Abstract:Late Triassic basic rocks were discovered in the Xiacangjie area of Songpan-Ganzi terrane, and their petrography, geochemistry and baddeleyite U-Pb chronology were studied. The basic rocks are composed of basalt and diabase, both of which belong to calc-alkaline series with strong alteration, and the formation age of diabase is 208.0±7.0 Ma. La/Nb value is 1.13～1.95, La/Ta value is 7.96～25.79, TiO₂ content is 1.51%～2.22%, and Zr/Nb value is 11.35～16.33, indicating that the magma of the basic rocks originated from the mixed source region of the lithospheric mantle and the asthenosphere mantle. According to the calculation results of the (Yb/Sm)_P-(Tb/Yb)_P model, it is speculated that the basic rocks in the Xiacangjie area may be derived from the partial melting of about 5% of the spinel and garnet transition phase (garnet accounts for about 0~25%) in the lithospheric mantle induced by the asthenospheric materials. Ancient baddeleyites captured in the rocks are found. Light rare earth elements are enriched in the rocks, heavy rare earth elements are depleted, and Nb, Ta and Ti elements are weakly depleted. Combined with the regional geological data, it is considered that Songpan-Garze terrane should have a continental crust basement, and its tectonic environment in the Late Triassic (<211 Ma) was the post-collisional intraplate extension environment.

Abstract:Phonolite represents the final evolution product of the sodic alkaline magma in the continental volcanic province, and revealing its genetic mechanism is of great significance for understanding the magmatic evolution process of the continental volcanic province. A systematic mineralogical, petrological and geochemical study of the phonolite exposed in the Tuoyun Mesozoic-Cenozoic volcanic basin in the Southwestern Tianshan Mountains, China, has been carried out to reveal the magma series and magmatic evolution process of Tuoyun volcanic rocks. Tuoyun phonolite is characterized by the presence of alkali feldspar, clinopyroxene, fayalite and amphibole phenocrysts, and nepheline can be seen in the groundmass. In terms of geochemical composition, Tuoyun phonolite is characterized by high Na₂O (7.9%~8.6%) and K₂O (5.2%~6.3%). The total rare earth element ranges from 408×10^-6 to 470×10^-6, and the chondrite-normalized REE patterns have obvious Eu anomaly. In the primitive mantle-normalized trace element spider diagram, the samples show negative anomalies of Ba, Sr, P, Ti and positive anomalies of Nb, Ta, Zr and Hf. The depleted Nd isotopic composition shows that phonolite is genetically related to the associated basanite. Based on the MELTS thermodynamic simulation, the phonolite could be produced by the basanite through fractional crystallization of alkali feldspar(36%), clinopyroxene (21%), spinel (10%), fayalite (6%) and amphibole (5%). Further EC-AFC modeling exhibits that the phonolites has suffered crust contamination to some degrees(10%) during the evolution. The study shows that the Tuoyun volcanic rocks belong to the peralkaline series of basanite-phonotephrite-phonolite, and the phonolite represents the final evolution product of the peralkaline rock series in Tuoyun volcanic basin.

Abstract:Critical metal minerals are recently proposed resource concept worldwide and are important to the deve-lopment of strategic industries, but the level of awareness is still low. The Luozha pluton is located in the east of the Himalayan belt and invaded the Southern Tibet detachment system. On the northeast of this pluton, mica schist is captured by the tourmaline-bearing leucogranite. The mica schist is mainly composed of phlogopite, chlorite and minor biotite. Whole-rock element geochemical data indicate that the mica schist contains higher Al₂O₃ (13.38%~14.32%), K₂O (6.09%~9.66%), FeO^* (27.11%~30.09%), MgO (15.25%~17.21%), TiO₂ (0.09%~0.26%), and is enriched in Li (650×10^-6~1 031×10^-6), Rb (1 649×10^-6~2 773×10^-6), Cs (98×10^-6~229×10^-6), Tl (5.7×10^-6~12.1×10^-6), Ga (121×10^-6~148×10^-6). The geochemical data of phlogopite show that similar to the whole rock, phlogopite also is enriched in Li-Rb-Cs-Ga, and these critical metal elements are incorporated into phlogopite by replacement of K. Chronological data indicate that zircon records widespread detrital age and Cenozoic metamorphic events. Therefore, it can be concluded that the original rock of mica schist in the Luoza area is sedimentary rock, which was captured during the invasion of leucogranite and underwent low-level metamorphism. The phlogopite mineralization reported in this paper is a new type of lithium ore genesis: metamorphic transformation type. The discovery of the metals thallium and gallium in the Himalayan orogenic belt suggests that critical metals also have mineralization potential in addition to rare metals. Our data suggest that the Himalayan belt is another important target area for the exploration of critical metals. This paper provides new ideas for establishing metallogenic models of critical metals in the Himalayan orogenic belt. It is necessary to strengthen the exploration of critical metals in sedimentary or metasedimentary rocks in the Himalayan orogenic belt and the other orogenic belts in the future.

