华北克拉通新生代玄武岩携带的地幔橄榄岩Fe同位素地球化学及含金云母地幔岩岩石学研究

In recent years, thanks to the improvement of analytical methods and the use of MC-ICP-MS, Fe isotope can be measured precisely. Fe isotope shows considerable variation both in biological and inorganic processes (from low T to high T) in nature, Therefore, Fe isotope has become one of the exciting frontier sciences and has favorable prospects of the application to the geosciences and life sciences. Based on a comprehensive review of available references in the related field, this study focuses on the development of techniques for high-precision measurement of iron isotope using MC-ICP-MS, and application of the techniques developed to study the Fe isotopes as well as major and trace element compositions of minerals (Ol, Opx, Cpx and Sp) from spinel peridotitic xenoliths from Cenozoic alkaline basalts to investigate Fe isotopic features of the lithospheric mantle beneath the North China Craton. The minerals from these xenoliths are similar to those off-cratonic peridotites world-wide, but are remarkably different from those on-cratonic peridotites and clinopyroxenes from these spinel lherzolites exhibit two types of chondrite-normalized REE patterns i.e. LREE-depleted and flat or spoon-shaped. It is noted that total abundances of REE in clinopyroxenes from these peridotites show a broad negative correlation with Cr# numbers of Cpx and Sp. The Fe isotope results show that the spinel peridotitic xenoliths have small but distinguishable Fe isotopic variations in minerals (generally Ol < Opx < Cpx) and samples, and the isotopic range in spinel is relatively large. Positive linear relationship with the ε57Fecpx/ε57Feopx ratio close to one unit has been observed between Fe isotopes of coexistent Opx and Cpx, indicating that the Cpx and Opx have generally reached Fe isotopic equilibrium. However, Fe isotopes between the Ol and Sp show apparent disequilibrium. The broadly negative correlation between mineral Fe isotopes and oxygen fugacity (fo2), metasomatic indexes such as spinel Cr#, (La/Yb) N and (La/Sm) N ratios of clinopyroxenes suggest that Fe isotopic variations in different minerals and peridotites were probably produced by melt-peridotite interaction. This study further confirms the previous observation that the lithospheric mantle has distinguishable and heterogeneous Fe isotopic variations at a scale of xenoliths. Mantle metasomatism that induces the interaction of the lithospheric mantle peridotite with metasomatic agent is a most potential mechanism for the Fe isotope fractionation in mantle peridotites. Therefore, Fe isotope could be a new and powerful tool to probe the evolution of the lithospheric mantle. We also report mineral compositions, clinopyroxene trace element concentrations and Sr-Nd isotopes for newly-discovered phlogopite-bearing spinel lherzolite and olivine clinopyroxenite xenoliths from three different localities （Hannuoba, Hebei Province; Jining Sangyitang, Inner Mongolia; Hebi, Henan Province）of the North China Craton. Systematic comparisons with phlogopite-free spinel lherzolite xenolith from the same locality reveals that the phlogopite-bearing peridotitic xenoliths have relatively higher Al2O3, CaO, Na2O, K2O, TiO2 contents and lower MgO contents than those phogopite-free counterparts. The former also has higher LREE concentrations, but relatively less radiogenic Sr-Nd isotopic ratios. This demonstrates that mantle metasomatism can not only enrich the basaltic components and trace element concentrations, but also make a decrease in Mg# of the peridotites and olivines and a relative depletion in Sr-Nd isotopes. 87Rb/86Sr-87Sr/86Sr isochrons of the phlogopite-bearing xenoliths indicate that mantle metasomatism happened in the Mesozoic and/or Cenozoic time. The metasomatic agent was derived from the asthenosphere. The result also manifests that the widespread similarity of the geochemical features such as major and trace elements and isotopic compositions in the Cenozoic lithospheric mantle beneath the North China Craton to those “oceanic” lithospheric mantle could be as a result of the ubiquitous presence of the interaction between the old refractory peridotites and the infiltrated asthenospheric melt, rather than the actually newly-accreted lithospheric mantle.

内蒙古白云鄂博超大型REE-Nb-Fe矿床脉状矿化时代与成矿流体特征

Bayan Obo REE-Nb-Fe ore deposit is the largest REE deposit in the world. Owing to its unique type and tremendous economic value, this deposit has widely attracted interests from geological researchers and vast amount of scientific data have been accumulated. However, its genesis, especially ore-forming age and REE sources, have been under dispute for a long time. On the basis of previous research works, this paper mainly conducts studies on the Early Paleozoic ore-forming event in the Bayan Obo deposit. The following results and conclusions can be suggested: Sm-Nd isotopic analytical results of bastnaesite, beloeilite, albite and fluorite samples from a coarse-crystalline ore lode present an isochron age of 436±35Ma. Besides, Rb-Sr isotope dating of the coarse-crystalline biotite lode that intruded into banded ores gives an isochron age of 459±39Ma. The two ages verify the exist of Early Paleozoic ore-forming event at Bayan Obo, which characterized by extensive netted mineralization of REE fluorocarbonates, aeschynite and monazite, accompanied by widely fluorite-riebeckite-aegirine-apatite alteration. Sr-Nd isotope composition of vein minerals is located between EMI and ancient lower crust component in the ISr(t)-εNd(t) correlation diagram, indicating that there is a crustal contamination during veined mineralization. A large area late Paleozoic granitoids are distributed in the southeast region of east open pit of the mine. The granitoids intruded directly into the ore-bearing dolomite, and produced intense skarnization. Moreover, at 650-660m of the drill core on 22 line and 1598m level flat in the south of East Open Pit, we firstly found skarnization rocks. Single grain and low background Rb-Sr isochrone dating on phlogopite in skarn gives 309±12Ma. Considering the intruded contacting relationship, the late Paleozoic granitoids, already extended to the under part of REE ore bodies, must be posterior to the latest intense REE mineralization, and is only a destructive tectonic and magmatic activity. Fluid inclusion types of fluorite in the Bayan Obo deposit consist of multiphase daughter mineral-bearing inclusion, two or three phase CO2-bearing inclusion and two phase aqueous inclusion. Petrography, laser Raman analysis and microthermometry study indicate that the fluids involving in REE-Nb-Fe mineralization at Bayan Obo might be mainly of H2O-CO2-NaCl-(F-REE) system. The presence of REE-carbonate as a daughter mineral in fluid inclusions shows that the original ore-forming fluids are rich in REE elements.

