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Autophagy modulation has been considered a potential therapeutic strategy for oral squamous cell carcinoma (OSCC). A previous study confirmed that baicalein might possess significant anti-carcinogenic activity. However, whether baicalein induces autophagy and its role in cell death in OSCC are still unclear. The aim of this study was to investigate the anticancer activity and molecular targets of baicalein in OSCC in vitro. In this study, we found that baicalein induced significant apoptosis in OSCC cells Cal27. In addition to showing apoptosis induction, we also demonstrated baicalein-induced autophagic response in Cal27 cells. Moreover, pharmacologically or genetically blocking autophagy enhanced baicalein-induced apoptosis, indicating the cytoprotective role of autophagy in baicalein-treated Cal27 cells. Importantly, we found that baicalein triggered reactive oxygen species (ROS) generation in Cal27 cells. Furthermore, N-acetyl-cysteine, a ROS scavenger, abrogated the effects of baicalein on ROS-dependent autophagy. Therefore, we found that baicalein increased autophagy through the promotion of ROS signaling pathways in OSCC. These data also suggest that a strategy of blocking ROS-dependent autophagy to enhance the activity of baicalein warrants further attention for the treatment of OSCC.

Hypocrellin A (HA), a fungal perylenequinone from bambusicolous Shiraia species, is a newly developed photosensitizer for photodynamic therapy in cancer and other infectious diseases. The lower yield of HA is an important bottleneck for its biomedical application. This study is the first report of the enhancement of HA production in mycelium culture of Shiraia sp. S9 by the polysaccharides from its host bamboo which serve as a strong elicitor. A purified bamboo polysaccharide (BPSE) with an average molecular weight of 34.2 kDa was found to be the most effective elicitor to enhance fungal HA production and characterized as a polysaccharide fraction mainly composed of arabinose and galactose (53.7: 36.9). When BPSE was added to the culture at 10 mg/L on day 3, the highest HA production of 422.8 mg/L was achieved on day 8, which was about 4.0-fold of the control. BPSE changed the gene expressions mainly responsible for central carbon metabolism and the cellular oxidative stress. The induced generation of H 2 O 2 and nitric oxide was found to be involved in both the permeabilization of cell membrane and HA biosynthesis, leading to enhancements in both intra- and extracellular HA production. Our results indicated the roles of plant polysaccharides in host-fungal interactions and provided a new elicitation technique to improve fungal perylenequinone production in mycelium cultures., (© 2023. The Author(s), under exclusive licence to Springer Nature B.V.)

