The giant phenocryst adamellite is an important magmatism record of the Mongol Ocean plate in the late period of the Early Paleozoic Era. Their formation age and geochemical characteristics are significant to reveal the tectonic framework and evolution history of the Mongol Ocean plate at that period. The paper presents the zircon U-Pb age of the giant phenocryst adamellite in Southeast Mongolia by LA-ICP MS method. The U-Pb age of zircon of adamellite given is (454.3±3.8) Ma, belonging to the Late Ordovician. The geochemical data of granite show its high-K calc-alkaline nature. The granite is also characterized with high silicon, with SiO2 being 69.82%-75.16%, Al2O3 12.91%-14.49%, and Na2O/K2O 0.60%-0.77%, peraluminous, with aluminum saturation index being in the range of 1.11-1.22, and Mg# index of 39-44. The total content of REE is 43.47×10-6-158.11×10-6, δEu=0.26-0.49. The REE distribution pattern of adamellite is demonstrated by a significant negative Eu anomaly and a "swallow-type" shape. The spider diagrams of trace elements standardized by primitive mantle show apparent enrichment of Rb, Th, U, K, Zr, Hf, strong depletion of Ba, Sr, P, Ti and medium to slight depletion of Nb and Ta. The initial 143Nd/144Nd values are high (0.512449-0.512507), and the average value is 0.512477. The εNd(t) values are all positive (0.2-1.3). The characters of major elements, trace elements, and isotopes show that the giant phenocryst adamellite in the Southeast Mongolia was formed at an extensional geotectonic environment during the transitional period from syn-collision to post-orogenic tectonic systems. The extensional tectonics and the underplating of mantle-derived basic magmas are suggested to be the main dynamic mechanism to form the granite. Since the adamellite is the important magma record of the Mongol Ocean plate subduction in the early Paleozonic, the present research is helpful to reveal the tectonic evolution and the characters in the Palaeo-Mongolia Ocean plate area.

The mineral exploration in complex surface conditions has always been a difficult problem in China so as in foreign exploration blocks. The exploration area 13451X is a thick cover grassland located in Sukhbaatar Province of Mongolia. In this work, for the first time we used the XLT-592WZ hand-held X fluorescence spectrometer to collect data in the field, and determined a metallogenic target area. The early scanning exploration using X-ray fluorescence identified the W, As, Pb, Zn, Cu and Fe anomalies, and geochemical surveys delineate a tungsten polymetallic ore-prospecting area. Twenty-threetrenches and drilling projects suggest a tungsten ore body in the ore-prospecting area. This tungsten orebody mainly appears in veiny, blocks or brecciated form, and its surrounding rock is granite porphyry or quartz porphyry. The ores are dominated by wolframite with trace of scheelite, and silicification and fluorite can be found. It is thus inferred that this deposit is of the high-temperature hydrothermal type. We can conclude that the use of portable X-ray fluorescence spectrometer for qualitative and semi-quantitative analysis in the field is effective, and that this method can be widely applied in similar areas.

Located between the northern margin of Erlian-Hegenshan suture zone and the pericontinental accretion zone of the southeastern margin of the Siberia plate,the Bayinsukhtu granitic body is an intrusive complex composed of monzonitic granites emplaced at Carboniferous and Triassic-Jurassic respectively.Geochemical analyses suggest that both of the two periods of monzonitic granites are characterized by high contents of silica,Al2O3 and alkali,low contents of calcium and magnesium.They are enriched in LILE and depleted in HFSE,with moderately enrichment of LREE,weak fractionation of LREE from HREE and negative Eu anomalies(δEu = 0.35-0.66).Based on the petrologic and geochemical features,the Carboniferous monzonitic granite is classified as mainly high-K,calc-alkaline,metaluminous to weakly peraluminous syn-orogenic I-type granite,while the latter is A-type granite.Isotope geochemistry of the Carboniferous granite shows that values of eNd(t) and(87Sr/86Sr)i range from 0.9 to 1.5,and from 0.700 62 to 0.704 82,respectively,which indicates that the granitic magma was likely derived from a young mantle source or an accretionary island arc with some degree of crustal contamination.However,the Triassic-Jurassic granite has lower eNd(t) but higher(87Sr/86Sr)i values relative to the Carboniferous granite,ranging from-0.3 to 0.3 and from 0.709 96 to 0.710 19,respectively.This indicates the granite derived from the same source with relatively high degree of crustal contamination.The dating of zircons from the monzonitic granites determined by LA-ICP-MS yielded a weighted age of(296±3.5) Ma,indicating that in the late Carboniferous the studied area was a syn-collision pericontinental tectonic environment.According to geochemical analysis of Late Triassic-Early Jurassic granite,it is presumed that the syn-collisional magmatism lasted till Triassic-Jurassic,probably suggestive of a long duration of collision.

