ABSTRACT Within the Mamupu deposit (southern Yulong porphyry copper belt, eastern Tibet), the development of lamprophyre dykes serves as a prominent indicator of Late Eocene magmatism. This research presents an integrated analytical framework—comprising SIMS zircon U–Pb geochronology, whole‐rock major and trace element geochemistry, and Sr–Nd–Pb isotopic systematics—to decipher the petrogenetic evolution and geodynamic setting of these dykes. The Mamupu lamprophyres yield a crystallisation age of 37.42 ± 0.63 Ma. From a geochemical perspective, these lamprophyre dykes exhibit a distinct potassic calc‐alkaline affinity, evidenced by their elevated potassium (K 2 O = 4.98–5.28 wt%) and total alkali (K 2 O + Na 2 O = 9.27–9.53 wt%) concentrations. The trace element systematics are defined by substantial total REE abundances (ΣREE = 624.4–693.8 ppm), with multi‐element patterns showing marked enrichment in light REE (LREE) and large‐ion lithophile elements (LILEs), contrasted with a significant deficit in high‐field‐strength elements (HFSEs). The Sr–Nd–Pb isotopic systematics, characterised by initial 87 Sr/ 86 Sr ratios of 0.70555–0.70561, ε Nd ( t ) values ranging from −2.5 to −0.3, and 206 Pb/ 204 Pb ratios between 18.868 and 18.937, collectively underscore a hybrid magma source involving significant crust–mantle interaction. These geochemical features preclude an origin from simple mantle partial melting or fractional crystallisation, and they also rule out extensive crustal assimilation. Consequently, the Mamupu lamprophyres are postulated to have originated from the hybridisation of two end‐members: potassic melts derived from a metasomatised, enriched lithospheric mantle (EM II) influenced by subduction fluids, and felsic components generated by the partial melting of a thickened lower crust. The localisation of these lamprophyres was governed by an extensive strike‐slip fault developing in response to the India–Eurasia continental collision. This magmatism likely facilitated the genesis of the Mamupu Cu–Au deposit by providing essential thermal flux and potentially sourcing metallogenic components for the southern segment of the Yulong belt.

Rhenium (Re) in of the important metals, and it plays an irreplaceable role material in defense and industry. Rhenium is rarely found as natural independent mineral, and it primarily occurs the form of isomorphous substitution within molybdenite (MoS2), typically associated with porphyry-skarn type Cu (-Mo/-Mo-Au) deposita. Currently, Re resources are limited and unevenly distributed, and the enrichment mechanisms and key controlling factors of Re deposits remain unclear. Using 3,427 molybdenite Re-Os analysis results from 484 magmatic hydrothermal combined with previous related research, this study concludes the following: (1) Hydrothermal deposits with molybdenite that is rich i Re (Re >= 100x10(-6)) mainly formed in the Mesozoic (similar to 140Ma) and Cenoznie (similar to 20Ma), showing two peak periods; (2) Compared to other types, molybdenite from porphyry Cu (-Au) and Cu-Mo deposits the richest in Re. Among the three types of different ore deposits in China, and porphyry, skarn, and quartz-vein deposits, Re-rich molybdenite is always the most prevalent in Au-enriched subtypes; (3) Although factors such as oxygen fugacity and differentiation degree of magma, the temperature and pH of ore forming fluids, and Mo grade in deposits may influence the final Re content in molybdenite, more research evidence implied that, the magma source is likely considered the key factor responsible for the Re content variations between different deposits in China, especially between different subtypes; (4) As estimated, the preliminary total Re resource from magmatic hydrothermal deposits in China is approximately 3,000 tones, indicating significant potential for Re mineralization. Among these, porphyry Cu-Mo deposits exhibit the highest potential for Re mineralization, primarily concentrated in the Gangdese porphyry copper belt, the Eastern Tianshan porphyry copper belt, and the Middle-Lower Yangtze River Valley porphyry copper belt.