Selective catalytic reduction (SCR) has been one of the most efficient and widely used technologies to remove nitrogen oxides (NO x ). SCR research has developed rapidly in recent years, which can be reflected by the dramatic increase of related academic publications. Herein, based on the 10,627 documents from 2001 to 2020 in Web of Science, the global research landscape and hotspots in SCR are investigated based on a comprehensive bibliometric analysis. The results show that SCR research has developed positively; the annul number of articles increase sharply from 246 in 2001 to 1092 in 2020. People's Republic of China and Chinese Academy of Sciences are the most productive country and institution, respectively. The global collaboration is extensive and frequent, while People's Republic of China and USA have the most frequent research cooperation. Applied Catalysis B-Environmental is the leading publication source with 711 records. Five major research areas on SCR are identified and elaborated, including catalyst, reductant, deactivation, mechanism, and others. Zeolite is the most widely studied SCR catalyst, while copper, silver, platinum, and iron are the most popular metal elements in catalyst. Ammonia (NH 3 ) is dominated among various SCR reductants, while hydrocarbon reductant has gained more attention. Sulfur dioxide (SO 2 ) and vapor are the two most concerned factors leading to catalyst deactivation, and catalyst regeneration is also an important research topic. Density functional theory (DFT), in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and kinetics are the most widely used methods to conduct mechanism study. The studies on "low temperature," "atomic-scale insight," "elemental mercury," "situ DIRFTS investigation," "arsenic poisoning," "SPOA-34," "Cu-CHA catalyst," "TiO 2 catalyst," and "Ce catalyst" have been the hotspots in recent years., (© 2023. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Over the last century, anthropogenic greenhouse-gas (GHG) emissions have changed the global climate, and agriculture plays an important role in the global flux of GHG. Agricultural management practices, such as split N applications and the use of controlled-release fertilisers have significantly increased the crop yield and N-use efficiency by balancing the N demand of crops and the N availability of soils. However, the impacts of these practices on GHG emissions (in particular in wheat-peanut relay intercropping systems) have not been evaluated in detail. In this study, a common compound fertiliser and a controlled release compound fertiliser (CRF) were used the day prior to sowing, at the jointing stage of wheat and at the peanut anthesis stage in ratios of 50-50-0% (JCF100), 35-35-30% (JCF70) and 35-35-30% (JCRF70), with a control treatment of 0 kg ha -1 . The findings demonstrated that treatment JCF70 achieved increases in yields of 9.7% and 14.6% for wheat grain and peanut pod, respectively, compared to treatment JCF100; however, this treatment also significantly increased soil emissions of CO 2 and N 2 O. In addition, cumulative emissions of CO 2 and N 2 O were higher in the peanut growing season by 74.4 and 31.7%, respectively, than in the wheat growing season owing to the relatively higher soil temperature during the former season. Fertilisation combined with irrigation, was found to be the main cause of GHG emissions. Under the same fertiliser rate and N-management style, JCRF70 further increased the yield of peanut pods and the total combined yield of peanut and wheat by 10.3% and 8.9%, respectively, compared to treatment JCF70. The cumulative CO 2 and N 2 O emissions in treatment JCRF70 were 20.4-45.4% less than those in treatment JCF70. The total global warming potentials of CO 2 and N 2 O were lowest in treatment JCRF70 owing to it providing the highest grain yield. Therefore, N application with three splits, together with the use of a slow-release fertiliser, may be a simple and effective approach to enhance the grain yield whilst reducing the GHG emissions., (© 2021. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Heavy metal(loid) (Cd, Co, Cr, Ni, Cu, Zn, Pb, V, Tl, and As) and Pb isotope compositions of two black shale weathering profiles were determined to investigate the geochemical behaviors of these toxic elements during black shale weathering and the heavy metal(loid) contamination and source apportionment of Pb in black shale-associated soils. Black shale has higher heavy metal(loid) concentrations than the upper continental crust and the worldwide average shale. In contrast, the surface soils have much higher heavy metal(loid) concentrations than the profile soils. The heavy metal(loid) concentrations in black shale-associated soils are higher than the Chinese and worldwide soil background values, except for Co and Pb. Black shale-associated soils, especially the surface soils, have higher average concentrations of As, Cd, Cr, Ni, Cu, and Zn than Chinese, Dutch, and Canadian soil guidelines. The enrichment factor (EF) and geoaccumulation index (I geo ) values indicate various degrees of heavy metal(loid) contamination in these soils, particularly for the heavy metals Cd, Tl, and V and metalloid As. Co and Pb contamination in these soils is not a current concern. According to the mass transfer coefficient (τ Ta,j ) values, Cd, Co, Ni, and Zn show overall losses, and other metals (Cr, Cu, Pb, and V) exhibit different behavior in the studied black shale weathering profiles. Based on a simple binary Pb isotopic mixing model, black shale is the dominant contributor to the Pb in black shale-associated soils (70.5-91.1% to profile soils and 81.2-88.8% to surface soils), and vehicle exhaust contributes less (8.9-29.5%) to the Pb in profile soils. Vehicle exhaust can exert an impact on the Pb isotopic evolution at depth intervals of 60-80 cm below the soil surface., (© 2021. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Scheelite, one kind of common REE-rich and U-bearing hydrothermal mineral, is extensively developed in various types of gold deposits, which can be used to record nature and timing of metallogenesis. The Zhaishang Carlin-like gold deposit in the Qinling Orogen is a giant Au deposit, hosting 127t of Au @ 2.67 g/t with economic concentrations of tungsten and antimony. The study reports two types of scheelite based on the characteristics of petrography and geochemistry. Sch A shows significant oscillatory zoning with dark gray cathodoluminescence (CL) response, whereas Sch B displays patchy textures with brighter CL response. Systematic LA-ICP-MS U-Pb dating of Sch A and Sch B yields ages of 227.1 ± 3.2 Ma and 226.2 ± 6.9 Ma, respectively. The new dates, constraining the Zhaishang Au-W mineralization to ~ 227Ma, coincide well with the western Qinling magmatism, metallogenic and tectonic events. There are significant variations in concentration, the Sch A has low REE content (mean = 41.3 ppm), negative Eu-anomaly with slightly positive Ce-anomaly, whereas Sch B, with small negative or positive Eu-anomaly, has higher REE content (mean = 247 ppm) and higher positive Ce-anomaly. The positive correlation of Eu.sub.N and Eu.sub.N.sup.* records oxidizing condition during the whole W mineralization event. Additionally, Sch B intergrown with selenides with an increase in the Ce-anomaly supports that the latter has higher oxygen fugacity environment. The Sr isotope signature for scheelite supports that ore-forming metals mostly inherited the host rock component, while the proportion of magma-derived Sr increased in the Sch B. Fluid-rock interactions co-precipitated Au and W caused by the release of Fe and Ca cations and the increase of pH. The study highlights that scheelite as a recorder can help in deciphering the nature and timing of metallogenesis of the studied Au-Sb-W deposit, and thus other similar Au-W deposits., Author(s): Guoming Weng [sup.1] [sup.2], Jiajun Liu [sup.1] [sup.2], Emmanuel John M. Carranza [sup.3] [sup.4], Degao Zhai [sup.1] [sup.2], Jianping Wang [sup.1] [sup.2], Huan Wang [sup.5], Bin Zhang [sup.1] [sup.2], [...]

Pyrite, the most common sulfide mineral, is a ubiquitous component of many hydrothermal gold deposits. Geochemical patterns within the refractory pyrite structure represent a valuable repository of information that can help constrain the sources of ore-forming materials, and the evolution of ore-forming processes over time. However, there are still a lot of debates on the mechanisms of physico-chemical processes in ore-forming fluid controlling trace element and sulfur isotope distributions in pyrite during growth. In our manuscript, we use cutting-edge complementary microanalytical methods to understand the origin and evolution of zoned gold-bearing pyrite in samples from the largest gold deposit in the Ailaoshan gold belt, SW China, Zhenyuan (exceeding 100t Au, average grade: 5.3 g/t). Pyrite, arsenopyrite, chalcopyrite, and stibnite are the most abundant sulfide minerals in most orebodies. Of these, pyrite is dominant and is also the most important host for gold. Two types of pyrite can be clearly distinguished: framboidal pyrite and hydrothermal pyrite. Gold is most commonly hosted by hydrothermal pyrite. Framboidal pyrite, mainly hosted by carbonaceous slate, hosts negligible Au, and features low [delta].sup.34S values ranging from - 35.0 (± 0.9) to - 25.6 (± 1.0)â°. Hydrothermal pyrite is characterized by complex intra-grain zoned textures with alternating As-rich and As-poor bands readily recognizable on backscattered electron images. Scanning electron microscopy and trace-element analyses show that both visible and invisible gold occur only in the As-rich bands. Compared to the As-poor bands (72.1% of Au concentration data < 1.96 ppm, n = 43), the As-rich bands are characterized by far higher concentrations of Au (up to 1420 ppm), Cu, Ag, Sb, and Tl, but lower concentrations of Co and Ni. In-situ sulfur isotope analysis indicates that the [delta].sup.34S values of As-rich zones range from - 7.3 (± 0.6) to 2.9 (± 0.6)â° and are similar to those of As-poor zones (from - 6.9 (± 0.7) to 2.8 (± 0.6)â°), but distinct from the framboidal pyrite. Combined with published fluid inclusion data and a probable age for the magmatic event associated with mineralization, these data suggest that magmatic-hydrothermal fluids contributed most ore-forming materials and that periodic boiling led to formation of the rhythmic As-rich and As-poor bands in pyrite. Our data for pyrite constrain the evolution of ore-forming processes and provide new insights into the formation of zoned pyrite, with the conclusions having broad implications for analogous hydrothermal gold deposits worldwide., Author(s): Huichao Zhang [sup.1] [sup.2], Nigel J. Cook [sup.3], Hongrui Zhang [sup.2], Zengqian Hou [sup.2], Peng Chai [sup.2], Wei Li [sup.4], Sarah Gilbert [sup.5] Author Affiliations: (1) https://ror.org/01wd4xt90, grid.257065.3, 0000 [...]