内蒙古克什克腾旗小东沟斑岩型钼矿床的成矿作用

In this paper, the Xiaodonggou porphyry molybdenum deposit located in the Xarmoron molybdenum metallogenic belt is chose as the research area. We have analyzed the petrology of the Xiaodonggou pluton in detail and made chemical analysis of the major and trace elements, Rb-Sr and Sm-Nd isotope, common lead isotope and SHRIMP zircon U-Pb dating et al; in the other hand, we use the molybdenite to make common lead analysis and Re-Os isotopic dating. The Xiaodonggou pluton is rich in silicon, potass, zirconium, and low in REE. In addition, it has no minus Eu abnormity and show a isotopic composition high in εNd(t) and low in Sri, indicating its magma origining from the melting of juvenile thicken lower crust. In the meanwhile, it contained the features of high temperature, quick melting, quick segregation and quick emplacement. The common lead analysis of the pluton orthoclase and molybdenite show that the former transfer from orogen to mantle and the latter come from mantle, which is consistent to the molybdenite sulfur isotopic and quartz oxygen isotopic composition, demonstrating that the rock and ore-forming materials of deposit having different sources, magma from the lower crust mixing with mantle fluid. In plus, we use the physical experiments results of the water-magma reaction to explain the interaction of magma and mantle fluid. In the deep crust, these two systems uplifted in a immiscible state; when they reached low depth, the stream film between fluid-magma collapsed, and the magma was broken into small agglomerates by the fluid, then they mixed thoroughly. The SHRIMP zircon U-Pb dating gave a result of 142±2Ma and the molybdenite Re-Os dating result is 138.1±2.8Ma, corresponding to the big tectonic transition period of 140Ma, when the major stress field changing from south and north to west and east. At this time, the Da Hinggan ling ranges area was under an extensive background, underplating proceeded and mantle materials could add into the magmas forming in the lower crust. So, from the above analysis, we propose the following model for the Xiaodonggou porphyry molybdenum deposit: in the early Cretaceous period, the Da Hinggan ling ranges area was under a extensive background, the adding of mantle fluid containing ore materials into heated lower crust made it melting to produce magmas. Following more mantle fluid got into the magma room and urged the magma to segregate from the source quickly. The fluid and magma uplifted together, when they arrived at shallow depth, the fluid-magma became unstable and the latter was broken into many small agglomerates with fluid connecting them in the interspaces. Because of the H+, K+ and various elements existing in the fluid, it would reacted with the magma and the rock through alteration and ore minerals crystallized out, forming the Xiaodonggou porphyry deposit with disseminated mineralization phenomenon.

内蒙古龙头山Ag-Pb-Zn多金属矿床成矿模式及找矿模型

The recent years research indicated that middle-south section of Da Hinggan Mountains metallogenic belt has two periods(Hercynian and Yanshanian) characteristics of metallogenesis, as well as the most of ore deposits in the area closely relate to Permian strata. Longtoushan ore deposit discovered in 2004 is an Ag-Pb-Zn polymetallic ore deposit born in Permian and located in the east hillside of the metallogenic belt, which has considerable resources potentials. It has important research value for its good metallogenic location and blank research history. Base on the detail field geology studies, the geology characteristics of "two stages and three kinds of metallogensis" has established. According to further work through geochemistry research including trace element, REE, S, Pb and Sr isotope, as well as petrography, microtemperature measurement, Laser Raman analysis and thermodynamics calculation of fluid inclusion, origin and characteristic of the ore-forming material and fluid has been discussed. And a new technology of single pellet Rb-Sr isochrones has been tried for dating its born time. Bae on above work, study of ore deposit comparison has been carried out, and metallogesis controlling factor and geological prospecting symbol have been summarized. Finally, metallogenic model and prospecting model have been established. According to above, the next step work direction has been proposed. Main achievement of the paper are listed as follow: 1.Longtoushan ore deposit has experienced two metallogenic periods including hot-water sedimentation period and hydrothermal reformation period. There are three kinds of metallizing phase: bedded(or near-bedded) phase, vein-shaped phase and pipe-shaped phase. The mian metallogenic period is hot-water sedimentation period. 2.Ore deposit geochemistry research indicated that the metal sulfides have charcateristic of hot-water sedimentation metallogensis, but generally suffered later hydrothermal transformation. The barite mineral isotope content is homogenous, showing the seabed hot-water sedimentation origin characteristic. Wall rock, such as tuff is one of metallogenic material origins. Both of Pb model age and Rb-Sr isochrone research older age value than that of strata, possibly for been influenced by hydrothermal transformation, and interfusion of ancient basis material. 3.There are two kinds of main metallogenic fluid inclusion in barite of the Longtoushan ore deposit, which are rich gas phase( C type) and liquid phase (D type). Their size is 2～7um, and principal components is H2O. Both kinds of fluid inclusion have freezing point temperature -7.1～-2.4℃ and -5.5～-0.3℃, salinity 4.0～10.6wt% and 0.5～8.5wt%, homogeneous temperature 176.8～361.6℃ and 101.4～279.9℃, which peak value around 270℃ and 170℃, respectively. Density of the ore-forming fluid is 0.73～0.97g/cm3, and metallogenic pressure is 62.3×105～377.9×105Pa. Above characteristic of the fluid inclusion are well geared to that of ore deposit originated in seabed hot-water sedimentation. 4.Through the comparison research, that Longtoushan ore deposit has main characteristic of hot-water sedimentation ore deposit has been indicated. Ore-forming control factor and prospecting symbol of it has been summarized, as well as metallogenic model and prospecting model. Next step work direction about prospecting has also been proposed finally.

