Abstract:Weizhou island in Beihai City of Guangxi is the largest Quaternary volcanic oceanic island in China. The surface of the island is covered with Middle Pleistocene (Q2)basaltic volcanic rocks of effusive facies, Late Pleistocene (Q3) sedimentary pyroclastic rocks of air-all accumulation facies and Holocene (Q4) basaltic volcanic rocks of explosive-usive facies. Among them, Middle Pleistocene is dominated by basalt whereas Holocene by basanite or picritic basanite, with the former having higher SiO2 and lower MgO than the latter. In geochemistry, these basaltic rocks are enriched in light rare earth elements without Eu anomaly and strong incompatible elements without Nb anomaly. These rocks have lower Th/La (0.14～0.28), La/Nb (0.52～0.91), Rb/Nb (0.45～1.09)and 87Sr/86Sr (0.70352～0.70443) ratios and higher εNd values (+3.2～+5.2) than other Cenozoic basalts in South China. These characteristics show that Late Pleistocene volcanic rocks were formed through fractional crystallization of olivine and plagioclase, that Holocene basaltic volcanic rocks represent primary magma formed by partial melting, and that crustal contamination seems not important in the formation and evolution of these two sorts of magma. Based on tracing of trace elements and isotopes, the authors infer that the source of volcanic rocks in Weizhou island is the same as that of the oceanic island. The magma must have originated from asthenosphere without the involvement of lithosphere components. Weizhou island represents asthenosphere window in epicontinental lithosphere of South China. Therefre, it is inferred that there exists a sub-lume in the depth of Leiqiong region and Beibu Bay, which belongs to Nanhai sea mantle plume whose activity lasted until Holocene.

Abstract:The Emeishan and the Siberian large igneous provinces (LIP) represent two major magmatic events close to the Permian_Triassic boundary. Theyare characterized by similar major element, microelement, and Sr, Nd and Pb isotopic compositions. However, the variation ranges of the incompatible element ratios and isotopic ratios are much narrower in the Emeishan LIP than in the Siberian LIP. Compared with the Siberian LIP, the Emeishan basalts have somewhat higher Fe8 and Sm/Yb ratios, suggesting a relatively greater depth and a lower degree of melting. Their source regions are garnet lherzolite. Based on the Nd isotopic characteristics, the εNd value of Emeishan and Siberian plume is estimatedto be approximately 2, close to that of the primitive mantle. In combination with other geochemical characteristics, it is proposed that the two LIPs might have originated from the same super_plume derived from the core-mantle boundary.

Abstract:Petrology, geochemistry, formation environment and isotopic geochronology of Precambrian amphibolites in Alxa area are reported in this paper. Amphibolites in different group complexes, formation complexes and complex rock bodies all crop out in layers, and their protoliths are mainly ferrian tholeiite characterized geochemically by high potassium and titanium as well as rich REE and LREE. These characteristics are remarkably different from features of typical oceanic tholeiite, TH_1 and TH_2 tholeiite of Archean rock assemblages. Various geochemical diagrams indicate that amphibolites are mainly formed in an intraplate environment characterized by intraplate depression or epicontinental faulted depression. Isotopic geochronology shows that amphibolite in Diebusige group complex was formed in Neo_archean. ~(39)Ar_~(40)Ar age and isotopic age of hornblende from biotite_bearing amphibolite are 1?918 Ma and 1?919 Ma respectively, suggesting that they underwent metamorphism of amphibolite faces in Paleoproterozoic. Amphibolite in Bayanwulashan formation complex was formed between (2?271) Ma and 2?264 Ma. Amphibolite in Boluositanmiao gneiss complex was intruded by granitic gneiss of 1?818 Ma and 1?839 Ma. According to geochemical characteristics of amphibolite in the complex and the same sort of rocks in Bayanwulashan formation complex, it is concluded that it was formed in early Paleoproterozoic. Accurate isotopic chronological data of amphibolite from Delhetongte formation complex in Alxa Group are not available, but the average zircon ion probe age of garnet_muscovite_biotite_quartz_schist in the same layer is 1?363 Ma, which indicate that the amphibolite was probably formed in Meso_proterozoic.

