their geochemical diversity reveal an evolved magmatic system. The two types of leucogranites are probably formed by crystal-melt fractionation and plagioclase accumulation at different stages during the solidification of the magma chamber. The discovery of ca. 30 Ma leucogranites in the Gangdese Batholith, in combination with the Oligocene–Miocene high Sr/Y Gangdese granitoids and coeval Himalayan leucogranites (HLGs), indicate the coexistence of diverse granitic rocks in southern Tibet may principally result from partial melting of local deep crustal materials. A new petrogenetic model which illustrates the evolution and multiple emplacements of crystal mush in a granitic magma chamber is proposed for the formation and magmatic evolution of leucogranites in melts from juvenile lower crust in Tibet. [ABSTRACT FROM AUTHOR]