北山及邻区古生代-早中生代增生与碰撞大地构造格局

The Beishan orogenic collage locates at the triple-joint among Xinjiang, Gansu, and Inner Mongolia Provinces, at which the Siberian, Tarim and North China plates join together. It also occupies the central segment of the southern Central Asian Orogenic Belt (CAOB). The main study area in the present suty focused on the southwest part of the Beishan Mountain, which can be subdivided into four units southernward, the Mazhongshan continental block, Huaniushan Arc, Liuyuan suture zone and Shibanshan-Daqishan Arc. 1. The Huaniushan Arc was formed by northernward dipping subduction from the Orcovician to Permian, in which volcanic rocks ranging from basic to acidic with island arc affinity were widely developed. The granitiod intrusions become smaller and younger southward, whichs indicates a southward rollback of slab. The granitiod intrusions are mainly composed of I type granites, and their geochemical compositions suggest that they have affinities of island arc settings. In the early Paleozoic（440Ma-390Ma）. The Shibanshan-Daqishan Arc, however, were produced in the southernward dipping subduction system from Carboniferous to Permian. Volcanic rocks from basic to acidic rocks are typical calcic-alkaline rocks. The granitiod intrusions become smaller and younger northernward, indicating subdution with a northernward rollback. The granitiod intrusions mainly consist of I-type granites, of which geochemical data support they belong to island arc granite. 2. Two series of adakite intrusions and eruptive rocks have been discovered in the southern margin of the Huaniushan Island Arc. The older series formed during Silurian (441.7±2.5Ma) are gneiss granitoid. These adakite granites intruded the early Paleozoic Liuyuan accretionary complex, and have the same age as most of the granite intrusions in the Huanniushan Arc. Their geochemical compostions demonstrate that they were derived from partial melting of the subudcted oceanic slab. These characteristics indicate a young oceanic crust subduction in the early Paleozoic. The late stage adakites with compositons of dacites associate with Nb-enriched basalts, and island arc basalts and dacites. Their geochemistries demonstrate that the adakites are the products of subducted slab melts, whereas the Nb-enriched basalt is products of the mantle wedge which have metasomatized by adakite melts. Such a association indicates the existences of a young ocean slab subduction. 3. The Liuyuan suture zone is composed of late Paleozoic ophiolites and two series of accretionary complexes with age of early Paleozoic. The early Paleozoic accretionary complex extensively intruded by early Palozioc granites is composed of metamorphic clastics, marble, flysch, various metamorphic igneous rocks (ultramafic, mafic and dacite), and eclogite blocks, which are connected by faults. The original compositions of the rocks in this complex are highly varied, including MORB, E-MORB, arc rocks. Geochronological study indicates that they were formed during the Silurian (420.9±2.5Ma and 421.1±4.3Ma). Large-scale granitiods intruded in the accretionary complex suggest a fast growth effect at the south margin of the Huaniushan arc. During late Paleozoic, island arc were developed on this accretionary complex. The late Paleozoic ophiolite has an age of early Permian (285.7±2.2Ma), in which the rock assemblage includes ultra-mafic, gabbros, gabbros veins, massive basalts, pillow basalt, basaltic clastic breccias, and thin layer tuff, with chert on the top.These igneous rocks have both arc and MORB affinities, indicating their belonging to SSZ type ophiolite. Therefore, oceanic basins area were still existed in the Liuyuan area in the early Permian. 4. The mafic-ultramafic complexes are distributed along major faults, and composed of zoned cumulate rocks, in which peridotites are surrounded by pyroxenite, hornblendites, gabbros norite and diorite outward. They have island-arc affinities and are consistent with typical Alaska-type mafic-ultramafic complexes. The geochronological results indicate that they were formed in the early Permian. 5. The Liuyuan A-type granite were formed under post-collisional settings during the late Triassic (230.9±2.5Ma), indicating the persistence of orogenic process till the late Triassic in the study area. Geochronological results suggested that A-type granites become younger southward from the Wulungu A-type granite belt to Liuyuan A-type granite belt, which is in good agreement with the accretionary direction of the CAOB in this area, which indicate that the Liuyuan suture is the final sture of the Paleo-Asin Ocean. 6. Structural geological evidence demonstrate the W-E spreading of main tectonic terrenes. These terrenes had mainly underwent through S-N direction contraction and NE strike-faulting. The study area had experienced a S-N direction compression after the Permian, indicating a collisional event after the Permian. Based on the evidene from sedimentary geology, paleontology, and geomagnetism, our studies indicate that the orogenic process can be subdivided into five stages: (1) the pre-orogenic stage occurred before the Ordovicain; (2) the subduction orogenic stage occurred from the Orcovician to the Permian; (3) the collisional orogenic stage occurred from the late Permian to the late Triassic; (4) the post-collision stage occurred after the Triassic. The Liuyuan areas have a long and complex tectonic evolutional history, and the Liuyuan suture zone is one of the most important sutures. It is the finally suture zone of the paleo-Asian ocean in the Beishan area.

