Abstract:The mantle peridotites widely distributed along the Yarlung Zangbo River ophiolite zone are fresh rocks not subjected to serpentinization. Therefore, the observation under microscope and the whole rock chemical analysis are simple and convenient means for investigating their genesis and the mantle activity. Recent studies of abyssal peridotites show that they are not melt residues of batching or fractional melting of pyrolite directly after melt extraction of MORB. Petrological studies of peridotites from Luobusa ophiolite massif also indicate that the mantle peridotites are not simple residues of primary pyrolite either. Nevertheless, residue peridotites in Luobusa ophiolite were formed by two times of partial melting, i.e., the ultrahigh pressure silicates (octahedral spinel) from the transitional zone experienced melting and extracted MORB melt, and then the low pressure peridotites in the upper mantle were partially metlted again, thus forming residue peridotites.

Abstract:Located within West Kunlun terrane on the southern margin of Caledonian Kudi-Subashi suture zone in Qinghai_Tibet plateau and formed from the end of Ordovician to the beginning of Devonian, Kudibei rock body consists of early monzonitic granite and late granite, which are composed of microcline, plagioclase, quartz and biotite. Biotite assumes anhedral interstitial form and was crystallized later than ligh_colored minerals. The accessory mineral zircon has perfect crystal faces of (110) and (111), suggesting relatively high crystallization temperature 215 (850~900℃). Chemical composition is characterized by rich K, Th, REE, Nb, Zr, Y and poor Ca, Mg, Ba, Sr and transitional elements. All these characteristics show that it belongs to A-type granite. Both Sr, Nd, O isotopes and Rb/Sr ratios demonstrate that the protoliths are oceanic crust surface abyssal sediments. On the basis of regional tectonic framework, combination of associated rocks and structural discrimination diagram, the authors analysed the formation environment of this rock body. The results show that the rock body was formed in a relatively stable extension environment of late orogeny and belongs to A-type granite. It was em- placed during the falling off of oceanic plate sheets and formed by earlier successive partial melting of oceanic crust sediments which subsided with the subduction of the oceanic plate. The researches indicate a mechanism for the recycle of crustal materials to the earth crust and are of great significance to the investigation of Early Paleozoic tectonic evolution of Qinghai_Tibet plateau and its geodynamic mechanism.

Abstract:Hannuoba basalts, which erupted in early Miocene of Neogene, are located on the northern margin of North China Block as a basaltic plateau and cover an area of about 1700km2.These basalts consist of intercalated alkaline basalt and subalkaline basalt with mantle xenoliths in basanite and alkaline dorgalite. The ages of basalts vary upward from 24.5 Ma to 13.6Ma.The distinct geological character is that the early alkaline basalt and the late subalkaline basalt are in rhythmicity, as has been recognized by many geologists. In general, SiO2increases gradually (42.91%→50.17%) from basanite, alkaline-olivine basalt, olivine tholeiite to quartz tholeiite, Mg#is usually 0.55~0.63 in basanite, 0.63~0.66 in alkaline-olivine basalt, and 0.59~0.66 in olivine tholeiite. Correspondingly, norma-tive nepheline decreases and hypersthene and quartz ncrease. The REE partition patterns vary with the rock types of the basalt, i.e., bulk REE concentration decreases from basanite to quartz tholeiite, LREE decreases and HREE increases slightly. Rare earth elements and other incompatible elements are ifferentiated extensively. On the whole, the incompatible elements istribution patterns resemble those of OIB. In La/Sm-La plot, the samples studied are projected as an inclined array from upper right to lower left, and accordingly the rock types change from basanite to quartz tholeiite. The concentration of compatible element Cr varies from low to high to medium and the concentration of Ni increases slightly from basanite to tholeiite, but the change is not so remarkable, and Co shows no notable changes. All of this suggests a partial melting process and the melting extent increases from basanite to quartz tholeiite. When the geological and geochemical characteristics are related to high temperature and high pressure melting experiments on peridotite, it can be concluded that the main magmatic process is the incremental partial melting. Gravitational instability caused by local thermal anomaly may induce the diapiric ascent of mantle material , leading to depressure partial melting. Phase change also occurs in Al_rich phase such as garnet. When the mantle diapir ascends to the spinel stability field, melting sequence of mineral phases is Cpx→Spn→Opx→Ol (Ito & Kennedy, 1976). Melting of Cpx which is the main Na_bearing phase in mantle peridotite will produce normative nepheline basanite magma. Further melting will cause Spn which contains the main part of Cr in peridotite and some other minerals like Opx to enter the melt, leading to decrease of SiO2and increase of Cr in melt and resulting in the composition of alkaline olivine basalt. With the increasing of melting, more Opx enters melt, thus the norm ne and Cr concentration decreases and norm hy increases, making the melt composition move towards olivine tholeiite. When the mantle diapir enters the plagioclase stability field, there occurs incongruent melting of Opx, i. e., En→Ol+SiO2. This will form quartz tholeiitic magma.The mantle plume theory is used to interpret the induction of diapir and the generation of Hannuoba basalts. Deep mantle hot plume supplied the heat needed for partial melting and some of incompatible elements_rich fluids to decrese the solidus temperature. This caused diapiric ascent of mantle material and consequently the pressure release. On the way up, diapirite would melt at different phase stability depths. The mantle plume might have occurred several times in the same place under the stationary plate (Van Keken, 1997) and caused rhythmic basalt eruptions. The mantle plume theory can also be used to explain the correlation with OIB type of incompatible element distribution pattern. Hence the petrogenetic model can be called multicyclic increment partial melting.

