Abstract:The Lincang batholith located in southern Three River region is the largest felsic intrusion in southwestern China. The Mengku pluton is one of the major alkali feldspar granite intrusions within the Lincang batholith. Based on field investigations, the authors studied the geochronology, petrology and geochemistry of the Mengku pluton. The results show that the pluton was emplaced in the Middle Triassic (236.2±3.7 Ma), much older than the previously conceived Early Cenozoic. This means that the distribution and abundance of magmatism of the Cenozoic intrusion province in the southern Three River region should be reevaluated. After a careful examination of whole-rock major and trace elements, Sr isotope and zircon trace elements, the authors believe that the Mengku pluton was of S-type affinity and originated from high extent of fractional crystallization of melts generated by metasedimentary crustal anatexis. The Mengku pluton is part of the Lincang batholith. The alkali feldspar granite is another important rock type that has never been reported in the Lincang batholith, which was previously considered to be composed of biotite monzogranite and granodiorite.

Abstract:The Erchangfang plutons at the Keketuohai area in southern Altay orogenic belt are mainly composed of biotite granodiorite, and the authors studied their LA-ICP-MS zircon U-Pb ages and major and trace elements. The results shows that the zircon ²⁰⁶Pb/²³⁸U weighted average age is 398.0±3.5 Ma(MSWD=1.3), indicating that the plutons were formed in the early-middle Devonian period. The SiO₂ values range from 65.40% to 69.31%, σ from 1.27 to 1.65, and A/CNK from 0.92 to 1.02, suggesting intermidiate-K, calc-alkaline, metaluminous rocks. In addition, they are enriched in LILE (Cs, Rb, Th, U) and LREE, with obvious negative anomalies of HREE and HFSE (Nb, Ta, Zr, Hf) and Eu (δEu=0.48～0.65), thus resembling granitoid rocks formed in island-arc. Combined with the data obtained from the southern margin of Altay, the authors hold that the Erchangfang plutons were generated by partial melting of the lower crust underplated by mafic magma of the mantle in an island-arc setting of active continental margin, accompanied by magma mixing.

Abstract:Eclogites and blueschists are exposed mainly as slices or variable tectonic lenses within garnet phengite schists in Habutengsu area, southwestern Tianshan Mountains, Xinjiang. In this paper, petrography, mineralogical chemistry and p-T conditions of the eclogites and blueschists were studied in detail. The eclogites could be divided into four groups, i.e., glaucophane eclogites, paragonite eclogites, epidote eclogites, and glaucophane-garnet amphibolites (retrograde eclogites), whereas blueschists could be divided into three groups, namely glaucophane-bearing garnet-muscovite-albite schists, garnet-muscovite-glaucophane schists and garnet-muscovite-glaucophane-quartz schists. Major mineral assemblages are Grt+Omp+Pg+Ep for the fresh eclogites, Grt+Gln+Amp for the retrograde eclogites, and Grt+Gln+Phe+Pg+Ab+Qtz for the blueschists. Porphyroblastic garnets show perfect prograde zoning, with X_Mn and X_Fe deceasing and X_Mg and X_Ca increasing from the core to the rim, which indicates a process of increasing temperature and prograde metamorphism. According to the paragenetic assemblages of inclusions within garnet as well as in matrix, four stages of metamorphism were recognized, viz., pre-peak lawsonite-blueschist facies metamorphic stage, peak eclogite facies stage (t=543～579℃, p=1.5～1.6 GPa), retrograde epidote-blueschist facies stage (t=～450℃, p<1.0 GPa), and post-peak retrograde blueschist-greenschist facies stage (t<400℃, p<0.5 GPa). The p-T pseudosection calculation shows that the peak metamorphic conditions were 520～550℃ and 1.7～1.9 GPa for the eclogites, and 520～620℃ and 1.7～2.3 GPa for the blueschists, similar to the results of traditional geothermobarometer. Previous researchers reported coesites preserved in some eclogites and country rocks, which suggested that partial eclogites and partial country rocks within the southwestern Tianshan metamorphic belt underwent UHP metamorphism, but this conclusion is inconsistent with the results constrained by the eclogites in this study. The possible reasons might be as follows: ① the eclogites were affected by later thermal events, which led to the partial variation of both minerals and whole rock compositions. On the basis of the changed whole-rock compositions, the traditional thermobarometer Grt-Cpx-Phe and phase equilibrium simulations certainly show relatively low pressure results, and ② not all eclogites from the southwestern Tianshan underwent UHP metamorphism, and HP-UHP eclogites may represent the metabasites subducted to different depths.

