东天山后碰撞镁铁-超镁铁岩镍铜硫化物矿床PGE地球化学示踪与富集规律研究

Eastern Tianshan area, a Paleozoic complex trench-arc-basin system, experienced multi-period sudbuction and collision in geological history. A large number of Early Permian mafic-ultramafic intrusions emplaced along deep faults in post-collision extension tectonic stage and hosted a series of magmatic Cu-Ni sulfide deposits. This paper sets newly-discovered Tianyu magmatic Cu-Ni sulfide deposit related to small intrusion as an example. On basis of the study of ore-forming mechanism of Cu-Ni deposit, we compared PGE content and discussed enrichment mechanism and regularity of mafic-ultramafic rocks and ores in Jueluotage tectonic belt and Central Tianshan Massif. PGE and Cu, Ni, S contents correlate with each other. PGE is mainly controlled by S content.Samilar PGE distribution patterns of mafic-ultramafic show that complex originated from the same parental magma; Pd/Ir and Ni/Cu ratios indicate that high-Mg basaltic magma and deep sulfide segregation happened during magma evolution process. PGE and Cu-Ni ores are enriched in liquid sulfide and only individual samples completely control by monosulfide solid solution. Comparison of all control factors, early segregation of sulfide and quality of supply of magma may be the key factors leading to the Eastern Tianshan magmatic copper-nickel sulfide deposits don’t reach PGE grade, but we do not rule out the possibility of occurrence continuous mafic-ultramafic rocks and PGE-rich layer in deep.

东天山镁铁-超镁铁岩铜镍硫化物矿床通道式成矿机制与岩体含矿性评价研究

A mafic-ultramafic complex belt well developed in Eastern Tianshan, Xinjiang, NW China, which contains a series of Cu-Ni sulfide deposits. This area is the important production basis for Cu-Ni deposits, including Tulargen deposit, Hulu deposit, Huangshan-Huangshandong deposit, Hulu deposit, Xiangshan deposit, Tianyu deposit, Chuanzhu deposit. In China, especially Eastern Tianshan, it is prevalent that large Cu-Ni deposits occurred in small intrusions, typically including Jinchuan, Kalatongke, et al., so the ore-forming mechanism and evaluation rule for those small intrusions are very meaningful and of universal significance. On the basis of the research to typical Cu-Ni deposits, ore-forming conditions and processes are summarized through which to evaluate the ore-bearing potential for barren intrusions and unexplored mafic-ultramafic intrusions. By the contrast, metallogenic rule and mechanism of ore genesis are concluded, and evaluation system is preliminarily set up on the basis of these conclusions. Quantitatively simulation for the composition of olivine is introduced for the first time in China to discuss the interaction between magma and sulfide, and a new method to calculate the Mg-Fe composition of primitive magma is developed. Interaction between magma and sulfide liquid is used to get the Ni content in sulfide liquid. Sulfur isotopic characteristics in sulfide minerals in country rocks and ores are used to judge crustal sulfur introduction, which is applied for the first time in China. Re-Os isotopic characteristics are related to the ore-forming process, to interpret the process of enrichment of chalcophile elements. On the basis of the evaluation system, Mati, Chuanzhu, Luodong, Xiadong, those intrusions are evaluated to their ore-bearing potential. According to the studies to typical Cu-Ni deposits, conduit-type ore-forming model is set up, and the characteristics of the model are concluded systematically. The evaluation system and conduit-type ore-forming model can be helpful to the evaluation of mafic-ultramafic intrusions in this and similar mafic-ultramafic intrusion belts. The studied typical deposits and mafic-ultramafic intrusion include Tulargen deposit, Hulu deposit, Huangshandong deposit, Chuanzhu deposit, Mati intrusion，Luodong intrusion, Xiadong intrusion, and others. Through studies, there are similar characteristics for Tulargen and Hulu deposits in magma origin, composition of primitive magma（MgO=12.5%, FeO=12% and MgO=11%, FeO=10.5% respectively）, magma evolution, mechanism of sulfide segregation and conduit-type ore-forming process. By Re-Os isotopic system, the ore forming date of Tulargen deposit is 265.6±9.2Ma, which is consistent to regional metallogenic event, but little younger. The Mg-Fe composition of primitive magma of Baishiquan, Huangshandong area, Kalatongke is lower than that of Tulargen and Hulu deposit, showing common basalt composition. The Mg# value（Mg#=(Mg/Mg+Fe）increases gradually from Kalatongke to Baishiquan to Huangshan-Huangshandong East. Baishiquan intrusions show relatively higher crustal contamination by evidence of trace element, which indicates the lower magma original source, from depleted mantle to crust. One break is the discovery of komatiitic intrusion, Xiadong intrusion, which shows characteristics of highly magnesium (Max Fo=96). The primitive magma is calculated of MgO=28%，FeO=9%, belonging to komatiitic magma. Tectonic evolution of Eastern Tianshan is discussed. By the statistics of ore-forming data of porphyry copper deposits, magmatic sulfide Cu-Ni deposits, orogenic hydrothermal gold deposits, we believe that those deposits are the successive products of oceanic subduction, are and back-arc basin collision and post-orogenic extention. And Cu-Ni sulfide deposits and orogenic gold deposits occurred in the stage of post-orogenic extention. According to the conclusions, the conduit-type ore-forming mechanism of magmatic sulfide deposit is set up, and its characteristics and conditions are concluded as well. The conduit-type ore-forming system includes magma generation, sulfide segregation, enrichment of chalcophile elements, interaction of sulfide and magma, sulfide collection in limited space in magma conduit and bottom of the chamber, which make a whole ore-forming system.The ore-forming process of Cu-Ni sulfide deposits is concluded as three steps: 1. mantle derived magma rises upward to the middle-upper crust; 2. magma suffers crustal contamination of different degrees and assimilates crustal sulfur, which leads to sulfur saturation and sulfide segregation. Sulfide liquid interacts with magma and concentrates chalcophile elements; 3. enriched sulfide located in the conduit(Tulargen) or bottom of the chamber (Hulu). Depleted magma rises upward continuously to form barren complexes. For the practical cases, Tulargen deposit represents the feeding conduit, and Hulu deposit represents the bottom of the staging magma chamber. So the deeper of west of Tulargen and southwest of Hulu are the favorite locate for ore location. The evaluation for ore potential can be summarized as follows: (1) Olivine can be served as indicator for magma evolution and events of sulfide segregation; (2) Sulfur isotopic characteristics is an efficient method to judge sulfur origin for magmatic sulfide deposit; (3) Re-Os content of the ores can indicate interaction between sulfide and silicate magma and crustal contamination; (4) PGE mineralization is effected by degree of partial melting of mantle; (5) Cu/Zr is efficient parameter to judge sulfide segregation; (6) The effects of multiple magma fractionation and emplacement are important, for inverse order shows the destruction to previous solid lithofacies and orebodies. Mati, Chuanzhu, Xiadong, Luodong, mafic-ultramafic intrusions are evaluated using evaluation system above. Remarkable Ni depletion is found in olivine of Mati, and southwest of the intrusion can be hopeful location for ore location. Chuanzhu intrusion has remarkable evidence of sulfide segregation, but the intrusion represents the narrow feeder conduit, so the wide part of the conduit maybe the favorite location for sulfide to deposit. The ore potential of Luodong and Xiadong is not good. Both the intrusions show no Ni depletion in olivine, and there is no sulfide in country rocks, so no crustal sulfur is added into the magmatic system. For Sidingheishan, a very large intrusion, the phenomenon of sulfide segregation is found, but there are no favorite places for sulfide to deposit. So the Cu-Ni ore potential maybe not good, but PGE mineralization should be evaluated further.

