Abstract:The Zhongdian porphyry copper polymetallic metallogenic belt in northwestern Yunnan is an important copper resource base in China. Pushang is a newly discovered porphyry copper spot in the metallogenic belt. The ore-bearing composite rock mass is mainly composed of quartz diorite porphyrite and quartz monzonite porphyry. In order to explore the genesis, tectonic setting, material migration process and metallogenic potential of the rock mass, this paper studies the petrochemistry and alteration component characteristics of fresh quartz diorite porphyrite and altered quartz diorite porphyrite respectively. The results show that the contents of SiO₂ (61.16%) and K₂O (4.20%) in the altered quartz diorite porphyrite are higher than those in the fresh quartz diorite porphyrite (58.24% and 3.06%, respectively), while the contents of Al₂O₃ and Na₂O are significantly lower. However, they all have the characteristics of enrichment of large ion lithophile elements (Rb, Ba, K, Sr) and depletion of high field strength elements (Zr, Nb, Ta, Ti), and have higher Ba/Nb values (75.7 and 93.2, respectively) and lower Ce/Pb values (3.16 and 5.70, respectively). It shows the characteristics of granite in typical arc environment. The (La/Sm)_N of the fresh quartz diorite porphyrite is high (average value is 8.18), and there is no obvious negative Eu anomaly. There is a positive correlation between SiO₂ and Rb, Zr/Sm ratios, indicating that it has experienced the fractional crystallization of hornblende. The ratios of Ba/Rb (<50) and Nb/La (<1) are low, the ratio of Th/La (>0.25) is relatively high, and the ratio of Rb/Sr (0.09) is between the upper mantle (0.034) and the crust (0.35), indicating that the magma source area is related to subduction, and the magma source is crust-mantle mixed source. A large number of components in the altered quartz diorite porphyrite include Fe₂O₃^T, CaO, K₂O, Th, Ta, HREE, Cu, Mo, W, Ag and other ore-forming elements, and the migrated components include Na₂O, MgO, MnO, Sr, Ba, U and LREE, indicating that the Pushang altered quartz diorite porphyrite was affected by alkaline alteration dominated by potassium metasomatism, and the ore-forming hydrothermal fluid causing mineral alteration was rich in Cu, Mo and other ore-forming metals. The hornblende phenocrysts with high Sr/Y and V/Sc ratios are widely developed in the quartz diorite porphyrite, indicating that the original magma is characterized by rich water and high oxygen fugacity. Sericitization is widely developed in altered rocks, and Cu migrates in a large amount. All samples are in the Cu-Au mineralized area in the lithochemical composition and metal mineralization exclusivity discrimination illustration. Based on the above characteristics, the Pushang quartz diorite porphyrite has the potential to form Cu-Au deposits.

Abstract:Zhuoma Pb-Zn deposit is located at the Zhongdian area on the western side of the Ganzi-Litang conjunction zone in northwest Yunnan. The ore is hosted in Zhuoma medium-acidic complex porphyry (porphyrite). Previous studies only focused on the ore bodies related to quartz-monzonite porphyry within the complex rock mass, but there is relatively little research on the ore bodies in quartz-diorite porphyrite. Based on mineralogical observations, in-situ trace elements analysis of sphalerite by laser ablation inductively coupled plasma mass spectrometer (LA-ICP-MS) was carried out. Combined with in-situ sulfur isotope analysis of pyrite, pyrrhotite, and sphalerite, it aims to determine the genetic type and ore-forming temperature of the deposit. The study found that sphalerite in the Zhuoma deposit is characterized relatively enriched Fe, Mn and depleted Cd, Ga, Ge, In and Sn. Among them, Fe, Mn, and Cd enter sphalerite in the form of solid solutions. Copper and Pb exist in the form of microscopic mineral inclusions, and indium exists in the form of micro-minerals combined with cadmium. The δ³⁴S values of sulfides in this deposit ranges between -1.83‰ and +2.30‰. The Zn/Cd ratio of sphalerite ranges from 200 to 322, indicating a close relationship between the source of ore-forming materials and magmatism. The calculation results of the sulfur isotope equilibrium thermometer are from 271℃ to 517℃. The calculation results of the GGIMFis thermometer, the FAS thermometer and the FA6 thermometer for trace elements of sphalerite are 257±17~366±31℃, 234~296℃ and 245~311℃ respectively. Combined with the characteristics of trace elements ratios of sphalerite, it is considered that the precipitation of Pb-Zn ore-forming materials in the Zhuoma deposit occurs in a mesothermal environment. In the sphalerite trace elements ternary diagrams and t-SNE plot, most of the measured points fall within the area of the deposit type related to magmatic hydrothermal fluids. It is considered that the lead-zinc ore body produced on the top of the complex porphyry in the Zhoma deposit is a shallow-seated hydrothermal vein type. This study provides a geological and geochemical basis for understanding the genesis of lead-zinc ores and the exploration direction in the Zhongdian area.