内蒙古中部道郎和都格铜多金属矿的地质特征矿床类型及找矿模式研究

Daolangheduge copper polymetallic deposit is located on east edge of Ondor Sum-Bainaimiao metallogenic belt, which is a prospective area of porphyry copper deposit, in Xianghuangqi of central Inner Mongolia. Geotectonically, it occurred in the continental margin accretion belt along the north margin of North China Plate, south of the suture zone between North China Plate and Siberian Plate. The intrusive rocks in this area mainly consist of intermediate-acid magmatic rocks, and the quartz veins, tourmaline veins and the transitional phase are comparatively developed. According to our research, the ore-bearing rock body is mainly quartz diorite while the surrounding rock is mainly biotite granite. Besides, the wall rock alteration are mainly propylitization, pyritization and silicification, which consist of epidotization, actinolitization, chloritzation and so on. The metallic minerals are mainly chalcopyrite and pyrite. In addition, the primary ore is mainly of quartz-chalcopyrite-pyrite type. Above all, Daolangheduge copper polymetallic deposit is suggested to be categorized in the porphyry copper type. With isotopic dating and geochemical research on quartz diorite of ore-bearing rock body, the zircon LA-ICP-MS U-Pb dating of two samples yields an age of 266±2 Ma, falling into the range of late Permian Epoch. It is the first accurate age data in Xianghuangqi area, so it should play a key role in the research of deposit and magmatic rocks in this area. With the major elements and trace elements analysis of 14 samples, the quartz diorite should be among the calc-alkaline series, the geochemical characteristics show higher large-ion lithophile elements of Rb, Sr and LREE, low high-field strength elements of Nb, Ta and high transition elements of Cu, Cr . Also, the REE patterns have negative Eu anomalies. With the same analysis of 4 sample for the biotite granite, the geochemical characteristics show higher Rb, Th,, Zr, Hf and LREE, low Nb, Sm and HREE and Eu has no anomaly. It should be among the calc-alkaline series, over aluminum quality and has characteristics of Adakites. According to isotopic dating and geochemical characteristics of ore-bearing rock body, it is suggested that its materials mainly derived from upper mantle that had fractional crystallization and its magma source region may be affected by fluid metasomatism of paleo-asian ocean. It should be an extensional process of post-orogeny according to regional tectonic evolution. Consequently, because of the decrease of temperature and pressure, the ore forming fluid was raised to surface and mineralized accompanied by magmatic activity which might occur in south of the suture zone. By geological survey, further geophysical and geochemical work is needed. In this area, we have accomplished high precision magnetic prospecting, high density electrical survey, gravity prospecting, soil geochemical prospecting, X-ray fluorescence analyzer prospecting and so on. According to geophysical and geochemical abnormal and surface occurrence, 11 drills are arranged to verification. The type of ores are mainly quartz-chalcopyrite-pyrite ores within 3 drills by drill core logging. Although the grade as well as the scale of already-found Cu deposits are insufficient for industrial exploitation, the mineralization prospect in this region is supposed to be great and the potential in mineral exploration at depth is excellent.

