Abstract:The Baishiquan mafic-ultramafic intrusions associated with magmatic Cu-Ni-PGE sulfide deposits are located in central Tianshan block of northern Xinjiang. They are Late Permian mafic-ultramafic rocks which intruded into the Mid-Proterozoic sequences comprising schists, gneisses and marbles. They display ellipse and irregular forms in plan, and are basin-shaped in the cross section. The Baishiquan intrusions are comtposed of pyroxene peridotite, olivine pyroxenite, troctolite, hornblendite, gabbro, hornblende-gabrro and diorite. Peridotite and pyroxenite are main rock types hosting Cu-Ni-PGE ores. The rock-forming minerals are comtposed of the assemblage of olivine, orthopyroxene, clinopyroxene, hornblende, plagioclase ly surrounded by orthopyroxene, clinopyroxene and plagioclase oikocrystals with and biotite. Olivine is normal- Fo being 80--85, which overlap minerals of the magmatic Cu-Ni-PGE sulfide deposits. Pyroxene is dominated by bronzite, endiopside ands- mall amounts of hypersthene and diopside. Plagioclase is usually characterized by rhythmic and reverse zones, consisting of An ranging from 50 to 70. Hornblende was formed at the last stage and enclosed olivine, pyroxene and plagioclase. According to these characteristics, the primary magma of such mafic-ultramafic intrusions must have been mantle-derived tholeiitic magma.

Abstract:Located in Inner Mongolia, the northern edge of the North China craton, Jining Cenozoic basalts belong to the generalized “Hannuoba Basalts". A lot of peridotite xenoliths as well as some pyroxene, feldspar and titanomagnetite megacrysts were discovered for the first time in the alkali basalt southeast of Sanyitang. Most of these xenoliths are spinel lherzolites with the assemblage of olivine + orthopyroxene + clinopyroxene + spinel. The pyroxene megacrysts are mostly diopside and augite in composition. Feldspar megacrysts are mainly anorthoclase and minor plagioclase. The equilibrium temperature represented by these spinel lherzolite xenoliths is about 950℃ at 1.5 GPa, which is almost the same as that of the Hannuoba xenoliths and reflects the temperature of spinelphase in the lithospheric mantle beneath the northern edge of the North China craton. The crystallization temperature and pressure of clinopyroxene megacrysts are higher than those of lherzolite xenoliths, implying an origin deeper than that of the peridotite xenoliths. Petrography and mineral chemistry of these xenoliths indicate that they are fragments of the upper mantle captured by basaltic magmas along the ascending way. The high Mg# (89.5～91.7) and high NiO (0.29%～0.55%) contents of olivines demonstrate that Jining peridotite xenoliths are derived from the infusible lithospheric mantle.

Abstract:Kayakedengtage complex, located in southeastern Qimantage Mountain of the East Kunlun Mountains, consists of gabbro, diorite, quartz diorite, granodiorite, adamellite and syenogranite which are products of a typical magmatic mixing process. The SHRIMP dating of gabbro and adamellite samples yielded magmatic ages of 403.3±7.2 Ma and 394±13 Ma and inherited zircon age of 1116Ma. The morphological features of zircons from gabbro and adamellite indicate that the zircon crystallization temperatures of these two rocks are 850～900℃ and 600～850℃, respectively, which implies the formation depth of the complex. The dating results provide important data for the evolutionary history of the EastKunlun orogenic belt.

Abstract:The contents of such platinum-group elements as Ir, Ru, Rh, Pt and Pd in Jianguo basalts and Wulahada Mg-high andesites were determined using ICP-MS after a nickel sulfide fire assay preconcentration. They display positive slope in the mantle-normalized pattern. The Pd/Ir values higher than those of the primitive mantle suggest the fractionation of PGE in Fuxin volcanic rocks. PGE fractionation in the basalts is attributed to the fact that Ir can be potentially fractionated in spinel and alloys but Pd resides in sulfides during partial melting. The PGE in Wulahada Mg-high andesites might be affected by the phases separated from earlier melts during fractionation. The negative Pt anomaly in Fuxin volcanic rocks probably results from Fe-Pt alloys residing in the mantle.

Abstract:Compositional inhomogeneity of the needle_exsolution magnetites in olivine from Bixiling garnet peridotite was recognized by means of map analysis using electron probe microanalysis (EPMA). Some needle-exsolution magnetites have relatively high Cr concentration, whereas others have relatively high Ti concentration. It is suggested that the distribution of titanium and chromium might have been inhomogenous in the original β -olivine-phase, resulting in the compositional difference observed in the needle_exsolution magnetites. This implies that the olivine originally existed as spinel-phase which was stable in the mantle. The present study therefore provides valuable information for determining the formation depth of the garnet peridotite and for understanding the mechanism of continental subduction.