Abstract:Based on thin section analysis, scanning electron microscopy analysis, cathodoluminescence analysis and physical property analysis, the authors studied the sandstone composition, the relative importance of chemical diagenesis and physical diagenesis, authigenic minerals, pores and physical properties to reveal the formation mechanism of Chang 6 sandstone reservoir with low-permeability in the upper Triassic Yanchang Formation of Huaqing area, Ordos Basin. The authors selected 15 diagenetic parameters to quantitatively evaluate and divide the diagenetic facies of Chang 6 sandstones on the basis of an integrated study of sedimentary facies and diagenetic processes. The results show that the Chang 6 sandstones have experienced strong physical diagenesis and weak chemical diagenesis, and hence the primary pores are the most important reservoir space; in addition, it is the compaction and calcite cementation that cause the porosity reduction and poor reservoir quality. The reservoir quality of sandstones affected by the northeastern provenance is significantly better than that affected by the southwestern provenance. Furthermore, the southwestern sandstones, showing weak cementation and strong compaction diagenetic facies and strong calcite cementation and moderate-strong diagenetic facies, have poor reservoir quality, whereas the northeastern sandstones, especially the middle sand bodies, which show chlorite cementation and weak-moderate compaction diagenetic facies, have good reservoir quality and are thus recommended as preferred exploration zones.

Abstract:Located in Tethys Himalayan sub-terrane, the Zhaxikang Pb-Zn-Ag-Sb polymetallic ore deposit is not only a representative ore deposit in the antimony-gold metallogenic belt but also among a few deposits that have reached large-scale reserves. The Zhaxikang deposit has abundant assemblages of ore minerals and gangue minerals with complex ore-forming process, which indicates that recognition of ore-formaing stages and periods is very important for the study of the ore-forming process and also of indication significance for the understanding of the regional metallogenic belt. Based on summarizing the previous cognitions of the mineralization process as well as mineral paragenetic assemblages and crosscutting relationship of ore veins, the authors formulated a model for 3- period, 6-stage and 13-sub-stage complex ore-forming process, which indicates that the metallogenic process of the Zhaxikang deposit resulted from superimposition and remobilization of several stages of ore fluids, and the later antimony-bearing fluid was superimposed upon and reconstructed the pre-existent lead-zinc ore body. The overprinting and remobilization process has universal meaning for the study of the regional metallogenic belt and suggests the potential of finding lead-zinc deposits in the Tethys Himalayan Sb-Au metallogenic belt.

Abstract:Located in the eastern part of the West Tianshan Mountains, the Airikenqiken ore district, discovered in recent years as a Cu-Mo deposit, possesses an important position in the Middle Asia metallogenetic belt. The main ore-hosting rock is monzogranite. The deposit possesses four banded alliterated belts, namely potassic belt, silicification belt, phyllic belt and propylitization belt, controlled mainly by fractures in the south margin of Nalati. The authors analyzed K-feldspar in ore veins and sericite in rock bodies, and the K/Ar dating results show that the age of metallogenesis is 268.35±4.05 Ma and that of the mineralization is 321.43±4.24 Ma. Elements analyses show that the magmatic body has high Si (SiO₂=71.01%～73.94%), high alkali (Na₂O+K₂O=5.53%～7.80%), low Ca (CaO=1.95%～2.93%), high Sr (>417×10^-6), and low Y (<12.3×10^-6), with the enrichment of LILE (Ba, Th, Rb, K) and depletion of HFSE (Nb, Ta, Ti), whereas trace elements characteristics imply lower-crust related genesis. In addition, fluid inclusions in this deposit are mainly directional fluid intrusions, and most of them are of metamorphism genesis. They have low-temperat ure and low- salinity characteristics, quite different from features of typical porphyry deposits. The authors hold that this district didn't form deposit during magmatic intrusion in Carboniferous period, but it experienced pre-enrichment of metals. Hydrothermal process in Permian period played the most important role in the formation of the ore deposit, which was closely related to the ductile shear zone in that the ductile shear process provided channel and force for the upward migrating ore-forming hydrothermal fluids.