Abstract:The Mesozoic Lanping Basin in western Yunnan Province is one of the most important ore-hosting sedimentary basins between the Sanjiang orogenic belt in southeastern Qinghai-Tibet Plateau and the western margin of the Yangtze platform, SW China. The Bijiashan ore concentration area at the southwest part of this basin contains vast stratified fluorite-antimony hydrothermal deposits and occurrences, and always was highly concerned by the academics and industry. The ore-bearing rocks, the underlying and overlying strata were classified into the Upper Triassic strata by local geologists. However, the lack of accurate chronological evidence has seriously affected our understanding of regional stratigraphic framework, tectonic evolution and ore genesis. In this contribution, we have carried out a systematic field geological investigation on the ore-bearing rocks in the Zhujie fluorite-antimony ore field at the north of the Bijiashan ore concentration area. The field geology shows that the main fluorite-antimony ore-bearing horizons of the uppermost member of the Upper Triassic Sanhedong Formation (T₃s^3-2) is mainly composed of crystalline vitreous tuff, siliceous breccias and siliceous rocks, which is a sedimentary-volcaniclastic assemblage, and the orebodies occur in stratiform and/or lenticular shape. The clastic rocks of the overlying Maichujing Formation(T₃m) are also interbedded with multiple layers of lithocrystalline vitreous tuff. The zircon U-Pb dating results show that the weighted average zircon U-Pb age of the ore-hosting crystalline vitreous tuff from the second part of the upper member of the Upper Triassic Sanhedong Formation (T₃s^3-2) is 239.4 Ma, and the weighted average zircon U-Pb age of the lithocrystalline vitreous tuffs from the lower members of the T₃m Formation range from 252.2 Ma to 216.1 Ma, both of which have similar dated age spectra of the inherited zircons. Combined with the analysis data of regional geology, the ore-bearing rocks of the upper member of the Upper Triassic Sanhedong Formation (T₃s³) in the Zhujie ore field deposited at the late Middle Triassic, which represents the proximal volcanic- sedimentary depositions coeval with the arc-volcanism. Whilst the Upper Triassic formations were originated from the filling of uplift and denudation of the arc magmatic rocks, which record multiphase transition of regional basin-range events. Therefore, the known orebodies in the Zhujie fluorite-antimony ore field is a volcanic hydrothermal sedimentary deposit associated with coeval volcanism. The association of siliceous rock and tuff is an important prospecting mark for similar fluorite-antimony deposits in this ore field and adjacent areas with great prospecting potentials.