阿尔泰南缘侧向增生过程中的VMS矿床：地质、地球化学特征与成矿机制

The Chinese Altai is one of the most important volcanogenic massive sulfide (VMS) deposit districts in China. All orebodies were lenticular or bedded and stratabounded by a suite of early Devonian volcanic-sedimentary rocks. Hydrothermal feeder zones developed under some of the orebodies. All the ores are massive or laminated, and show typical characteristics of VMS deposit. Based on the mineralizing time and the metal assembles, we divide 3 metallogenic stages: 1, Fe orefroming stage associated with basaltic and sedimentary rocks during very early Devonian; 2, Cu-Pb-Zn oreforming stage associated with rhyolitic and sedimentary rocks during early Devonian; 3， Cu-Zn oreforming stage in the dacitic and basaltic rocks during mid. Devonian. The hosting rocks for all orebodies are different, but they show very similar geochemical and isotopic characteristics. All the felsic rocks show enriched lighted rare earth elements (REE) patterns (La/Yb>5), and with an obvious Eu negative anomalies (Eu/Eu*<0.6). In the meanwhile, all the mafic rocks show flat REE pattern and no Eu anomalies. The Ashele basalt show an apparent Ce negative anomalies (Ce/Ce* <0.76), All the volcanic roks in Chinese Altai show the decoupled property between the high field strength elements (HFSE) and large ion lithophile elements (LILE). The negative Nb, Ta characteristics with respect to adjacent elements indicate that subduction-modified source. The Nd(t) of the hosting rocks for all orebodies changed in a small range (-1.5~5), and the (87Sr/86Sr)i change in a big range. The initial Sr value of the hosting rocks in Mengku and Tiemuerte are obviously affected by the seawater (0.705~0.710), and initial Sr values of hosting rocks Ashele change in a small range (0.704~0.706). All Sr-Nd isotopes of ores have the same range with the hosting rocks, indicating that both the ores and volcanic rocks have the same island arc source. The mean sulfur isotopes of sulfides from Ashele and Mengku are 6.2‰ and 3.4‰, respectively, indicating a deep magmatic source. However, the sulfur isotopes of sulfides from Keketale, Tiemuerte and Keyinbulake changed in -15.8‰~9.9‰, -23.5‰~1.87‰, -8.3‰~1.6‰, respectively. And the big sulfur isotope range indicated that the sulfur of the ores was a combination biogenic and magmatic source. All volcanic rocks from the VMS deposits in the southern Chinese Altai show a typical subduction related environments. Based on the regional and locally geological evidence, here we propose that the southern Chinese Altai is an island arc system, and all VMS deposits formed during the lateral accretion process. No VMS deposit formed during the formation of the island arc during Silurian; Fe VMS deposit formed during the beginning of the opening of the backarc basin in very early Devonian; Cu-Pb-Zn VMS deposits formed during the mature stage of the backarc basin in early Devonian; at last the Cu-Zn VMS deposit formed during the rifted stage of the island arc itself.

