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.

Abstract:

This paper discusses the petrogenesis of the two-mica granite and its genetic relationship with pegmatite in Jiajika area, west Sichuan Province, by detailed field investigation and laboratory analysis. The whole rock analytical results show that SiO₂ content of two-mica granite is 73.93%~75.06%, and total alkali is 7.90%~8.36% with high concentration of K, suggesting high-K calc-alkaline series; the content of Al₂O₃ is 14.24%~14.77%, and A/CNK=1.14~1.24, implying strong peraluminous S type granite; ΣREE=31.18×10^-6~41.67×10^-6,LREE/HREE=4.15~6.41,δEu=0.46~0.70, and CaO/Na₂O=0.07~0.12(<0.3),indicating that its source might have been pelite with rare content of psammite, and high ratio of Al₂O₃/TiO₂ (133.1~279.8) implies that it is high-pressure-low-temperature post-collision granite. The SiO₂ content of the granite pegmatite is 72.59%~80.91%, the total alkali is 5.26%~10.60%, Al₂O₃ is 11.79%~17.64%, σ=0.74~3.80; A/CNK=0.98~2.38; ΣREE=4.03×10^-6~8.29×10^-6, LREE/HREE=2.61~10.40, and δEu=0.18~0.68. There are considerable differences between two-mica granite and granite pegmatite in the aspect of the content of major and trace elements. And there is close genetic relationship between granite and pegmatite in the area. Magma immiscibility might be the key factor for the formation of (ore-bearing) granite pegmatite. The pegmatite melt riched in volatile components might be separated during the upwelling of granite magma and metasomatized minerals in wall rock to further concentrate rare metal elements during its migration. The difference between two-mica granite and pegmatite might cause the apparent differences in REEs and elements such as Th, Sr, Ti, Y, Rb and Nb. The different characteristics of pathways and environments that the pegmatite melt passed and emplaced might have resulted in element concentration variance in different sites. In comparison with two-mica granite, there existed a certain degree of jumping characteristic during the formation and evolution of the pegmatite in Jiajika area.

Abstract:

Guilin Chicken Blood Red Jasper (CBRJ) is a kind of quartz jasper. It is characterized by bright red to black colors and high hardness. However, few researches have been focused on the field occurrence, geological background, rock structure and genesis of its color. Field surveys indicate that the Guilin CBRJ is hosted in low-grade metamorphic sandstones which experienced vapor-water hydrothermal metamorphism and iron oxide dissemination. It occurs in the Sanmenjie Formation of Neoproterozoic Danzhou Group in Longsheng area in the north of Guangxi. Tectonically, the ore deposit of Guilin CBRJ is located at the juncture of Yangtze and Cathaysian plates, which has undergone a complex geological process. Its formation was related to multi-phase tectono-magmatic activities from Neoproterozoic to Triassic. Detailed analyses of mineralogy, micro-texture and geochemical composition of Guilin CBRJ were carried out by polarizing microscope, X-ray diffraction, and electronic microprobe. The results indicate that the CBRJ is mainly composed of quartz and hematite, with dolomites in some samples. Quartz grains exhibit two types of allotriomorphic equigranular texture and idiomorphic porphyroblastic texture. The latter one, in which distinct enlargement texture can be observed, reveals a metasomatic metamorphism phase. Hematite occurs in three types: ① single crystal existent between or inside the quartz particles, ② dusty crystals wrapped in the quartz particles, and ③ disseminated crystals filled between the quartz particles. The Fe³⁺ in the hematite should be responsible for the color of the CBRJ. Electron microprobe analysis shows that the hematites of single crystal and disseminated crystals have 78.9%～85.6% iron oxides, but the dusty crystal is too small to be analyzed. In combination with the different generations of quartz and hematite, the authors have reached the conclusion that the formation of different types of these minerals in the Guilin CBRJ was consistent with the regionally geological evolution in this area.