Abstract:The Hexi large strontium deposit in western Yunnan Province is located in the northern part of the Meso-Cenozoic Lanping Basin, southeast margin of the Qinghai-Tibet Plateau. The ore bodies mainly occur in the carbonate rocks of the Upper Triassic Sanhedong Formation, and are also abundant in the gypsum-bearing sand-mudstones of the Miocene Jinding Group. They are controlled by the near S-N-extending reverse fault and the near E-W-exten-ding strike-slip fault during the metallogenic stage. After the petrography observation and mineral chemical compositions analysis, the hydrothermal celestine can be divided into three generations of Cls1, Cls2 and Cls3, respectively. Cls1 mainly has an heteromorphic granular structure, while Cls2 and Cls3 exhibit an idiomorphic columnar or lamellar structure, and Cls2 is characterized by Sr-Ba solid solution oscillating rings, revealing that the ore precipitation had undergone a rapid to slow crystallization process. The Sr and S isotopic tracing results show that the celestine has an uniform ⁸⁷Sr/⁸⁶Sr value of 0.707 695~0.707 792, with an average value of 0.707 740, which is consistent with the Sr isotopic compositions of adjacent Sanhedong Formation limestones and the Late Triassic seawaters. The δ³⁴S value of celestine (17.26‰~17.49‰, with an average value of 17.36‰) is slightly higher than that of the Jinding Group gypsum (12.5‰~15.0‰). This indicates that the formation of Sr-rich fluid may be related to the high-pressure dehydration of the Sanhedong Formation limestone caused by gravity compaction and deep source heat flow, and the ore-bearing hydrothermal fluid concentrated at the favorable structural traps in the Sanhedong Formation during the early stage. Influenced by the regional tectonic stress changes and deep heat effect driven by the India-Eurasia collision process, these ore-bearing hydrothermal fluid migrated upward along the near S-N-extending reverse structure and mixed with the oxidizing lacustrine basin brine of the Jinding Group at the shallow surface. The hydrothermal sedimentary-type mineralization of the Jinding Group and hydrothermal filling metasomatism-type mineralization of the Sanhedong Formation simultaneously occurred. Hence, the Hexi strontium deposit is an epigenetic hydrothermal filling-type deposit with a continental hydrothermal sedimentary origin in nature.

Abstract:The large Jiulong calcite deposit, located at the northwest part of Central Yunnan Paleozoic Basin in southwest margin of the Yangtze platform, is the only giant crystal calcite deposit discovered so far in central Yunnan Province, SW China. The ore genesis is still unclear. In this paper, based on geological investigation and petrographic observation, the giant crystal calcite ore zone, dolomitic rock zone, and mottled calcilization rock zone are selected to carry out mineral chemistry, C-O isotopic composition and fluid inclusion analysis of different types of calcites and ore-hosting rocks, and calcite U-Pb dating. The results show that the proved orebodies are mainlyhosted along the beddings of the hosting limestones in the stratiform shape, and others exist in the bedding horizons and steeply dipping fault fracture zones in the form of large vein types. Both limbs of the NE-SW-extending Wenlin syncline and the transitional segments of the secondary "dome-and-basin" structure are favorable ore-depositional areas. And the middle and upper successions of the Lower Permian Maokou Formation (P₁m) limestone are the main ore-hosting rocks. The Jiulong calcite deposit is of low-temperature epigenetic origin deposit with prominent features of hydrothermal fluid replacement and filling and ore-structure controlling. The ore-forming fluid is featured by the Cl-Na·Ca type basin brine, and ore-formation materials and fluids are mainly originated from the cyclic interaction between the ore-hosting sediments and underlying basement sequences. There may be the addition of deep magmatic hydrothermal fluid. The small temperature variation, slow nucleation rate, and long-term crystallization process are the key mechanism of the ore-formation of giant crystal calcites. The metallogenic age of this deposit is 36.0±4.0 Ma, that is the Eocene-Oligocene times. Therefore, the ore-formation of the Jiulong calcite deposit is the evolutionary product of the regional tectonic-controlling basin fluid during the Himalayan age, representing the remote respondence to the Cenozoic Indo-Eurasian collisional orogeny in the Central Yunnan Paleozoic Basin.