Abstract:Phurcalite found in the Zhutongjian deposit of the Xiazhuang uranium ore field in northern Guangdong Province is associated with microcrystal quartz and meta-autunite in space. The mineral occurs as fibrous, fascicular and radiating aggregates and is bright yellow and transparent with vitreous luster. Its streaks are light yellow in color. The Mohs' hardness is about 3. Phurcalite has a perfect cleavage on {010}, good cleavages on {100} and {001}, and greasy luster conchoidal fracture. Under plainlight, phurcalite is light yellow, and it assumes high order bright interference color under crossed nicols. Phurcalite is a symmetrical extinction, biaxial negative, and positive elongation mineral. The chemical composition of phurcalite (EPMA, average of 15 points) is UO₃ 68.64%, P₂O₅ 11.70%, CaO 9.21% and impurity 0.28%, with H₂O 9.25%, totaling 99.26%. According to the data O=16, the empirical formula should be (Ca_2.02, K_0.05, Mg_0.01)_2.08(UO₂, TiO₂, PbO)_2.97O_1.97(PO₄)_2.03· 6.32 H₂O. On the basis of the analyses of XRD, the system of phurcalite is orthorhombic, the space group is Pbca, and the unit cell parameters are a=1.742 3(5) nm, b=1.603 2(4) nm,c=1.359 9(2) nm; α=β=γ=90°, and V=3.798 64 nm³. Furthermore, the maxima (in cm^-1) of the obtained infrared-absorption spectrum were observed: 3 427.10, 1 622.05,1 062.62, 973.26 and 890.91. These features are very similar to those of the known phurcalite.

Abstract:The plagioclase crystals in trachyandesite from the Late Jurassic Manitu Formation in Wuchagou of the Da Hinggan Mountains have obvious corrosion phenomenon and well-developed zoning texture. The feldspar nomenclature diagram shows that the plagioclases consist mainly of labrador and surbodinately oligoclase and andesine. The variations of the minor elements (Fe, Sr, Ba, etc.) composition can determine the formation mechanisms of reverse zoning on the basis of investigating the causes of plagioclase zoning. According to the evidence from the electron microprobe analyses and textures of the plagioclase, the authors also analyzed the variation curves of trace elements Fe and Sr with An and, on such a basis, reached the conclusion that the zoning resulted from three magma mixing events in the process of plagioclase crystallization.

Abstract:The Yaochang and Sishanling iron deposits are located respectively in southern and northwestern margin of North China block. A systematic study of chemical composition, pyroelectricity and oxygen isotope components of magnetite samples revealed some important information. The magnetite samples are all characterized by high values of Ni and low values of Co, indicating that the mineralization was related to deep materials. They have similar PAAS-normalized REY distribution patterns and are enriched in light REE, with moderately positive Eu anomalies and lightly negative Ce anomalies; nevertheless, the magnetite in the Sishanling iron deposit has a more obvious Eu positive anomaly. The average δ¹⁸O values and thermoelectric coefficients of magnetites from these two deposits are 7.1‰ and 2.3‰, -59.05 μV/℃ and -57.18 μV/℃ respectively. Based on chemical analyses and other typomorphic peculiarities of magnetite, the authors hold that the magnetite is of the volcanic-sedimentary metamorphic origin, but magnetite samples from the Sishanling iron deposit have relatively low isomorphic extent and a more homogeneous structure. A systematic comparison with the main terrains in North China block in such aspects as oxygen isotope and REE compositions indicates that the oxygen isotope components of rich and poor ores show regularity related to different mechanisms of mineralization and enrichment. The values of δ¹⁸O in poor ores are related to the metamorphic grade of different terrains, consistent with oxygen isotope fractionation. Systematic investigation of the Ce/Ce^* and Eu/Eu^* ratios of BIFs from Archean-Peleoproterozoic strata in North China block indicates relatively low redox levels in the seawater, but with the growth of North China block, the oxygen-free environment exerted less effect on the formation of BIFs, which was unfavorable for the generation of banded iron formation.