Tourmaline mineral has various chemical composition and multi-isomorphism on the same position.Their formation temperature and pressure range is very extensive,can be stable in the temperature of the earth's crust pressure range,and can keep balance with various geological fluid.The main and trace elements spread rate of tourmaline structure is extremely low.And tourmaline mineral hardness is bigger,after forming can withstand erosion,weathering,diagenesis,metamorphism process and save the composition and structure when they formed.Through analysis the trace elements,stable isotopes(including B,Li,Nd,etc),radioactive isotopes(K-Ar,Ar-Ar,etc) which composite tourmaline can tracer the diagenesis and mineralization environment,including the source of the fluid,redox condition,temperature and pressure,formation age and mineral instruction significance in the exploration.

A set of volcanic rocks was newly discovered in Paleozoic strata in the southern Mongolia. The Rb-Sr age of the volcanic rocks is (370±21) Ma, being comparatively consistent with their host stratum age proposed by former researchers. Based on petrologic and geochemical study, the volcanic rocks are contemporaneous and homologous basically. However, their lithology varies significantly, and they are composed mainly of andesites and minorly of basalts, rhyolite and dacites. Their mantle source has apparently modified by the subducting slab. The original magma for the volcanics came from the mantle modified by fluids originally contained in the subducted slab, and was contacted late by the overlying crust during its ascending. It is suggested that the inhomogenous nature and strong fractionation of the magmas are the main reasons for the diversity of varied volcanic rocks (andesite, basalt, rhyolite and dacite) in the set. It is suggested that these volcanic rocks were formed in an island arc environment during the closing of the ancient Asian Ocean. This implies that the formation of these volcanic rocks took place before the collision between the North China plate and the Siberia plate during Late Paleozoic.

Porphyry copper deposits,as one of the most important copper deposits in the world,play a vital role in modern economic and science.Since Schwartz(1947) firstly defined "Porphyry copper deposit",geologists had paid great attentions on it.Proceedings on formation mechanism and evolution process of porphyry copper deposits show that formation of copper-rich porphyry magma involved a series of processes as follows:formation of ore-bearing magma related to subduction of oceanic crust or detachment of continental lithospheric crust,crystallization and fractionation of magma and enrichment of ore-forming fluids and material in median magma chamber,crystallization and solidification of ore-rich porphyry magma in shallow crust,interaction between ore-rich porphyry magma and ambient rocks.Porphyry copper deposits were final products of the "product line".Finally,some hot topics of origin of porphyry copper deposits and ore-forming magma were discussed in this contribution.

Located between the northern margin of Erlian-Hegenshan suture zone and the pericontinental accretion zone of the southeastern margin of the Siberia plate,the Bayinsukhtu granitic body is an intrusive complex composed of monzonitic granites emplaced at Carboniferous and Triassic-Jurassic respectively.Geochemical analyses suggest that both of the two periods of monzonitic granites are characterized by high contents of silica,Al2O3 and alkali,low contents of calcium and magnesium.They are enriched in LILE and depleted in HFSE,with moderately enrichment of LREE,weak fractionation of LREE from HREE and negative Eu anomalies(δEu = 0.35-0.66).Based on the petrologic and geochemical features,the Carboniferous monzonitic granite is classified as mainly high-K,calc-alkaline,metaluminous to weakly peraluminous syn-orogenic I-type granite,while the latter is A-type granite.Isotope geochemistry of the Carboniferous granite shows that values of εNd(t) and(87Sr/86Sr)i range from 0.9 to 1.5,and from 0.700 62 to 0.704 82,respectively,which indicates that the granitic magma was likely derived from a young mantle source or an accretionary island arc with some degree of crustal contamination.However,the Triassic-Jurassic granite has lower εNd(t) but higher(87Sr/86Sr)i values relative to the Carboniferous granite,ranging from-0.3 to 0.3 and from 0.709 96 to 0.710 19,respectively.This indicates the granite derived from the same source with relatively high degree of crustal contamination.The dating of zircons from the monzonitic granites determined by LA-ICP-MS yielded a weighted age of(296±3.5) Ma,indicating that in the late Carboniferous the studied area was a syn-collision pericontinental tectonic environment.According to geochemical analysis of Late Triassic-Early Jurassic granite,it is presumed that the syn-collisional magmatism lasted till Triassic-Jurassic,probably suggestive of a long duration of collision.

The obvious differences of petrophysical properties in the studied region have provided reliable geophysical basis for the high precision magnetic prospecting.The paper reports the results of high precision magnetic survey in the 13451 mining area by using the H_C-95 hand-held helium(~4He) optical pumping magnetometer.The result recognizes the hidden mafic-intermediate volcanic rocks when discerning the lithological boundary.By continuation processing the magnetic data,the authors point out the important structural boundary.The perfect combination of magnetic data and geological mapping has made geophysical method better serve the geological work at cover region. It also provides significant reference for delineating the beneficial ore-forming positions.

<正>钨矿是中国的优势矿种,已探明储量集中分布在华南地区。进入21世纪以来,在北方造山带(境内外)地区新发现了一批大中型钨矿床和远景区,既填补了找矿空白,也为深入认识该区域复杂的地壳演化历史提供了新的证据。1北方造山带钨矿的分布、类型、时代(1)新疆北部:特克斯县大恩别列白钨矿(西天山,中央地块,小型,矽卡岩型,泥盆纪黑云母斜