The Yulong copper belt is a globally representative collision-type porphyry copper belt, yet significant differences exist in mineralization scale, deposit types, and elemental assemblages between its northern and southern segments. As a newly discovered medium-sized Pb-Zn-Ag-Au deposit in the southern segment, the Jicuo deposit has not undergone systematic scientific investigation, hindering understanding of its genesis and exploration targeting. This study integrates field geological surveys, petrographic analysis, electron probe microanalysis, LA-ICP-MS zircon U-Pb dating, Hf isotopes, whole-rock major-trace elements, and Sr-Nd isotopes to determine deposit type and petrogenesis. Results reveal a metal zoning pattern of Au-Ag-Pb-Zn -> Pb-Zn-Ag mineralization. Ore textures, alteration assemblages, metallic mineral associations, and sphalerite FeS contents (16 similar to 20mol/mol) align with intermediate-sulfidation epithermal systems. Silver primarily resides in galena, boulangerite, and selenian polybasite, while gold occurs in arsenopyrite and pyrite. Pyrite exhibits core-to-rim increases in Au, As, and Co concentrations, with variable As/Sb ratios indicating significant hydrothermal fluid fluctuations, suggesting boiling as the primary gold precipitation mechanism. Granite porphyry related to mineralization yields zircon U-Pb ages of 39.38 +/- 0.28Ma and 39.41 +/- 0.32Ma. These shoshonitic rocks show high SiO2, alkalis, low MgO and Cr, enriched LILEs (K, Rb, LREEs), and depleted HFSEs (Nb, Ta, Ti, HREEs). Their isotopic characteristics ((Sr-87/Sr-86)(i)=0.7080-0.7082, epsilon(Nd)(t)=-3.49 similar to-3.34, zircon epsilon(Hf)(t)=-0.40 similar to+1.00 with t(DM)(2)=1140 similar to 1047Ma) indicate derivation from thickened lower crustal melting with minor mantle input, formed under crustal thickening during India-Eurasian collision. Identification of the Jicuo intermediate-sulfidation epithermal deposit confirms the southern Yulong belt's potential for collision-related porphyry systems, providing important guidance for regional mineral exploration.

Critical factors controlling Fe-enriched wolframite formation in the quartz vein-type wolframite deposit are in controversy. The Jiaoxi and Anglonggangri are typical examples of quartz vein-type wolframite mineralization found in western Lhasa terrane. The Jiaoxi wolframite comprise dominantly early h & uuml;bnerite with late ferberite, whereas, the Anglonggangri wolframite are mainly ferberite. Wolframite U-Pb dating yields direct timing of 11.0 +/- 0.2 Ma and 9.7 +/- 0.2 Ma for Jiaoxi and Anglonggangri tungsten mineralization, respectively. Ages together with enrichment of Nb, Ta, Ti, and Sc and depletion of Sr and most Eu anomaly within Anglonggangri wolframite confirm that metals and fluids were mainly derived from the ore-forming garnet-muscovite granite. Iron and Mn mapping of garnet in the garnet-muscovite granite suggests this granite has changed from the early Mn-enriched to late Fe-rich affinity. Therefore, initial ore-forming fluids exsolved from garnet-muscovite granite have Fe-rich composition, that was significantly modified during tungsten mineralization. Positive trend between Mg and Fe/ (Fe + Mn) of wolframite indicates biotite breakdown from country rock of biotite-muscovite granite to add Fe and Mg into fluid during greisenization. Meanwhile, decomposition of plagioclase and K-feldspar provided Ca, Sr, and Eu to form late scheelite. Enrichment of Sr with positive Eu anomaly and decline of REE, Nb, and Ta are typical features of the highly evolved and modified fluid. Positive and negative Eu anomalies within the same wolframite grains reveal the oxidized character and fluctuating composition of fluid during wolframite precipitation. By contrast, negative Eu anomaly and low Mo abundance of scheelite indicate the reducing fluid during scheelite crystallization. Identification of metal and fluid sources for Anglonggangri ferberite highlights the evolved granites play more crucial roles on ferberite formation than early h & uuml;bnerite crystallization and Fe addition from country rocks during hydrothermal interaction.

