Petrochemistry ,Chronology and Tectonic Setting of Strong Peraluminous Anatectic Granitoids in Yunkai Orogenic Belt , Western Guangdong Province ,China

Arguments persist on the genesis and ages for the banded-augen （rapakivi） anatectic granitoids （charnockite） extensively outcropped in the Yunkai （云开） region, western Guangdong （广东） Province. Their petrochemistry, SHRIMP dating, deformational and metamorphic structure were studled. The results show that most granitoids are A/CNK〉1. 1, CaO/Na2O= 0. 62-1. 61 （average 0.94〉0.3）, Al2O3/TiO2 =16.6-60.6 （average 23.68）, depleted high field strong elements Ta, Nb, Zr, strong peraluminous high-K calcalkaline and calcalkaline granitoids in the post-collisional tectonic environment of a subduction-collision orogenic belt in an active-continental margin. The temperatures of charnockite and gneissic garnet-bearing biotite monzonitic granite are obviously higher than those of banded-augen （rapakivi） biotite monzonitic granite, and charnockite and gneissic garnet-bearing biotite monzonitic granite with the evolutional characteristics of A-type granites. The forming ages from banded-augen （rapakivi） biotite monzonitic granite to charnockite and gneissic garnet-bearing biotite monzonitic granite, whose crystallizing zircon SHRIMP ages are （465±10） Ma, （467±10 ） Ma, （435±11 ） Ma and （413±8） Ma, respectively, become younger. This shows that there was an oceaniccontinental subduction-collision and post-collisional extension-delamination-underplating between the Yangtze and Cathaysia plates during the Caledonian, and the granitoids experienced compressional uplift and extensional exhumation during the lndosinian. This provides important evidence of subduction collision of the Yangtze plate to the Cathaysia plate during the Caledonian in South China.

Huanggang Intrusive Complexin Northern Tongbai Area:Island-Arc Tectonic Environment and Its Geological Significance

The Huanggang intrusive complex in northern Tongbai area was formed in Early Paleozoic. It mainly consists of ultra basic, basic, intermediate and acid rocks, dominated by intermediate and basic rocks. The complex belongs to calc alkaline series. Geochemical characteristics of major and trace elements show that the complex was derived from the fractional crystallization of co source magma. It is suggested that the complex was formed in island arc tectonic environment and was closely related to the northward subduction of the Erlangping back arc basin. Thus, the subduction of the back arc basin can induce the island arc type magmatism similar to the one formed in the setting of ocean plate subduction.

Deep Structures in China and Its Adjacent Areas: Plate Tectonics and Its Metallogenic Significance

This paper proposes a new tectonic pattern of the deep-seated structures in China and its adjacent areas (including the T - A - B system of the Ryukyu Islands). This is based on studies of the gravity field and gravity inversion coupled with the summation of the most recent achievements in geophysical studies. From a plate-tectonic point of view, the metallogenic characteristics and their indications at depth, as well as relevant geophysical-geological characteristics of four tectonic environments of the Chinese continent are analysed, and a classification of composite metallogenic provinces and belts and prediction of metallogenic prospects are made. The author extends the Kunlun-Qilian-Qinling tectonic belt to the T-A-B system of the Ryukyu Islands through the NW deep boundary of the Hangzhou Bay, and also proposes the following basic views' the migration and superposition of tectonic environments led to the formation of a composite metallogenic system; the change in the tectonic environment resulted in the superposition of various types of mineral deposits; seismic activities and metallogeny are mutually inducing factors. These views will be helpful to a discussion on the tectonic environments and metallogenic regularities.

Sequence Stratigraphy and Tectonic Environment of the Chartai Group,Inner Mongolia

The Middle Proterozoic Chartai Group separated by two unconformities consists of three depositional se-quences: the Shujigou Formation-Zenglongchang Formation (DS Ⅰ), the Agulugou Formation (DS Ⅱ), andthe Liuhongwan Formation (DS Ⅲ). The carbonate platform and back-platform basin are the basic environ-ment model of the Chartai Group. The syndepositional faults on the oceanward side of the carbonate platformand large-scale slumping in the soft sediments are important marks of facies tracts. The newly establishedZenglongchan uplifting, an epeirogenetic uplifting, plays an important role in the formation of thepalaeogeographic framework of the Chartai Group. The stratigraphic correlation between the Chartai Groupand the Bayan Obo Group is made for the first time by using sequence stratigraphic principle and model estab-lished by P.R. Vail. The Chartai Group, which was deposited on the northern passive continental margin of theNorth China platfom, represents the platform cover.

Tectonic environment and cause of earthquakes in the Three Gorges reservoir area

Seismotectonics in the Three Gorges reservoir area is investigated by using the P-wave tomography with earthquakes that occurred before the impoundment of the reservoir. The result indicates that most of these events occurred in or around the velocity-gradient belts between high-velocity and low-velocity anomalies. These belts have similar characteristics to buried-fauh zones. Stresses generated by movement of partially molten upper-mantle materials and thermal stress may have jointly contributed to the seismic activities along the faults and such buried faults, and possibly activated new earthquake ruptures.