Abstract:Based on analysing the rare earth elements and geochemical characteristics of Devonian cherts from Qingzhou-Fangchen ocean trough and Hechi-Nandan platformal basin in Guangxi and Linshan-Hengyang platformal basin in Guangxi-Hunan, it is considered that the sedimentary environment of these cherts is a deep-water basin, and that sedimentary cherts constitute two genetic types, namely normally deposited cherts and hot-water deposited cherts. Furthermore, all these phenomena prove that Hechi-Nandan and Linshan-Hengyang platformal basins were formed by linear strike-slipping tectonic movement in Devonian.

Abstract:There exist two periods of genetically different granitoids in Sawuer Mountain of Xinjiang, whose Rb-Sr isotopic ages are 314.9~320.3 Ma and 295~296 Ma respectively. Based on these data in combination with their emplaced strata and their relations with volcanic rocks, it is considered that these two types of granitoids are of Middle and Late Hercynian respectively.

Abstract:The sedimentation of Upper Sinian carbonate rocks along the northern margin of the middle Yangtze platform occurred in two facies areas, namely shallow-water platform and deep_water platformal basin ,which include seven facies zones. There exists close relationship of Sr content and Sr/Ca×1000 ratio to the sedimentary environment, i.e., the values increase obivously from the shallow-sheal facies to the deep-water platformal basin facies. This is attributed to the infuence of the difference in carbonate mineralogy in different sedimentary environments on the Sr distribution and also to the diagenetic environment which depends upon the sedimentary environment. The content of the trace element Sr and the Sr/Ca×1000 ratio can therefore be used to judge sedimentary facies.

Abstract:There are two kinds of spinels in a granulite terrain of Yushujgou, South Tianshan Mountain. One occurs in the intermediate and basic granulite units and is characterized by enriched Al and poor Cr, belonging to Al-spinel. In thin sections it shows dark green color and subhedral to anhedral form, and coexists with other metamorphic minerals, suggesting a neogenic metamorphic mineral of granulite facies. The other occurs in the adjacent ultramafic rock unit, belonging to Cr_spinel. In thin sections, it is dark brown in color and is scattered among olivine, clinopyroxene and orthopyroxene as irregular grains, indicating a stable residual mineral in the process of granulite facies metamorphism. The spinel in the ultramafic rock unit belongs to I-type spinel, as proposed by Dick et al . This implies that the ultramafic rock is a part of oceanic lithosphere mantle. Characteristics of these two kinds of spinels not only indicate that the whole terrain underwent granulite facies metamorphism but also provide direct mineralogical evidence for the argument that Yushugou ophiolite suite of granulite facies lies in an environment of oceanic basin.