Abstract:

The Hongyuntan iron deposit is hosted in pyroclastic rocks of the Lower Carboniferous Yamansu Formation. The ore bodies occur as layers, stratoid bodies or lenses. The principal ore mineral is magnetite, together with minor maghemite, specularite, pyrite and trace chalcopyrite. The gangue minerals include garnet, diopside, actinolite, chlorite, tremolite, epidote, biotite, albite and quartz. The ore structures are mainly of massive and disseminated forms, with occasional banded or veined forms. The ore textures are of subhedral-anhedral granular and metasomatic types. The wall rock alteration shows symmetrical zoning, and the alteration colors change from dark to light from ore bodies outwards. On the basis of observed mineral assemblages and ore fabrics, two periods of ore deposition were recognized, i.e., skarn period and hydrothermal ore-forming period, which could be further subdivided into four metallogenic stages, namely skarn stage, retrograde alteration stage (main ore-forming stage), early hydrothermal stage and quartz-sulfide stage. Electron microprobe analyses show that the end member of garnet is mainly andradite-grossularite. The composition of pyroxene is mainly diopside-asteroite. The amphiboles is composed mainly of actinolite and tremolite with minor magnesiohornblende. The composition of these skarn minerals suggests that skarn in the Hongyuntan iron deposit is calcic skarn, belonging to metasomatic skarn. The characteristics of main and trace elements suggest that the formation of magnetite was closely related to the skarn. In combination with geological characteristics, the authors suggest that the skarn might have resulted from interaction between Ca-rich pyroclastic and Fe-rich magmatic hydrothermal fluid which was transported along the fault system. The formation of magnetite was hence related to the regressive metamorphism of the skarn.

Abstract:

This paper has mainly recommended a mineral abbreviation list (see Table 2 and Table 3). Table 2, which contains 243 minerals, was compiled by IUGS Subcommittee on the Systematic of Metamorphic Rocks (SCMR) in 2007. The author selected other 29 minerals and, on such a basis, formulated Table 3. Thus, the total mineral abbreviations come to 272. It is hoped that they can be popularized in future and become more and more perfect through utilization, so as to provide a basis for ultimate standardization and unification.

Abstract:

This paper presents partition coefficients of 69 chemical elements (Li, Rb,Cs, K, Na, Ca, Ba, Sr, Mn, Fe, Mg, Cu, Pb, Zn, Co, Ni, Be, La, Ce, Nd,Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Y, Sc, Cr, In, Ga, Al, B,Cd, Sb, Bi, U, Th, Zr, Hf, Si, Ti, Ge, Sn, Mo, Nb, Ta, W, V, P, F, Cl,S, N, O, C, As, Pu, Re, Os, He, Ne, Ar, Kr and Xe) and the univalent radical (OH) in 28 minerals (olivine, clinopyroxene, orthopyroxene, amphibole,biotite, Phlogopite, plagiocla-se, K--feldspar, quartz, magnetite, ilmenite, garnet,zircon, apatite, allanite, topaz, sphene, cordierite, hauyne, leucite, nepheline,whit-lockite, brookite, petovskite, melilite, armalcolite, spinel and rutile) from 8 types of rocks, namely metaluminous (ultra) basic rock, peralkaline (ultra) basic rock, metaluminous intermediate rock, peralkaline intermediate rock,metaluminous acid rock, peralkaline acid rock, peraluminous acid rock and ultra-acid rock. It is found through an integrated ahalysis and comparison that the composition and structure of minnerals and melts seem to be the most important factors controlling mineral-melt element partitioning. Importanceshould be attached to minral structure and Al-supersaturation of melt which have, not been discussed by research workers. Finally, the present state and theproblems to be solved in the study of mineral--melt element partition coefficients are analysed, and the future trends of this research field are predibted.

Abstract:

本文以表格的形式列举了经国际矿物学协会(IMA)新矿物与矿物命名委员会(CNMMN)批准、并于2003年度正式发表的新矿物共55种,其中硅酸盐31种,磷酸盐5种,砷酸盐2种,硫酸盐4种,硫化物3种,碳酸盐2种,钒酸盐2种,硼酸盐1种,硒化物1种,硫盐1种,氧化物1种,氢氧化物1种,复杂卤化物1种.文中表格依次列出了矿物的中外文名称及化学式、晶系及晶胞参数、主要粉晶数据、物理性质、光学性质、产状及共生(伴生)组合等.

Abstract:

The combination of multi-collector inductively coupled plasma mass spectrometry (MC-ICPMS) and laser ablation provides a useful tool for tracing the geological process by analyzing minerals under microscales. As one of the non-traditional stable isotopes, boron isotope has attracted more and more attention. In this study, the authors developed an in-situ method for high-precision analysis of B isotope in tourmaline with high-content boron and muscovite with low-content boron. Tourmaline and glass reference materials were applied to correcting the mass fractionation respectively, and in-situ B isotopes of two natural samples from southwestern Tianshan were also tested. In addition, the boron isotope of the in-house standard T-PKU was calibrated as -13.07‰±0.42‰ (2SD, n=66). The above testing results reveal that the condition of LA-MC-ICPMS is stable for a long term and suitable to producing high quality data about tourmaline with minimum spot size of 10 μm and muscovite with > 20×10^-6 B concentration. The B isotopes of tourmaline and paragonite in Tianshan samples are helpful for tracing fluids sources.