浑善达克沙地全新世气候变化与风沙活动—夏日淖湖泊沉积记录

Atmospheric dust as an important factor for climate feedbacks is mainly derived from and drove by the aeolian activities of the semi-arid regions in Asia. Therefore, reconstructing the history of aeolian activities in this region has a great significance in understanding the dynamics of past and future climate changes. This paper made a systematical sedimentology, geochemisty and high-resolution chronology analysis on the sediments from the Xiarinao Lake, which located in Hunshandake Desert, Inner Mongolia, and compared with the meteorological records for identifying the indicator of aeolian activities and climate changes. Based on above work, the evolution history of the aeolian activities and climate changes since 11,000 a BP was reconstructed and the dynamics of the aeolian activities and climate changes in the Hunshandake Desert was discussed. The indicator of aeolian activities was established through the comparison of the clastic and chemical records with the meteorological registers in recent 50 years: 1. The sediments of Xiarinao Lake are mainly derived from eaolian clastic materials and composed of two major components: one is the sand fraction (<4 ) similar to the composition of sand dunes, the other is the silt fraction (>4 ) similar to the atmospheric dust. The sand content and the median grain size, particularly the sand content, show a close association with the intensity of wind, indicating that the particle-size composition of the sediments reflect the variations of the aeolian activities. 2. The proportion of soluble salts relative to the total carbonates in the sediments was correlated to the arid degree registered in meteorological records, suggesting that arid degree might be associated with changes of wind speed and the relative proportion of soluble salts to the total carbonate could be used as the indicator of aridity. 3. The δ18O of authigenic calcite in the Xiarinao Lake show a well correlation with both the atmosphere precipitation and variation of the moisture indicated by the concentrations of soluble salts, suggesting that δ18O of anthigenic calcite is a reliable indicator of humidity. Based on above studies, the evolution history of the aeolian activities and climate changes since 11,000 a BP was reconstructed. At the same time, their association and underlying dynamics was discussed: 1. The evolution history of the eaolian activity was reconstructed by the sand content and median grain size. The result showed that aeolian activities had experienced several different climate periods in the Holocene: the aeolian activities fluctuated with a 500-year cycles during the interval from 10,900 to 8200 a BP; no significant aeolian activities had been developed from 8200 to 6300 a BP; during the interval of 6300 to 2600 a BP, sand content and media grain size had increased gradually, the sand content increased from about 5% to 25%, indicating the intensity of aeolian activity increased in the Hunshandake Desert; since 2600 a BP, intensity of aeolian activity has become stronger and activated the sand dunes. 2. The relative arid degree indicated by the proportion of soluble salts relative to the total carbonate show that both the wind speed and dry degree had being increased since 11,000 a BP. During the interval of 10900 to 6300 a BP, no detectable soluble salt was found in the sediments, indicating the humidity condition; the proportion increased to 20% from 6300 to 4200 a BP, showing the climate became drier; the little change of proportion (20%) suggest that the climate was relative stable during the interval of 4200 to 2600 a BP; after 2600 a BP, the proportion increased, showing the climate became further dry. 3. The δ18O evolution of the lake water was established through analysis of authigenetic calcite δ18O for revealing the variations of relative effective humidity in the Hunshandake Desert. δ18O maintained around -6 ‰ during the interval of 10900 to 8200 a BP, showing the climate was a little dry relative to that of the whole Holocnene; in the period of 8200 to 6300 a BP, δ18O had the most negative values, indicating that it was the most humid interval in Holocene; from 6300 to 4200 a BP, δ18O increased from about -7.5 ‰ to about -3 ‰ gradually, suggesting increased aridity; since 4200 a BP, the climate has become stable and dry. On the whole, the records in this study show that the variation of the relative humidity and aridity is consistent with that of summer monsoon in the Hunshandake Desert. The relationships among the grain size, soluble salts relative content, and the authigenic calcite δ18O indicate aeolian activities is controlled by the aridity in the studied area, and the increased aeolian activities is closely associated with the temperature changes under the relative dry condition. The high wind speed under the low temperature leads to the increased aeolian activity, and the temperature change associated with the aeolian activities might be related with the perturbations of the Siberian High Pressure.

内蒙古赤峰红花沟地区早中生代构造－岩浆活动特征及金成矿作用

Honghuagou gold field, Inner Mongolia, is selected as the study area for the dissertation. The geological background for gold mineralization, geology of gold deposits, ore-controlling factors, physical and chemical conditions, material sources, genesis and ore-forming epoch for gold mineralization are studied in the dissertation. Especially, the Early Mesozoic tectonic and magmatic activities and their relationship with gold mineralization are studied with special efforts. Based on the study, the criteria for ore-prospecting are systemically summarized, target areas for ore-prospecting are circled and their gold reserves is estimated. Based on the first discovery of Early Mesozoic ductile zone which show the detachment features and the study on the emplacement of Early Mesozoic maficintermediate dyke swarms, the author present that the studied area was mainly in extensional uplift state during Early Mesozoic. The tectonic evolution can be divided into two stages. The extension was dominated by ductile metamorphose at early stage, whose geodynamics was related with the post orogenic extension after the collision between the Northern China Plate with Siberia Plate. The extension at late stage was featured by the intrusion of diorite and the emplacement of dyke swarms, whose geodynamics was related with mantle uplift. The gold deposits in the area are just the products of the tectonic and magmatic activities resulted from Early Mesozoic extension. The plagio-amphibolite from Archean metamorphic rocks is partially melted under the influence of underplating caused by mantle uplift, result in the formation of diorite magma. The gold in metamorphic rocks will also be melted into magma pond, and ascend into the upper parts of crust along with the intrusion of magma. The gold-bearing hydrothermal fluids is formed during magma differentiation, and caused the precipitation and concentration of gold in favorable geological conditions, result in the formation of gold deposits. The fracture caused by the emplacement of dyke swarms break a path for the ascending and movement of hydrothermal fluids, some of them become parts of ore-controlling and host structure. The gold is thought to be formed in Early Mesozoic, not in Yanshanian epoch.