大别山碰撞造山带逆冲推覆构造运动学和动力学研究

Since the discovery of coesite-bearing eclogites in Dabie and Sulu region over ten years ago, the Dabie collisional orogen has been the "hot-spot" across the world. While many great progresses have been made for the last decade in the researches on the Dabie and Sulu UHP metamorphic rocks in the following fields, such as, petrology, mineralogy, isotope chronology, and geochemistry, the study of the structural geology on the Dabie orogen is still in great need. Thrust and nappe tectonics commonly developed in any collisional orogenic belt during the syncollisional process of the orogen. It is the same as the Dabic collisional orogen is concerned. The paper put much stress on the thrust and nappe tectonics in the Dabic orogenic belt, which have been seldom systematically studied before. The geometric features including the division and the spatial distribution of various thrust and nappe tectonics in the Dabie orogen have been first studied, which is followed by the detailed studies on their kinematic characteristics in different scales varying from regional tectonics to microtectonics. In the thesis, new deformation ages have been obtained by the isotopic methods of ~(40)Ar-~(39)Ar, Sm-Nd and Rb-Sr minerals-whole rock isochrons on the mylonites formed in three ductile shear zones which bounded three different major nappes in the Dabie collisional orogenic belt. And the petrological, geochemical characteristics of some metamorphic rocks as well as the geotectonics of their protoliths, which have also deformed in the ductile shear zone, are analyzed and discussed. In the paper, twelve nappes in the Dabie orogen are first divided, which are bounded by various important NWW or NW-strike faults and three NNE-strike faults. They are Shangcheng Nappe, Huoshan Nappe, Yuexi Nappe, Yingshanjian-Hengzhong Nappe, Huangzhen Nappe, Xishui-Huangmei Nappe, Zhoudang Nappe, Suhe-Huwan Nappe, Xinxian Nappe, Hong'an Nappe, Mulan Nappe and Hhuangpi-Susong Nappe. In the Dabie orogen, three types of thrust and nappe tectonics belonging to two stages have been confirmed. They are: (1) early stage ductile thrust -nappe tectonics which movement direction was top-to-the-south; (2) late stage brittle to ductile-brittle thrust-nappe tectonics which are characterized by double-vergence movement, including top-to-the-north and top-to-the-south; (3) the third type also belongs to the late stage which also characterized by double-vergence movement, including top-to-the-east and top-to-the-west, and related to the strike-slip movement. The deformation ages of both Wuhe-Shuihou ductile shear zone and Taihu-Mamiao ductile shear zone have been dated by ~(40)Ar-~(39)Ar method. ~(40)Ar/~(39)Ar plateau ages of biotite and mica from the mylonites in these two shear zones are 219.57Ma and 229.12Ma. The plateau ages record the time of ductile deformation of the ductile shear zones, which made the concerned minerals of the mylonites exhume from amphibolite facies to the middle-upper crustal conditions by the early stage ductile thrust-nappe tectonics. The mineral isochons of Sm-Nd and Rb-Sr dating on the same mylonite sample of the metamafic rocks are 156.5Ma and 124.56Ma respectively. The two isochron ages suggest that the mylonitic rock strongly deformed in the amphilbolite facies at 156Ma and then exhumed to the upper crustal green schist condition at 124Ma with the activities of the Quiliping-Changlinggang ductile shear zone which bounded to the southen edge of Xinxian Nappe. Studies of the petrological and geochemical characteristics of some meta-mafic rocks and discussion on the geotectonics of their protoliths indicate that their protoliths were developped in an island arc or back-arc basin or active continental margin in which calc-alkline basalts formed. This means that arc-accretion orogeny had evolved in the margins of North china plate and/or Yangtze plate before these two plates directly collided with each other during the evolution process of Dabie orogen. Three-stage evolution of the thrust-nappe tectonics in Dabie collisional orogen has been induced based on the above-mentioned studies and previous work of others. And a possible 3-stage exhumation model (Thrust-Positive Flower Structure Model) has also been proposed.

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.

阿尔金蛇绿混杂带构造岩石组合及其大地构造意义

The Alytn fault is a huge left-slip fault zone within the Asian continent, and locates such zone that is linked to main tectonic units in the western China, which makes it is very important to the tectonic framework and ore distribution in the western China. Selecting two ophiolite zones (namely Hongliugou-Lapeiquan ophiolite zone and Sulamutage ophiolite zone) respectively located within the southern and northern part of the Altyn fault and based on analysis of field geology characteristics and geochemistry, this paper recognized the rock types (mainly mafic and ultramafic rocks) within the melanges and subdivided each lithological unit based on tectonic environment. At last, this paper rebuilt the paleo-tectonic framework in the Alytn region by the method of tectonic facies and discussed its tectonic evolution with the theory of collision orogens. Combining former results with hard field observation and geochemical analysis, this paper acquired such recognitions to two ophiolte zones within the Altyn fault zone as follows: To the typical regions (Hongliugou, Lapeiquan, Mangya and Sulamutage) within the two ophiolte zones in the Altyn fault zone, this paper offered the field geology profiles. Field geology characteristics show that they are composed of melange bases (mainly abyssal flysch and carbonate rocks) and melange blocks from various tectonic environments, often with fault contact among each lithological units, belonging to typical ophiolitic melange zone. The ultramafic rocks outcropped at the Altyn region are all harzburgites. Remant grains of primary minerals have melted residual texture and elastic deformation texture under high temperature and pressure. The whole-rock analyses show their low TiO_2 contents (0.01～0.04%), low Al, Ca and high MgO contents and wide Mg~# range (89.35～95.57). Rare earth patterns have two types, namely tabacco pipe-shped and LREE-shaped, of which the former is often seen. The chondrite-nomalized Yb values of these analyses are all lower than 1. The spinels have low Ti and high Cr content and most spinels have Cr# higher than 60. All of the above characteristics show that the ultramafic rocks in the Altyn fault zone are components of metmorphic peridotites of ophiolite from depleted mantle source and most ophiolites from this zone belong to supra-subduction zone (SSZ) type ophiolite with a few mid-ocean ridge basalt (MORB) type. Geochemical analyses show that the melange blocks within the Altyn ophiolitic melange zone have different characteristics from various tectonic environments. This paper recognized such tectonic-lithological assemblages as mid-ocean basalts, oceanic island basalts, oceanic island arc tholeiites, island arc calalkaline basalts and island arc granites and inferred that these tectonic-lithological units respectively belongs to such tectonic units as ophiolites, oceanic islands and/or oceanic seamounts, oceanic island arc and a~creting arcs, which show these blocks from oceanic crust and subduction zone for the most part. For the Altyn ophiolites, the chronological data show they become new from the north to the south. Combined with the study on late slip of Altyn fault and North Qilianshan orogeny, the author inferred that the Altyn region had belonged to one part of the North Qilianshan accreting wedge-arc orogeny at paleozoic, and later huge left-slip made it locate modem site.

