Geochronology and Geochemistry of Ore-related Granitoids in the Giant Gariatong Rb Deposit,Tibet and Implications for Rb Metallogeny in China

Rubidium(Rb)deposits mostly occur in the South China and Central Asia orogenic belts and are often closely associated with highly differentiated granites.This study investigates a newly-discovered giant Rb deposit at Gariatong in the Central Lhasa terrane in Tibet.Detailed field studies and logging data revealed that the Rb mineralization mainly occurs in monzogranite and is related to greisenization.LA-ICP-MS U-Pb dating of zircon yielded ages of 19.1±0.2 Ma and 19.0±0.2 Ma for greisenized monzogranite and fresh monzogranite,respectively.The monzogranites are characterized as strongly peraluminous,with high contents of SiO2,Al2O3,K2O and Na2O as well as a high differentiation index.They are enriched in light rare earth and large ion lithophile elements with significant negative Eu anomalies and depleted high fieldstrength elements.Petrological and geochemical features of these ore-related monzogranites suggest that they are highly fractionated S-type granites,derived from remelting of crustal materials in a post-collisional setting.The geochemistry of zircon and apatite points to a low oxygen fugacity of the ore-related monzogranite during the magma’s evolution.The discovery of the Gariatong Rb deposit suggests that the Central Lhasa terrane may be an important region for rare metal mineralization.

Landslide Hazard Assessment in the Northern Mountainous Areas of Tianshan Mountains Based on GIS

China is a country prone to geological disasters, especially in the northern mountainous areas of the Tianshan Mountains in Xinjiang, where the surface vegetation is sparse and the rainfall is concentrated, which is prone to landslides and brings a lot of losses to the local people. Based on the field investigation, this paper evaluates the landslide susceptibility in the northern mountainous area of Tianshan Mountains. The frequency ratio method is used to calculate the landslide probability, and the landslide index (LSI) is formed to represent the landslide susceptibility. The slope unit method is used to determine the landslide units, which values were calculated by the average of the landslide index. According to the calculated LSI range of 4.53 - 20.60. It is divided into 4 grades, LSI = 4.53 - 9, which is an area that is not prone to landslides, with an area of 891.69 km2. LSI = 9 - 11 indicates an area where landslides are more likely to occur, with an area of 1252.31 km2. LSI = 11 - 13 indicates the area is more prone to landslides, with an area of 714.86 km2. LSI > 13 indicates the most prone area for landslides, with an area of 924.60 km2.

Evaluation of the Collapse Susceptibility of the Northern Foot of the Tianshan Mountains

Collapse is a geological disaster second only to landslides and occurs in large numbers every year in the northern foothills of the Tianshan Mountains in Xinjiang, China. We collected a variety of data such as topography, geological vegetation coverage, and human activities, and used spatial correlation analysis to eliminate factors with strong correlations. The frequency of collapse was calculated by the frequency ratio method and a hierarchical map was made. The result shows, in low susceptibility zone (LSI = 0 - 4), only 3 collapses happened, and 0.39% of total collapses. In middle susceptibility zone (LSI = 4 - 7.5), 35 collapses happened, and 5.66% of total collapses. In high susceptibility zone (LSI = 7.5 - 10), 64 collapses happened, and 10.36% of total collapses. In extremely high susceptibility zone (LSI = 10 - 14), 516 collapses happened, and 83.5% of total collapses. Using the GIS-based frequency method, the susceptibility to collapse was calculated and mapped, which was in good agreement with the actual landslide data. Collapse susceptibility results provide guidance for engineering construction.