Abstract:The southwestern Sulu terrane in eastern China is divided into four fault-bounded lithological units, which are from northwest to southeast orthogneiss unit (Unit Ⅰ), supracrustal rock unit (Unit Ⅱ), kyanite_bearing quartzite-marble unit (Unit Ⅲ) and paragneiss_schist unit (Unit Ⅳ). Inclusions of index minerals in zircon separates of 93 samples from these units were identified by means of laser Raman spectroscopy and electron microprobe analysis. Coesite and coesite-bearing ultrahigh-pressure (UHP) mineral assemblages occur in zircon separates of various amphibolite-facies metamorphic rocks within Units Ⅰand Ⅱ, whereas aragonite- and phengite-bearing high-pressure (HP) mineral assemblages are preserved in zircons within many amphibolite- to greenschist-facies metamorphic rocks in Units Ⅲ and Ⅳ. All the above evidence together with previousstudies yields p-T estimates of peak metamorphic recrystallization at 723～852℃ and p≥2.8×103 MPa for UHP rocks, and at 500～600℃ and p=1.2×103～2.5×103 MPa for HP rocks. The spatial distribution of these p-T estimates and recent surface mapping result constrain an exact boundary between UHP and HP belts within southern Sulu terrane along a ductile shear zones in Donghai region.

Abstract:Based on field observations and indoor researches, the authors hold that there exists an unconformity between Sinian Wanlong Formation and Badaojiang Formation in southern Jilin, as evidenced by three paleo_weathering crusts discovered there. In the past, however, the contact was believed to be a conformity contact. Chemical analysis shows that there is a remarkable change of chemical components from base rocks to the paleo_weathering crust. Unlike CaO and LOI, the total amount of SiO_2 Al_2O_3 of the weathering crusts has increased from 13.57% to 55.63%, suggesting the existence of an obvious formation process of paleosol. The variation of chemical index of alteration (CIA) and that of moving index of mass from the base rocks to the weathering crust show the same trend. CIA is up to 39.43%, whereas the moving index of mass of Ca is up to -0.97, implying that Ca component has been almost completely depleted. All the above analyses show that these weathering crusts belong to the second paleosol formation stage of carbonate rocks, i.e., they were developed by the accumulation of undissolved materials in base rocks and hence belong to the 2nd_order sequence surface.

Abstract:The distribution of heavy minerals in sediments is affected by such factors as provenance, geological setting, palaeoclimate and palaeoenvironment, which constitute sensitive indexes for the evolution of basins and mountains. The characteristics of sediments and heavy minerals in Kuche River section have been studied in this paper. According to the results obtained, the tectonic evolution of Kuche depression and South Tianshan in Mesozoic and Cenozoic can be divided into four periods, namely early and middle Triassic, late Triassic to early Cretaceous, Paleocene to Miocene, and Pliocene to the present, with the uplift of Tianshan in the last period being most intense. The palaeoclimate evolution of Kuche depression and South Tianshan in Mesozoic and Cenozoic can be divided into three periods, i.e., early Triassic (arid_semiarid), middle Triassic to middle Jurassic (humid_semihumid), and late Jurassic to the present (semiarid_arid).

Abstract:Based on a study of physical and optical properties and chemical contents of ruby and sapphire from Heilongjiang Province, together with a preliminary discussion on the color_causing factors of these two minerals, it is believed that ruby and sapphire in Heilongjiang Province can be divided into red and blue series consisting totally of twelve colors. Their physical and optical properties and chemical contents show remarkable differences. Spectral analysis shows that the color of ruby is caused by the color_causing elements nickel, chromium and iron, whereas the color of sapphire by the color_causing elements iron and titanium. The variations of their color shading and tone result mainly from the iron content and Fe~(3 )/Fe~(2 ) ratio.

Abstract:With the physical gas adsorption, the inner diameter of clinochrysotile in nature was studied. The result shows that this technique is more effective than transmission electron microscope (TEM) in the study of inner diameter of clinochrysotile nanotubes. It has the following merits: (1) it can be applied to a lot of samples; (2) the information of size, distribution and variation of the inner diameter of ringent nanotubes can be acquired; (3) according to the N_2 adsorption and desorption processess of ringent nanotubes, the special physical and chemical characteristics can be thoroughly studied; (4)combining with the other methods, we can obtain more information and parameters, such as the outer diameter.

Abstract:The synthesis and the product of polyaniline / montmorillonite nanocomposite materials were studied. The montmorillonite was modified by quaternary ammonium salt after the exchange of its interlayer cations with Na~ . With the affinity between the quaternary_ammonium_cation/montmorillonite and the organic compounds, the aniline monomer as the guest substance was inserted in the interlayer of montmorillonite. And then the polyaniline/montmorillonite nanocomposite materials were synthesized by using the technique of in_situ polymerization. The results of XRD, SEM, TG_DTA show that the inserting of the aniline monomer can remarkably enlarge the interlayer space of montmorillonite, and the polyaniline/montmorillonite nanocomposite materials completely lose the X_ray diffraction, morphological and thermal properties of montmorillonite and the quaternary_ammonium_cation/montmorillonite. It is also shown that montmorillonite layers have been peeled off and dispersed into polyaniline and the polyaniline/montmorillonite nanocomposite materials have been synthesized.