内蒙古东部喀喇沁地区早中生代底侵作用

Mafic granulite xenoliths have been extensively concerned over the recent years because they are critical not only to studies of composition and evolution of the deep parts of continental crust but to understanding of the crust-mantle interaction. Detailed petrology, geochemistry and isotope geochronology of the Early Mesozoic mafic-ultramafic cumulate xenoliths and mafic granulite xenoliths and their host diorites from Harqin area, eastern Inner-Mongolia have been studied here. Systematic Rb-Sr isochron, ~(40)Ar-~(39)Ar and K-Ar datings for mafic-ultramafic cumulate xenoliths give ages ranging from 237Ma to 221Ma. Geochemical research and forming temperature and pressure estimates suggest that cumulates are products of the Early Mesozoic mantle-derived magmatic underplating and they formed in the magmatic ponds at the lowermost of the continental crust and are later enclaved by the dioritic magma. Detailed study on the first-discovered mafic granulite xenoliths reveals that their modal composition, mineral chemistry and metamorphic P-T conditions are all different from those of the Precambrian granulite exposed on the earth surface of the North China craton. High-resolution zircon U-Pb dating suggests that the granulite facies metamorphism may take place in 253 ～ 236Ma. Hypersthene single mineral K-Ar dating gives an age of 229Ma, which is believed to represent a cooling age of the granulite. As the host rock of the cumulate and granulite xenoliths, diorites intruded into Archean metamorphic rocks and Permian granite. They are mainly composed of grandodiorite, tonalite and monzogranite and show metaluminous and calc-alkaline features. Whole rock and single mineral K-Ar dating yields age of 221 ～ 223Ma, suggesting a rapid uplift in the forming process of the diorites. Detailed field investigation and geochemical characteristics indicate that these diorites with different rock types are comagmatic rocks, and they have no genetic correlation with cumulate and granulite xenoliths. Geochemical model simulating demonstrates that these diorites in different lithologies are products of highly partial melting of Archean amphibolite. It is considered that the Early Mesozoic underplating induced the intrusion of diorites, and it reflects an extensional geotectonic setting. Compression wave velocity V_P have been measured on 10 representative rock samples from the Early Mesozoic granulite and mafic-ultramafic cumulate xenoliths population as an aid to interpret in-situ seismic velocity data and investigating velocity variation with depth in a mafic lower crust. The experiments have been carried out at constant confining pressures up to 1000MPa and temperatures ranging from 20 ℃ to around 1300 ℃, using the ultrasonic transmission technique. After corrections for estimated in situ crustal pressures and temperatures, elastic wave velocities range from 6.5 ～ 7.4 km s~(-1). On the basis of these experimental data, the Early-Mesozoic continental compression velocity profile has also been reestablished and compared with those of the present and of the different tectonic environments in the world. The result shows that it is similar to the velocity structure of the extensional tectonic area, providing new constraints on the Early Mesozoic continental structure and tectonic evolution of the North-China craton. Combining with some newly advancements about the regional geology, the thesis further proposes some constraints on the Mesozoic geotectonic evolution history, especially the features of deep geology of the North China craton.

内蒙古乌拉特中旗北部宝音图群研究

The Baoyintu Group, lies in Wulate-zhongqi, Inner Mongolia, is a set of medium-grade metamorphic rock series which undergoes complex deformations. It consists of pelite schist, greenschist, plagioclase amphibolite quartzite and marble. The pelite schist is the main rock type and contains the classic medium pressure metamorphic minerals. The author divided Baoyintu group into five assemblages, investigated the rock association and plotted geological section of each assemblage in this area. Based on the systemically study of structural geology, petrology, geochemistry and mineralogy, the author reconstructs the protolith, sedimentary environment and tectonic evolution, discusses the mesoscopic and microscopic structure, metamorphism, geochemistry characters and the correlation between porphyroblast growth and deformation-metamorphism. There are three phase deformations in the research area: the earliest one occurred as the Baoyintu group deformed and metamorphosed and the main structure pattern is tight fold within layers during the Dl, large scale reversed fold and two phase faults (Fl fault and F2 fault) during the D2, and superimposed fold and F3 fault during D3. The F3 trancate the Wenduermian group of Silurian. The second and third phase deformation are relate to the orogenic event of late period of early Paleozoic. According to the rock association ,characteristics of the rocks and research of geochemistry, we get some information of the sedimentary environment and tectonic evolution of Baoyintu group. The source rocks are a set of terrigenous deposits-volcanic formation which reflect the history of the tectonic setting: stable- active-restable. And there are two sedimentary cycle from first assemblage to fifth assemblage: from first assemblage to fourth assemblage is a course of progression and the fifth assemblage is a start of regression. We also get the information of the P-T-t path by studying petrographies and calculating temperature and pressure. The path is not similiat to any classic type. And the interpretation is different from the traditional opinion. The P-T-t path reflects the dynamic course of convergence and uplift, magma underplating, back-arc extension and convergence of continental margin. Applying the theory of deformation partitioning to this area, the author discuss the relationship between deformation and porphyroblast growth, and get the conclusion of the sequence of deformation and metamorphism. At the first time we measure the distribution of chemical composition within the porphyroblast by XRF, confirm the theory of deformation partitioning quantitative and get new understanding about growth phase of porphyroblast and growth mode of porphyroblast: porphyroblast grow in the manner as "rose flower", the growth is controlled by the deformation. The elements distribution in porphyroblast reflects the growth manner and indicate history of metamorphism and deformation. So, we can deduce the metmorphism and deformation from the elements distribution in porphyroblast.