The regolith-hosted rare earth element (REE) deposits in the Nanling Mountain Range, South China, are the most important source of heavy REE (HREE) in the world. A perplexing thing is that only a few of these deposits are relatively enriched in HREE and most of them are actually light REE (LREE)-enriched, although they are all originated from the granitic bedrocks with similar HREE concentrations. This is supposed to be related to the redistribution of REE in the weathered bedrocks due to groundwater-rock interaction, however, it remains enigmatic how REEs are mobilized and fractionated in the interaction. Titanite is an important REE contributor to the regolith-hosted REE deposit. Here, we investigate textural and compositional variations of the titanite from the granitic bedrocks to weathered profiles in the Zuokeng regolith-hosted REE deposit, the largest one that is newly discovered in this region. Together with thermodynamic modelling, we deduce the nature of the fluids, temperature range for titanite alteration, and the mechanism of REE fractionation. Primary titanite is of magmatic in origin and shows relatively high REE contents and negative Eu anomaly on the chondrite-normalized REE pattern. Secondary titanite is commonly associated with chloritized biotite and is characterized by extremely low REE, high Al.sub.2O.sub.3, F and significant positive Eu anomaly, typical of authigenic origin due to chloritization of biotite under oxidized conditions in supergene environment. From the bedrocks upward to the surface, primary titanite is gradually replaced by calcite, synchysite-(Ce) and TiO.sub.2 in the weathered bedrocks. This is interpreted as the result of infiltration of the F, carbonate-rich, alkaline fluids derived from local groundwater through the bedrocks. The irregular dark patches in primary titanite display typical alteration texture and may have formed through fluid leaching of primary titanite. The patches in primary titanite have lower REE concentrations and higher LREE/HREE ratios than magmatic domains, indicating that the groundwater preferentially scavenges HREE from primary titanite, leaving behind LREE in weatherable secondary minerals, such as synchysite-(Ce) and allanite. Mass balance calculation results also confirm that more HREE are lost from weathered bedrocks than LREE. Therefore, the interaction of groundwater and granitic bedrocks may be favorable to enrich LREE rather than HREE in the regolith. This may explain why most regolith-hosted REE deposits like Zuokeng in South China are of predominant in LREE. This study highlights the role of groundwater in mobilizing, fractionating and enriching REE from the granitic bedrocks to resultant regolith-hosted REE deposits., Author(s): Jingzhao Dou [sup.1], Christina Yan Wang [sup.1] [sup.2] [sup.3], Yanlu Xing [sup.4], Wei Tan [sup.1] [sup.2] [sup.3], Zisong Zhao [sup.1] [sup.5] Author Affiliations: (1) grid.454798.3, 0000 0004 0644 5393, [...]

The Yangchuling porphyry W-Mo deposit is an oxidized tungsten deposit in the Jiangnan tungsten belt, which is the largest tungsten belt in the world. Both W- and Mo-mineralization predominantly occur in the cupola of a monzogranite porphyry with abundant mafic dikes and microgranular mafic enclaves (MMEs). Acicular apatite in MMEs and similar SIMS U-Pb zircon ages of the monzogranite porphyry (149.7 ± 1.1 Ma) and MMEs (148.7 ± 1.3 Ma) suggesting mixing of mafic and felsic melts. Plagioclase phenocrysts are oscillatory zoned with An-rich and An-poor zones with lower .sup.87Sr/.sup.86Sr.sub.initial values and higher contents of Mg, Ti, and Sr in the An-rich zones and resorption surfaces in An-poor bands. These textures reflect multiple injection of mafic magma into the magma system responsible for the formation of the Yangchuling deposit. Whole rock Sr-Nd isotope data and zircon Hf-O isotope data indicate 60-70% contribution from the enriched mantle and 30-40% from the crust to the ore-forming granitic rocks. The W and Mo endowments of the Yangchuling deposit and other W-Mo deposits in the Jiangnan tungsten belt have different sources. Whereas W is derived from the melting of supracrustal metasedimentary rocks, Mo is contributed by mafic magmas. The latter is inferred from (i) the close relationship of Mo mineralization with mafic dikes and MMEs rather than the more evolved monzogranite porphyry and (ii) higher Mo concentrations in scheelite from MMEs (3020-3406 ppm) than in scheelite from the host monzogranitic porphyry (540-1886 ppm). On the scale of the whole Jiangnan tungsten belt, granitic rocks with more intense Mo mineralization have higher [epsilon]Hf zircon values that demonstrate higher input of mantle material to the deposit-forming granites., Author(s): Shiwei Song [sup.1], Jingwen Mao [sup.1], Rolf L. Romer [sup.2], Wei Jian [sup.1] Author Affiliations: (1) grid.162107.3, 0000 0001 2156 409X, MNR Key Laboratory for Exploration Theory and Technology [...]