Multistage tungsten mineralization was recently discovered in the Mamupu copper-polymetallic deposit in the southern Yulong porphyry copper belt（YPCB）, Tibet. This study reports the results of cathodoluminescence, trace element and Sr isotope analyses of Mamupu scheelite samples, undertaken in order to better constrain the mechanism of W mineralization and the sources of the ore-forming fluids. Three different types of scheelite are identified in the Mamupu deposit: scheelite A（Sch A） mainly occurs in breccias during the prograde stage, scheelite B（Sch B） forms in the chlorite-epidote alteration zone in the retrograde stage, while scheelite C（Sch C） occurs in distal quartz sulfide veins. The extremely high Mo content and negative Eu anomaly in Sch A represent high oxygen fugacity in the prograde stage. Compared with ore-related porphyries, Sch A has a similar REE pattern, but with higher ΣREE, more depleted HREE and slightly lower( 87 Sr/ 86 Sr)i ratios. These features suggest that Sch A is genetically related to ore-related porphyries, but extensive interaction with carbonate surrounding rocks affects the final REE and Sr isotopic composition. Sch B shows dark（Sch B-I） and light（Sch B-II） domains under CL imaging. From Sch B-I to Sch B-II, LREEs are gradually depleted, with MREEs being gradually enriched. Sch C has the highest LREE/HREE ratio, which indicates that it inherited the geochemical characteristics of fluids after the precipitation of HREE-rich minerals, such as diopside and garnet, in the early prograde stage. The Mo content in Sch B and Sch C gradually decreased, indicating that the oxygen fugacity of the fluids changed from oxidative in the early stages to reductive in the later, the turbulent Eu anomaly in Sch B and Sch C indicating that the Eu anomaly in the Mamupu scheelite is not solely controlled by oxygen fugacity. The extensive interaction of magmatic-hydrothermal fluids and carbonate provides the necessary Ca 2+ for the precipitation of scheelite in the Mamupu deposit.

The Kongquehe Sag, located in the western Lop Nur, has abundant pore subsurface brine. In order to study the source and origin, we tested and analyzed the hydrochemical composition and stable isotopes of the subsurface brine. The findings reveal that the brine exhibits a moderate to low degree of mineralization, with values ranging from 50.50 g/L to 91.14 g/L. The stable isotope compositions of unconfined and confined waters are different, with the mean values of δD being −8.00‰ and −51.75‰ and the mean values of δ18O being 10.08‰ and −6.01‰. These values are indicative of an intense evaporative environment prevalent in the Kongquehe Sag area. Furthermore, the 87Sr/86Sr ratios vary between 0.710642 and 0.710837, and δ34S values range from 9.2 to 10.7. These data suggest the long-term evolution of sulfur substances, predominantly through dissolution and sedimentation processes, with minimal influence from redox reactions. The data garnered from this research not only offer a novel perspective of the insights gained into the hydrochemical characteristics and the stable isotope signatures of the brines in the Kongquehe Sag area but also enriches the theoretical framework concerning the source and origin of subsurface brines, potentially informing future exploration strategies.

Lacustrine strata-bound magnesite deposits associated with Alpine-type ultramafic rocks are hydrothermal in origin. The magnesite ores of the Kamado deposit are unconformably underlain by mid-Jurassic marine carbonate and ultramafic rocks of the Bangong-Nujiang ophiolite suite and are in fault contact with hanging wall rocks composed of siliceous sinter. Three types of cryptocrystalline magnesite ores can be identified in Kamado: (1) strata-bound massive magnesites, representing the main ore type in the upper part; (2) banded ores in the lower part; and (3) some vein and stockwork ore in the ultramafic wall rocks. Integrated scanning electron microscopy, C–O isotope analysis, and geochemical analyses were carried out on the Kamado deposit. The results indicate that: (1) the orebody is composed of magnesite, with accessory minerals of aragonite, opal, and chromite; (2) the siliceous sinter and relatively high B (32.0–68.1 ppm) and Li (14.7–23.4 ppm) contents of the magnesite ores reflect long-term spring activity in Kamado; (3) the light carbon (δ13CV-PDB: −4.7 ± 0.3‰ to −4.1 ± 0.6‰) and oxygen isotopic compositions (δ18OV-SMOW: +12.3 ± 0.3 to +16.3 ± 0.1‰) of the stockwork ores in the foot wall rocks indicated that the carbon in fractures in the ultramafic rocks is from a mixture of marine carbonate and oxidized organic-rich sedimentary rocks, reflecting a typical “Kraubath-type” magnesite deposit; and (4) the relatively heavy carbon isotopic (δ13CV-PDB: +8.7 ± 0.4‰ to +8.8 ± 0.3‰) composition of the banded magnesite ores in the lower segment may have formed from heavy CO2 generated by anaerobic fermentation in the lakebed. Additionally, the carbon isotopic (δ13CV-PDB: +7.3 ± 0.3‰ to +7.7 ± 0.7‰) composition of the massive magnesite ores in the upper segment indicates a decline in the participation of anaerobic fermentation. As this economically valuable deposit is of the strata-bound massive ore type, Kamado can be classified as a lacustrine hydrothermal-sedimentary magnesite deposit, formed by continuous spring activities under salt lakes on the Tibetan Plateau, with the Mg mainly being contributed by nearby ultramafic rocks and the carbon mainly being sourced from atmosphere-lake water exchange, with minor amounts from marine carbonate strata.