新疆东昆仑蛇绿岩岩石学、地球化学特征及其大地构造意义

The East Kunlun area of Xinjiang (briefly EKAX) is the western part of broadly speaking East Kunlun orogenic zone. The absence of geological data (especially ophiolites) on this area has constrained our recognition to its geology since many years. Fund by National 305 Item (96-915-06-03), this paper, by choosing the two ophiolite zones (Muztag and Southwestern Margin of Aqikekule Lake ophiolite zones) exposed at EKAX as the studied objects and by the analysis of thin section, electron probe, XRF, ICP-MS, SEM and Sm-Nd isotope, totally and sys ematically dealt with the field geological, petrological, minerological, petrochemical and geochemical characteristics (including trace, rare earth element and Sm-Nd isotope) and the tectonic setting indicated by them for each ophilite zone. Especially, this paper discussed the trace and rare earth element patterns for metamorphic peridotites, their implications and related them to the other components of ophiolite in order to totally disclose ophiolite origins. Besides, this paper also studied the petrological, geochemical and paleobiological characteristics for the cherts coexsisted with the Muztag ophiolite and the tectonic setting indicated by them. Based on these, the author discussed the tectonic evolution from Proterozoic to Permian for this area. For Muztag ophiolite, their field geological, petrological, minerological, petrochemical and geochemical characteristics show that: ① outcropped along the Muztag-Jingyuhu fault with west-to-east strike, the ophiolite is composed of such three components as metamorphic peridotites, cumulates and volcanic rocks; ② metamophic peridotites consist of such types as lherzolites, serpentinized lherzolites and serpentinites, only pyroxenites is seen of cumulates and volcanic rocks include basalts, basaltic andesites and andesites; ③ mineralogical data on this ophiolite suggest it formed in supra-subduction zone (SSZ)environment, and its mantle wedge is heterogeneous; ④ whole-rock TiO_2 and Al_2O_3 of metamorphic peridotites indicate their original environment with the MORB and SSZ characteristics; ⑤ metamorphic peridotites have depleted LREE and flat REE patterns and volcanic rocks have enriched LREE patterns; ⑥ trace element characteristics of metamorphic peridotites imply that they had undergone Nb and Ta enrichment event after partial melting; ⑦ trace element characteristics of volcanic rocks and their tectonic diagrams show they are formed in the spreading and developed island arc environment with back-arc basin, such as rifted island arc, which is supported by the ε_(Nd)(t) -2.11～+3.44. In summary, the above evidence implies that Muztag ophiolite is formed in SSZ environment, where heterogeneous mantle wedge was metasomatised by the silica-enriched melt from subducted sediments and/or oceanic crust, which makes the mantle wedge enriched again, and this enriched mantle wedge later partially melted to form the volcanic rocks. For Southwestern Margin of Aqikekule Lake ophiolite, their field geological, petrological, minerological, petrochemical and geochemical characteristics show that: ① it outcropped as tectonic slices along the near west-to-east strike Kunzhong fault and is composed of metamorphic perodotties, cumulates and volcanic rocks, in which, chromites are distributed in the upper part of metamorphic peridotites as pods, or in the lower part of cumulates as near-strata; ② metamorphic peridotites include serpentinites, chromite-bearing serpentinites, thlorite-epidote schists and chromitites, of which, chromitites have nodular and orbicular structure, and cumulates include pyroxenits, serpentinites, chromite-bearing serpentinites, chromites and metamorphically mafic rocks and only basalts are seen in volcanic rocks; ③ Cr# of chromites suggest that they formed in the SSZ and Al_2O_3 and TiO_2 of metamorphic peridotites also suggest SSZ environment; ④metamorphic peridotites have V type and enriched LREE patterns, cumulates have from strongly depleted LREE, flat REE to enriched LREE patterns with universally striking positive Eu anomalies and basalts show flat REE or slight enriched LREE patterns with no Eu anomalies; ⑤ trace element and Sm-Nd isotope characteristics of metamorphic peridotites imply their strikingly heterogeneous mantle character(ε_(Nd)(t)+4.39～+26.20) and later Nb, Ta fertilization; ⑥ trace element characteristics of basalts and their tectonic diagrams show they probably formed in the rifted island arc or back-arc basin enviromnent. In summary, the above evidence shows that this ophiolite formed in the SSZ environment and melts from subudcted plate are joined during its formation. Rare earth element, whole-rock and sedimentary characteristics of cherts with the Muztag ophiolite show that they formed in the continental margin environment with developed back-arc basin, and radiolarias in the cherts indicate that the upper age of Muztag ophiolite is early carboniferous. Based on the accreted wedge models of Professor Li Jiliang for Kunlunshan Mountain and combined with study on the two typical ophiolite profiles of EKAX, the author discussed the tectonic evolution of EKAX from Proterzoic to Permian.