The textures and compositions of hydrothermal apatite grains have been reported in many iron oxide-apatite (IOA), porphyry, and rare-earth elements (REE) polymetallic deposits. However, such information for apatite in hydrothermal gold deposit is not available. In this study, we present integrated textural, elemental, and in situ oxygen isotopic data of hydrothermal apatite grains from the Hatu gold deposit (56t Au, average grade: 5 g/t) in the West Junggar, Northwest China, to investigate the detailed mineralization processes and nature of ore-forming fluids. Hydrothermal apatite is present within the quartz-sulfide ores at the Hatu gold deposit. Apatite grains of the Hatu gold ores contain abundant fluid inclusions and fine sulfide crystals, indicating that they are closely related to gold mineralization. Three types of hydrothermal fluorapatite (Ap1, Ap2, and Ap3) were revealed by Cathodoluminescence (CL) imaging. The Ap1 and Ap2 formed in the auriferous ore-forming stage, whereas the Ap3 formed in the post-ore stage. The three types of apatite have distinct total REE concentrations (216-751 ppm for Ap1, 14-120 ppm for Ap2, and 914-1422 ppm for Ap3) as well as chondrite-normalized REE distribution patterns. The textures and compositions of different apatites are inconsistent with dissolution-re-precipitation processes but instead point to three episodes of apatite formation in the Hatu hydrothermal system. The Ap3 has different REE and lower Eu/Eu* values (0.97-1.72) than Ap1 (1.34-4.50) and Ap2 (1.69-4.95), indicating a change of fluid compositions and a decrease of oxygen fugacity from the auriferous ore-forming stage to post-ore stage. All three types of apatite (Ap1, Ap2, and Ap3) show relatively high and consistent oxygen isotope compositions ranging from 14.2 ± 0.3â° to 15.2 ± 0.2â°, from 14.5 ± 0.2â° to 15.0 ± 0.3â°, and from 13.8 ± 0.3â° to 15.4 ± 0.2â°, respectively. Their calculated [delta].sup.18O.sub.fluid values are higher than magmatic-hydrothermal fluids but consistent with those from metamorphic fluids derived from meta-basalts. The near-zero [delta].sup.34S values of hydrothermal pyrite grains in the gold ores are much higher than those of pyrite framboid grains in the ore-hosted sedimentary rocks (- 41.1 to - 24.3â°), suggesting the sulfur may be derived from meta-basalts rather than sedimentary rocks in the mining area. Taken together, we suggest that Hatu is an orogenic gold deposit formed by fluids and metals derived from metamorphic de-volatilization of meta-basalts at depth. Our study highlights that a combination of CL imaging, in situ trace elements, and oxygen isotope compositions of hydrothermal apatite can be a novel and powerful tool to trace the nature of ore-forming fluids in the hydrothermal gold deposits., Author(s): Jiahao Zheng [sup.1] [sup.2] [sup.3], Ping Shen [sup.3], Wanyi Feng [sup.1] Author Affiliations: (1) grid.411604.6, 0000 0001 0130 6528, Zijin School of Geology and Mining, Fuzhou University, , 350108, [...]

The Daye district represents one of the largest concentrations of skarn deposits in eastern China. There are two major types of skarn deposits (Fe skarn vs. Cu skarn) within this district, both genetically related to late Mesozoic high-K calc-alkaline granitoids. In this study, we present in situ compositional and Sr-Nd isotopic investigations of apatite from granitoids associated with Fe skarn and Cu skarn deposits to put constraints on the magma source, evolution, and volatile composition, which provide significant new insights into the genesis of the two contrasting mineralization styles in the Daye district. Apatite from granitoids related to Cu skarns and Lingxiang Fe skarn has [epsilon].sub.Nd(t) values of - 8 to - 4, similar to that of the contemporaneous mafic rocks in the Daye district, which were dominantly derived from an enriched lithospheric mantle source. Apatite in granitoids associated with the Chengchao Fe skarn has lower [epsilon].sub.Nd(t) values of - 15 to - 9, suggesting larger degrees of contaminations from ancient lower crust materials. Fractionation models based on apatite Sr/Y and Eu/Eu* ratios, suggest that magmas related with the Cu skarns have experienced amphibole-dominated fractionation under high pressure and hydrous conditions, whereas those associated with Fe skarns have undergone plagioclase-dominated fractionation at relatively low pressure and dry conditions. Based on results of apatite compositional analysis and apatite-melt partitioning data, the estimated magma Cl contents for the Fe skarn range from 3260 to 13,940 ppm, significantly higher than those for the Cu skarn (Cl = 430-5990 ppm). Apatite from Fe skarn-related intrusions has (.sup.87Sr/.sup.86Sr).sub.t ranging from 0.7073 to 0.7082, whereas the variety from Cu skarn-related intrusions displays lower (.sup.87Sr/.sup.86Sr).sub.t of 0.7054-0.7061. These Sr isotope data, combined with whole-rock S isotopes of this study and previous investigations suggest that the Fe skarn-related intrusions have assimilated larger amount of evaporite-bearing carbonate during magma ascent and emplacement. The assimilation process may have not only promoted magmatic water exsolution but also provided sufficient amount of Cl.sup.- and [Formula omitted], which facilitated effective complexation and transportation of Fe.sup.2+ and subsequent oxidization of ferrous Fe to precipitate magnetite, respectively. We suggest that evaporite assimilation into the granitoid magmas has played a crucial role in the large-scaled Fe skarn mineralization in the Daye district. This study highlights that apatite is a sensitive petrogenetic-metallogenic indicator for granitoids and thus can be useful in mineral exploration., Author(s): Run-Jie Zhou [sup.1], Guang Wen [sup.1], Jian-Wei Li [sup.1], Shao-Yong Jiang [sup.1] [sup.2], Hao Hu [sup.1], Xiao-Dong Deng [sup.1], Xin-Fu Zhao [sup.1], Dai-Rong Yan [sup.3], Ke-Tao Wei [sup.4] [sup.5], [...]

