Abstract:For the first time, the HP-UHP(high-pressure to ultrahigh-pressure) garnet quartzite has been discovered from the Late Paleozoic Hongqiyingzi metamorphic supracrustal rock characterized by amphibolite facies paragneisses in Chongli County, North Hebei Province. The garnet quartzite occurs as separate tectonic lenses within garnet biotite plagioclase gneisses. It mainly consists of garnet and quartz, with a small amount of amphibole, plagioclase and barite,and possesses accessory mineral assemblage of apatite, ilmenite and copper-iron sulfide. Garnets are characterized by a high Grs+And value (23.08%~29.38%) with the end-member components of Alm_51.70~61.87 Grs_23.08~28.45 Prp_11.31~16.75Sps_1.25~2.45, belonging to almandine-pyrope-grossular garnet series. Compared with the HP granulites of North China Craton and retrograded eclogite in Chicheng County, the garnets of studied samples are richer in Grs+And and poorer in Prp than the former, and poorer in Prp than the latter. Apatite is fluorapatite with the contents of fluorine from 1.65% to 3.29%. Garnets surrounding the apatite inclusions often have radial decompression expansion joints, which is interpreted as the result of retrogression of HP-UHP metamorphic rock. Barite may be the result of decompression and dissolution of apatite during the exhumation of HP-UHP garnet quartzite, which is accompanied by the formation of copper iron sulfide. Thermobarometric computation shows that the temperature and pressure conditions for the formation of garnet quartzite are 667~710℃ and 1.189~1.279 GPa, respectively, which are consistent with the pressure properties shown by mineralogical characteristics. Zircon SHRIMP U-Pb isotopic dating obtains two different groups of ages which from detrital zircons and metamorphic zircons separately. The former has higher value of Th/U from 0.23 to 3.81, which indicates that typical of magmatic crystallized zircon, ranging from 485. 5 to 304.9 Ma and mainly from 369.8 to 348.8 Ma with a weighted mean age of 359.4±3.8 Ma. The protolith of garnet quartzite may be the terrigenous clastic rock at the continental margin, and the clastics chiefly from Late Paleozoic (~359 Ma) magmatic rocks. The latter has lower value of Th/U from 0.05 to 0.18, ranging from 277.0 to 259.4 Ma, with a weighted average age of 268.1±2.9 Ma, which is interpreted as the peak metamorphic age of HP-UHP garnet quartzite, indicating that HP-UHP metamorphism occurred in the late Paleozoic (~268 Ma), and may be related to the addition of some continental crust materials during the southward subduction of the ancient Paleo-Asian oceanic crust.

Abstract:The Oligocene to Miocene adakitic rocks are widely distributed in the southern Lhasa terrane, and their petrogenesis is crucial for understanding the post-collisional evolution of the Gangdese magmatic arc. Here, we conducted petrological, geochemical, zircon U-Pb geochronological, and in-situ zircon Hf isotopic studies of the Early Miocene biotite granites from the Quxu area in the middle segment of the Gangdese arc. The studied four biotite granites are classified as calc-alkaline, metaluminous to weak peraluminous granitoids, and show geochemical affinities to adakites, characterized by high SiO₂, Al₂O₃, K₂O and Sr contents, low Y and Yb contents, enrichment in LREE and depletion in HREE, and high Sr/Y (165~278) and (La/Yb)_N (26.6~39.7) ratios. Zircon U-Pb dating yields identical ages of 21~19 Ma, which are interpreted as the crystallization ages of the magmatic rocks. Zircon εHf(t) values ranges from -0.9~+12.7 and are mostly positive, reflecting variable contributions from juvenile and ancient crustal materials. The crustal thickness of the Gangdese arc in Early Miocene is estimated to be approximately 70~80 km based on the Sr/Y and (La/Yb)_N ratios. Our presented new data, combined with previous data, supports the proposition that the Gangdese magmtic arc underwent significant Cenozoic crustal thickening resulted from the tectonic shortening during and after the india-Asia continental collision, as well as the addition of mantle-derived magmas. We proposed that the breakoff of the deeply subducted Indian continent and/or delamination of the thickened Gangdese lithosphere resulted in the upwelling of asthenosphere and partial melting of the thickened lower crust, leading to the widespread occurrence of post-collisional adakitic rocks.