Abstract:The Silurian-Devonian evolution of the East Kunlun Orogen (EKO) is controversial. A-type granites are often used to constrain the timing of tectonic transformation during the orogenic process. The Baidungou granite pluton, located in the Wulonggou goldfield in the eastern part of the EKO, has not been systematically studied in previous research. Therefore, this paper takes it as the research object to study its petrogeochemistry, zircon U-Pb geochronology and Hf isotopes. The zircon U-Pb dating shows the crystallization age of the intrusion is 417.9±3.5 Ma. Petrogeochemical studies reveal that the intrusion is characterized by high silicon (SiO₂ =71.2%~77.2%) and alkali (K₂O+Na₂O=8.23%~10.7%), low MgO (0.04%~0.22%) and CaO (0.09%~0.95%), enriched large ion lithophile elements (Rb, K, Th, U), depleted high field strength elements (P, Ti), obvious negative europium anomaly, and 'gull type’ REE patterns. Combined with high Ga/Al and TFeO/MgO values and Zr saturation temperatures of whole rocks, the intrusion is classified as A-type granite. In addition, the zircon εHf(t) values vary from -0.6 to 1.9 and two-stage Hf model ages range from 1 442 to 1 284 Ma, suggesting that this A-type granite was mainly derived from the partial melting of early felsic magmatic rocks with similar Hf isotopes. This granite exhibits characteristics of the A2-type, indicating that it formed in a post-orogenic extensional environment. The EKO developed a large number of A2-type granites nearly contemporaneous with this granite, reflecting it had entered the post-collision extension stage during the Late Silurian.

Abstract:The Oligocene granitic rocks in the Sangri area are mainly composed of quartz monzodiorite, monzogranite and syenogranite. The weighted average ages are 31.2±0.5 Ma, 31.0±0.5 Ma and 29.0±0.1 Ma, respectively, and the emplacement age is the Oligocene. The rocks are developed abundant melanocratic enclaves of different shapes. The K₂O content is 3.24%~5.73%, belonging to the high potassium calc-alkaline rock, with the characteristics of metaluminous to peraluminous rock evolution (A/CNK: 0.90~1.02, 0.98~1.07, 1.10~1.29). The rocks are LREE enriched type and the europium depletion shows an evolutionary characteristic from weak to strong (Eu/Eu^*: 0.66~0.75, 0.40~0.55, 0.04~0.09). They are relatively enriched in LILEs such as Rb, HFSEs such as Th, U, and LREEs such as (La, Ce) Nd, Sm, but depleted in LILEs such as Ba, Sr and HFSEs such as Nb, P, Ti (Ta). The fitting curves formed by SiO₂ vs. other major elements, rare earth elements and trace elements are highly coupled and the R² values are all greater than 0.90, which indicated they were products of the evolution of the same magma at different stages. The average zircon saturation temperature (t_Zr) is about 700℃ which may represent the initial temperature of melt formation. Based on the analysis of enclaves, structural styles, petrogeochemical characteristics and Hf isotopes, etc., the petrogenetic type of Oligocene granites in the Sangri area belongs to I-type granite. They were formed in the tectonic environment of rapid uplift due to the intracontinental collision of the Indian and Asian continents. The formation mechanism was the delamination or convective removal of the Indian continental slab during low-angle subduction. A small amount of fluid was released during the slab sinking process which caused the partial melted mantle-derived magma underplating and induced lower crust melting of the Lhasa terrane to form mix-derived magma. At the same time, the magma emplaced along the northeast-trending extensional fault in the Sangri area, eventually further leading to the continental crust accretion of the Tibetan Plateau. It enriches the evolutionary history of multi-phase accretion of the Qinghai-Tibet Plateau continental crust.