Abstract:Carbonate minerals are the most common hydrothermal alteration minerals in Mississippi Valley-type lead-zinc (MVT) deposits. They record the characteristics of ore-forming fluids and their elemental or isotopic compositions can be a vector to ore bodies. However, there are different genesis types of carbonate minerals in MVT deposits, so it is difficult to distinguish ore-related carbonate minerals from those ore-unrelated carbonate minerals only by virtue of petrographic observation. As such, additional geochemical information is helpful. This paper carried out borehole assay, petrography observation, analyses of C-O-Sr isotopes and in situ trace elements for ore-related and ore-unrelated calcite from the giant Duocaima MVT Pb-Zn deposit in Qinghai province of China. The ore-unrelated calcite that formed earlier than Pb-Zn mineralization (pre-ore, Cal1) is spatially independent of the ore zones and distributed throughout the country rocks, i.e., the Late Permian Jiushidaoban Formation limestone. It shows dark brown to brownish yellow color in cathodoluminescence (CL) images without obvious oscillatory zone. The ore-related calcite precipitated slightly younger than Pb-Zn mineralization (syn-ore, Cal2) and mainly occurs within and above the ore zones. It has granular crystal shape and the assemblage with residual vugs, with dark yellow to bright orange color in CL images with oscillatory zone. Relative to Cal2, Cal1 is more similar in C-O-Sr isotopes and elemental compositions to the wall-rock limestone, suggesting the compositions of Cal1 were greatly affected by the wall rocks during the water-rock interaction. Compared with Cal1, Cal2 has higher Mn, Fe, Zn, and Pb concentrations and U/Th and V/Cr ratios, lower Mg and Sr concentrations and LREE/HREE ratios, and weaker negative Ce anomaly. It indicates that the Cal2-related ore-forming fluid has higher temperature and relatively reduced conditions. Together with data from MVT Pb-Zn deposits worldwide, it shows that higher Mn, Fe, Zn (possibly including Pb) concentrations and lower LREE/HREE ratio can help identify ore-related carbonate minerals in MVT deposits.

Abstract:The immiscibility between silicate melt and sulfate melt widely exists in the nature, which is closely related to the enrichment of metalic elements and mineralization. Currently, the experimental study on the immiscibility process between basic silicate and sulfate melt is still weak, as well as the partition behavior of elements in such process. In this study, we designed a geochemical simulation experiment, which is kept normal pressure and 1 200℃ for 12 hours, and then cooled to room temperature within 5 minutes. Cooled samples were analyzed in detail by micrography, EPMA and in-situ LA-ICP-MS. The results show that sulfate can be miscible with basic silicate melt in a certain proportion at 1 200℃, and cooling will cause immiscibility between them. After cooling, the sample forms two distinct layers. The upper layer is mainly sulfate phase and contains magnesioferrite and forsterite crystals. The lower layer is mainly silicate glass phase, and contains sulfate globes and mineral crystals such as magnesioferrite, hauyne and hematite. The crystallization separation of hauyne caused by cooling and the immiscibility between sulfate melt and silicate melt may be the reason for the low S content and relative reduction of sulfur rich and relatively oxidized mantle derived basic shallow intrusive and volcanic rocks. The analysis results of major and trace elements show that Na, Ca, K and REEs tend to enter the sulfate melt in the immiscibility process. The content of rare earth elements in early immiscible sulfate melt is not high, which has little effect on the content of rare earth elements in silicate melt. However, the content of rare earth elements in the immiscible sulfate melt formed in the late stage and low relative temperature is significantly higher than that in the early exsolved sulfate melt and residual silicate melt. The partition behavior of metalic elements in sulfate melt has a certain correlation with electronegativity, and the partition coefficient increases with the decrease of electronegativity. The partition behavior of rare earth elements shows that sulfate melt plays an important role in the enrichment of rare earth elements, but it can not cause the strong differentiation of light and heavy rare earth elements.