攀西地区红格、新街岩体的岩石地球化学特征

The mafic-ultramafic layered intrusions in the Panxi, China contain large V-Ti-magnetite deposits. These layered intrusions are related with the Emeishan continental flood basalts in space and time. Two layered intrusions, Hongge and Xinjie have clear PGE mineralization at the base of the intrusions. Thus the detailed investigations of these two intrusions not only have a geological but also have an economic significance. This thesis aims to characterize the elemental and Sr-Nd isotopic features of diverse rock zones within the intrusion on the basis of systematic studies of the major, trace element and isotope ratios, therefore to constrain the petrogenesis, mantle source and evolution of the Hongge and Xinjie intrusions. Generally, both Hongge and Xinjie intrusions show the same Fe-Ti-rich and Si-M-poor characteristics. They are also enriched in rare-earth elements (REE) and large-ion lithophile elements (LILE) as well as in Sr-Nd isotope ratios (Hongge: initial Sr = 0.7056-0.7076, ε_(Nd)(t) and (Nd/Sm)_N-ε_(Nd)(t) plots, the Hongge intrusion has a similar elemental and isotopic features to the Emeishan low-Ti (LT) basalts, whereas the Xinjie intrusion was close to the Emeishan high-Ti (HT) basalt. Therefore, the Hongge intrusion may be co-genetic with the LT basalt, formed by the partial melting of the spinel-garnet transition mantle that had a slight enriched isotope character. In contrast, the Xinjie intrusion and the HT basalts are probably derived from the garnet-phases mantle with a primitive isotope character. The involvement of the components of mantle wedge into the source is considered to be the major reason of the REE and LILE enrichment and Nd isotope depletion in the Xinjie intrusion. In contrast with the systematic variations in TiO_2 content, Mg#, transition elements (Ni, Cu, Co), REE concentrations, and La/Yb, La/Sm ratios from the lower zone to upper zone, the different rock zones of the Hongge intrusion have no clear Sr-Nd isotope variations. This suggests that the Hongge intrusions were formed by the crystal fractionation from the same magma source. The rhythm may be formed by slow injection of the co-genetic magma during the crystal fractionation. The increase in K_2O and Al_2O_3 contents, REE abundance, and the degree of the REE fractionation in the base of the intrusion, together with the relatively low ε_(Nd)(t) value, may imply that the base of the Hongge intrusion was contaminated with the local crust rocks. Xinjie intrusion shows the clearly elemental and isotopic differences in diverse cumulus cycles. The observation of the systematic variations in TiO_2 content, Mg# value, transition elements (Ni, Cu, Co), REE concentrations, and La/Yb, La/Sm ratios in first cycle was not occurred in second cumulus cycle. In addition, the ε_(Nd)(t) value in second cumulus cycle is apparently higher than that of the first one. Thus the abruptly elemental and isotopic changes at the base of second cycle demonstrate that there is considerable new and depleted magma addition to the residue magma after the crystallization of the first cycle. These features are very similar to those of the well-known PGE-rich Bushveld and Stillwater layered intrusions. The PGE mineralization in Xinjie intrusion is much better than in Hongge intrusion. Therefore, the layered intrusion similar to the Xinjie in Panxi area posses the better prospects for the PGE deposits.

西秦岭晚古生代弧前盆地沉积与成矿作用

The Western Qinling Orogenie belt in the Taibai-Fengxian and Xihe-Lixian areas can be subdivided into three units structurally from north to south, which are the island-arc, forearc basin and accretionary wedge, respectively. The forearc basin developed in the Late Paleozoic mainly controls sedimentation and some larger lead-zinc and gold deposits in the western Qinling. Stratigraphically, the island arc is dissected into the Liziyuan Group, the Danfeng Group and the Luohansi Group. The metavolcanic rocks include basic, intermediate and acidic rocks, and their geochemistry demonstrates that these igneous rocks generated in an island arc. Where, the basalts are subalkaline series charactered by low-medium potassium, with enriched LREE, negative Eu anomaly, and positive Nd anomaly. Cr-content of volcanic rocks is 2-3 times higher than that of island arc tholeiite all over the world. In addition, the lightly metamorphosed accretionary wedge in the areas of Huixian, Chengxian, Liuba and Shiqun is dominated by terrigenous sediments with carbonatite, chert, mafic and volcanic rocks. The age of the wedge is the Late Palaeozoic to the Trassic, while previous work suggested that it is the Silurian. The Upper Paleozoic between the island arc belt and accretionary wedge are mainly the sediments filled in the fore arc basin. The fillings in the forearc basin were subdivided into the Dacaiotan Group, the Tieshan Group, the Shujiaba Group and the Xihanshui Group, previously. They outcropped along the southern margins of the Liziyuan Group. The Dacaotan Group, the Upper Devonian, is close to the island arc complex, and composed of a suite of red and gray-green thick and coarse terrestrial elastics. The Shujiaba Group, the Mid-Upper Devonian, is located in the middle of the basin, is mainly fine-grained elastics with a few intercalations of limestone. The Xihanshui Group, which distributes in the southern of the basin, is mainly slates, phyllites and sandstones with carbonatite and reef blocks. The Tieshan Group, the Upper Devonian, just outcrops in the southwest of the basin, is carbonatite and clastic rocks, and deposited in the shallow -sea environment. The faults in the basin are mainly NW trend. The sedimentary characteristics, slump folds, biological assemblages in both sides of and within those faults demonstrate that they were syn-sedimentary faults with multi-period activities. They separated the forearc basin into several sub-basins, which imbricate in the background of a forearc basin with sedimentary characteristics of the piggyback basin. The deep hydrothermal fluid erupted along the syn-sedimentary faults, supported nutrition and energy for the reef, and resulted in hydrothermal-sedimentary rocks, reef and lead-zinc deposits along these faults. The sedimentary facies in the basin varies from the continental slope alluvial fan, to shallow-sea reef facies, and then to deep-water from north to south, which implies that there was a continental slope in the Devonian in the west Qinling. The strata overlap to north and to east respectively. Additionally, the coeval sedimentary facies in north and south are significantly different. The elastics become more and more coarser to north in the basin as well as upward coarsing. These features indicate prograding fillings followed by overlaps of the different fans underwater. The paleocurrent analyses show that the forearc basin is composed of thrust-ramp-basins and deep-water basins. The provenance of the fillings in the basin is the island arc in the north. The lead-zinc deposits were synchronous with the Xihanshui Group in the early stage of development of the forearc basin. They were strongly constrained by syn-sedimentary faults and then modified by the hydrothermal fluids. The gold deposits distributed in the north of the basin resulted from the tectonic activities and magmatism in the later stage of the basin evolution, and occurred at the top of the lead-zinc deposits spatially. The scales of lead-zinc deposits in the south of the basin are larger than that of the gold-deposits. The Pb-Zn deposits in the west of the basin are larger than those in the east, while the Gold deposits in the west of the basin are smaller than those in the east. Mineralizing ages of these deposits become younger and younger to west.