Abstract:Background value of geochemical elements is an important geochemical index for regional prospecting prediction. The Gangdese-Himalayan orogenic system in Xizang was selected to collate and clean the regional geochemical data. The outliers were iterated using the mean value (X) plus and minus three times standard deviation (S) as the threshold value, and the median (m) of the remaining data was calculated to find out the background values and enrichment characteristics of 39 elements in different secondary units, then the prospecting prediction was made. The results show that the geochemical background of 39 elements of Gangdese-Himalaya in Xizang is highly varied and differentially enriched. Metallogenic elements such as Li, Be, Sn, W, Au, Sb, Pb and Zn are enriched in the Himalayan terrane, while Au and Cr are mainly enriched in the Yarlung Zangbo River suture zone. The Ladakh-Gangdese-Chayu arc basin system is enriched with Cu, Mo, Pb, Zn, Au, Ag and other ore-forming elements, and the enrichment degree increases gradually from north to south. The comprehensive analysis shows that the different tectonic-magmatic evolution processes of different tectonic units lead to the differential enrichment of elements, and then develop different types of mineralization. On this basis, according to the combination characteristics of elements, 7 prospecting prospects of class Ⅰ, 9 prospecting prospects of class Ⅱ and 17 prospecting prospects of class Ⅲ are delineated. The results of the study have certain guiding significance for the new round of prospecting strategy breakthrough action.

Abstract:The Jurassic magmatic arc is located on the southern margin of the Gondwanan arc, in which Jurassic subduction-related Cu-Au and Miocene collision-related Cu-Mo porphyry deposits are developed. However, little is known about the diagenetic links between subduction- and collision-related porphyry Cu deposits. In this paper, Nd isotope, ΔFMQ and Eu/Eu^* value mapping has been carried out within the Jurassic magmatic arc, based on published whole-rock major and trace elements, Sm-Nd isotope and zircon trace elements data. The mapping results show that the main development area of Jurassic subduction-related porphyry Cu-Au deposits has high εNd(t) and young Nd mode ages during the Jurassic period, which exhibit juvenile crustal features, while the development location of Miocene collision-related porphyry Cu-Mo deposits is near the interface of the crustal contact between the old and juvenile crust during the Jurassic period. Jurassic porphyry Cu-Au deposits were basically developed in areas with high ΔFMQ and Eu/Eu^* value magmas during the Jurassic period, and Miocene porphyry Cu-Mo deposits were developed in areas that exhibit either areas of high ΔFMQ and low Eu/Eu^* value or areas of low ΔFMQ and Eu/Eu^* values during the Jurassic period. This indicates that during the Jurassic period, the magma in the area where the Jurassic porphyry Cu-Au deposits are located had higher oxygen fugacity and water content compared to the magma in the area where the Miocene porphyry Cu-Mo deposits were developed. Water-rich and oxidised magmas provided sufficient S and metallogenic metals for the development of Jurassic porphyry Cu-Au deposits by inhibiting early sulphide saturation of deeper magmas. Comparatively, the magma of the Miocene porphyry Cu-Mo development region may have failed to reach conditions that inhibited early sulphide saturation in the deeper magma due to the mixing of ancient crustal components, which triggered early sulphide saturation, leading to the formation of large amounts of Cu-bearing lower crustal accretion and inhibiting its mineralisation in the Jurassic. The Indian-Eurasian collision resulted in the bottom intrusion of thermochondritic melts, which triggered the remelting of Cu-bearing lower crustal heap crystals, providing a favourable source of metals for the formation of the Miocene porphyry Cu-Mo deposits.