Abstract:

High grade black jadeite is a kind of upscale and fashionable jade material that has become one of the jadeites characterized by fastest growing values in the past 20 years. Based on a comparison of mineralogical and geochemical characteristics between black jadeites (inky black jades）from different producing areas of the world, the authors hold that the black jadeites currently on the market can be mainly classified into jadeite jade, omphacitic jadeite jade and hornblende jade whose main components are jadeite, omphacite and dark green hornblende respectively. They include black chicken jade, ink jadeite and black kosmochlor from Myanmar and jade negro and galactic gold from Guatemala, with black chicken jades similar to those from Myanmar also seen in Japan and Kazakhstan. The research results suggest that the main mineral composition, jade structure and inclusion characteristic combinations of black jadeite jades from different producing areas have their respective typomorphic natures, which can be used as the distinctive characteristics for their sources.

Abstract:

Early Paleozoic volcanic rocks in Tianshui and Baoji areas along the eastern segment of North Qilian orogenic belt consists of Hongtubu basaltic lavas and Chenjiahe intermediate-acid volcanic rocks. Geochemical analyses show that Hongtubu basaltic lavas are similar to the intercalated basalts in Chenjiahe intermediate-acid volcanic rocks in characteristics, both fallen in the tholeiite series with high TiO2 (1.50%～2.73%). Their∑REE are 65.97×10-6～133.46×10-6 and 78.04×10-6～175.55×10-6 respectively， both are slightly enriched in LREE ［(La/YbN being 2.00～4.40 and 2.71～4.40 respectively］，and both have no obvious Eu anomaly or weak Eu negative anomaly（δEu being 0.85～1.10 and 0.85～0.99 respectively）. Basalts from two groups are typically characterized by selected enrichment of LILEs, low abundances of HFSEs relative to NMORB, and prominent troughs of Nb and Ta, with low Nb/La ratio（0.28～0.43）, which indicates the affinity of these volcanic rocks to island arc tholeiite（IAT）. In addition, εNd（t）（+2.22～+4.08）values of basalts suggest that their mantle sources are similar to the depleted mantle source. Zr/Nb=17.21～36.33 and Ce/Nb=5.73～8.17, implying geochemical characteristics of N-MORB. Sr, Nd and Pb isotopes from Hongtubu basalts are similar to those in Chenjiahe basalts in composition. In the diagrams of εNd(t)-(87Sr/86Sr)t, (207Pb/204Pb)t-(206Pb/204Pb)t,(87Sr/86Sr)t-(206Pb/204Pb)t and εNd(t)-(206Pb/204Pb)t for basalts, the data are fallen in the DM, EMⅠand EMⅡ areas, probably with a little crustalontamination, indicating that the magma of basalts might have had a mixed gin.Thentermediate-acid volcanic rocks from Chenjiahe belong to the calc-alkaline series,they have relatively high abundances of REE∑REE=127.51×10-6～276.01×10-6）, and are significantly enriched in LREE[（La/YbN= 4.79～13.51]. Most intermediate-acid volcanic rocks show weak Eu negative anomaly (δEu=0.53～1.20). The trace element patterns of Chenjiahe acid volcanic rocks are similar to those of the ocean ridge granite (ORG), with marked troughs of Nb, Ta, Zr and Hf. A synthetic study shows that the Chenjiahe intermediate-acid volcanic rocks in the eastern segment of North Qilian orogenic belt were formed in an island-arc setting, whereas the Hongtubu basalts were formed in an intra-arc rift setting (or an initial back-arc basin setting), probably being products of the early spreading evolution of the island_arc system towards the back-arc basin in the eastern segment of North Qilian during late Early Paleozoic. The results obtained provide evidence for the existence of the trench-arc-basin system at the juncture of Qilian and North Qinling orogenic belts.