东南极格罗夫山地区的土壤特征及其环境研究

The Grove Mountains, including 64 nunataks, is situated on an area about 3200km2 in the inland ice cap of east Antarctica in Princess Elizabeth land (72o20'-73°101S, 73°50'-75o40'E), between Zhongshan station and Dome A, about 450km away from Zhongshan station (69°22'S, 76°22'E). Many workers thought there was no pedogenesis in the areas because of the less precipitation and extreme lower temperature. However, during the austral summer in 1999-2000, the Chinaer 16 Antarctic expedition teams entered the inland East Antarctica and found three soil spots in the Southern Mount Harding, Grove Mountains, East Antarctica. It is the first case that soils are discovered in the inland in East Antarctica. Interestingly, the soils in this area show clay fraction migration, which is different from other cold desert soils. In addition, several moraine banks are discovered around the Mount Harding. The soil properties are discussed as below. Desert pavement commonly occurs on the three soil site surfaces, which is composed of pebbles and fragments formed slowly in typical desert zone. Many pebbles are subround and variegated. These pebbles are formed by abrasion caused by not only wind and wind selective transportation, but also salt weathering and thaw-freezing action on rocks. The wind blows the boulders and bedrocks with snow grains and small sands. This results in rock disintegration, paved on the soil surface, forming desert pavement, which protects the underground soil from wind-blow. The desert pavement is the typical feature in ice free zone in Antarctica. There developed desert varnish and ventifacts in this area. Rubification is a dominant process in cold desert Antarctic soils. In cold desert soils, rubification results in relatively high concentrations of Fed in soil profile. Stained depth increases progressively with time. The content of Fed is increasing up to surface in each profile. The reddish thin film is observed around the margin of mafic minerals such as biotite, hornblende, and magnetite in parent materials with the microscope analyzing on some soil profiles. So the Fed originates from the weathering of mafic minerals in soils. Accumulations of water-soluble salts, either as discrete horizons or dispersed within the soil, occur in the soil profiles, and the salt encrustations accumulate just beneath surface stones in this area. The results of X-ray diffraction analyses show that the crystalline salts consist of pentahydrite (MgSO4-5H2O), hexahydrite (MgSO4-6H2O), hurlbutite (CaBe2(PO4)2), bloedite (Na2Mg(S04)2-4H2O), et al., being mainly sulfate. The dominant cations in 1:5 soil-water extracts are Mg2+ and Na+, as well as Ca2+ and K+, while the dominant anion is SO42-, then NO3-, Cl- and HCO3-. There are white and yellowish sponge materials covered the stone underside surface, of which the main compounds are quartz (SiO2, 40.75%), rozenite (FeSOKkO, 37.39%), guyanaite (Cr2O3-1.5H2O, 9.30%), and starkeyite (MgSO4-4H2O, 12.56%). 4) The distribution of the clay fraction is related to the maximum content of moisture and salts. Clay fraction migration occurs in the soils, which is different from that of other cold desert soils. X-ray diffraction analyses show that the main clay minerals are illite, smectite, then illite-smectite, little kaolinite and veirniculite. Mica was changed to illite, even to vermiculite by hydration. Illite formed in the initial stage of weathering. The appearance of smectite suggests that it enriched in magnesium, but no strong eluviation, which belongs to cold and arid acid environment. 5) Three soil sites have different moisture. The effect moisture is in the form of little ice in site 1. There is no ice in site 2, and ice-cement horizon is 12 cm below the soil surface in site 3. Salt horizon is 5-10 cm up to the surface in Site 1 and Site 2, while about 26cm in site 3. The differentiation of the active layer and the permafrost are not distinct because of arid climate. The depth of active layer is about 10 cm in this area. Soils and Environment: On the basis of the characteristics of surface rocks, soil colors, horizon differentiation, salt in soils and soil depth, the soils age of the Grove Mountains is 0.5-3.5Ma. No remnants of glaciations are found on the soil sites of Mount Harding, which suggests that the Antarctic glaciations have not reached the soil sites since at least 0.5Ma, and the ice cap was not much higher than present, even during the Last Glacial Maximum. The average altitude of the contact line of level of blue ice and outcrop is 2050m, and the altitude of soil area is 2160m. The relative height deviation is about 110m, so the soils have developed and preserved until today. The parental material of the soils originated from alluvial sedimentary of baserocks nearby. Sporepollen were extracted from the soils, arbor pollen grains are dominant by Pinus and Betula, as well as a small amount Quercus, Juglans, Tilia and Artemisia etc. Judging from the shape and colour, the sporepollen group is likely attributed to Neogene or Pliocene in age. This indicates that there had been a warm period during the Neogene in the Grove Mountains, East Antarctica.

