Abstract:Phlogopite-amphibole pyroxenite xenoliths within alkaline basic-ultrabasic aubvolcanic complex are composed of diopside, titanium-rich pargasite, high-titanium phlogopite, apatite and ilmenite, exhibiting threeling, cataclastic and kink-banded textures. Compared with original spinel lherzolite from eastern China, the xenoliths are enriched in TiO2, Fe2O3, CaO,Na2O, K2O, with an apparent depletion in MgO. Chondrite-normalized REE patterns and primordial mantle normalized trace elements data show that they are enriched in REE (especially LREE) and incompatible trace elements. Petrographic, mineralogical and chemical characteristics indicate that the xenoliths are metasomatized mantle xenoliths, which represent the anomalous mantle of early Palaeozoic rift in northern Daba Mountain. Mantle plume was the most probable agent for producing the xenoliths. with the ascending of the mantle plume, major metasomatic agents changed from melts to fluids.

Abstract:The present paper describes geochemical characteristics of Jinsha River ophiolites in Baimaxueshan, Shusong, Gongka and Jiyidu areas of Deqen County. Verious rocks assemblages of the ophiolites are exclusively of LREE-enriched patterns, and their genesis and tectonic setting are discussed here. It is pointed out that the trace element and REE characteristics of basalts could be interpreted by mixing N-MORB with OIB, and that Jinsha River Ophiolites were probably formed in a tectonic environment characterized by the superimposition of spreading ridge and mantle plume, similar to things of Iceland.

Abstract:There are four types of Mesozoic igneous rock assemblages in western Shandong. Five 40Ar/39Ar plateau ages of representative rocks from three assemblages were determined. The four assemblages are as follows: a—quartz monzodiorite-monzonite porphyry and syenite porphyry assemblage: the representative Tongshi complex was emplaced in Paleozoic strata and unconformably covered with Middle Jurassic Wennan Formation; the plateau age of hornblende from quartz monzodiorite porphyry is 189.8±0.2 Ma, whereas that of hornblende from monzonite porphyry is 188.4±1.6Ma. b-pyroxenite-monzodiorite-syenite assemblage: the representative Shagou intrusive body was emplaced in Archean granite, and the plateau age of biotite from pyroxenite is 115.1±1.1Ma. c—olivine noritic gabbro-two pyroxene dioritequartz monzonite assemblage: the representative rock body in Zhouping area was emplaced in volcanic rocks of Cretaceous Qing-shan Group; the plateau age of biotite from olivine noritic gabbro is 112.5±1.3Ma,while that of biotite from quartz monzonite is 115.1±0.3Ma. In early years, 67 individual mineral and whole rock K-Ar ages for this assemblage as well as one Rb-Sr isochron age and one Sm-Nd isochron age were determined. Statistics show that the modal age values are in the range of 110-132Ma, which are comparable with our40Ar/39Ar ages. d—diorite porphyry-quartz monzodiorite porphyry-granite porphyry assemblage, exemplified by the rock bodies in Tongjing area; no individual mineral samples suitable for40Ar/39Ar age determination have been collected in this area, and the age values avaibable are concentrated in the range of 110-126 Ma. There existed two periods of magmatic activities in western Shandong: the Early Jurassic igneous activity seemed not so strong and was merely confined to the southern part of western Shandong, forming K-Ca-high alkaline—K-high alkaline rock series; the Early Cretaceous igneous activity was ubiquitous in the whole area: the southern part of western Shandong shows features of alkali-high magma, whereas in the northern part, the early rocks are of calc-alkali ones, but the late rocks have higher potassic content. The igneous rock assemblage near Yishu faulted zone is characterized by well-developed granitic rooks.

Abstract:Petrology, petrological chemistry and trace element characteristics of lamprophyre in the Denggezhuang and Jinqingding mining areas of Jiaodong shows that it belongs to barkevikite-plagioclase lamprophyric series, derived from the upper mantle. Lamprophyric veins, which mainly spread parallel to gold ore veins, might have provided some ore-forming materials and volatiles for gold mineralization. The characteristics of lamprophyre and its intimate connection with gold mineralization suggest that geologic activities related to gold mineralization took place not only in the crust but also in the upper mantle.