内蒙古岱海DH99a岩芯沉积物碳含量变化与湖区全新世气候变迁

Daihai Lake, a graben-type closed lake, lies ca. 10 km east of Liangcheng County, Inner Mongolia, north-central China. For its location at the transition of semi-humid and semi-arid areas, and in the north edge of the East Asian monsoon, the lake is sensitive to changes in climate and environment. Based on analyses of total inorganic carbon (TIC), total organic carbon (TOC) and the ratio of total organic carbon to total nitrogen (C/N ratio) of DH99a core sediments recovered in the central part of Daihai Lake, the data suggest Holocene climatic history of the lake region is reconstructed. In this paper, the TIC and TOC contents of the lake sediments are closely related to climate changes. 1) Changes in TIC content of the lake sediments is closely related to climate, which directly reflect changes of temperature in the lake region, i.e., higher TIC content is linked with warmer temperature and stronger evaporation; 2) Changes in TOC and C/N ratio reflect the regional precipitation, i.e., relatively higher TOC content and C/N ratio indicate higher rainfall which results in stronger river flow and more organic matter entering into the lake. Data of the TIC content, TOC content and C/N ratio of DH99a core sediments suggest that climatic history of the Daihai Lake region is characterized by 4 stages. During the interval of ca. 11200-7500 a BP, higher TIC content, relatively lower TOC content and C/N ratio value indicate a warmer and slight dry condition over the lake area. From ca. 7500 to 4500 a BP, high values of TIC content, with an increase in TOC content and C/N ratio suggest the climate was warm and humid. Changes of TIC content, TOC content show that both temperature and precipitation displayed obvious fluctuations during the period, i.e., slightly cool and humid ca. 7500-6700 a BP, warm and moist ca. 6700-5300a BP, mild and comparatively humid ca. 5300-4500a BP. Between ca. 4500 and 2900 a BP, TIC content and TOC content decreased gradually while fluctuating, C/N ratio displayed a decreasing trend. These data imply that the climate generally became cooler and drier than the preceding period. The lowest values of TIC content, TOC content and C/N ratio during the interval of ca. 2900-0 a BP, demonstrate that the climate was severe, and became cool and dry. However the relative higher values of TIC content, TOC content and C/N ratio between ca. 1700 and 1300 a BP may denote an increase both in temperature and in precipitation. Data of TIC content, TOC content and C/N ratio in Daihai DH99a core sediments indicate that the warm period was asynchronous with the humid time, the warm interval began in ca. 11200 a BP, and ended in ca. 2900 a BP. The humid period was ca. 7500-2900 a BP. During ca. 7500^500 a BP, the climate was warm and humid, which was the climatic optimum of the Holocene Epoch in the Daihai Lake region. Data of TIC content, TOC content and C/N ratio in Daihai DH99a core sediments imply that the Holocene climate was unstable, the fluctuating events happened occasionally. Such as the cold and dry climate in ca. 4400-4200a BP, the warm and humid climatic condition in the period between ca.1700 and 1300a BP.

地球化学新方法在隐状矿床找矿预测中的应用研究

With the progress of prospecting, the need for the discovery of blind ore deposits become more and more urgent. To study and find out the method and technology for the discovery of blind and buried ores is now a priority task. New geochemical methods are key technology to discover blind ores. Information of mobile components related to blind ores were extracted using this new methods. These methods were tested and applied based on element' s mobile components migrating and enriched in geophysical-geochemical process. Several kinds of partial extraction techniques have tested based on element' s occurrence in hypergenic zone. Middle-large scale geochemical methods for exploration in forest and swamp have been tested. A serious of methods were tested and applied effetely about evaluation of regional geochemical anomaly, 1:25000 bedrock or soil geochemical methods sampling based on the net in dendritic water system instead of the normal net. 1. Element related with ores can be mobiled to migrate upwards and be absorpted by surface soil. These abnomal components can be concentrated by natural or artificial methods. These trace metalic ions partially exist in dissovlvable ion forms of active state, and partially have been absorbed by Fe-Mn oxide, soil and organic matter in the soil so that a series of reaction such as complex reaction have take place. Employing various partial extraction techniques, metallic ions related with the phase of the blind ores can be extracted, such as the technique of organic complex extraction, Fe-Mn oxide extraction and the extraction technique of metallic ions of various absorption phases. 2.1:200000 regional geochemical evaluation anomaly methods: Advantageous ore-forming areas were selected firstly. Center, concentration, morphological feature, belt of anomaly were choosed then. Geological and geochemical anomalies were combined. And geological and geochemical background information were restrained. Xilekuduke area in Fuyun sheet , Zhaheba area in Qiakuerte sheet, the west-north part in Ertai sheet and Hongshanzui anomaly in Daqiao sheet were selected as target areas, in Alertai, in the north of Xinjiang. in Xilekuduke area, 1:25000 soil geochemical methods sampling based on the net in dendritic water system was carried out. Cu anomaly and copper mineralization were determined in the center area. Au , Cu anomalies and high polarization anomaly were determined in the south part. Prospecting by primary halo and organic complex extraction were used to prognosis blind ore in widely rang outcrop of bedrock. 1:25000 bedrock or soil geochemical methods sampling based on the net in dendritic water system were used in transported overburden outside of mining area. Shallow seismic method and primary halo found a new blind orebody in mining area. A mineralization site was fou and outside of Puziwan gold mine, in the north of Shanxi province. Developing middle-large scale geochemical exploration method is a key technique based 1:200000 regional geochemical exploration. Some conditions were tested as Sampling density , distribution sites of sample, grain size of sample and occurrence of element for exploration. 1:50000 exploration method was advanced to sample clast sediment supplement clast sediment in valley. 1:25000 bedrock or soil geochemical methods sampling based on the net in dendritic water system was applied to sample residual material in A or C horizon. 1:2000 primary or soil halo methods used to check anomalies and determine mineralization. Daliang gold mineralization in the northern Moerdaoga was found appling these methods. Thermomagnetic method was tested in miniqi copper-polymetallic ore. Process methods such as grain size of sample, heated temperature, magnetic separating technique were tested. A suite of Thermomagnetic geochemical method was formed. This method was applied in Xiangshan Cu~Ni deposit which is cover by clast or Gobi in the eastern Xinjiang. Element's content and contrast of anomaly with Thermomagnetic geochemical method were higher than soil anomaly. Susceptibility after samples were heated could be as a assessment conference for anomaly. In some sectors thermo-magnetic Cu, Ni, Ti anomalious were found outside deposits area. There were strong anomal ies response up ore tested by several kind of partial extraction methods include Thermomagnetic, enzyme leach and other partial extractions in Kalatongke Cu-Ni deposit in hungriness area in the northern of Xinjiang. Element's anomalies of meobile were mainly in Fe-Mn oxide and salt. A Copper mineralization site in Xilekuduke anomaly area had been determined. A blind ore was foung by shallow seismic and geochemical method and a mineralization site was found outside this mining area in Puziwan gold deposit in shanxi province. A Gold mineralization site was found by 1:50000 geochemical exploration in Daliang, Inner Mongolia.