Obtaining reliable petrochronological and geochemical data from metamict zircon may be challenging. Metamict zircon and crystalline apatite from the Meiwu granodiorite and its microgranular enclaves from the Paleo-Tethys belt are examined to constrain their crystallization ages and the genetic mechanism of related skarn mineralization. The metamict zircon yields highly disturbed .sup.206Pb/.sup.238U dates. Transmission electron microscopy shows that radiation damage forms nanoscale-banded damaged zones, leading to spurious dates. The coexisting apatite has not accumulated radiation damage, and apatite crystals from the granodiorite and its enclaves yield reasonably precise LA-ICPMS U-Pb Tera-Wasserburg concordia lower intercept dates of 240.2 ± 3.8 and 239.9 ± 4.0 Ma (2[sigma]), with MSWDs of 1.0 and 2.1. Considering the fast cooling of the granite, the U-Pb dates effectively represent crystallization ages for these rocks. Compositional analysis shows that there are no Ce anomalies in apatite in either the granodiorite or enclave, indicating low oxygen fugacities. Apatite crystals from enclaves have weaker negative Eu anomalies, higher Sr, and lower HREE and Y contents than those in granodiorite. The compositions confirm enclaves as products of water-rich melts, resulting in amphibole fractionation and suppression of plagioclase crystallization. The hydrous magma induced production of hydrothermal-fluids that mobilized metals dispersed in dry magma and concentrated them into mineralization traps, which contributed to the formation of widespread skarns in Paleo-Tethys belt. This study demonstrates that apatite is effective in tracing the evolution of magmatic systems containing metamict zircon., Author(s): Hao-Cheng Yu [sup.1], Kun-Feng Qiu [sup.1] [sup.2] [sup.3], Callum J. Hetherington [sup.4], David Chew [sup.5], Ya-Qi Huang [sup.1], Deng-Yang He [sup.1], Jian-Zhen Geng [sup.6], Hai-Yang Xian [sup.2] Author Affiliations: [...]

Lamproites and kimberlites are natural probes of the subcontinental lithospheric mantle providing insights into the Earth's continental lithosphere. Whole-rock major-, trace-element and Sr-Nd-Pb isotopic compositions of the Paleozoic (~ 253 Ma) lamproite dikes from the Baifen zone of the Zhenyuan area in southeastern Guizhou Province (in the southern Yangtze Block, South China) are presented. The Baifen lamproites are characterized by high MgO (7.84-14.1 wt%), K.sub.2O (3.94-5.07 wt%) and TiO.sub.2 (2.69-3.23 wt%) contents, low SiO.sub.2 (41.3-45.7 wt%), Na.sub.2O (0.21-0.28 wt%) and Al.sub.2O.sub.3 (6.10-7.20 wt%) contents. All lamproites have elevated Cr (452-599 ppm) and Ni (485-549 ppm) abundances, as well as high Ba (1884-3589 ppm), La (160-186 ppm), Sr (898-1152 ppm) and Zr (532-632 ppm) concentrations. They show uniform REE distribution patterns that are strongly enriched in light REEs relative to heavy REEs [(La/Yb).sub.N = 71.1-87.6], and exhibit OIB-like geochemical features with obvious enrichment of both LILEs and HFSEs in the primitive mantle-normalized multi-element distribution diagram. Moderately radiogenic Sr (.sup.87Sr/.sup.86Sr.sub.i = 0.706336-0.707439), unradiogenic Nd (.sup.143Nd/.sup.144Nd.sub.i = 0.511687-0.511704 and [epsilon].sub.Nd(t) = - 12.2 to - 11.9), and low initial Pb (.sup.206Pb/.sup.204Pb.sub.i = 16.80-16.90, .sup.207Pb/.sup.204Pb.sub.i = 15.34-15.35 and .sup.208Pb/.sup.204Pb.sub.i = 37.43-37.70) isotopic compositions are obtained from the rocks. They yield old model ages of T.sub.DM(Nd) = 1.48-1.54 Ga. These signatures suggest that the Baifen lamproite magmas are alkaline, ultrapotassic and ultramafic in character and mainly represent mantle-derived primary melts, which have undergone insignificant crustal contamination and negligible fractional crystallization. The Baifen lamproites originated from a veined metasomatized lithospheric mantle source. We envisage that they were derived by partial melting of old, mineralogically complex metasomatic vein assemblages in the subcontinental lithospheric mantle beneath the southern Yangtze Block. The source region experienced ancient mantle metasomatism with complex modification by enriched fluids and melts. The metasomatic agents are most likely to originate from pre-existing slab subduction beneath the southeastern margin of the Yangtze Block. Tectonically, the Baifen lamproites were emplaced at the southern margin of the Yangtze Block, and they formed in an intraplate extensional setting, showing an anorogenic affinity. In terms of time and space, the genesis of Baifen lamproites is presumably related to the Emeishan large igneous province. The Emeishan mantle plume is suggested as an effective mechanism for rapid extension and thinning of the lithosphere, followed by decompression melting of the subcontinental lithospheric mantle. Combined with the thermal perturbation from asthenospheric upwelling induced by the Emeishan mantle plume, the lamproite magmas, representing small volume and limited partial melts of ancient enriched mantle lithosphere, arose. We propose that the generation of the Baifen lamproite dikes probably was a consequence of the far-field effects of the Emeishan mantle plume., Author(s): Lu Xiang [sup.1] [sup.2], Jianping Zheng [sup.1], Mingguo Zhai [sup.2] [sup.3], Wolfgang Siebel [sup.4] Author Affiliations: (1) grid.503241.1, 0000 0004 1760 9015, School of Earth Sciences, State Key Laboratory [...]