大兴安岭南段中生代火山-侵入杂岩带的双层叠置构造体制兼论滇中武定、易门碳酸质火山岩年代、来源及矿库与找矿研究

These are two parts included in this report. In the first part, the zonation of the complexes in its series, lithofacies, the depth of magma source and chambers is discussed in detailed for the first time based on the new data of petrol-chemistry, isotopes, tectono-magma activity of Mesozoic volcano-plutonic complexes in the southern Great Hinggan Mts. Then, the genetic model of the zonality, double overlapped layer system, is proposed. The main conclusions are presented as follows: The Mesozoic volcanic-plutonic complexes in the southern Great Hinggan were formed by four stages of magma activity on the base of the subduction system formed in late Paleozoic. The Mesozoic magmatic activity began in Meso-Jurassic Epoch, flourished in late Jurassic Epoch, and declined in early Cretaceous Epoch. The complexes consist dominantly of acidic rocks with substantial intermediate rocks and a few mefic ones include the series of calc alkaline, high potassium calc alkaline, shoshonite, and a few alkaline. Most of those rocks are characterized by high potassium. The volcano-plutonic complexes is characterized by zonality, and can be divided mainly into there zones. The west zone, located in northwestern side of gneiss zone in Great Xinggan mountains, are dominated of high potassium basalts and basaltic andesite. The middle zone lies on the southeast side of the Proterozoic gneiss zone, and its southeast margin is along Huangganliang, Wushijiazi, and Baitazi. It composed of dominatly calc-alkaline, high potassium calc-alkaline rocks, deep granite and extrusive rhyolite. The east zone, occurring along Kesheketong Qi-Balinyou Qi-Balinzuo Qi, is dominated of shoshonite. In generally, southeastward from the Proterozoic gneiss zone, the Mesozoic plutons show the zones-mica granitites zone, hornblende-mica granitite zone, mica-hornblende granitite zone; the volcanic rocks also display the zones of calc alkaline-high potassium calc alkaline and shoshonites. In the same space, the late Paleozoic plutons also display the same zonality, which zones are combined of binary granite, granodiorite, quartz diorite and diorite southeast wards from the gneiss. Meso-Jurassic Epoch granite plutons almost distribute in the middle zone on the whole. Whereas late Jurassic Epoch volcanic rocks distribute in the west and east zone. This distribution of the volcano-plutonic complexes reveals that the middle zone was uplifted more intensively then the other zones in Meso-Jurassic and late Jurassic Epoches. Whole rock Rb-Sr isochron ages of the high potassium calc-alkaline volcanic rocks in the west zone, the calc-alkaline and high potassium calc-alkaline granite the middle zone, shoshonite in the east zone are 136Ma, 175Ma and 154Ma, respectively. The alkaline rocks close to the shoshonite zone is 143Ma and 126Ma. The isochron ages are comparable well with the K-Ar ages of the rocks obtained previously by other researchers. The compositions of Sr ans Nd isotopes suggest that the source of Mesozoic volcanic-plutonic complexes in Great Hinggan Mts. is mostly Paleo-Asia oceanic volcanic-sedimentary rocks, which probably was mixed by antiquated gneiss. The tectonic setting for Mesozoic magmatism was subductive continental margin. But this it was not directly formed by present west Pacific subduction. It actully was the re-working of the Paleozoic subduction system( which was formed during the Paleo-Asia ocean shortening) controlled by west Pacific subduction. For this reason, Although Great Hinggan Mts. is far away from west Pacific subduction zone, its volcanic arc still occurred echoing to the volcanic activities of east China, it, but the variation trend of potassium content in volcano-plutonic complexes of Great Hinggan is just reverse to ones of west Pacific. The primitive magmas occurred in the southern Great Hinggan Mts. Include high-potassium calc-alkaline basalt, high potassium calc-alkaline rhyolite, high potassium rhyolite, non-Eu negative anomaly trachy-rhyolite et al. Therefore, all of primitive magmas are either mafic or acid, and most of intermediate rocks occurring in the area are the products of Mesozoic acid magma contaminated by the Paleozoic volcanic- sedimentary rocks. The depth of those primitive magma sources and chambers gradually increase from northwest to southeast. This suggests that Paleozoic subduction still controlled the Mesozoic magmatism. In summary, the lithosphere tectonic system of the southern Great Hinggan Mts. controlling Mesozoic magmatism is a double overlapped layer system developing from Paleozoic subduction system. For this reason, the depth of crust of the southern Great Hinggan Mts. is thicker than that of its two sides, and consequently it causes regional negative gravity abnormity. The second part of this report shows the prolongation of the research work carried on in my doctor's period. Author presents new data about Rb-Sr and Sm-Nd isotopic compositions and ages, geochamical features, genesis mineralogy and ore deposit geology of the volcanic rocks in Kunyang rift. On the base of the substantial work, author presents a prospect of copper bearing magnetite ore deposit. The most important conclusions are as follows: 1. It is proved that all of these carbonatites controlled by a ringing structure system in Wuding-Lufeng basin in the central Yunnan were formed in the Mesoproterozoic period. Two stages could be identified as follows: in the first stage, carbonatitic volcanic rocks, such as lavas(Sm-Nd, 1685Ma), basaltic porphyrite dykes(Sm-Nd, 1645Ma), pyroclastic rocks and volcaniclastic sedimentary rocks, formed in the outer ring; in the second stage, carbonatitic breccias and dykes(Rb-Sr, 1048 Ma) did in the middle ring. The metamorphic age of the carbonatitic lavas (Rb-Sr, 893 Ma) in the outer ring was determined. The magma of carbonatitic volcanic rocks derived mainly form enriched mantle whose basement is depleted mantle that had been metasomated by mantle fluid and contaminated by Archaean lower crust. Carbonatitic spheres were discovered in ore bearing layers in Lishi copper mining in Yimen recently, which formed in calcite carbonatitic magma extrusion. This discovery indicates that the formation of copper ore deposit genesis relates to carbonatitic volcanic activity. The iron and copper ore deposits occurring in carbonatitic volcanic- sedimentary rocks in Kunyang rift results from carbonatitic magmatism. Author calls this kind of ore deposits as subaqueous carbonatitic iron-copper deposit. The magnetic anomaly area in the north of Lishi copper mining in Yimen was a depression more lower than its circumference. Iron and copper ores occurrig on the margin of the magnetic anomaly are volcanic hydrothermal deposit. The magnetic body causing the magnetic anomaly must be magnetite ore. Because the anomaly area is wide, it can be sure that there is a large insidious ore deposit embedding there.