白云鄂博超大型Fe-Nb-REE矿床碳酸盐脉状体的包裹体研究

白云鄂博矿床是世界上最大的Fe-Nb-REE矿床,其矿床成因一直是中外地质学家争论的焦点.而矿床附近的碳酸盐脉状体则成为赋矿白云岩岩浆成因的直接因素,该文拟从包裹体的角度对矿区碳酸盐脉状体进行研究,对其成因进行探讨,并对其与赋矿白云岩的关系作初步的讨论.通过对碳酸盐脉状体包裹体在包裹体类型,组合,均一温度,盐度,成分等方面的研究,发现不同区域,不同产状的碳酸盐脉状体包裹体特征存在较大的差异,这反映了其在岩石成因方面的差异:(1)都拉哈拉和尖山附近:为典型的岩浆成因;(2)宽沟背斜核部:可能是富碳酸盐盐熔体侵入构造裂隙形成的;(3)白云镇东北部(CV31,CV32)可能为侵入到混合岩中的热液脉;(4)东介勒格勒以南:具有明显的沉积特征.

中国地下工程氡污染健康影响与防护研究-以内蒙古自治区为例

由于对人体健康的危害，氡越来越受到世界各国的广泛关注。经济的发展，使我国地下公共场所大量涌现，但其空气中氡浓度的大规模调查及系统研究还属空白。本论文采取瞬时法（美国SUN公司的1027型连续测氰仪）与累积法（CR一39SSNTD）相结合的测量方法，对我国23个城市的地下工程进行了为期一年的监测，获得了实测数据700多个。在监测的同时，收集了每个测点的各种相关情况资料。论文以内蒙古自治区的呼和浩特、包头、集宁、鄂尔多斯四个城市为例，从环境地球化学角度出发，在研究了各个测点的各种情况之后，探讨了氧在不同类型工程和不同城市的浓度规律。对长期有人在内工作的地下工程内氛所致工作人员的有效剂量当量进行了估算。最后对氨异常的测点进行了原因分析，并提出了地下工程内氰污染的治理和防范措施。本次研究主要得出以下结论：1、地下工程中氰浓度的季节变化规律为：从总平均值看，夏高冬低。与前人对坑道的调查结果一致，与地上氨浓度的变化规律相反。从两季浓度差来看，两季浓度差从大到小依次为：隧道类工程）单建式铜室类工程＞结建式嗣室类工程。2、总体来看内蒙三类工程的氰浓度值：隧道类工程）结建式铜室类工程）单建式铜室类工程。不管是单季还是年平均值，各城市三类工程的氧浓度都遵循隧道类．工程远大于结建式铜室工程和单建式铜室工程的规律。通过对结建式桐室工程和单建式铜室工程的对比分析，发现在地下工程内工程上部有无建筑物阻隔，并不是影响氨浓度高低的重要因素，即氰的纵向扩散作用小于横向扩散作用。3、呼和浩特、包头、集宁、鄂尔多斯四个城市的氛浓度年平均值分别为：190Bq／m3、700Bq／m3、190Bq／m3、270Bq／m3。去掉仅有一季结果的侧点值，包头、鄂尔多斯的氨浓度年平均值为：62oBq／m3、250Bq／m3。呼和浩特、包头、集宁、鄂尔多斯四个城市的氛浓度单季值的范围分别为：31-830Bq／m3、57-3500Bq／m3、26一65oBq／m，、64一69OBq／m'，；年平均值的范围分别为：39一580Bq／m：'、94一210oBq／m：，、35-460Bq／m3、110-390Bq／m3。呼和浩特、包头、集宁、鄂尔多斯四个城市分别有30.0%、44.4%、33.3%、50.0%的工程年平均氧浓度在200Bq／时以上。四个城市氦浓度的普遍水平：包头）鄂尔多斯）集宁）呼和浩特。4、对所有单建式铜室类地下工程和结建式铜室类工程内工作人员所受剂量当量进行了估算。单建式地下工程内工作人员所受剂量当量的范围是1.247mSv-6．SOgmsv，平均值是2.610Sv。结建式地下工程内工作人员所受剂量当量的范围是1．195Sv-8.531mSv，平均值是2.572mSv。两类地下工程内工作人员所受氨照射剂量当量都很高，有一半的工程剂量当量是地面上公众人员剂量当量0.924mSv的两倍以上。5、不管是从浓度角度还是从剂量估算角度分析，地下工程内的氛水平都比较偏高，需要采取一定防护措施，对现有状况进行改善。6、通风是地下工程防治氡污染最简便易行、见效最快的措施。使用防氡涂料是最经济的措施。

The Tamaricetea arceuthoidis: a new class for the continental riparian thickets of the Middle East, Central Asia and the subarid regions of the Lower Volga valley

The new class, the Tamaricetea arceuthoidis, is described covering riparian and intermittent shrubby vegetation of the Irano-Turanian Region in the southwestern and Central Asia and the Lower Volga valley. The dominating species are species of the genus Tamarix that refer high water table in arid and semi-arid habitats with high to moderate salinity. This new class is an ecological analogon of the Nerio-Tamaricetea occurring in the Mediterranean Basin.