Abstract:Lithium is an important strategic metal mineral, and spodumene granite pegmatite is an important source of lithium resources. Recently, the spodumene granite pegmatite group has been newly discovered in Chaka Mountain area of the northern margin of Qaidam. This paper determines the mineral formation, evolution and mineralization age of spodumene granite pegmatites through petrography, mineralogy and chronology. The spodumene granite pegmatite has two phases of mineral assemblages. In the early stage, there are coarse-grained spodumene, coarse-grained K-feldspar, coarse-grained muscovite, coarse-grained plagioclase, coarse-grained quartz and coltan, which belong to the product of the melt crystallization stage. The late stage is composed of cookeite, Li-rich mica, wormlike spodumene and fine allomorphic quartz, which is the product of post magmatic hydrothermal metasomatism. Therefore, it can be inferred that there are two stages of lithium mineralization, and the local alteration of early spodumene and the formation of later lithium minerals indicate that there is a process of lithium activation and reprecipitation in the system. The coltan associated with spodumene gives a U-Pb age of 241.0 ± 1.3 Ma, indicating that the melt crystallization age of the spodumene granite pegmatite is the early lithium mineralization age, and the ore body is the product of Indosinian period.

Abstract:The origin of dolomite has been widely concerned by the geologists. Nowadays, microorganisms can be used to synthesize dolomite with high order in the laboratory, but the correlation between the origin of natural dolomite and the characteristics of the original sedimentary environment has yet to be fully revealed. In this study, the dolomitic carbonate sedimentary strata of Mantou Formation in western Shandong Province are selected as the research object. Through the analysis of mineralogy element geochemistry, the origin of dolomite in this formation is preliminarily judged and the paleosedimentary environment of dolomite formation is reconstructed. The relationship between them is discussed. The semiquantitative results show that the average content of dolomite in this set of strata is 52.45%. The ratio of Sr/Cu (mean value is 23.59) and Ga/Rb (mean value is 0.17) indicates that it is characterized by hot and arid paleoclimate. δ¹³C (mean value is -1.56‰) and δ¹⁸O (mean value is -6.68‰) indicate that this set of strata is marine sedimentation, and it is speculated that the average paleotemperature is 23.5℃. Furthermore, the paleoredox features a smooth transition from weak reduction to oxidation. The mean value of δ¹³C in the limestone stratum is -0.80‰, while that in the dolomite stratum is -6.52‰. The pronounced enrichment of light carbon in the sample and the combination of macro stack structure indicate that dolomite is of biological origin. In this study, the characteristics of paleoclimate, paleoredox conditions, paleotemperature and paleoproductivity in the dolomite sedimentary environment are obviously coupled with dolomite development, providing a relevant basis and indicating significance for dolomite biogenesis.