Abstract:

The geochemical characteristics and abnormal sources of As, Cd, Cr, Cu, Hg, Ni, Pb and Zn in the soil of Southern Xuancheng were analyzed and studied by using the 1:250 000 land quality geochemical survey data. It is found that the geological background is the main controlling factor for the content of soil elements, and that the spatial distribution characteristics of heavy metal elements in the surface and deep soil in the area are significantly consistent with the geological background and sedimentary environment. The high content of heavy metal in the soil parent rock geological background (Hetang Formation, Piyuancun Formation and Lantian Formation, etc) is the main influencing factor for the high anomaly of soil heavy metal elements. In addition, mining and atmospheric dry and wet deposition are also one of the factors affecting high anomaly of heavy metals in soil. It is found that Pb, Hg, Cd and Cr in soil have input sources of atmospheric dry and wet deposition. The main impact index of heavy metal in soil pollution risk in the survey areas was Cd. The proportion of samples that soil Cd exceeded the control value of soil pollution risk of agricultural land was 2.56%. The morphological analysis results show that soil Cd is mainly in ion-exchange state. Combined with crops investigation, it is found that there is a certain ecological risk in the area with high abnormal soil Cd.

Abstract:

The Cuonadong leucogranite is one of the most important parts of North Himalayan leucogranite belt. Geochemical data show that Cuonadong leucogranite is the calcium alkaline and strong peraluminous granite with high silica (SiO₂ is 74.20%~74.52%), poor iron (Fe₂O₃ is 0.04%~0.20%, FeO 0.04%~0.58%), poor magnesium (MgO is 0.06%~0.14%), and calcium alkaline (σ is 2.15~2.32) as well as strong peraluminous nature (A/CNK is 1.11~1.15). Its total rare earth is relatively low (∑REE is 47.24×10^-6~57.59×10^-6), with enrichment of LREE (LREE is 39.85×10^-6~49.23×10^-6), depletion of HREE (HREE is 6.91×10^-6~8.68×10^-6) and obvious negative Eu anomaly (0.49~0.80). It is characterized by an enrichment of some large ion lithophile elements (Rb, Th, U, K) and loss of high field strength elements (Nb, Ta, Zr Ti). Zircon U-Pb dating results show that the Cuonadong leucogranite's formation time is Miocene (21 Ma), which belongs to the peak of the late stage of north Himalayan leucogranite (24~12 Ma). Zircon εHf(t) values are negative with a wide variation (-3.92~-17.64), which shows that its magma source was the crust, mostly from the metapelite, with the probable mixing of many kinds of materials in its source. The petrogenesis of Cuonadong leucogranite is that the high Himalayan crystalline rock series experienced decompression melting during the rapid pull-back of the plate in the post-collision tectonic setting, with the initial magma crystallization temperature being 675~702℃.

Abstract:

Quantitatively determining the timescale during mantle-derived magma ascent from the source to eruption or emplacement is essential for the understanding of magmatism, however, the timescales of eruption/emplacement are still poorly constrained. Shanxi Datong Cenozoic volcanic field, north of the North China Craton, is an ideal area for the investigation. In this study, we focused on the mantle olivine xenocrysts entrained in ca. 0.2 Ma Shenquansi alkali basalt, and its timescale of residence in the host magma prior to eruption. According to mineral chemistry, cores of these mantle olivine xenocrysts have Fo values up to 97.7, which can be defined as extremely magnesian olivine. They are also characterized by the extremely low contents in Ca, Mn and Ni, suggesting they were captured from metasomatized mantle peridotite. Moreover, both of the mantle olivine xenocrysts display complex CaO profiles, attributed to complex magmatic processes in the magma plumbing system. The reaction rim widths of one olivine xenocryst vary significantly, implying it has experienced multiple crack processes when captured or dur- ing transport. The Fo values of the mantle olivine xenocrysts rims are about 70, indicating they are in diffusion equilibrium with the host magma (alkali basalt) at rims. Timescales obtained by Fe-Mg diffusion chronometry of olivine mantle xenocrysts show that they have only resided in the magma for months. For a lithospheric mantle thickness of 40~70 km, the fastest average ascent rate may exceed 500 m/d.

