Adsorption difference of Pb^(2+) and Zn^(2+) in sandstone and breccia

The adsorption difference of Pb^2_+ and Zn^2+ in sandstone andbreccia of Pb-Zn Mine of Yunnan Province was studied by using moderninstrument analysis method and fractal geometry theory. The resultsshow that the adsorption capacity (Q) of Pb^2+ in this two rocks isbigger than that of Zn^2_+, and Q in various initial concentrationsolutions obeys Freundlich experiential formula. The value of 1/n onthe adsorption PB^2+ and Zn^2+ and Zn^2+ in sandstone hardly has anydifference, But the value of k differs observably.

Crystal Structure of Natural Non-metamict Ti- and Fe^(2+)-rich Chevkinite-(Ce)

The crystal structure of non-metamict Ti- and Fe2+-rich chevkinite-(Ce) has been redetermined with the single -crystal sample collected from Bayan Obo, Inner Mongolia, China. The chemical formula of the sample is Ce4Fe2Ti3Si4O22. The crystals are monoclinic with the unit cell parameters a = 13.4656(15) ?, b = 5.7356(6) ?, c = 11.0977(12) ?, β= 100.636(2)o, V = 842.39 (16) ?3 and Z = 2. The structures of Ti- and Fe2+-rich chevkinite-(Ce) were refined with space groups P21/a and C2/m. Least-squares refinement results show that both structural models of Ti- and Fe2+-rich chevkinite-(Ce) are very good, R[F2>2σ(F2)] =0.027 with P21/a and R[F2>2σ(F2)] =0.021 with C2/m. In order to illustrate the relationship between the two space groups P21/a and C2/m, the distribution of diffraction intensities was inspected. Pseudo extinction was found, i.e., reflections with h+k=2n are systematically strong, while those with h+k=2n+1 are weak. By neglecting the systematically weak (h+k=2n+1) reflections the space group becomes C2/m. There is a mirror plane in the C2/m perpendicular to the b axis. However, oxygen atoms in the P21/a model are of a symmetrical relationship with the corresponding pseudo mirror plane. It is concluded that the crystal structure of non-metamict Ti- and Fe2+-rich chevkinite-(Ce) is a superstructure with the space group of P21/a, which is of pseudo symmetry corresponding to the space group C2/m.

FORMATION AND EVOLUTION OF THE CENOZOIC THRUST FOLD BELT IN JINPING, SICHUAN

The Jinping orogenic belt in Sichuan, China consists mainly of the Jinpingshan intracontinental thrust-nappe belt, foreland thrust-nappe belt and foreland uplift belt. Based on analyses about the characteristics of the structural units in this area, the authors propose in this paper that Chapuzi-Bazhe revival fault belt is the regional boundary fault, and points out that after the formation of the Pre-Sinian basement, the western edge of the Yangtze paraplatform was turned into the passive continental margin in Sinian to Triassic, then into the Mesozoic collision orogenic belt, and finally into the Cenozoic orogenic belt through intracontinental orogeny.

SHRIMP U-Pb zircon dating for the dacite of the Sangxiu Formation in the central segment of Tethyan Himalaya and its implications

Petrology and SHRIMP U-Pb zircon chronol- ogy are reported for the dacite of the Sangxiu Formation in the central segment of Tethyan Himalaya to the southeast of Yangzuoyong Co. Twenty-one measured zircon grains from a dacite sample of the Sangxiu Formation can be divided into two groups, which include long columnar magmatic zircons of 133±3.0 Ma, representing the age of volcanism in the Sangxiu Formation, and inherited zircons consisting of core and overgrowth rim, in which ages of the three cores are 2244±16, 1153±33 and 492±25 Ma respectively; and the age of one overgrowth rim is 132.7±5.2 Ma. These ages are con- sidered to represent the remelting of accretionary crust at different periods resulting from the volcanism of Sangxiu Formation. These volcanic rocks in the Sangxiu Formation, for which age is close to that of Bunbury basalt in south- western margin of Australia, and older than that of Rajma- hal basalt in northeastern India, maybe considered as the products of early activity of the hotspot represented by the Rajmahal basalt.

Zircon SHRIMP U-Pb dating for the Cangshuipu volcanic rocks and its implications for the lower boundary age of the Nanhua strata in South China

The continental volcanic rocks and volcaniclastic sedimentary conglomerates of the Cangshuipu Formation occur well in Yiyang of Hunan Province, consisting of a wedge-shaped succession of Neoproterozoic strata that overlie with high-angle unconformity the flysch turbidites of the Lengjiaxi Group in the Upper Mesoproterozoic Eonothem. SHRIMP zircon U-Pb dating gives a weighted mean age of 814 ( 12 Ma for the dacitic volcanic agglomerates from the lowest part of the volcanic rocks in the Cangshuipu Formation. This age is younger than previously reported values of 921-933 Ma for the volcanic rocks from the Cangshuipu Formation. Our new dating represents the lower boundary age of the Neoproterozoic System in the studied area. The younger age for the Cangshuipu volcanic rocks is supported by the following observations: (1) Lower Neoproterozoic strata (814-1000 Ma) are missing in the studied area; (2) the Nanhua rift system was initiated at about 820 Ma; and (3) an age of ~820 Ma may be taken as the lower boundary timing of the Nanhua System (even Neoproterozoic) in South China.