Abstract:The Tulasu Pb-Zn deposit is one of the typical base metal deposits in the Tulasu basin, Western Tian-shan, Xinjiang. The outcropped orebody is hosted in the Late Paleozoic Dahalajunshan Formation tuff and controlled by the N-S trending tensional fault. The minerals in the ores mainly consist of galena, sphalerite, chalcopyrite, pyrite, quartz and calcite. The ores are characterized by the occurrence of filling textures in open space, including cave, drusy, comb and breccia textures. LA-ICP-MS U-Pb dating on zircons in ore-hosting tuff gave weighted average age of 372.5±4.3 Ma, indicating that the tuff resulted from the subduction of North Tianshan Ocean beneath the Yili-Central Tianshan Plate. A large amount of liquid-rich two-phase aqueous inclusions are developed in the ore-bearing quartz, with homogenization temperatures and salinities in the ranges of 130~210℃ and 8.1%~16.9% NaCl_eq, respectively. In addition, vapor-rich two-phase aqueous inclusions, vapor mono-phase inclusions and daughter mineral-bearing three-phase inclusions are locally observed. Both the fluid inclusions and ore textures show that fluid boiling and subsequent temperature decrease could be the important mechanism for the Pb-Zn precipitation. Galena has narrow δ³⁴S range of -2.2‰~0.5‰, indicating a contribution of magmatic-sourced sulfur. The ²⁰⁶Pb/²⁰⁴Pb, ²⁰⁷Pb/²⁰⁴Pb and ²⁰⁸Pb/²⁰⁴Pb ratios of galena range from 18.208 to 18.264, 15.588 to 15.617 and 37.954 to 38.088, respectively, similar to those of gold deposits and ore-hosting volcanic rocks in the region, indicating that the ore-forming metals were sourced from the Dahalajunshan Formation volcanic rocks. Based on the information from geology, fluid inclusions and isotopes, the Tulasu Pb-Zn deposit is considered to be an intermediate-sulfidation epithermal deposit. For the further prospecting in the Tulasu basin, in addition to the low-sulfidation Au deposits that may occur near the identified Pb-Zn deposits, intermediate-sulfidation base metal mineralization should also be paid attention underneath the discovered low-sulfidation Au deposit and its vicinity.

Abstract:The systematic process mineralogy study of Xiahaoping gold mine in Song County, Henan Province, was carried out by means of chemical analysis, scanning electron microscope and automatic quantitative analysis (MLA), including chemical composition of raw ore, mineral composition, occurrence state of gold, dissemination characteristics of main gold-bearing mineral, and mineral liberation characteristics. The results indicate that the main valuable metal in the mine is gold, with a grade of 3.75×10^-6. The gold deposit is mainly composed of quartz, K-feldspar, albite, pyrite and ankerite, and a small amount of hematite, fluorite, dolomite and calcite. The gold in the raw ore is mainly hosted in pyrite, and most of pyrite is embedded in quartz and feldspar particles in the form of fine and micro-fine particles. The content of natural gold in the raw ore is very low, and mostly exist in the form of individual natural gold particles. Gold-bearing mineral pyrite, galena and sphalerite have a relatively high liberation degree when the raw ore is ground to P₈₀=0.074 mm (-0.074 mm particle size content accounts for 80%), which is in favour of recovering by flotation.

Abstract:Dangba spodumene deposit is located in the southeast of Sichuan Ke'eryin orefield. The No.Ⅵ vein is a newly discovered rare metal pegmatite vein in the mining area, and the ore research degree is low. In order to reasonably develop and utilize the lithium resources of the Dangba spodumene deposit and provide theoretical basis for the formulation of beneficiation process, the detailed process mineralogy research of the spodumene ore from No.Ⅵ vein of the Dangba spodumene deposit was studied by microscopic observation, electron probe microanalysis(EPMA), laser ablation plasma mass spectrometry (LA-ICP-MS), X-ray diffraction analysis (XRD), Tescan integrated mineral analyzer (TIMA), and mineral liberation analyzer (MLA). The results show that the content of Li₂O in the ore is 0.99%, the main ore mineral is spodumene, while the gangue minerals mainly include feldspar and quartz, followed by mica. Although the particle size of spodumene crystals is uneven, they are mostly concentrated in the range of medium to coarse particles (320~1 280 μm), which belongs to the ore type that is homogeneous and easy to dissociate. Lithium mainly occurs in spodumene, with a lithium-partition ratio of 97.8%. Nb and Be are associated with lithium and reach the comprehensive recycling indices. The mean content of Li₂O in spodumene is 6.88% by LA-ICP-MS. The spodumene contains FeO (0.45%~0.73%) by EPMA, and a small amount of impurities such as Fe and Mn and other are filled in the cleft and cracks of spodumene, which will limit the grade of spodumene concentrate.