Abstract:The Jiajika pegmatite type lithium deposit in Kangdi of Sichuan Province is the largest lithium deposit in China. Nevertheless, researches are very insufficient on the source of its ore-forming fluid. More than 400 primary inclusions in the Jiajika deposit were analyzed by the authors. The results show that the homogenization temperatures of CO2-NaCl-H2O inclusions and brine inclusions change gradually into each other. When the homogenization temperatures are lower than 300℃,the salinity of CO2-NaCl-H2O fluid is lower than that of NaCl-H2O fluid. The capturing pressure of CO2-NaCl-H2O fluid is larger than that of NaCl-H2O fluid. These data show that the ore-forming fluid evolved from CO2-NaCl-H2O to NaCl-H2O with the falling temperature and pressure, which is similar to the fluid evolution of the Keketuohai pegmatite deposit in Altay and the Tanco deposit in Canada. The laser Raman test shows that the main compositions of CO2-NaCl-H2O fluid inclusions are CO2 and H2O，with no hydrocarbon detected, which is consistent with characteristics of the fluid derived from the mantle and related to magmatism. The composition of O and H isotopes is located in the area of magma water in diagram, and the δ13CV-PDB‰ values are -3.4‰～-7.3‰. The formation time of pegmatite dikes is later than that of the granite body. These characteristics indicate that the ore-forming fluid resulted from fractional crystallization of magma, with the participation of some connate water at the late stage.

Abstract:Reconstruction of deformation and metamorphic processes and conditions can be carried out by studying micro-features of rock and minerals. This paper has investigated the microstructures, quartz fabrics, and mineral chemistry of mylonites from the ductile shear zone of the granite-greenstone belt in Seerteng area, Inner Mongolia. Synthetic analyses reveal that the mylonites underwent four evolutionary processes of deformation and metamorphism, such as lower-amphibolite facies regional metamorphism, retrograde epidote-amphibolite facies metamorphism and deformation, progressive recrystallization and retrograde greenschist facies metamorphism and deformation. The temperature and pressure combination of four metamorphic stages defines a clockwise p-T path, with the superimposition of a later anticlockwise p-T path.

Abstract:Rutile is a common Ti_bearing accessory mineral in eclogites. In the 100～2000 m borehole samples of the Chinese Continental Scientific Drilling Project, rutile appears in different amounts in rutile eclogite, phengite eclogite and kyanite eclogite. It, together with other minerals, can be wrappedin major metamorphic minerals such as garnets and omphacites, or can wrap otherminerals. Inclusions in rutiles from CCSD UHP eclogites were studied by electron microprobe. The result shows that the inclusions such as omphacites, Hf-rich zircons, high-Al sphenes, pargasites, katophorites and clinozoisites were formed during the progradation of eclogite-facies to peak metamorphism. With the exhumation of the Sulu UHP metamorphic belt, the eclogites underwent extensive retrograde metamorphism, and lots of minerals such as rutiles and omphacites experienced retrograde metamorphism too. Ilmenites coexisting with rutiles were subjected to different extents of retrometamorphism, yielding Fe-rutile and ulvospinel. Therefore, some retrograde mineral assemblages such as symplectites of diopside + plagioclase, low-Al sphene, magnesiotaramite were found in retrograded rutile.

Abstract:Within the diamond anvil cell, the Raman spectroscopic study of phengite was developed at room temperature and under various pressures from 1 atmp to 20 GPa. The authors analyzed the correlation of the modes 266, 708 and 3618 cm-1 with the variation of pressure. The mode of 708 cm-1 increases linearly with the increase of pressure, i.e., y (Raman shift, cm-1)=0.5238x (pressure, GPa) +712.31, and R2 (correlation coefficient)=0.9656, and the mode disappears at 4.7 GPa as a result of substituting Si for Al. The mode of OH- band and the intensity decrease linearly with the increase of pressure, i.e., y=-0.3402 x+3617.8 and R2=0.9662, and the mode disappears at 18 GPa, which is assumed to be the maximum pressure for the dehydration of phengite at room temperature.

Abstract:This paper reports some preliminary results obtained from field petrographic work, laser Raman microspectroscopy and electron microprobe analysis carried out on the Au-bearing Qiyugou breccia pipes. The adularia-calcite assemblage was recently discovered in the breccia gold deposit. Two stages of gold mineralization in the breccia pipes, i.e., pervasive and veined, were distinguished. The early pervasive alteration of actionlite, green biotite, epidote, chlorite and minor sericite replaced breccias and rock flour, followed by later adularia and calcite alteration filling the open space. Vein ores associated with quartz, sericite, and minor calcite alteration occur in NE-trending faults that cut pervasive ores. These results show that adularia-calcite alteration is associated with gold mineralization. The discovery of the adularia-calcite assemblage in the area suggests that the Qiyugou pipes are genetically of low-sulfidation epithermal type.