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.

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 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:

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:

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:

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:

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:

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:

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:

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:

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:

There are several types of xenoliths, such as monzonite, quartz diorite porphyry, black rock and greisen schlieren, in the alkali feldspar granite of the Yaogangxian tungsten deposit, Hunan Province. The xenoliths are different in geological and geochemical characteristics, sources and evolution paths, which implies the genesis and magma evolution history of the Yaogangxian granite. In this paper, the authors studied the petrology, geochemistry of the xenoliths, alkali feldspar granite, and monzonite batholiths formed in late Jurassic period. It is detected that the monzonite inclusion (Ⅰb) came from early crystallization of deep magma chamber similar to the monzonite batholith. The quartz diorite porphyry and black rock xenoliths seem to have been the residue of Precambrian metamorphic rocks in the melting. The greisen schlieren resulted from the transition from the alkali feldspar granite stage to the magma-hydrothermal stage. The fine biotite granite xenolith (Ⅲb) in the quartz porphyry was captured from the supplementary granite which was differentiated from the main magma, or from the granite pluton formed from the supplementary rocks. The granite (Ⅰ) was rich in volatiles, which resulted in strong contamination of the xenoliths, and a certain amount of fluorite, mica, tourmaline and sulfide minerals formed in the xenoliths. The Yaogangxian granite is a product of the intrusion of highly fractionated magma derived from the magma chamber equivalent to monzonite batholith. The quartz porphyry magma directly resulted from the residue of segregation from fractional crystallization of magma chamber, rather than from the alkali feldspar granite of Yaogangxian. It is suggested that the magma evolved in order of magma chamber (main) (coarse monzonite) → fine biotite granite (supplementary) → alkali feldspar granite → magma-hydrothermal transition fluid (tungsten mineralization) → quartz porphyry veins.

Abstract:

Two kinds of carbonate hosted Pb-Zn deposits, namely carbonate-rich Pb-Zn deposits and fluorite-rich Pb-Zn deposits, extensively exist in the same Pb-Zn metallogenic belt in the world according to the classification based on gangue mineral assemblages. The relationship between the two kinds of deposits remains unclear. In the middle part of the 'Sanjiang' metallogenic belt in the Tibetan Plateau, the Dongmozhazhua carbonate-rich Pb-Zn deposit and the Mohailaheng fluorite-rich Pb-Zn deposit occur in the same carbonate-hosted Pb-Zn ore concentration area. In the two deposits, the carbonate strata are host rocks, the thrust faults are the main ore-controlling structures, the main orebody attitudes are of stratabound type, and sphalerite and galena are the main ore minerals. However, calcite and dolomite are the main gangue minerals in the Dongmozhazhua deposit while calcite and fluorite are the main gangue minerals in the Mohailaheng deposit. The geochemical features of rare earth elements (REE) in calcium-bearing minerals are different in the two deposits. The REE values of calcite in the Dongmozhazhua deposit are mainly characterized by obvious fractionation of LREE and HREE, enrichment of LREE, negative Eu anomalies and 'V'_shaped curves of chondrite-normalized REE patterns with right deviation. In contrast, the REE values of calcite and fluorite in the Mohailaheng deposit are chiefly characterized by no obvious fractionation between LREE and HREE, negative Eu anomalies and 'M'_shaped curves of chondrite-normalized REE patterns with right deviation. The total concentrations of REE (∑REE) of calcite (0.46×10^-6～10.79×10^-6) in the Dongmozhazhua deposit are higher than those in the Mohailaheng deposit (0.25×10^-6～5.88×10^-6). The geochemistry of the REE indicates that calcium-bearing minerals in the two deposits were all precipitated from a kind of hydrothermal fluids which had nothing to do with igneous activities. The salinity and reducibility of the fluids decreased with the sulfide precipitation. The two kinds of deposits had similar hydrothermal fluids; nevertheless, there existed another kind of fluid for the Mohailaheng deposit, which was a kind of fluorine-rich fluid from deep metamorphic basement. This fluorine-rich fluid controlled the location of the fluorite-rich carbonate hosted Pb-Zn deposits and could be used to explain the phenomenon why this kind of Pb-Zn deposits were more easily precipitated near the main thrust faults and the lowest carbonate strata in the region. The result achieved by the authors could answer the question why the carbonate-rich Pb-Zn deposit and the fluorite-rich Pb-Zn deposit can occur in the same region and same time in the world.

Abstract:

Beishan area is located in the west of Inner Mongolia and Gansu Province, which is the conjunction zone of Tarim plate, Sino-Korea plate and Kazakhstan plate and plays an important role in the study of the Central Asia Orogenic Belt (CAOB). The relationship of the three plates is so complicated that there exists much controversy concerning Paleozoic tectonic evolution in this area. Granitoids, especially Late Paleozoic granitoids, are widely distributed in Beishan area, which are of great importance in the study of Paleozoic magmatic evolution. Through analyzing the spatial and temporal distribution of the Late Paleozoic granitoids, we can find the relationships between these granitoids and explore the crust-mantle interaction in Beishan area during Late Paleozoic, which is important for determining the geotectonic evolution of this area. In the southern belt of Beishan, the most important tectonic event in Permian is the formation of Yin'aoxia rift zone, which makes the study of Late Paleozoic evolution more complex. The results of studying Xijianquanzi granite lying in the southern belt of Beishan in such aspects as major elements, trace elements, REE and LA-ICP-MS zircon U-Pb geochronology have provided new evidence for regional tectonics. The LA-ICP-MS zircon U-Pb age of Xijianquanzi granite is 266.1±2.2 Ma, and the Hf modal ages are 746～871 Ma. εHf(t) values are +1.3～+4.7 with an averageof +2.7, which implies the mixture of crustal and mantle.derived magmas. This feature coincides with that of other areas in the Central Asia Orogenic Belt (CAOB). Therefore, the granites in the belt may have similar magma sources. The granitic body mainly consists of monzonitic granites which belong to alkaline series with high content of SiO2 (74.33%～76.67%), Na2O+K2O (9.26%～9.57%, NK/A=0.9～1.08) and K2O (Na2O/K2O<1) . In addition, chondrite-normalized REE patterns and primitive mantle normalized geochemical patterns of all samples are approximately parallel to each other, which shows that they evolved from the same magma source. Chondrite-normalized REE patterns of the intrusive body are of “V" types and show enrichment of light rare earth elements (LREE) with low ratio of (La/Yb) N (3.18～5.29) and negative Eu anomalies (δEu =0.10～0.16). Except for Eu, the abundance of rare earth elements are demonstrably over 10 times that of chondrite. Depletion of Nb, Ba, Sr, Ti, P and enrichment of Rb, Th, K can be seen in the spidergram. Based on regional geological and geochemical characteristics, the authors have reached the conclusion that the Xijianquanzi intrusive body is an alkali-rich potassium-high granite which is a mixed product of crustal and mantle-derived magmas and was formed at the stage of rifting in the post-collisional extensional period, affected greatly by Yin'aoxia rift zone. This implies that the area entered into the stage of rifting in Middle Permian.