Abstract:In Jiepaiyu area, Shimen County, Hunan Province, there exist a number of top-like breccias, which occur either in groups or as isolated ones, constitute steep ridges or hills and usually take elliptical or isometrical forms at surface and conical or cylindrical forms branching upward in profile, with the branches exhibiting stock, dike or irregular forms.On the basis of formation characteristics of top-like breccias, it is believed that these toplike breccias are of hot spring origin. Silicalites in the top-like breccias are most probably silica sinters deposited from hot spring water. Trace elements in breccias are similar to those in sedi- ments from modern hot springs. A rock-forming model for top-like breccias of hot spring type is proposed in the paper: circulating, migrating in strata and heated by the deep thermal flow system, the percolating meteoric water might extract ore elements and mineralizing agents from the strata, producing ore-forming fluid. when this fluid ascended along faults, explosive breccia and karst breccia were formed as a result of drastic explosions of hot spring gases and related substances under the sealed and reduced conditions.Various breccias may yield large-sized uranium deposits, gold deposits, polymetallic deposits and realgar deposits. The largest realgar-orpiment deposit ever discovered in China occurs in these breccias. The top-like breccias may serve as excellent ore-hosting and ore-controlling geological bodies and hence have important ore-prospecting significance.

Abstract:The analytical data of carbon and oxygen stable isotopic composition of carbonate rocks from saline lakes on Qinghai-Xizang plateau indicate that carbonate sediments in saline lakes are rich in carbon-13 and oxygen-18. Most of the values coincide with values of marine carbonates,with relatively high Z value. So when using carbon and oxygen stable isotopic values or Keith and Weber’s Z value as the discrimination oriteria for sedimentary environments, one must consider the characteristics of saline lakes so as to avoid incorrect results.

Abstract:Spinels are widely present in peridotite and pyroxenite xenoliths within Cenozoic alkali basalts of eastern China, with their abundance typically ranging from 1% to 10%. They are small (0.1—1mm) and irregular crystals, sometimes forming graphic intergrowths with py-roxene or olivine. Spinels from deep-seated xenoliths of Cenozoic basalts in eastern China belong to picotite and hercynite. Spinels from kimberlites, their mantle xenoliths and diamonds are dominated by aluminochromite, followed in order by ferrochromite, with rare picotite. Compared with those from pyroxenite xenoliths, spinels from peridotite xenoliths in Xenozoic basalts of eastern China are higher in Cr2O3, Cr/(Cr+Al), Cr/(Cr+Al),Cr/(Cr+Al+Fe3+),Cr2O3/(Cr2O3+ Al2O3+MgO+TFeO) amd MgCr2O4+FeCr2O4-mol,but lower in Al2O3. The reasons are as follows: chromium is a compatible element, but aluminium is an incompatible element; peridotites in basalts belong to the residual upper mantle after the removal of basaltic melts derived from partial melting of the upper mantle, and to mantle-derived xenoliths, thus causing their spinels to be rich in Cr and poor in Al. Pyroxenites in basalts are crystallization products of basaltic magma in the upper mantle, with their spinels poor in Cr and rich in Al. Studies reveal that Cr2O3content, Cr/(Cr+Al), Cr/(Cr+Al+Fe3+),Cr2O3/(Cr2O3+ Al2O3+MgO+TFeO),MgCr2O4and FeCr2O4of spinels from deep-seated xenoliths in basalts are notably low relative to those of macrocrystalline spinels from kimberlites, their mantle-de-rived xenoliths and diamonds, suggesting that the formation pressure of spinels in xenoliths of basalts is lower than that of spinels in kimberlites, their xenoliths, and diamonds.

Abstract:Samples of phlogopite-vermiculite (phl-ver) interstratified minerals from Weili mine, Xinjiang, have been studied. Using the single crystal sheets of phl-ver samples, the authors measured the basal spacing of seven phl-ver samples with X-ray diffractometer. The structure factors and the coefficient of variation (CV) of the basal spacing obtained were calculated. According to the result of X-ray diffraction analysis the samples of phlogopite-vermiculite interstrati- fied minerals might be divided into two groups: (1) the regular 1∶1 interstratified mineral of phlogopite and vermiculite layers, specifically called hydrophlogopite; (2) the segregated interstratified minerals of phlogopite layers and hydrophlogopite layers. The calculated and the observed structure factors for 001 diffractions vary similarly with the index 1. So the regular interstratified structure of ph1-ver is defined as a regular 1∶1 interstratified structure.