The Haxi gold deposit located in the Hatu-Saertuohai metallogenic belt of the west Junggar region, China, is a newly discovered gold deposit with proven reserves of similar to 10 tons of gold and an average grade of 6.70 g/t. Primarily, the deposit is hosted in the early Carboniferous Tailegula Formation, controlled by the NEE-trending Anqi fault. The gold ore bodies contain gold-bearing quartz veins and altered basalt. The ore mineral is domi-nated by abundant sulfides, such as pyrite, arsenopyrite, chalcopyrite, and a little gersdorffite. To date, three types of fluid inclusion in quartz veins have been identified: liquid-gas (V-type), CO2-H2O (C-type), and liq-uid-rich (L-type). The ore-forming fluids exhibit medium homogenization temperatures (Th) of 226 degrees C-325 degrees C with low salinities of 2.24-9.34 wt% NaCl equivalent and low densities from 0.72 to 0.88 g/cm(3). The Delta D values range from-115.3%o to-100.7%o, with an average value of-109.1%o; the Delta 18O values range from 11.3%o to 12.2%o, with an average value of 11.8%o; and the Delta 34S values in sulfide range from 0.3%o to 1.8%o, with an average of 1.2%o. The average values of Pb-206/Pb-204, Pb-207/Pb-204, and Pb-208/Pb-204 in sulfide are 18.059, 15.547, and 37.996, respectively. To summarize, the metallogenic fluids were derived not from a single source but from late magmatic-hydrothermal fluid mixed with paleo-atmospheric water; furthermore, the ore-forming materials principally originated from a crust-mantle mixed source. The Pb model age calculated using Hautman's formula is 347-365 Ma, leading to the speculation that the metallogenic period may be Devonian-Carboniferous.

Methods for extracting mineralized alteration information using remote sensing images have recently become both efficient and cost-effective. Technology involving the extraction of alteration information based on multi-spectral data has been widely practiced and effectively verified. In recent years, research on fine mineral extraction methods based on hyperspectral data has also been rapidly developing. The Yulong copper belt is a porphyry copper belt located in China with high prospects for mineralization. However, most previous studies focused on the northern section of the Yulong copper belt, with limited exploration of the southern section. In this study, alteration information of the southern section of the Yulong copper belt was extracted from remote sensing data from Landsat-8 OLI, ASTER, and ZY1-02D, and the prospecting potential of this area was evaluated. Principal component analysis was used to extract iron oxide and hydroxyl alteration from Landsat-8 data, in addition to Al hydroxyl and propylitic alterations from ASTER data. Considering the challenge of the extraction of too many pseudo-anomalies using traditional methods, the mixture-tuned matched filtering (MTMF) method was used to more accurately extract iron oxide alterations. Regarding hyperspectral data, the minimum noise fraction and pure pixel index algorithms were used to extract white mica and carbonatite endmembers. The MTMF method was also used for alteration mapping, which took advantage of sub-pixel abundance mapping to finely divide the white mica and carbonatite alterations into five classes. The extraction results of multi-source remote sensing data were then compared and analyzed to avoid occasional single-image extraction results, which confirmed the superiority of the hyperspectral remote sensing and MTMF methods. Combined with field verification, the mineralization alteration information coincided with the spatial location of the Secuo, Mamupu, and Jicuo deposits, which confirmed the accuracy of alteration information extraction. The results of this study confirmed the application potential of remote sensing alteration information extraction in the field of mineral resource exploration. The results have important reference significance for further geological prospecting and exploration in the southern section of the Yulong copper belt.