Abstract:

In this paper,LA-ICP-MS zircon U-Pb dating was carried out for four samples of volcanic rocks from Qingshan Group in Jiaodong area and, as a result, their concordant ages were obtained, which are 119.4±0.9 Ma, 118.2±1.0 Ma,120.2±0.9 Ma and 120.0±0.8 Ma, respectively. The results show that all the volcanic rocks in Jiaodong area were formed from about 120 Ma to 118 Ma in the Early Cretaceous period. The ages of Qingshan Group volcanic rocks from Shandong Province controlled by Tan-Lu fault are similar to those from the Su-Wan segment of the Tan-Lu fault zone,but younger than those around the Tan-Lu fault zone,which indicates that the duration of volcanic eruption along Tan-Lu fault is probably longer than the duration in other areas under the background of lithospheric thinning in eastern China. Geochemically, all the intermediate and acidic volcanic rocks have high K₂O, ALK, LREE values and low MgO, TiO₂, Ni, Cr, HREE values. According to the geochemical features, the volcanic rocks can be subdivided into trachyte-trachydacite and rhyolite. The trachyte-trachydacite is characterized by LILE enrichment(Rb,Ba,K)and HFSE depletion(Nb,Ta,Ti,P), but the rhyolite exhibits stronger depletion of Ba,Sr and HFSE (Ti,P). Compared with the rhyolite,the trachyte-trachydacite possesses higher Sr and Ba values as well as La/Nb and Ba/Nb ratios,but lower Rb/Ba ratios and δEu values. All these data indicate that they might have been derived from different magma sources. It is inferred that the trachyte-trachydacite rocks were derived from the mixture of the partial melting of the lower crust(Yangtze Craton or North China Craton)and enriched lithospheric mantle. In addition, the rhyolites were related to the partial melting of the lower crust in the regional extension environment and high geothermal anomaly background with crystallization differentiation during the magma evolution.

Abstract:

Cordierite is a mineral material characterized by low thermal expansion coefficient and good thermal shock resistance. Cordierite mineral material is relatively rare in nature, so cordierite is synthesized usually by the method of artificial synthesis. Based on the newest investigation results of synthetic cordierite, this paper deals with the progress of researches on such synthesis methods of cordierite as high purity oxide solid reaction at high temperature, natural mineral solid reaction at high temperature, the utilization of industrial wasted materials, the employment of agricultural wasted materials, the sol-gel and the low-temperature combustion synthesis. At present, the method of natural mineral solid reaction at high temperature is used for the preparation of cordierite in industry. In spite of a lot of advantages, this method also has many disadvantages. Therefore, the development trend of cordierite synthesis seems to solve the problem as to how to apply other synthesis methods to industrial preparation.

Abstract:

At present, the infrared transmission spectroscopy is the best technique for determining whether jadeite is polymer-impregnated or not, and the infrared reflectance spectroscopy is a nondestructive and rapid determination method that provides mainly the fundamental frequency vibration spectra data of minerals and shows new application potentials in gemological research, especially in the identification of gem species. The gemological application of IR reflectance spectroscopy and the identification system of IR spectra of gems, including a database of 318 spectra and a searching and identifying program, are described in this paper.

Abstract:

Petrology, geochemical and Nd isotopic data are reported for the Neoproterozoic Danba metabasalt in the Kangdian Rift on the western margin of the Yangtze block. Samples were collected from alkaline basalts, which are enriched in MgO, TiO₂, with Mg^# being 0.51～0.59. They have high total rare earth elements and show high fractionation between LREE and HREE. The trace elements are characterized obviously by enrichment of Th, Nb, Ta, Zr, Hf and LREE but depletion of Y and HREE. Their geochemical and Nd isotopic characteristics suggest that they are similar to OIB. The basaltic magma was generated in an intraplate setting, and was generated by partial melting of OIB mantle source region, with variable degrees of contamination of SCLM during magma ascending; in addition, some samples might have experienced contamination of the lower crust. These samples reveal some plume magmatism characteristics in petrochemistry, and imply that magmatism was probably related to the Neoproterozoic plume event, which resulted in the breakup of Rodinia supercontinent.

Abstract:

As more and more treated turquoises appear on Chinese gem market, the authors collected lots of turquoises from different deposits on Chinese gem market in order to sum up the characteristics of the natural turquoises on Chinese gem market. At the same time, different types of treated turquoises were studied to find general difference between them and natural turquoises. The results show that natural turquoise and treated turquoise have different shades of color, inclusions and appearances. IR spectra of both natural and treated turquoises were studied, indicating that there are absorption peaks at 1 735, 1 600 and 1?500 cm^-1 in treated turquoises, which are caused by the man-made polymer. If the turquoise is treated by polymer, there are absorption peaks at 1 735, 1 600 and1 500 cm^-1 in a turquoise, and this can serve as convincing evidence in this aspect.