The Permian Huangshanxi Ni-Cu-hosted intrusion, located in the southern Central Asian Orogenic Belt in NW China, is dominated by cumulus olivine and orthopyroxene. Various types of compositional zonings in cumulate phases were studied using high-resolution synchrotron X-Ray fluorescence imaging, electron microprobe, laser ablation inductively coupled plasma mass spectrometry and secondary ion mass spectrometry, to shed light on the relationship between the orthopyroxene-rich cumulate and sulfide accumulation. Normal, oscillatory, and sector zonings of Cr in orthopyroxene from both lherzolites and olivine websterites were noted, likely due to the different cut orientation of orthopyroxene crystals composed of sector-zoned cores and reverse-zoned rims. Significant Fe-Mg-Al-Si variations found in the exterior regions of the grains do not correspond to the Cr zoning. However, Cr content is positively correlated with Ti-Al contents in interior regions of orthopyroxene, reflecting coupled charge substitution during the development of sector zoning, and indicating diffusion-modified Fe-Mg-Al-Si variation in the exterior regions. Primary Cr-sector zoning in the core is likely the result of rapid in situ growth in a boundary layer at the cumulus stage, probably induced by Si addition from wall rocks and crystallization under supersaturated conditions. In addition, some olivine shows Mg-Fe-Mn-Ca-Cr variations in the rim but not in the core, and both core and rim of olivine show a uniform O isotope composition, illustrating that they have not been modified by post-cumulus processes. Given the distinct difference in O isotopic signatures between mantle-derived melts and crustal materials, olivine O isotope composition could be used to decipher the relative degree of Si addition at crystallization. The Fo value, O isotopic signature and trace element content in the cores of olivine grains from different depths show systematic variations, dividing the sulfide-bearing cumulate into two intervals; the lower and upper lherzolite zones with harzburgitic rocks at the contact. In the lower zone, the olivine [delta].sup.18O values increase upward from ~ 6 to ~ 7â° and the oxygen fugacity decreases from QFM to QFM-2, suggesting increasing contamination by more reduced crustal materials. Over the same interval, the modal proportion of orthopyroxene and modal orthopyroxene/olivine ratio increase with increasing depth with little variation in whole-rock Mg#, clearly illustrating that the non-cotectic orthopyroxene proportions resulted from Si addition from the wall rock. In the upper zone, the decrease in [delta].sup.18O values, and increase in olivine nucleation density, Fo value and oxygen fugacity suggest there was a pulse of sulfide- and olivine-charged magma into the magma chamber, that mixed with resident magma to form a hybrid bottom layer in contact with the early-crystallized orthopyroxene-rich cumulate pile. The sulfide content decreases up-section in the lower zone, and then increases again towards the top of the cumulate sequence. This, combined with the compositional variations with depth, suggests that sulfides in the Huangshanxi Ni-Cu deposit settled downward during at least two sulfide-loaded magma pulses. The fast-growing orthopyroxene-rich cumulate may have acted as a permeability barrier, preventing sulfide percolation into the lower cumulate formed during the first magma pulse. Overall, sector zoning in orthopyroxene and compositional variations in olivine suggest that Si and reduced material addition during contamination is of great importance in forming magmatic Ni-Cu deposits hosted by olivine- and orthopyroxene-dominated intrusions., Author(s): Ya-Jing Mao [sup.1] [sup.2] , Stephen J. Barnes [sup.3] , Ke-Zhang Qin [sup.1] [sup.2] [sup.4] , Dongmei Tang [sup.1] [sup.2] , Laure Martin [sup.5] , Benxun Su [sup.1] [sup.2] [...]

The Zhuangzi Au deposit in the world-class Jiaodong gold province hosts visible natural gold, and pyrite as the main ore mineral, making it an excellent subject for deciphering the complex hydrothermal processes and mechanisms of gold precipitation. Three types of zoned pyrite crystals were distinguished based on textural and geochemical results from EPMA, SIMS sulfur isotopic analyses and NanoSIMS mapping. Py0 has irregular shapes and abundant silicate inclusions and was contemporaneous with the earliest pyrite-sericite-quartz alteration. It has low concentrations of As (0-0.3 wt.%), Au and Cu. Py1 precipitated with stage I mineralization shows oscillatory zoning with the bright bands having high As (0.4-3.9 wt.%), Au and Cu contents, whereas the dark bands have low contents of As (0-0.4 wt.%), Au and Cu. The oscillatory zoning represents pressure fluctuations and repeated local fluid phase separation around the pyrite crystal. The concentration of invisible gold in Py1 is directly proportional to the arsenic concentration. Py1 is partially replaced by Py2 which occurs with arsenopyrite, chalcopyrite and native gold in stage II. The replacement was likely the result of pseudomorphic dissolution-reprecipitation triggered by a new pulse of Au-rich hydrothermal fluids. The [delta].sup.34S values for the three types of pyrite are broadly similar ranging from + 7.1 to + 8.8â°, suggesting a common sulfur source. Fluid inclusion microthermometry suggests that extensive phase separation was responsible for the gold deposition during stage II mineralization. Uranium-Pb dating of monazite constrains the age of mineralization to ca. 119 Ma coincident with a short compressional event around 120 Ma linked to an abrupt change in the drift direction of the subducting Pacific plate., Author(s): Xing-Hui Li [sup.1] [sup.2] [sup.4] , Hong-Rui Fan [sup.1] [sup.2] [sup.3] , Kui-Feng Yang [sup.1] [sup.2] [sup.3] , Pete Hollings [sup.4] , Xuan Liu [sup.1] [sup.3] , Fang-Fang Hu [...]