The Mamupu copper polymetallic deposit is characterized by multistage magnetite, but the genesis and fluid evolution process of this deposit are still obscure. Three types of magnetite were identified in Mamupu based on comprehensive textural observations and paragenesis. Mag1 occurs as subhedral to euhedral crystals, and smooth Mag1a and porous Mag1b can be distinguished under Backscattered Electron (BSE). Mag2 is characterized by 120 degrees triple junction textures and has been replaced by hematite. Mag3 is commonly replaced by hydrothermal fluids and exhibits well-developed oscillatory zoning and core (Mag3a)-rim (Mag3b) textures. The geochemistry of Mamupu magnetite suggests that they are of hydrothermal origin. Mag1 has undergone extensive fluid-rock interactions, whereas the sharp contacts with Mag1a and Mag1b and the microporosity of Mag1b imply that the Mag1b was generated by the coupled dissolution reprecipitation of the Mag1a grains. This process may be triggered by low-temperature and high-salinity fluid produced by intensive water-rock interaction between ore-bearing magmatic-hydrothermal fluid and carbonate surrounding rock of the Jiaoga Formation. The 120 degrees triple junction textures of Mag2 indicate that it was formed during a fluid-assisted recrystallization process, and Mag2 replaced by hematite represents the increase in oxygen fugacity. From Mag3a to Mag3b, the contents of V and Mn increased while the contents of chalcophile elements decreased, suggesting a decrease of oxygen fugacity and the precipitation of sulfide, which represents the beginning of the sulfide stage. Moreover, petrography and geochemistry data of magnetite represented that the breccia ore of Mamupu belongs to skarn mineralization. The geochemical characteristics of magnetite show that Cu-Au and W-Mo in Mamupu precipitated in different stages, representing the transformation from a relatively oxidized environment in the early stage to a relatively reduced environment in the late stage. These results reveal that trace elements in magnetite can be utilized to define the genesis and evolution of the skarn deposit. In addition, it can also restrict the precipitation mechanism of ore-forming elements in the deposits. However, detailed textural observations should be carried out before experimental research.

A world-class Sn province in South China contains granite- and porphyry-related Sn deposits. In this paper, we investigate the source of Sn, based on a study of Early Cretaceous (145-134 Ma) ore-barren granites and granite porphyries, ore-barren rhyolites, and Sn-bearing granite porphyries in the Mikengshan (MKS)-Qingxixiang (QXX)-Yanbei (YB) area of South China. The ore-barren rhyolites have enriched whole-rock Nd and zircon Hf isotopic compositions [epsilon Nd(t) = - 9.1 to - 10.5; epsilon Hf(t) = - 5.9 to - 13.8]. The ore-barren granites and granite porphyries have A-type granite characteristics and less enriched Nd-Hf isotopic compositions [epsilon Nd(t) = - 4.9 to - 3.2; epsilon Hf(t) = - 6.0 to + 1.7] than the ore-barren rhyolites. The Sn-bearing granite porphyries have similar rare earth element and trace element patterns to the ore-barren rhyolites. In addition, they have similar Nd but less enriched Hf isotopic compositions [epsilon Nd(t) = - 8.9; epsilon Hf(t) = - 3.3 to + 0.4] compared with the ore-barren rhyolites. The average Delta FMQ values of the studied volcanic (-0.50) and intrusive (-0.21) rocks indicate reduced condition during magma evolution. We suggest that the ore-barren rhyolites were likely derived by partial melting of Paleoproterozoic to Mesoproterozoic crustal metasedimentary rocks and that the Sn-bearing granite porphyries were possibly formed by partial melting of Paleoproterozoic metasomatized mantle-derived crustal rocks. Whereas, the ore-barren granites and granite porphyries were likely generated by partial melting of a hybridized source consisting of ancient and late Mesozoic juvenile crustal rocks. We propose that the reduced redox state and ancient crustal sources played an important role for Sn mineralization in the MKS-QXX-YB area.