Abstract:The Qingcaoshan mineralization area is located on the northwest side of the Duolong mining area, with a large area of magmatic rocks exposed on the surface and developed porphyry-type copper mineralization. However, the geochemical characteristics and origin and evolution of the magmatic rocks are not yet clear, which restricts further evaluation of the prospecting potential of this mineralization area. For this purpose, detailed zircon U-Pb geochronology, zircon trace elements, rock geochemistry, Sr-Nd isotopes, and hornblende electron microprobe analyses were conducted on the exposed magmatic rocks in the Qingcaoshan mineralization area to explore the source area and evolution process of the magmatic rocks, determine their temperature and pressure conditions, magma oxygen fugacity, and water content, and provide support for further evaluating the regional prospecting potential. The study shows that the ore-forming magmatic rocks in the Qingcaoshan mineralized area mainly consist of granodiorite porphyry, diorite porphyry, and monzonitic granite porphyry, with diagenetic ages concentrated between 120~118 Ma. The zircon U-Pb age of the postmineralization aplite is 114 Ma, all of which are products of Early Cretaceous magmatic activity. The average crystallization temperatures of zircons in granodiorite porphyry, diorite porphyry, and monzonitic granite porphyry during the mineralization period were calculated based on the Ti content in zircons, which were 604, 689 and 684℃, respectively. The average oxygen fugacity lg (f_O2) was -18.58, -15.77 and -14.18, respectively. The range of ΔFMQ variation was ΔFMQ-0.46~ΔFMQ+2.38, ΔFMQ-5.66~ΔFMQ+4.28 and ΔFMQ-1.32 ~ΔFMQ+6.24. The diorite porphyry and granodiorite porphyry belong to the high-potassium calcium alkaline-potassium basalt series, and quasi aluminum-weak peraluminous magmatic rocks, with arc magmatic rock properties; The (⁸⁷Sr/⁸⁶Sr)_i value ranges from 0.707 4 to 0.709 3, and the εNd(t) value ranges from -7.1 to -5.3, located in the region between the depleted mantle and the lower crust evolution line, showing the characteristics of crust-mantle mixed origin. The electron probe results of hornblende show that the average water content of diorite porphyry is 7.4%. The study proves that the Cretaceous magmatism of Qingcaoshan originated from the partial melting of mantle wedges caused by subducted slab, and was mixed by crustal materials, and shows the characteristics of high oxygen fugacity and high water content, indicating that the Qingcaoshan mineralized area has good potential for porphyry copper mineralization.

Abstract:A series of Early Cretaceous A-type granites are developed in the central-western part of the Central Lhasa subterrane in Xizang, but no related A-type granites have been found in the eastern section, which constrains the understanding of the deep dynamics of the central Lhasa subterrane. In this paper, petrographic, zircon U-Pb chronology, zircon Hf isotope geochemistry and whole-rock geochemistry studies were carried out on the monzonitic granites in the Menba area based on detailed field geological investigations. The zircon ²⁰⁶Pb/²³⁸U weighted average age of this monzonitic granite measured by LA-ICP-MS dating is 120.9±0.8 Ma, indicating that the Menba monzonitic granite was formed in the Early Cretaceous. The Menba monzonitic granite has a high content of SiO₂ (69.69%~75.81%, average 73.84%), a high content of total alkali (Na₂O+K₂O) (8.22%~9.34%, average 8.92%), a medium content of Al₂O₃ (12.77%~15.60%, average 13.74%), and a low content of MgO (0.01%~ 0.12%, average 0.05%), values of 1.08~1.22 for A/CNK and 1.12~1.27 for A/NK, suggesting that the Menba monzonitic granite is a peraluminous, high-K calc-alkaline-potassium basaltic series rock. The Menba monzonitic granite is relatively enriched in trace elements such as Zr, Hf, Ce, and Y, and relatively deficient in trace elements such as Ba, Ti, Sr, and P. It has strong negative Eu anomalies (δEu=0.04~0.11, average 0.07), high 10 000 Ga/Al values (1.99~4.18, average 3.06), FeO^T/MgO values (18.45~ 69.96, average 47.05), Y/Nb (1.07~2.42, average 1.77), Rb/Nb (6.70~12.16, average 9.83), and a rightward gently dipping "V" rare earth element distribution curve, indicating that the Menba monzonitic granite is an A2-type granite produced in a post-collisional and extensional environment. In addition, the negative to positive εHf(t) values (-2.7~+2.6), relatively old zircon Hf crustal model ages (t_DM2=1 352.8~1 016.8 Ma), and Nb/Ta values close to those of the crust indicate that the Menba monzonitic granite originated from the ancient lower crust with a small amount of mantle material. Combining the results of previous research, this paper suggests that the Menba monzonitic granite was formed in the collisional orogenic background of the Early Cetaceous Lhasa subterrane and Qiangtang subterrane, and that its genesis was due to the upwelling of soft-fluidic material caused by the breakup of subducting plates, which induced partial crustal melting, and that it originated from magma that was partially melted by crustal melting with a small amount of mantle material, and underwent the segregation and crystallisation of predominantly K-feldspars.