Abstract:Comparative studies of trace elements in coals were carried out for three mining areas in three different types of basins, i.e., the Haizhou openpit mine in Fuxin basin, the Meiyukou mine in Datong coalfield and the Antaibao openpit mine in Pingshuo coalfield, Shuoxian County. This paper summarizes characteristics and differences of trace elements in coals of the three different types of basins (faulted basin, epicontinental sea basin and large_size intracontinental down_warped basin), and points out that the main factors responsible for these differences are sedimantary environment for the formation of the peat bog, peat bog facies and source areas of the basins. The seawater-influenced Pingshuo coals have relatively high content of Li, Ti, Cu, Ga, Zr, Sn, Hf, Ta, W, Pb, Th, U and REE, the continental Datong coals are characterized by comparatively high Ni and Ba, and Fuxin coals are noted for evidently high Cr, Co, Rb, Mo, Cs and B. The depletion of Eu in coals are mainly related to the oxidation_reduction of the peat bog: the higher the oxidation of the peat bog, the more obvious the Eu depletion.

Abstract:The authors analysed naked and transformed groups of fibrous brucite, wollastonite, chrysotile asbestos, sepiolite, palygorskite, clinoptilolite, crocidolite and diatomaceous earth mineral dusts by IR under acid and alkali etching and strong mechanical and polarized molecular interaction. The results show that the active sites focus on ends in stick dusts and on defects or hole edges in pipe dusts. The inside active sites of dusts play a major role in small molecular substances. The shapes of dusts affect their distribution and densities of active sites. The strong mechanical force and weak chemical force change the active site feature of minerals, the powder process makes more surface goups naked and causes the increase of combined types. The dust activity is related to the types, contribution and degree of nakedness of surface groups.The studied surface groups of dusts are as follows: fibrous brucite: OH-, Mg(OH)+; wollastonite: Si-O-Si, Ca-O-Si; chrysotile asbestos: OH-, Mg(OH)+, Si-O; sepiolite:OH-, Si-O-Si, -Mg-OH2, -Al(Si)-OH; palygorskite: OH-, Si-O-Si(Al),-Mg(Al)-OH2, -Al(Si)-OH; clinoptilolite: Si-O-Si(Al), -Mg(Ca)-OH2, Ca-O; diatomaceous earth: -Si-O, Si-O-Si, -Si…OH; crocidolite: OH-, Si-O-Si, Mg (Fe)-OH. Due to the differences in surface composition and structure, the minerals show remarkable disparity in activity and character of surface groups: wollastonite, diatomaceous earth and clinoptilolite have independent surface OH-while fibrous brucite only has surface OH-.The one side surface group of chrysotile layer is the same as that of fibrous brucite, and stripped layers have more naked groups. The surface OH-of fibrous sepiolite and palygorskite is similar to that of crocidolite, whose nakedness is related to the surface structural defects and cleavages. The better developed the mineral defects, the higher the OH-(H2O+) content. The main H2O+form of clinoptilolite can be partly transformed into H+, NH+4or OH-. The acid etching process may change OH-concentration and distribution and increase the defects and porosity of mineral fiber surface . The alkali etching has no effect on Si - O and Si - OH but will destroy Al-O and Al-OH-acid sites of sepiolite, palygorskite and clinoptilolite. Some surface groups of remnants quite differ from original dusts; wollastonite and chrysotile asbestos remnants, for example, become SiO2. The surface process of small polarized molecule or middle molecule branch may produce ionization and new coordinate bond and change the active properties and level of original dusts, such as the porous minerals, which might play some assistant calalytic role in biochemical process.