The Mamupu skarn‐type Cu‐Au polymetallic deposit represents the first discovery of a medium deposit in the southern Yulong porphyry copper belt (YPCB), eastern Tibet. The Cu‐Au mineralization mainly occurs as chalcopyrite in breccia, within the plate‐like carbonate interlayer, being closely related to chloritization (e.g., chlorite, magnetite and epidote) and skarnization (e.g., diopside, tremolite and garnet). The ore‐related quartz syenite porphyry (QSP) and granodiorite porphyry (GP) were emplaced at 40.1 ± 0.2 Ma and 39.9 ± 0.3 Ma, respectively. The QSP of Mamupu is an alkaline‐rich intrusion, relatively enriched in LREE, LILE, depleted in HFSE, with no significant negative Eu and Ce anomalies, slightly high (87Sr/86Sr)i, low ∊Nd(t), uniform (206Pb/204Pb)i and ∊Hf(t) values, which indicates that the porphyry magma may be caused by both the mixing of metasomatized EM II enriched mantle and thickened juvenile lower crust. The QSP in the Mamupu deposit shares a similar genesis of petrology to other ore‐related porphyries within the YPCB. High oxygen fugacity and water content of the magmas are essential for the formation of porphyry and skarn Cu deposits. The QSP has similar high magmatic oxidation states and water content to the Yulong deposit, which indicates that the Mamupu has a high prospecting potential. Differences in the geological characteristics and scale of mineralization between the Mamupu and other YPCB deposits may be due to the different emplacement depths of ore‐related intrusions, as well as differences in the surrounding rocks.

The genesis of the Bangongco-Nujiang metallogenic belt (BNMB), located in the central portion of the Qinghai-Tibet Plateau, is closely related to the tectonic evolution of the Bangongco-Nujiang Ocean. Although the metallogeny of the western and central BNMB is well understood, the eastern part of this belt has not received much attention to date. The Jinmuguo deposit, the subject of this study, is a recently discovered porphyry Mo polymetallic deposit in the eastern BNMB. Here we present the geology, geochronology and isotopic characteristics of this deposit. Zircon U-Pb dating of the ore-related granite porphyry yielded an age of 118.6 +/- 0.7 Ma (n = 20) whilst Re-Os analyses of molybdenite constrain the timing of mineralization as 117.9 +/- 2.4 Ma (n = 4). These new age data suggest that magmatism and mineralization were coeval during early Cretaceous. In addition, the S isotope values of sulfide minerals from the Jinmuguo deposit show a narrow range of 2 parts per thousand to 4 parts per thousand, suggesting a magmatic sulfur source. The Pb isotopic character of sulfides indicates a heterogenous lead source. Whilster the H-O isotopic composition (dD values -84.8 parts per thousand to -69.1 parts per thousand, delta O-18(H2O) values 4.2 parts per thousand to 4.7 parts per thousand) is consistent with a dominantly magmatic hydrothermal fluid. Overall, our study of the mineralization and alteration characteristics suggests that the Jinmuguo deposit is a porphyry Mo polymetallic deposit related to early Cretaceous felsic magmatism. A comparison of the latter with the other deposits of the BNMB suggests that the entire belt has potential to host a diverse range of magmatic arc-related mineral deposit types.

The Lakang'e porphyry Mo (Cu) deposit, intermediate to large in size, is located in the eastern part of the southern Gangdese metallogenic belt. It is associated with a Miocene granodiorite porphyry (GDP). The alteration styles are mainly potassic and phyllic alteration, with minor argillic, chlorite, and carbonation alteration. In this study, we present whole-rock geochemical compositions, zircon LA-ICP-MS U-Pb data, zircon Hf isotope analyses, and zircon and apatite major and trace element compositions for the ore-bearing GDP and postmineralization quartz diorite porphyry (QDP) to constrain the formation of the Lakang'e Mo (Cu) deposit. The ore-bearing GDP, with a zircon U-Pb age of 13.83 0.20 Ma, was intruded after mineralization by the QDP, which was emplaced at 13.00 +/- 0.16 Ma. The GDP and QDP are high-K calc-alkaline series rocks with adakite-like features characterized by high contents of K2O and Al2O3, high Sr/Y ratios, strongly fractionated REE patterns, LILE enrichment, and HFSE depletion. The GDP and QDP have relatively low (Sr-87/Sr-86)i values (0.7051-0.7054) and high epsilon Nd(t) values (-0.87 to 0.59). Zircon grains from the QDP have high epsilon Hf(t) values (7.0-9.6), while zircon grains from the GDP show large epsilon Hf(t) variations ranging from -4 to 9.6, indicating that the magma source of the orebearing GDP included more continental crust than that of the postmineralization QDP. The zircon Ce4+/Ce3+ and Eu/Eu* ratios and apatite Mn and SO3 contents indicate that the postmineralization QDP had higher oxygen fugacity than the ore-bearing GDP. The oxygen fugacity of the ore-bearing magma present during apatite crystallization (generally below the Ni-Ni-O (NNO) buffer), was lower than that present during zircon crystallization (above the hematite-magnetite (HM) buffer). The F, Cl, and S contents in apatite show that the GDP and QDP were F and S rich and that the GDP had a higher F content than the QDP. A high oxygen fugacity, a Fand Srich magma and a Mo-rich crustal source were the key factors for the formation of the Lakang'e porphyry Mo (Cu) deposit. (C) 2020 Published by Elsevier B.V.