The picritic dykes occurring within fine-grained gabbro in the marginal zone and in the surrounding Proterozoic wall-rock marbles of the Panzhihua Fe-Ti oxide deposit closely correspond in bulk composition with the nearby Panzhihua intrusion. These dykes offer important constraints on the nature of the mantle source of the Panzhihua ore-bearing intrusion and its possible link to the Emeishan plume. U-Pb zircon dating of the picritic dyke yields a crystallization age of 261.4 ± 4.6 Ma, coeval with the timing of the main Panzhihua gabbroic intrusion and Late Permian Emeishan flood basalts. The Panzhihua picritic dykes contain 37.63-43.41 wt% Si[O.sub.2], 1.15-1.56 wt%Ti[O.sub.2], 11.43-13.25 wt% T[Fe.sub.2][O.sub.3], and 20.96-28.87 wt% MgO. Primitive-mantle-normalized patterns of the rocks are comparable to those of ocean island basalt. The rocks define a relatively small range of Os isotopic compositions and a low Os signature of -0.13 to +2.76 for [γ.sub.Os] (261 Ma). In combination with their Sr-Nd-Os isotopic compositions, we interpret that these rocks were derived from the Emeishan plume sources as well as the interactions of plume melts with the overlying lithosphere which had been extensively affected by eclogite-derived melts from the deep-subducted oceanic slab. Partial melting induced by an upwelling mantle plume that involved an eclogite or pyroxenite component in the lithospheric mantle could have produced the parental Fe-rich magma. Our study suggests that plume-lithosphere interaction might have played a key role in generating many world-class Fe-Ti oxide deposits clustered in the Panxi area. Keywords Os-Sr-Nd geochemistry * Zircon U-Pb geochronology * Panzhihua * Emeishan * Mantle sources * Mineralization, Introduction The Emeishan Large Igneous Province (ELIP) is well known as the host of one of the world's largest Fe-Ti oxide deposits. Based on their dominant host rocks, the Fe-Ti [...]

Geochronological, geochemical, whole-rock Sr-Nd, and zircon Hf isotopic analyses were carried out on the Jiasha Gabbro, mafic microgranular enclaves (MME) and host Longchahe Granite samples from the Gejiu area in the southeast Yunnan province, SW China, with the aim of characterizing their petrogenesis. Compositional zoning is evident in the gabbro body as the cumulate textures and mineral proportions in the gabbro interior are distinct from the gabbro margin. The Longchahe Granite largely comprises metaluminous quartz monzonite with distinctive K-feldspar megacrysts, but also contains a minor component of peraluminous leucogranite. The MME have spheroidal to elongated/lenticular shapes with sharp, crenulated and occasionally diffuse contacts with the host granite, which we attribute to the undercooling and disaggregation of mafic magma globules within the cooler host felsic magma. Field observations, geochronology, geochemistry, Sr-Nd and zircon Hf isotopic compositions point to a complex petrogenesis for this granite-MME-gabbro association. Zircon [sup.206]Pb/[sup.238]U ages determined by LA-ICP-MS for a mafic enclave, its host granite and the gabbro body are 83.1 ± 0.9 Ma, 83.1 ± 0.4 Ma and 83.2 ± 0.4 Ma, respectively, indicating coeval crystallization of these igneous rock units. Crystal fractionation processes can explain much of the compositional diversity of the Jiasha Gabbro. The geochemical features of the gabbro, such as high Mg# (up to 70) and Cr (up to 327 ppm), enrichment in LILEs (e.g., Rb, Ba, [K.sub.2]O) and LREEs, and depletion in HFSE (e.g., Nb, Ta, Ti), together with initial [sup.87]Sr/[sup.86]Sr ratios of 0.708-0.709 and negative ζNd(t) values (-5.23 to -6.45), indicate they were derived from a mantle source that had undergone previous enrichment, possibly by subduction components. The Longchahe Granite has a large range of Si[O.sub.2] (59.87-74.94 wt%), is distinctly alkaline in composition, and has Sr-Nd-Hf isotopic compositions ([([sup.87]Sr/[sup.86]Sr).sub.i] > 0.712, ζNd(t) = -6.93 to -7.62 and ζHf(t) = -5.8 to -9.9) that are indicative of derivation from a crustal source. However, the most primitive rocks of Longchahe Granite are compositionally distinct from any feasible crustal melt. We interpret the spectrum of rock types of the Longchahe Granite to have formed via mixing between crustally derived peraluminous leucogranite magma and mantle-derived magma of similar heritage to the Jiasha Gabbro. We speculate that this mixing event occurred early in the magmatic history of these rocks at relatively high temperature and/or deep in the crust to allow efficient physical mixing of magmas. Saturation and accumulation of K-feldspar and zircon in the mixed magma is invoked to explain the megacrystic K-feldspar and elevated [K.sub.2]O and Zr content of some of the granitic rocks. A later episode of magma mixing/mingling is preserved as the MME that have geochemical and isotopic compositions that, for the most part, are intermediate between the granite and the gabbro. The MME are interpreted to be fractionated melts of mafic magma related to gabbro that were subsequently injected into the cooler, partly crystalline granitic magma. Mingling and mixing processes within the convectively dynamic upper crustal magma chamber resulting in a hybrid (MME) magma. During this second mixing episode, element interdiffusion, rather than bulk physical mixing, is interpreted to be the dominant mixing process. Keywords Magma mixing * Magma mingling * Mafic microgranular enclaves * Gabbro * Gejiu, Introduction Petrologists have invoked a range of processes, including fractional crystallization, assimilation, crustal melting, and magma mixing, to explain the compositional diversity among plutonic rocks of the continental crust. In [...]