Abstract:

The newly-exposed lower strata of the Xiamaling Formation near Tielingzi Village in Jixian County contain rich siderites. This paper reports the basic geological characteristics of these siderite-rich strata in terms of the field outcrop, petrology and major elements. Studies show that the profile is characterized by black shale interbedded with silty iron-rich layers/siderite concrete layers, and also has minor siltstone. Some iron-rich strata have turned into limonite layers in the outcrop because of intense weathering. Siderite is the main iron mineral phase in the strata. Siderites can form iron concretes, showing micritic or microcrystalline granulitic textures under the microscope, or form silty ferruginous layers with almost a comparable amount of silty quartz; it can also distributed sporadically in siltstone and black shale with relatively coarse particles. There also exists very little siderite residue in weathered limonite layers. The overall features of major elements show that the strata are rich in SiO₂, TFe and TOC, but poor in MnO, CaO, MgO, P₂O₅ and S. Except for ferriciron in weathered layers, there is mainly ferrous iron in the strata. The TOC content decreases in order of siderite concrete, silty iron-rich layer, black shale and siltstone. The correlation diagram between TFe and Al₂O₃ content shows a negative correlation in iron-rich layers, while a positive correlation between them exists in normal black shale and siltstone, which suggests that iron in the former form originated from the ocean itself, while iron in the latter form originated mainly from terrigenous detritus. In addition, FeO content has a positive correlation with TOC content in fresh samples, which implies that the genesis of siderites may have some relationship with organic matter.

Abstract:

From the discovery of the first new mineral hsianghualite in 1958 to the end of 1995,74 new minerals found in China had been approved by IMA CNMMN. Among them, 2/3 were discovered after 1981. The discovery of new minerals in China has the following features:(1) With the development of analytical methods, the number of new minerals discovered per year increases gradually: from the end of 1950s to 1960s, only one new mineral was discovered every year on the average, whereas from 1980s till now, three new minerals were discovered averagely every year. (2) The structures of many new minerals have been determined. (3) Most of the new minerals are in the lower category, mainly in the monoclinic system, and perfect crystals are rare; hsianghualite has the most abundant crystal faces, whose ideal faces can reach 146. (4) Among those new minerals, silicates take the first place in number, followed by native elements, alloys, and then oxides. (5) The modes of occurrence of new minerals are varied, most of them occurring in oxidized zones of various deposits and deposits related to ma fic or ultramafic rock masses. There are a few new minerals occurring in skarn and placer deposits or even in cosmic dusts and meteorite.(6) The new minerals are characterized by wide but uneven distribution. Till now, new minerals have been discovered in 20 provinces or autonomous regions, especially in Hebei, Qinghai, Inner Mongolia and Henan. The number of new minerals found in North China is larger than that found in South Chine. (7) The number of discoverers of new minerals is in tens. The first discoverer of new mineral is Prof. Huang Yunhui, whereas Prof. Yu Zuxiang is the one who discovered the most numerous new minerals in China, totally disclosing 11 new minerals by himself or together with other experts. Most of the discoverers are members of the Chinese Academy of Geological Sciences, China University of Geosciences, and Institute of Geochemistry, Academia Sinica as well as other educational and scientific research institutions. The discovery of new minerals has promoted the development of mineralogy in China. Tens of discoverers were awardees of the National Natural Sciences Prize or the Science and Technology Progress Prize of the Ministry of Geology and Mineral Resources for the discovery and research results of new minerals in 1980s. More than 60 new mineals discovered in China were collected by the Geological Museum of China, with some of them exhibited in the Minerals and Rocks Exhibiting Room.

Abstract:

Indosinian S-type granites are widely distributed in central Inner Mongolia on the northern margin of North China landmass. Spread in nearly EW direction, the granites have formed a gigantic compound granite belt, with porphyritic biotite-admellite and moyite being the two main types. SiO2is abundant, Al2O3is 12.38%~15.34%. A/NKC (molecule ratio)>1.1, K2O/Na2O=1.1~3.1,δ=1.9~2.6,ΣREE is 45.778 ×10-6~486.501×10-6, andδEu=0.1~0.8. A series of zircon U-Pb surface ages (207~227 Ma) for the granites have been recently obtained from 1/50 000 regional geological survey. As the lithofacies and geochemical characteristics of the granites are similar to those of S-type granites, the authors conclude that the Indosinian granite in this area was formed in a post-collision setting instead of in the setting of syn-collision between North China plate and Siberia plate.