Located in the middle part of the Gangdese metallogenic belt in the Lhasa block, the Pusangguo deposit is a high-grade skarn type copper polymetallic deposit (Cu@1.42%, Pb + Zn@2.83%) formed in the contact zone between magma and the calcareous surrounding rocks and is the only large-scale Cu-Pb-Zn-(Co-Ni) deposit in the Gangdese metallogenic belt. Taking the intermediate-acid intrusions (biotite granodiorite and dioritic porphyrite) as the main research object, this study primarily carried on laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) U-Pb chronology on the zircon, whole-rock geochemistry, whole-rock Sr-Nd-Pb and zircon Hf isotopic study, aiming to confirm the timing and discuss the petrogenesis and geodynamic settings of the intrusions in Pusangguo. The results of LA-ICP-MS zircon U-Pb dating show that the biotite granodiorite and dioritic porphyrite were emplaced in 13.6 similar to 14.4 Ma and 13.6 similar to 14.6 Ma, respectively. The intrusions in Pusangguo deposit were formed in Miocene. Geochemically,, these intrusions belong to high-K calc-alkaline I-type granitoids. Both the biotite granodiorite and dioritic porphyrite are characterized by high Sr content (599 x 10(-6) similar to 1616 x 10(-6)), high Sr/Y ratio (48.2 similar to 132.3) and high La/Yb ratio (27.4 similar to 35.4), low Y content (10.38 x 10(-6) similar to 12.7 x 10(-6)) and Yb content (0.79 x 10(-6) similar to 1.17 x 10(-6)), showing the geochemical properties of adakitic rocks. In terms of whole-rock rare earth elements, the biotite granodiorite and dioritic porphyrite are enriched in light rare earth elements (LREEs) and large-ion-lithophile elements (LILEs), and are depleted in high-field-strength elements (HESE) such as the element Nb, Ta, P, and Ti. The compositions of Sr-Nd-Pb and zircon Hf isotopes, which are closely related to the intrusions associated with the Miocene porphyry-skarn deposits in the Gangdese metallogenic belt, have similar isotopic composition characteristics, indicating that they probably have the similar magmatic origin and are mainly derived from the thickened juvenile lower crust. The Pusangguo deposit adakitic intrusions were mainly formed in the post-collisional extensional tectonic setting. The transformation of collision extruding tectonic setting to post-collisional stretching background eventually led to the delamination of the continental Indian lithosphere (42 similar to 25 Ma) and the partial melting of enriched lithospheric mantle in Lhasa block and the formation of the Cu(Co)-bearing basic magmatic melts to underplate the thickened juvenile lower crust in Lhasa block (25 similar to 18 Ma). Then, the underplating of the basic magmatic melts could directly cause the partial melting of the garnet -bearing amphibole lithofacies in the thickened juvenile lower crust and then form the adakitic dioritic magmatic melts, which eventually formed the adakitic intermediate acid intrusions invaded (13 similar to 14 Ma) in the favorable structures and the skarn-type copper polymetallic orebodies in Pusangguo deposit.