Magnetite-Fluorite Rock:A New Rock Type of Hot Water Sedimentation

The new type hot water sedimentary rock -- magnetite-fluorite rock occurs as quasi-layers in flat parts of contact zones between rock body and strata in Bamianshan of Changshan County, Zhejiang Province, China. The main mineral assemblage is fluorite＋magnetite＋cassiterite. The rock shows typical laminated structure and obvious mosaic texture. Its formation temperature is between 123℃-160℃, averaging at 142℃. The major chemical composition of the rock includes CaF2, SiO2, Al2O3, FeO, and Fe2O3; the high-content microelement association includes W, Sn, Be, Rb, Sr, S, and CI; and the total content of REE is low （∑REE between 35.34×10^-6-38.35×10^-6）, showing LREE enrichment type of distribution pattern. Diagenesis： driven by the tectonic stress, the formation water heated in the deep strata had moved along the fissures or fractures in strata and had extracted components from the strata on the way, and finally stagnated in the flat parts of contact zones between rock body and strata. With drop in temperature, magnetite and fluorite were separated from the hot water and precipitated alternately, forming this hot water sedimentary rock with new type mineralogical composition, typical laminated structure, obvious mosaic texture and sub-horizontal occurrence. The characteristics of the new type mineralogical composition, sedimentary tectonic environment and chemical composition are different from that of the well-known traditional hydrothermai sedimentary rocks.

Geochemistry,Geochronology,Sr-Nd Isotopic Compositions of Jiang Tso Ophiolite in the Middle Segment of the Bangong- Nujiang Suture Zone and Their Geological Significance

The Jiang Tso ophiolite, situated in the middle segment of the Bangong- Nujiang Suture Zone, is a part of the easternmost Qieli Lake ophiolite subzone and is close to the south of Pung Lake ophiolite. The rock association of Jiang Tso ophiolite is relatively complete and is mainly composed of metamorphic peridotite, gabbro and diabase. Comparing with N-MORB, the ophiolite is high in Mg and low in Ti, K, Na, P, and is depleted in Nb, Ta, Hf, Th and enriched in Rb, Sr and Ba. Geochemical characteristics of the Jiang Tso ophiolite indicate it is of a supra-subduction zone type formed in the spreading ridge of back arc basin. The SHRIMP U-Pb dating of zircons from the gabbro yielded a weighted average age of 188.1±4.1 Ma （MSWD=1.4）, indicating the Jiang Tso ophiolite was formed in the late stage of early Jurassic. The Sr, Nd isotopic compositions show that the Tethyan mantle domain is the depleted mantle （DM）, with enriched mantle domain II （EMII）. They have the same Sr, Nd isotopic composition with the India Ocean MORB type.

A Preliminary Review on the Metallogeny of Pb-Zn Deposits in China

Lead and zinc resources are abundant in China, with the reserves of 100 million tons ranking only second in the world. There are more than 3000 lead-zinc mine areas nationwide. The classification of lead-zinc （Pb-Zn） deposits has been a highly controversial issue. From the standpoint of evaluating the potential of mineral resources, we construct a Pb-Zn deposit predictive type of classification scheme, and propose a Pb-Zn deposit comprehensive classification scheme （including 5 classes and 13 sub-types） that regards mineralization as the primary factor and the ore rock as secondary. According to the temporal and spatial distribution of Pb-Zn deposits, we conclude that a multi-period, multi-cycle orogenic environment is the most favorable for lead-zinc deposit growth, that the Proterozoic is the major eon for the growth of igneous-type deposits, the Paleozoic is an important development era for sedimentary Pb-Zn deposits, and the Mesozoic and Cenozoic are the heyday eras of magmatic type lead-zinc deposits. On this basis, we analyse the relationship between tectonic evolution and Pb-Zn metallogenic, and propose that the key factors determining geological mineralization are the metallogenic epoch of mineralization and tectonic environment, which determine the temporal and spatial distribution.

Gravity variation before the Akto Ms6.7 earthquake, Xinjiang

The relationship between gravity variation and the Akto Ms6.7 earthquake on November 11, 2016, was studied by use of mobile gravity observation data from the China continental structural environmental monitoring network. The result revealed that before the Akto earthquake, a high positive gravity variation was observed in the Pamir tectonic knots region （within a maximum magnitude of approximately ＋80 microgal）, which was consistent with the existing knowledge of gravity abnormality and the locations of strong earthquakes. In view of the recent strong seismic activities in the Pamir tectonic knots region, as well as the strong upward crust movement and compressive strain, it is believed that gravity change in the Pamir tectonic knots region reflects the recent strong seismic activities and crust movement.