Discrepant chemical differentiation and magmatic-hydrothermal evolution of high-silica magmatism associated with Pb–Zn and W mineralization in the Lhasa terrane

High-silica(SiO_(2)>70 wt.%)granites(HSGs)are the main source of W,Sn,and rare metals.However,abundant HSGs,temporally,spatially,and genetically associated with Pb-Zn mineralization,in the Lhasa terrane(LT),provided an ideal opportunity to study the key factors responsible for Pb-Zn enrichment,instead of W-Sn enrichment.Here we contribute to this topic through U-Pb dating of zircon and garnet,and whole-rock and Sr-Nd-Hf isotopic geochemistry of ore-related quartz porphyries in the Bangbule deposit and compared these results with published data from large and giant Pb-Zn and W deposits in the LT.The magmatism-alteration-mineralization event in the Bangbule deposit was recorded by robust zircon U-Pb ages of 77.3±0.9 Ma and hydrothermal garnet U-Pb ages of 75.7±4.8 Ma,which is 10-15 Ma earlier than the main Paleocene metallogenic event and the first record of late Cretaceous Pb-Zn polymetallic mineralization in the LT.The late Cretaceous-Paleocene magmatism and mineralization events are a response to the subduction of Neotethyan oceanic lithosphere,which occurred as a result of the collision of the Indian and Asian plates.These HSGs related to Pb-Zn mineralization,with high totalalkalis and low magnesian contents,are enriched in Ba,Th,and Rb,but depleted in Ti,Eu,Sr,and P.They belong to either the S-type,or I-type granites.The Sr-Nd-Hf isotopic compositions of the Pb-Zn mineralized granites demonstrate that they were generated by the partial melting of Proterozoic basement with or without mantle-derived melt input.This was consistent with the postulated source of W enrichment in the LT.The Pb-Zn and W related granites have similar zircon-Ti-saturation temperatures,comparable low whole-rock Fe_(2)O_(3)/FeO ratios,and zircon oxygen fugacity.This indicated that the Pb-Zn-W enrichment in the high-silica magma system could be attributed to a relatively reduced magma.The Pb-Zn related HSGs,abundant quartz and feldspar phenocrysts,and weak fractionation of twin-elements in wholerock analysis,can be used to reconstruct a model of the magma reservoir.We postulate that these features could be reproduced by silica-rich crystal accumulation in a magma reservoir,with a loss of magmatic fluids.The magma associated with W mineralization exhibited a higher level of differentiation compared to the Pb-Zn related magma;however,different groups of zircon texture with varying rare earth elements and concomitance of rare earth elements tetrad effect and high fractionation of twin-elements in wholerock are formed by a magmatic-hydrothermal transition in highly evolved system.As the source and oxygen fugacities of the Pb-Zn and W related magmas are similar,the absence of a giant W-Sn deposit in the LT may indicate that parent magmas with a low degree of evolution and magmatic-hydrothermal transition are not conducive to their formation.This implies that the rocks that originated as highly evolved silicaterich parent magmas,with a high degree of magmatic-hydrothermal alteration,would need to be targeted for W-Sn mineral exploration in the LT.In summary,our results emphasize that variations in chemical differentiation and the evolution of high-silica magmatic-hydrothermal systems can lead to differences in Pb-Zn and W enrichment.This has implications for the evaluation of the mineral potential of high-silica granites and hence their attractiveness as targets for mineral exploration.

A homogeneous dopamine-silver nanocomposite coating:striking a balance between the antibacterial ability and cytocompatibility of dental implants

Silver has been widely used for surface modification to prevent implant-associated infections.However,the inherent cytotoxicity of silver greatly limited the scope of its clinical applications.The construction of surfaces with both good antibacterial properties and favorable cytocompatibility still remains a challenge.In this study,a structurally homogeneous dopamine-silver(DA/Ag)nanocomposite was fabricated on the implant surface to balance the antibacterial activity and cytocompatibility of the implant.The results show that the DA/Ag nanocomposites prepared under the acidic conditions(pH=4)on the titanium surface are homogeneous with higher Ag^(+)content,while an obvious core(AgNPs)-shell(PDA)structure is formed under neutral(pH=7)and alkaline conditions(pH=10),and the subsequent heat treatment enhanced the stability of PDA-AgNPs nanocomposite coatings on porous titanium.The antibacterial test,cytotoxicity test,hypodermic implantation and osteogenesis test revealed that the homogeneous PDA-AgNPs nanocomposite coating achieved the balance between the antibacterial ability and cytocompatibility,and had the best outcomes for soft tissue healing and bone formation around the implants.This study provides a facile strategy for preparing silver-loaded surfaces with both good antibacterial effect and favorable cytocompatibility,which is expected to further improve the therapeutic efficacy of silver composite-coated dental implants.

Oxidized Dopamine Acrylamide Primer to Achieve Durable Resin-Dentin Bonding

The durability of the resin-dentin bonding interface is a key issue in clinical esthetic dentistry.Inspired by the extraordinary bioadhesive properties of marine mussels in a wet environment,we designed and synthetized N-2-(3,4-dihydroxylphenyl)acrylamide(DAA)according to the functional domain of mussel adhesive proteins.DAA’s properties of collagen cross-linking,collagenase inhibition,inducing collagen mineralization in vitro,and as a novel prime monomer for clinical dentin adhesion use,its optimal parameters,and effect on the adhesive longevity and the bonding interface’s integrity and mineralization,were evaluated in vitro and in vivo.The results showed that oxide DAA can inhibit the activity of collagenase and cross collagen fibers to improve the anti-enzymatic hydrolysis of collagen fibers and induce intrafibrillar and interfibrillar collagen mineralization.As a primer used in the etch-rinse tooth adhesive system,oxide DAA can improve the durability and integrity of the bonding interface by anti-degradation and mineralization of the exposed collagen matrix.Oxidized DAA(OX-DAA)is a promising primer for improving dentin durability;using 5%OX-DAA ethanol solution and treating the etched dentin surface for 30 s is the optimal choice when used as a primer in the etch-rinse tooth adhesive system.