密坑山-岩背地区为华南典型的锡成矿区,区内发育燕山期的花岗岩、斑岩和斑岩锡矿(如岩背锡矿).尽管该区锡矿与花岗质岩浆作用的关系密切,但区内花岗岩的时代与成因仍然存在争议.密坑山花岗岩体为密坑山-岩背地区最大的花岗岩体,侵入于上侏罗统鸡笼嶂组流纹质凝灰熔岩及火山碎屑岩中,主体岩性为钾长花岗岩.本文报道了密坑山钾长花岗岩的时代、地球化学特征.LA-ICP-MS锆石U-Pb定年结果显示,该岩体形成于早白垩世(～138 Ma).岩石具有高SiO2(74.42％～76.69％),富钾(K2O/Na2O=1.37～1.94),低Al2O3(12.39％～13.49％)和Mg#(11～19),弱过铝质(A/CNK=1.03～1.1),负Eu、Sr、Ba异常,富集高场强元素,以及高10000×Ga/Al比值(3.46～4.96)和略微高的锆石饱和温度(807～817℃),显示了铝质A型花岗岩的特点.同时,岩石也具有高Rb含量(842～1295)×10-6、Rb/Sr比值(90～255)以及稀土元素四分组效应,显示了高分异花岗岩的特点.因此,作者认为密坑山钾长花岗岩为高分异铝质A型花岗岩.花岗岩略微偏高的 εNd(t)值(-3.4～-4.6),反映成岩过程中或其源区有地幔组分的参与.综合区域岩浆岩和构造资料,认为密坑山钾长花岗岩形成于伸展背景中,很可能与俯冲古太平洋板块的后撤所导致的岩石伸展过程有关.

The time and mechanism of crustal thickening and initial surface uplift of the Tibetan Plateau remain highly controversial. Here we report on zircon U-Pb age, and mineral, element, and Sr-Nd isotope composition data for Eocene adakitic porphyries in the Laorite Co area of central-northern Qiangtang Block, central Tibet. Laser ablation-inductively coupled plasma-mass spectrometry zircon U-Pb age dating shows that the porphyries were generated at 42-41 Ma. All samples display adakitic geochemical characteristics, such as high SiO2 and Al2O3, and low Y and Yb contents, and high Sr/Y and La/Yb ratios with positive Sr and negligible Eu anomalies and Nb-Ta depletion. They also have low magnesium number (Mg #) (16-45) and high K2O (4.0-4.6 wt %) values, as well as high (Sr-87/Sr-86) i (0.7076-0.7080) and low epsilon Nd(t) (-5.9 to -4.4) values. These adakitic rocks were most probably generated by partial melting of thickened lower crust in the stability field of garnet, amphibole, and rutile but with relatively minor plagioclase. Moreover, such a crustal thickening process beneath this block likely occurred no later than the middle Eocene and was most probably caused by the southward subduction of the Songpan-Ganzi Block in the early Cenozoic. In addition, the occurrences of exposed adakitic porphyries unambiguously indicate that exhumation process occurred after their formation. Thus, these -42 Ma adakitic porphyries indicate the occurrence of significant exhumation since 42 Ma. Integrated with the thermochronological and paleoelevation data, we suggest that the initial surface uplift of the Qiangtang Block, triggered by crustal thickening, was underway by the middle Eocene (-42 Ma).

Reconstructing the evolutionary history of the Paleo-Tethys Ocean remains at the center of debates over the linkage between Gondwana dispersion and Asian accretion. Identifying the remnants of oceanic lithosphere (ophiolites) has very important implications for identifying suture zones, unveiling the evolutionary history of fossil oceans, and reconstructing the amalgamation history between different blocks. Here we report newly documented ophiolite suites from the Longmu Co-Shuanghu Suture zone (LSSZ) in the Xiangtaohu area, central Qiangtang block, Tibet. Detailed geological investigations and zircon U-Pb dating reveal that the Xiangtaohu ophiolites are composed of a suite of Permian (281-275 Ma) ophiolites with a nearly complete Penrose sequence and a suite of Early Carboniferous (circa 350 Ma) ophiolite remnants containing only part of the lower oceanic crust. Geochemical and Sr-Nd-O isotopic data show that the Permian and Carboniferous ophiolites in this study were derived from an N-mid-ocean ridge basalts-like mantle source with varied suprasubduction-zone (SSZ) signatures and were characterized by crystallization sequences from wet magmas, suggesting typical SSZ-affinity ophiolites. Permian and Carboniferous SSZ ophiolites in the central Qiangtang provide robust evidence for the existence and evolution of an ancient ocean basin. Combining with previous studies on high-pressure metamorphic rocks and pelagic radiolarian cherts, and with tectonostratigraphic and paleontological data, we support the LSSZ as representing the main suture of the Paleo-Tethys Ocean which probably existed and evolved from Devonian to Triassic. The opening and demise of the Paleo-Tethys Ocean dominated the formation of the major framework for the East and/or Southeast Asia.