Chronology and geochemistry of metavolcanic rocks from Heigouxia Valley in the Mian-Lue tectonic zone, South Qinling——Evidence for a Paleozoic oceanic basin and its close time

The metavolcanic rocks of greenschist fades developed at Heigouxia Valley in the Mian-Lue tectonic zone, South Qinling orogenic belt is a bimodal volcanic series. It is composed of K-poor, Na-rich tholeiite and dacite-rhyolite. The trace elements characteristics with flat REE pattern of these tholeiites are similar to those of MORB. The Sm-Nd whole rock isochron age of(242±21) Ma and Rb-Sr whole rock isochron age of (221±13) Ma of this metavolcanic series consistently indicate their rnetamorphic time. Their relatively high initial εNd value of +6.1 at the rnetamorphic age (242 Ma) suggest that the volcanic rocks were derived from a depleted MORB type mantle source. Their trace elements and Nd isotope compositions suggest an oceanic basin developed from a rift on the continental margin of the Yangtze Block during the late Paleozoic and closed in the Triassic, This is the first case clearly showing the existence of relict of late Paleozoic oceanic crust in Fast Qinling belt, which provides important evidence for the Mian-Lue tectonic zone as a structure zone.

A CARBONIFEROUS SUCCESSION OF CONODONT FAUNAS FROM NORTH QILIAN MOUNTAINS IN NW CHINA

The Carboniferous section in Jingyuau region, Gansu Province, is the important and representative section for Carboniferous strata in China. The Jingyuan Formation, named by Li Xinxue et al, in 1974 is the representative Middle Carboniferous stratigraphic unit. Therefore, it is necessary to add continually stratigraphic and paleontological materials for investigation of the Carboniferous system in China.

FUSULINID-BEARING STRATA AND FUSULINID ZONE FROM THE TAIYUAN FORMATION ON THE EAST BANK OF THE YELLOW RIVER IN SHANXI

The Xiangning-Hejin area is situated in the southernmost part of the coalfield on the east bank of the Yellow River and is on the SE border of the Shaanxi-Gansu-Ningxia stratigraphie region in N. China. The middle and upper parts of the Taiyuan Formation here generally contain the four layers of the Fusulinid-bearing limestones, namely G-1,G-2, G-3 and G-4 limestones from bottom upwards, in which there are abundant Fusulinids characterized by Pseudoschwagerininae. Hence

SOME RELEVANT FACTORS IN FORMATION AND DISTRIBUTION OF THE LATE CARBONIFEROUS HIGH-SEAM ZONE, SHANXI

During the Late Carboniferous Taiyuan and Shanxi stage, some relevant factors in the formation and distribution of the high-seam zone in Shanxi can be summed up as follows: 1. The Type of Lithofacies Association The sandstone-mudstone facies and the mudstone-sandstone facies are the best lithofacies association types in the high-seam zone formation, in which the clastic ratio is>8 and the sandmud ratio 1/2—2 (excluding the seam). 2. The Type of Phase-Cycle

DIVIDING OF LOCAL STAGE OF LATE CARBONIFEROUS STRATA IN NORTH CHINA

Widely used by most of the stratigraphic and paleontologic workers, the 'Taiyuan Formation' and the 'Shanxi Formation' essentially are chronostratigraphic units having the meaning of the stage. In recent years some workers

THE TRANSGRESSION OF THE CARBONIFEROUS SEA-WATER IN SHANXI

During Carboniferous Era, Shanxi was situated in the central part of North China’s gigantic subsidence zone which was between the Yinshan and Qinling gigantic latitudinal structural zones. In the late Middle Carboniferous, the southwest part in Shanxi was higher than

THE MIDDLE-LATE CARBONI FEROUS PALEOSTRUCTURE TYPES IN SHANXI

During the Late Paleozoic era, Shanxi was situated in the central part of N. China’s gigantic subsidence zone between the Yinshan and Qinling latitudinal structural zones. Analyzing the change law of sediment and lithofacies, the paleostructures of the Middle-late Carboniferous Benxi (Penchi), Taiyuan and Shanxi stages in Shanxi Province can be divided into the following principal types: 1. The Benxi