Abstract:Provenance analysis is an important way to understand basin mountain evolution. Understanding the provenance of the Upper Permian Xuanwei Formation in the southwest margin of Sichuan Basin is of great significance for reconstructing the evolution of the Late Permian Yangtze Craton perimeter. In this paper, the petrology and whole-rock geochemical analyses of mudstone and sandstone at the top of Xuanwei Formation in the Emeishan area are analyzed, and the provenance, sediment environment and tectonic setting are studied. The mudstone of the Xuanwei Formation is mainly composed of clay minerals with medium SiO₂ content (average 49.42%); the sandstone is mostly composed of volcanic rock fragments, containing a small amounts of quartz and feldspar, with medium SiO₂ content (average 40.12%), belonging to the greywacke series. Mudstone and sandstone of Xuanwei Formation have light rare earth element enrichment, heavier rare earth elements are more right-leaning. Compared with the continental upper crust, trace elements are relatively rich in high field strength elements (such as Nb, Zr) and relatively depleted in large ion lithophile elements (such as Sr, Ba). Combined with the published data of Permian sediments at the perimeter of the Yangtze Craton, it is considered that the source area of sediments at the top of Permian Xuanwei Formation experienced strong chemical weathering, and the depositional paleoenvironment was an oxygen-rich freshwater environment. The sediments at the top of Xuanwei Formation not only came from the Emeishan high-Ti basalt transported near the source, but also supplied by the Yangtze Craton. The western margin of the Yangtze Craton was deposited on the active continental margin during the Late Permian.

Abstract:The Alxa area in Inner Mongolia has experienced hundreds of millions years of geological activities, producing Gobi agate with rich colors and compact structure. The gem mineralogical characteristics and coloring causes of green Gobi agate were studied by conventional gemological test, polarizing microscope and scanning electron microscope observation, X-ray diffraction, electron microprobe analysis, infrared spectrometer and ultraviolet-visible-near infrared spectrophotometer. With naked eyes, the agate is dark green to brown green, translucent to opaque. The relative density, refractive index and Mohs hardness are all in line with the characteristics of quartzite jade stone. Through microscopic observation, celadonite is enriched in the surface layer and grows radially inward. Both calcite and quartz have cryptocrystalline texture. Through scanning electron microscope, celadonite is distributed between quartz and calcite in granular form. X-ray diffraction analysis shows that the mineral phase composition of green Gobi agate is quartz, calcite and celadonite. The EPMA results show that the main chemical composition of celadonite are SiO₂, FeO, Al₂O₃, K₂O and MgO. Infrared spectrum analysis also shows that there are characteristic peaks of corresponding groups of celadonite. The test results of surface celadonite under UV-Vis-NIR spectrophotometer show the characteristic spectra of Fe²⁺ and Fe³⁺. The charge transfer between Fe²⁺ and Fe³⁺ is the main reason for its coloration. Celadonite is the main chromic mineral of green Gobi agate.

Abstract:It is extremely effective that the mineral or fluid inclusions can preserve the information of either the chemical environment, temperature or pressure, which is during the growth of the host minerals. A good correlation can be proved between the molecular vibration of quartz inclusions in garnet and the ambient pressure, which is during high pressure metamorphism. It has been proposed, a quartz inclusions elastic Raman shift barometer, which is according to this characteristic. The principle is to calibrate the residual pressure by using the microlaser Raman spectrometer analysis of quartz inclusions and then recover the entrapment pressure conditions by combining the elastic modeling of quartz and garnet host. It belongs to the mineral physical spectroscopy barometer. Here, we introduce the basic principle and method of calculating metamorphic pressure by using the Raman shift of quartz inclusion and analyze the applicable conditions and limitations of the difficult method. The quartz inclusion Raman shift barometer is an effective method to restore the formation temperature and pressure of metamorphic rocks and has a wide application prospect.

Abstract:The paper is a systematic collection of 90 new minerals approved by the Commission on New Minerals, Nomenclature and Classification (CNMNC) of the International Mineralogical Association(IMA) in 2012, by listing mineral name, crystallochemical formula, crystal structure data, physical and optical properties, locality of origin and occurrence, relationship with other minerals, source of mineral names, chemical reaction and spectroscopic characteristics. It's very meaningful that Chinese names of 90 new minerals have been examined and revised under the authority of Chinese Commission of New Minerals and Mineral Names. As a part of the comprehensive introduction to discovery and research of new minerals in the world, this paper will provide reference for the work of discovering, researching and naming new minerals in China and promote the standardization of Chinese names of mineral species.