Abstract:The Jinchanghe deposit is a concealed mineral deposit located in the northern part of the Baoshan massif in Sanjiang region. The ore bodies occur in the skarn and marbleized limestone of Hetaoping Formation in lamellar and stratoid forms, and are controlled obviously by the NW-trending F2 fault and the NE-trending F10 fault. Four ore-forming stages, i.e., skarn stage, retrograde alteration stage, quartz sulfide stage and carbonate stage, were recognized based on the field relationship and mineral associations. Metallic minerals consist mainly of magnetite,chalcopyrite,pyrrhotite,pyrite,galena and sphalerite,whereas gangue minerals are composed of garnet, pyroxene, pyroxene, epidote, chlorite and ilvaite. With skarn minerals as the study objects and by using electron microprobe technology, the authors investigated the mineralogical characteristics. Electron microprobe analyses show that most of skarn minerals in the Jinchanghe ore deposit are calcium skarn minerals, and the end member of garnet is dominated by andradite, together with minor grossular. The clinopyroxene comprises hedenbergite and diopside. The amphibole in the Jinchanghe deposit includes actinolite, ferroactinolite and grunerite. Ilvaite contains relatively high iron and is commonly associated with magnetite. Skarn minerals are manganoan minerals in small amounts, comprising spessartine, manganoan hedenbergite, manganoan actinolite and manganoan ilvaite. There exists vertical alteration zonation from the depth to the shallow part and horizontal alteration zonation from east to west, varying in order of remote and buried pluton→calcium skarn zone with Fe→calcium skarn zone with Cu→manganoan skarn zone with Pb and Zn→marbleized limestone. The alteration zone of the Jinchanghe ore deposit indicates that there is a higher temperature and oxidation zone in the middle part of the vertical profile and in the east part of the horizontal profile. Compared with zoning models of skarn minerals in polymetallic ore deposits both in China and abroad, it is inferred that the remote magmatic hydrothermal fluid intruded through the cross-cutting zone of the two faults, and the infiltration effect occurred in the surrounding rocks, thus forming the ore bodies. The Jinchanghe ore deposit is therefore considered to be a copper-zinc-iron polymetallic concealed deposit in the distant contact zone.

Abstract:The Jilongshan Au deposit is a typical skarn deposit in southeastern Hubei Province, but its skarn mineralogy research is insufficient. The Jilongshan skarn Au deposit is exposed within the dolomitic limestone of Triassic Daye Formation and the Yanshanian granodiorite porphyry. The metal minerals mainly include natural gold, chalcopyrite, pyrite, molybdenite, bornite, sphalerite, galena, orpiment, realgar, and magnetite, whereas the skarn minerals are mainly garnet, diopside, epidote, wollastonite and phlogopite. The authors studied in detail the skarn mineralogical characteristics of different stages and conducted the electron microprobe analysis (EMPA). The results show that the garnet belongs to the calcium And-Gro series, the pyroxene is diopside, and the calcium-iron garnet-diopside gold-rich skarn combination was formed under the condition of high oxygen fugacity and relatively low acidity, with copper, gold metallogenic specialization. Along with the fluid evolu- tion, ore is associated with skarn in space, time and origin. In combination with the development of the porphyry ore body, the authors hold that the Jilongshan gold deposit may have a unified porphyry-skarn mineralization system, and there exists great prospecting potential in the depth.

Abstract:In this paper, the authors investigated in detail chemical composition of clinopyroxene from the Late Cretaceous shoshonite in Guangfeng and Yushan basins on the basis of electron microprobe analyses. The results show that all clinopyroxenes are composed of augite,which contains relatively low Al₂O₃ (2.34%～4.13%), high TiO₂ (1.19%～2.78%) and Na₂O (0.35%～0.49%), showing a typical alkaline series. The crystallization temperature and pressure of clinopyroxenes from the Late Cretaceous shoshonite in Guangfeng and Yushan basins are estimated by the formula that p(0.1 GPa)=-7.538 3+83.169 2(Al), t(℃)=1 056.898 6+902.797 8 (Al) from Thompson et al. (1974). The results show that the crystallization temperatures and pressures of clinopyroxenes are 1 151～1 202℃ and 0.12～0.58 GPa respectively. The clinopyroxenes resulted probably from fractional crystallization of relatively primitive magma in shallow magma chambers, equivalent to the upper crust. These clinopyroxenes were identical with clinopyroxenes in alkaline olivine basalt in the shallow source in such aspects as mineral chemical characteristics and formation environment but slightly different from clinopyroxene phenocrysts in the alkali olivine basalt in the deep source. They are evidently different from the tholeiite in mineral chemical characteristics. In addition, the compositions of the clinopyroxenes are consistent with those in intraplate basalt.