Abstract:The Yulong giant porphyry Cu deposit is located in the eastern margin of the Tibet Plateau. It is a typical representative of collisional porphyry copper deposits. Recent studies indicate disparities in the mineralization potential between the ore-forming and ore-bearing porphyries of the Yulong deposit. Here we present whole-rock main/trace elements, whole-rock Sr-Nd, zircon U-Pb, and zircon trace elements data for ore-bearing monzogranite porphyry and ore-forming granite porphyry of the Yulong deposit to delve into the magmagenesis of this deposit and the intrinsic factors influencing its mineralization potential. Zircon U-Pb dating shows that the Yulong porphyry were emplaced at ca. 42~41 Ma. Monzogranite porphyry and granite porphyry have similar Sr-Nd ratio, including high (⁸⁷Sr/⁸⁶Sr)_i (0.706 0~0.707 6 and 0.706 2~0.706 7) with low εNd(t) (-2.9~-2.0 and -4.6~-1.9). High K₂O (the average＞4%), low MgO, Mg^# and Cr, significant negative Nb and Tb anomalies, low Nb/U and Ce/Pb ratios were derived from partial melting of a thickened lower crust. Combine with adakitic signatures of monzogranite, including high SiO₂, Al₂O₃ and Sr contents, low Y and Yb contents with high Sr/Y and La/Yb ratios, we propose that the Yulong metallogenic mother magma originated from the partial melting of the Cenozoic lower crust. Zircon trace-element analysis shows that the two porphyries of Yulong have high Eu/Eu^*(>0.44), 10 000×(Eu/Eu^*)/Y(>3.6), (Ce/Nd)/Y(>0.01) and lower Dy/Yb (<0.31, average 0.22), suggesting that both porphyries have high and similar magma water content. Moreover, trace elements in zircons shows that monzogranite porphyry ΔFMQ= 0.29~2.29 (average 1.44), and granite porphyry ΔFMQ=1.07~2.74(average 1.80). They both have high magmatic oxygen fugacity, but the granite porphyry has a larger range of variation. In addition, the oxygen fugacity is higher than that of monzogranite, suggesting that different oxygen fugacity may affect the differences in mineralization.

Abstract:The Yulong porphyry copper belt in Xizang, located in the eastern part of the Tethys-Himalaya metallogenic belt, is a globally renowned copper mineralization prospect area. Despite the challenging natural conditions in the mining area, which pose difficulties for traditional surface exploration work, the sparse vegetation facilitates the extraction of remote sensing information. In this study, we used ASTER remote sensing imagery as the data source and applied principal component analysis (PCA) and imaging spectrometry to extract alteration and mineralization information from the Yulong porphyry copper belt. Specifically, PCA was used to extract information on iron staining alteration anomalies using ASTER bands 1～4, carbonate alteration anomalies using bands 1, 3, 4, and 5, Mg-hydroxyl alteration anomalies using bands 1, 3, 4, and 8, and Al-hydroxyl alteration anomalies using bands 1, 3, 6, and 7. Imaging spectrometry, on the other hand, involved techniques such as minimum noise fraction (MNF), pure pixel index (PPI), n-dimensional visualizer (n-D Visualizer), and mixture tuned matched filtering (MTMF) to map the distribution of alteration mineral information in the Yulong porphyry copper belt. By comprehensively analyzing the results obtained from both methods and considering geological factors such as stratum and tectonics, we constructed a remote sensing mineral exploration model and predicted four mineralization prospect areas. Finally, through comparison and verification with known mineral occurrences, we confirmed that the extracted mineralization alteration areas closely matched the actual mineral occurrences, demonstrating the effectiveness and reliability of these two methods. This study not only provides strong technical support for large-scale exploration in the Yulong porphyry copper belt but also lays a solid foundation for the precise delineation of future target areas.