The Nantianwan mafic intrusion in the Panxi region, SW China, part of the ~260 Ma Emeishan large igneous province, consists of the olivine gabbro and gabbronorite units, separated by a transitional zone. Olivine gabbros contain olivine with Fo values ranging from 83 to 87, indicating crystallization from a moderately evolved magma. They have 0.2 to 0.9 wt% sulfide with highly variable PGE (17-151 ppb) and variable Cu/Pd ratios (1,500-32,500). Modeling results indicate that they were derived from picritic magmas with high initial PGE concentrations. Olivine gabbros have negative ζNd(f) values (-1.3 to -0.1) and positive γOs(f) values (5-15), consistent with low degrees of crustal contamination. Gabbronorites include sulfide-bearing and sulfide-poor varieties, and both have olivine with Fo values ranging from 74 to 79, indicating crystallization from a more evolved magma than that for olivine gabbros. Sulfide-bearing gabbronorites contain 1.9-4.1 wt % sulfide and 37-160 ppb PGE and high Cu/Pd ratios (54,000-624,000). Sulfide-poor gabbronorites have 0.1-0.6 wt % sulfide and 0.2-15 ppb PGE and very high Cu/Pd ratios (16,900-2,370,000). Both sulfide-bearing and sulfide-poor gabbronorites have sNd(f) values (-0.9 to -2.1) similar to those for olivine gabbros, but their γOs(f) values (17-262) are much higher and more variable than those of the olivine gabbros. Selective assimilation of crustal sulfides from the country rocks is thus considered to have resulted in more radiogenic [sup.187]Os of the gabbronorites. Processes such as magma differentiation, crustal contamination and sulfide saturation at different stages in magma chambers may have intervened during formation of the intrusion. Parental magmas were derived from picritic magmas that had fractionated olivine under S-undersaturated conditions before entering a deep-seated staging magma chamber, where the parental magmas crystallized olivine, assimilated minor crustal rocks and reached sulfide saturation, forming an olivine- and sulfide-laden crystal mush in the lower part and evolved magmas in the upper part of the chamber. The evolved magmas were forced out of the staging chamber and became S-undersaturated due to a pressure drop during ascent to a shallow magma chamber. The magmas re-attained sulfide saturation by assimilating external S from S-rich country rocks. They may have entered the shallow magma chamber as several pulses so that several gabbronorite layers each with sulfide segregated to the base and a sulfide-poor upper part. The olivine gabbro unit formed from a new and more primitive magma that entrained olivine crystals and sulfide droplets from the lower part of the staging chamber. A transitional zone formed along the boundary with the gabbronorite unit due to chemical interaction between the two rock units. Keywords Platinum-group elements * Sr-Nd and Re-Os isotopes * Magma chamber process * Nantianwan intrusion * Emeishan large igneous province, Introduction The nature of the mantle source, crystal fractionation, crustal contamination and sulfide saturation have been documented to be important in the generation of a diversity of igneous rocks in [...]

Native metals and metal alloys are common in serpentinized ultramafic rocks, generally representing the redox and sulfur conditions during serpentinization. Variably serpentinized peridotites from the Santa Elena Ophiolite in Costa Rica contain an unusual assemblage of Cu-bearing sulfides and native copper. The opaque mineral assemblage consists of pentlandite, magnetite, awaruite, pyrrhotite, heazlewoodite, violarite, smythite and copper-bearing sulfides (Cu-pentlandite, sugakiite [Cu[(Fe, Ni).sub.8][S.sub.8]], samaniite [[Cu.sub.2][(Fe, Ni).sub.7][S.sub.8]], chalcopyrite, chalcocite, bornite and cubanite), native copper and copper-iron-nickel alloys. Using detailed mineralogical examination, electron microprobe analyses, bulk rock major and trace element geochemistry, and thermodynamic calculations, we discuss two models to explain the formation of the Cu-bearing mineral assemblages: (1) they formed through desulfurization of primary sulfides due to highly reducing and sulfur-depleted conditions during serpentinization or (2) they formed through interaction with a Cu-bearing, higher temperature fluid (350-400°C) postdating serpentinization, similar to processes in active high-temperature peridotite-hosted hydrothermal systems such as Rainbow and Logatchev. As mass balance calculations cannot entirely explain the extent of the native copper by desulfurization of primary sulfides, we propose that the native copper and Cu sulfides formed by local addition of a hydrothermal fluid that likely interacted with adjacent mafic sequences. We suggest that the peridotites today exposed on Santa Elena preserve the lower section of an ancient hydrothermal system, where conditions were highly reducing and water-rock ratios very low. Thus, the preserved mineral textures and assemblages give a unique insight into hydrothermal processes occurring at depth in peridotite-hosted hydrothermal systems. Keywords Native copper * Sulfides * Peridotite * Serpentinization * Santa Elena Ophiolite, Introduction Serpentinization is a widespread process that is found where ultramafic rocks react with seawater, hydrothermal fluids or metamorphic fluids within subduction zones (e.g., Cannat et al. 1992; Hyndman and [...]