SEVERAL DIVIDING PLANS ON THE BOUNDARY BETWEEN THE CARBONIFEROUS AND PERMIAN, SHANXI

At present, there are four principal dividing plans on the boundary between the Carboniferous and Permian, at home and abroad, i.e., the low er boundary of the Permian to be drawn (ⅰ) at the base of the Kasimovian stage. This work accepts the Leven and Scherbovieh’s dividing plan on the stage at 1978; (ⅱ) at the base of the As selian stage. This dividing plan is generally accepted by the stratigraphic and paleontologic workers; (ⅲ) at the base of the Sakmarian stage, and (ⅳ) at the base of the Artinskian stage. The stratotypic sections of most of the

THE KUYAK RIFT VALLEY, A CROSSCUTTER OF THE KUNLUN MOUNTAINS

The Kuyak Rift is located to the southeast of Minfeng (民丰) County, Xinjiang, and belongs to the western part of the Altun tectonic system. The well-developed section of the Rift about 300 km long and 10—20kin wide, starts from Lhazhulong in Xizang (Tibet) and ends in the southern margin of the Tarim Basin. In the northern part of the Rift stands over the accumulated terraces an abandoned castle called the 'Kuyak' pass served as the key to Xizang in ancient times. However,

DIVISION OF SILURIAN STRATA AND TABULATE AND HELIOLITIDA ASSEMBLAGES IN THE HAERKE MOUNTAIN IN XINJIANG

The Haerke Mountain is located in the western part of Southern Tianshan, covering an area 250km from east to west and 70--80 km from north to south, its extending direction is from NE to SW. Since the sixties the Regional Geological Surveying Team of Xinjiang has pronosed different divisions of the Silurian system.In 1981, the author collected

CORRELATION OF MARINE LIMESTONE AND SEAMS FROM TAIYUAN FORMATION, SHANXI

The Taiyuan Formation is one of the principal coal-bearing strata in Shanxi Province during the Late Palaeozoic. Being of marine-continental alternating sediments, the limestone, containing abundant marine faunas from different areas of Shanxi, has become the key of the correct corre-

ON THE AGE OF THE HEKOU FORMATION IN FUJIAN PROVINCE

The Hekou Formation was set by the Petroleum Geological Team of Fujian in 1979. The type-section of this formation located at Hekou Basin in western Ninghua County of Fujian consists mainly of red conglomeratic sandstone, siltstone and greyish-green mudstone with lime. Since Prof. Chen Xü proposed the age of Eogene for the corresponding Guanzhai red sandstone in western Fujian, bivalves and other fossils were first discovered by

THE LATE PRECAMBRIAN CRUSTAL EVOLUTION IN GUIZHOU PROVINCE

Strata of Upper Precambrian distribute widely and develop well in Guizhou Province. They may be divided into two stratigraphic provinces-the Yangtze and Jiangnan (Fig. 1). The sequence is composed of Fanjingshan Group (or Sibao Group), Banxi (or Xiajiang) Group and Sinian System (Table 1).

CORRELATION,DIVISION,FOSSILS AND GEOLOGIC AGE OF THE SHANXI FORMATION IN SHANXI PROVINCE

The stratotypic section of the Shanxi Formation in western hills of Taiyuan, Shanxi Province, its bottom boundary drawn at the base of the Beichagou sandstone and top demarcation at the base of the Luotuobozi sandstone, is of ma-

DIVIDING STAGE IN UPPER CARBONIFEROUS FUSULINID-BEARING LIMESTONES, SHANXI

There are 8 hayers of the Fusulinid-bearing limestone distributed widely and stably in the upper Carboniferous series of Shanxi, their unified names and sequence from bottom upward being Wuming Limestone, Wujiayu Limestone, Miaogou Limestone, Maogou Limestone, Xiedao Limestone, Dongdayao Limestone, Fucheng Limestone and Xiaodonggou Limestone (Table 1).

DISCOVERY OF MEISHUCUNIAN SMALL SHELLY FOSSILS AND THE PRECAMBRIAN-CAMBRIAN BOUNDARY IN WESTERN PART OF ZHEJIANG PROVINCE

In the late 1970s, small shelly fossils of the Precambrian-Cambrian transitional age in the western part of Yangtze Platform were widely studied. This note is the first report of Meishucunian small shelly fossils found in its eastern part (Fig. 1)