Abstract:Lawsonite eclogites are typical low-t and high-p metamorphic rocks formed during cold oceanic subduction. Lawsonite is an important carrier that brings water into deep mantle and hence plays a crucial role in fluid behavior of deep subducted slab, thus attracting widespread attention. This paper provides an overview of the progress in petrologic study of lawsonite and lawsonite-bearing eclogites in the past two decades: ① the distribution of lawsonite eclogites worldwide; ② the classification of lawsonite eclogites and modes of occurrence of lawsonite; ③ experimental studies and thermodynamic modelling upon the stability of lawsonite eclogites; ④ the formation and preservation of lawsonite eclogites; ⑤ fluid behavior in lawsonite eclogites. The above aspects, especially the last one, are long hotspots in the study of the subduction zone. Both prograde and retrograde veins commonly occur in blueschists and eclogites from Southwestern Tianshan. Further research on these veins will provide important constraints on fluid behavior during deep oceanic subduction.

Abstract:Rare earth elements are important tracers in probing the source of ore-forming fluid and discussing the process of hydrothermal mineralization. As a calcic mineral, fluorite is one of the most important gangue or ore minerals present under various temperature conditions in many hydrothermal deposits. REE³⁺ tends to enter the crystal lattice of fluorite, attributed to the similarity of ion radius and crystallochemistry between Ca²⁺ and REE³⁺. In addition, fluorite is a significant medium in the study of hydrothermal deposits. The rare earth elements in the fluorite are susceptible to the source of fluid, the condition of leaching rocks during migration and evolution, the chemical composition, redox conditions and the form of transportation in the fluid. Besides, the rare earth elements content and relative geochemical parameters of fluorite, such as ∑REE, LREE/HREE ratio, Eu, Ce, Y anomaly, Ta/Ca-Ta/La diagram, Y/La ratio and mode of occurrence of REE²⁺ (except Eu²⁺), and other rare earth element geochemical characteristics could provide important geological information concerning the source, physico-chemical property and the evolutionary process of the hydrothermal fluid, and they could also provide message crucial for developing metallogenic model and making inferences about the metallogenic potential of the regions in which they occur. However, with the development of the microanalysis technology, the in-situ trace element analysis of fluorite implies that it is probable that the distribution of trace elements (including rare earth elements) of fluorite is inhomogeneous at the micro level, which might result in the questioning of applying rare earth elements, obtained by the solution method, of fluorite in the hydrothermal deposit to probing the geological information. Therefore, it is necessary to pay more attention to the comprehensive study of fluorite in microstructure, fluid inclusion and isotopic analysis before applying the rare earth element geochemistry to probing relevant geological issues. Thus, in this paper, the authors summarized recent status and progress in rare earth elements geochemistry of fluorite, and discussed the dominant mechanisms leading to inhomogeneity in rare earth elements distribution in fluorite tentatively, looking forward to providing more valuable reference for rational understanding of rare earth element geochemistry of fluorite in the hydrothermal deposit.

Abstract:The technical reports devoted to the 11^th International Congress for Applied Mineralogy (11^th ICAM) which was held in Mianyang of Sichuan Province in July 8～10, 2013 are reviewed in this paper. These reports involve such research fields as environmental and medical mineralogy, industrial minerals, biominerals and biomaterials, advanced materials, process mineralogy, mining and metallurgy, mineral structure and surface, interaction of mineral with microorganisms and solid waste treatment and recycling.

Abstract:Granites can be divided into five types on the basis of their Sr and Yb content: high-Sr and low-Yb adakitic-type; low-Sr and Yb Himalaya-type; low-Sr and high-Yb Zhemin-type; very low-Sr and high-Yb Nanling-type and high-Sr and Yb Guangxi-type. Guangxi-type granites are exposed less in field and mainly composed of granodiorite, hornblende biotite granite, monzonitic granite and quartz syenite. Guangxi-type granites have low SiO₂, and are characterized by rich Al, Fe, K and P, belonging to shoshonite or high-K calc-alkaline series. Magma with high Sr and Yb content indicates lack of plagioclase and garnet in the residual phase. That means Guangxi-type granites are mainly composed of amphibolite plus/minus pyroxene, belonging to ultramafic rocks. Therefore, the condition for the formation of Guangxi-type granites was tough and needed high temperature at least. Guangxi-type granites are located in a narrow area in the phase diagram, above the plagioclase vanishing line, under the garnet appearing line and before the amphibolite disappearing line. Guangxi-type granites were formed under the pressure of about <1.0 GPa and at the temperature of >900℃ at least. These characteristics show that Guangxi-type granites were formed at the normal or thinning thickness of the crust with high temperature.