Abstract:Austinite and adamite are secondary arsenate minerals, which were discovered for the first time in ore caves of the No.98 gold vein oxidized zone within the Laodonggou gold deposit, In ner Mongolia.Austinitemostlyoccursassubhedraloreuhedraltransparentcrystals1 . 0×0 . 8 —4.0×3.0 mm in size, with the color being green or greenish; its calculated specific gravity is 4.32. Adamite occurs commonly as transparent aggregates or crystal 1.8×1.5—3.5×2.5mm in size, with the color being light yellow-green or colculess; its caloulated specific gravity is 4.44. Studies under microscope give the following optidal characteristics:Ng=1.778,Nm=1.760,Np=1.756, positive optical character of biaxial crystal, with optic angle of 46°for austinite, and Ng=1.761,Nm=1.738,Np=1.719, positive optical character of biaxial crystal, with optic angle of 87°for adamite. Chemical analysis (wt %) shows that the composition of austinite is CaO 21.57, ZnO 29.61, CuO 2.29, MnO 0.002, Fe2O30.02, As2O5 43.07, CO20.43 and H2O+3.68, making up a chemical formula of Ca0.99(Zn0.94Cu0.07)1.01 [(AsO4)0.97(CO3)0.03]1.00(OH),　and that the composition of adamite is ZnO 56.18, CuO 0.46, PbO 0.13, Fe2O30.004, As2O539.89 and H2O+3.31,making up a chemical formula of (Zn1.97Cu0.02)1.99(AsO4)(OH). As is detected by infrared spectral analysis, austinite contains minor CO2, and this is different from the feature of austimite reported by D. Radciffe et al. (1971). According to X-ray diffraction analysis, the unit cell parameters are a=0.7473nm,b=0.9017nm,c=0.5916nm for austinite and a=8304nm,b=0.8516nm,c=0.6054nm for adamite, respectively. The main ore mineral assemblage of the vein oxidized zone is scorodite+limonite+austinite+adamite+native gold+native silver+quartz+calcite+opal. The result of the study shows that adamite and austinite may be crystallized from acid to neutral solution under oxidation condition; nevertheless, the former is crystallized only when the solution has relatively high zinc ion activity. As these two arsenate minerals are of indication significance, their discovery contributes to the prospecting for secondary leaching type gold deposits.

Abstract:Muscovite in the deposit can be divided into four generations according to their formation spochs. Muscovite (Ⅰ) is in unaltered slates formed in regional metamorphic process, muscovite (Ⅱ) is in yellowish green slates formed in early quartz-carbonatization process, muscovite (Ⅲ) is in slates formed in W mineralizing process, and muscovite (Ⅳ)is in slates formed in Au-Sb mineralizing process.There are differences in chemical contents of muscovites of different generations. The contents of K, Cu, Pb and Th of muscovites in W mineralized slates are high; the contents of Ca, P, Ni, Zn, Sb and As of muscovites in Au-Sb mineralized slate are also high. Element ratios, such as Cu/Zn, Rb/Zn, Fe/(Co+Ni), Ti/P, Th/Nd, are different in muscovites of different generations. Multivariant analyses show that the natural associations of elements correspond with the main mineralizing processes. Crystallochemical formula of muscovites of the deposit was calculated based on EPA results. Interlayer cations are deficient obviously. Muscovites in the deposit belong to lepidomorphite, and are all of 2M1polytype. The values ofd060are all lower than 1.50°A.b0values show that the pressure of the mineralizing process is low. Crystallochemical parameters of muscovites can indicate the formation conditions of the deposit.Infrared spectra of muscovites of different generations were studied. There are differences in thermal analyses of muscovites of different generations.

Abstract:Tourmalines in granites and granite-related tin-polymetallic ore deposits of Dachang,Guangxi , belong to schorl-dravite series . Tourmalines from granites contain highΣFeO (14.79%—16.07%) but low MgO (0.92%—2.74%), Whereas tourmalines from orebodies have high MgO (7.71%—10.50%) but lowΣFeO content (0.19%—4.50%). It is obvious that the abundance of MgO becomes increasingly higher with the distance from granite. Such compositional and evolutional features are in accordance with the general law of granitic tourmalines, but different from features of exhalative tourmalines. In Dachang mine, tourmalines can be found in various horizons of the Changpo-Tongkeng deposit and also in different kinds of altered wall rocks, such as Middle Devonian argillutite and Upper Devonian siliceous shale, thick and thin banded limestones, lens-like limestones and marl, making up at least twenty-three kinds of tourmaline-bearing mineral assemblages. In the lattice of tourmaline crystal, Mg and Fe occupy the same Y site; in consequence, when Fe is dominant in hydrothermal solution, it is more easy to form schorl, but when Mg is dominant, dravite is more easy to form. There are many reasons for the high MgO content of tourmaline in the Changpo-Tongkeng deposit:(1) the granites in Dachang are relatively high in Mg compared with other tin-related granites;(2) the deposit is located far away from granite;(3)iron in hydrothermal solution tends to be incor- porated into such sulfides as pyrite and pyrrhotite, and magnesium incorporated into metasomatic minerals like dravite;(4)Mg derived from wall rocks may be another material source for the formation of dravite.