Abstract:As a type of magmatic-hydrothermal deposit, porphyry copper deposits are closely related to the migration of Cu from melts to fluids. Many pieces of research have shown that chlorine plays a crucial role in this process, thereby the chlorine content directly determines the fertility of magma. The chlorine required for the mineralization of porphyry copper deposits in arc settings mainly comes from the subducting oceanic crust. But such an end-member is absent during the formation of a collisional porphyry copper deposit, the origin of chlorine in collisional settings is still uncertain. To further advance the research on the above scientific issues, this review summarizes the mineral characteristics of chlorine-containing magmatic minerals;estimates the chlorine content of fertile magma in collisional settings via apatite;calculates the exchange coefficient of amphibole in juvenile lower crust;discusses the chlorine source for porphyry copper deposit in collisional settings. The results show that: ① the Cl content in apatite, amphibole and biotite can be used to indicate the Cl content in melt or fluid;② Fertile magma from collisional settings have lower Cl content than its counterpart from arc settings, but the barren magma from arc environment have higher Cl content than its counterpart from collisional settings;③ The juvenile lower crust in Gangdese belt are the products of arc magma, and the consequent high Cl content can be inherited by the amphibole;④ The ultrapotassic magma formed by partial melting of mantle wedge during subduction of Indian continental crust may have high Cl content. And the Cl content of the residual melt will be further increased by the crystallization of amphibole, which is promoted by the addition of water-riched ultrapotassic magma.

Abstract:The serpentine jade in Kuancheng County, Hebei Province has a delicate structure and can appear in flesh red or green colors. It is called "Rehe Jade" in the local market. This article systematically analyzed it through conventional gemological testing combined with laser Raman spectroscopy, electron probe, X-ray powder diffraction, laser ablation plasma mass spectrometry, and visible light absorption spectroscopy. Its radiation safety was tested by gamma spectrometer. The results show that the refractive index and relative density of the flesh red samples are both low, with 1.54~1.55 and 2.33~2.43. The flesh red samples contain main mineral of clinochrysotile and auxiliary minerals of calcite and diopside with fiber interwoven texture, and column-grain interwoven texture, and residual biological skeleton texture can be seen locally. The content of Fe and Mn in flesh red samples are relatively high, ranging from 184.9×10^-6~951.7×10^-6 and 106.4×10^-6~287.3×10^-6,respectively. The green sample has the refractive index of 1.55~1.56 and the relative density of 2.58~2.62. The green samples contain main mineral of antigorite and auxiliary minerals of talc and mackinawite, with more delicate fiber interwoven texture. The content of Fe in green samples is extremely high, ranging from 5 979×10^-6~6 359×10^-6. Combined with visible light absorption spectrum test, it is considered that the comprehensive effect of Fe³⁺, Fe²⁺, and Mn³⁺ is the main reason for the appearance of flesh red in samples, while the effect of Fe²⁺ and Fe³⁺ is the main reason for the green color. The radioactivity test result shows that the internal and external radiation indexes, and specific activity values of Kuancheng serpentine jade are lower than the standard requirements, and the sample has no radioactive hazard to the human body.

Abstract:The study of the chemical composition of mineral inclusions is of great significance in geology, mineralogy, and hydrocarbon exploration. The main methods currently investigated for the analysis of the chemical composition of inclusions are laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS), electron probe microanalysis (EPMA), laser Raman spectroscopy (LRS), Fourier transform infrared spectroscopy (FTIR), proton-induced X-ray emission spectroscopy (PIXE), synchrotron X-ray fluorescence spectroscopy (SXRF) and (conventional) secondary ion mass spectrometry (SIMS), etc. This paper briefly introduces the analytical characteristics of the above methods, focuses on the principles, characteristics, and technical advantages of time-of-flight secondary ion mass spectrometry (TOF-SIMS), which has wide potential for the characterization of mineralogical samples, and summarizes the progress and problems of the application of TOF-SIMS for the analysis of the chemical composition of mineral inclusions by domestic and foreign scholars, and gives an outlook on related fields.