大别（超）包产到户铁岩和阜新火山岩铂族元素斌存规律研究

The platinum-group elements (PGE), including Os, Ir, Ru, Rh, Pt and Pd, axe strongly siderophile and chalcophile. On the basis of melting temperature, the PGE may be divided into two groups: the Ir group (IPGE, >2000°C) consisting of Os, Ir and Ru, and the Pd group (PPGE, <20GO°C) consisting of Rh, Pt and Pd. Because of their unique geochemical properties, PGE provide critical information on global-scale differentiation processes, such as core-mantle segregation, late accretionary history, and core-mantle exchange. In addition, they may be used to identify magma source regions and unravel complex petrogenetic processes including partial melting, melt percolation and metasomatism in the mantle, magma mixing and crustal contamination in magma chambers and melt crystallization.Compared with other rocks, (ultra)mafic rocks have lower REE content but higher PGE content, so PGE have advantages in studying the petrogeneses and evolution of them. In this study, we selected (ultra)mafic rocks collected in Dabie Orogen and volcanic rocks from Fuxin Region. Based on the distribution and behaviour of platinum-group elements, combined with other elements, we speculate the magma evolution and source mantle of these (ultra)mafic rocks and volcanic rocks.Many (ultra)mafic rocks are widely distributed in Dabie Region. According to their deformation and metamorphism, we classed them into three types. One is intrusive (ultra)mafic rocks, which are generally undeformed and show no or little sign of metamorphism, such as (ultra)mafic intrusions in Shacun, zhujiapu, Banzhufan, qingshan, Xiaohekou, Jiaoziyan, Renjiawan and Daoshichong. The other one is ultrahigh pressure metamorphic (ultra)mafic rocks, some of them appeared as eelogites, such as complex in Bixiling and adjacent Maowu. Another one is intense deformed and metamorphic, termed as tectonic slice, alpine-type (ultra)mafic rocks. The most representative is Raobazhai and Dahuapin. However, there are many controversies about the formation of those (ultra)mafic rocks. Here, we select typical rocks of the three types. The PGE were determined by inductively coupled plasma mass spectrometry (ICP-MS) ater NiS fire-assay and tellurium co-precipitation.The PGE tracing shows that three components are needed in the source of the cretaceous (uitra)mafic intrusions. They could be old enriched sub-continental lithospheric mantle, lower crust and depleted asthenospheric mantle. The pattern of PGE also shows the primitive magma of these intrusions underwent S saturation. According to palladium, we can conclude that the mantle enrich in PGE. Distribution of PGE in Bixiiing and Maowu (ultra)mafic rocks display they are products of magmas fractional crystallization. The (ultra)mafic rocks in Bixiiing and Maowu are controlled by various magmatic processes and the source mantle is depleted in PGE. Of interest is that the mantle produced UHP (ultra)mafic rocks are PGE-depleted, whereas the mantle of cretaceous (ultra)mafic intrusions are enrich in PGE. This couldindicate that the mantle change from PGE-enriched to PGE-depleted during120-OOMa, which in accord with the time of tectonic system change in the East China. At the same time, (ultra)mafic intrusions in cretaceous took information of deep mantle, which means the processes in deep mantle arose structural movement in the crust The character of PGE in alpine-type (ultra)mafic rocks declared that the rocks had experienced two types of metasomatic processes - hydrous melt derived from slab and silicate melt. In addition, we analyze the platinum-group elements in volcanic rocks on the northern margin of the North China Craton, Fuxin. The volcanic rocks characterized by negative anomalies of platinum. This indicates that platinum alloys, which may host some Pt resided in the mantle. The PGE patterns also show that Jianguo alkali basalts derived from asthenospheric mantle source, but wulahada high-Mg andesites derived from lithospheric mantle.

中国东南部赣杭构造带基性岩浆活动及其意义

中国东南部晚中生代以来的动力学背景一直受到大量学者的关注，特别是大陆岩石圈地幔和大规模岩浆活动事件。华南地区广泛发育的基性脉岩，为研究中国东南部动力学背景提供了载体。前人分别从年代学、矿物学、岩石学和地球化学等方面对广布于华南（福建、广东、江西、海南、湖南等地区）基性岩进行了详细研究，并取得了许多重要成果。 赣杭构造带地处一级大地构造单元扬子地块和华夏地块结合部位，横跨江南元古宙岛弧和华南加里东造山带两个二级构造单元，长期控制两侧地质构造、岩浆活动、沉积、变质及成矿作用。带内发育的基性岩为认识构造带活动情况提供可能。但目前对构造带内的基性岩浆活动的研究较少，应用系统的矿物学、元素和同位素地球化学及同位素年代学等研究方法，对赣杭构造带中生代以来的基性岩体及基性脉岩进行了系统研究。并应用其形成时代、源区性质等结论对中国东南部岩石圈伸展减薄、地幔性质等地球动力学背景中的问题进行探讨。主要取得以下几点认识： 1. 系统进行资料收集，并在此基础上进行野外考察和采样，明确了赣杭构造带发育基性岩的岩石类型主要为辉长岩，辉绿岩及橄榄辉绿岩。主要分布在构造带的南侧，受主/次断裂控制明显。 2. 明确赣杭构造带基性岩体主要为辉长岩，落在粗面玄武岩-玄武岩-玄武粗面安山岩，碱性-亚碱性范围内各有分布，但以亚碱性居多。SiO2范围从45.11-53.47 wt%，MgO的范围从4.06-9.28 wt%，TiO2的范围从0.79-3.63 wt%。微量元素总体富集大离子亲石元素（LILE）（Ba、Rb）、轻稀土（LREE），而亏损高场强元素（HFSE）（Ta、Nb、Zr、Hf、Ti）和重稀土元素（HREE）。余江、东乡、枧头、虎头等近构造带样品，岩浆来源与OIB近似，Nb、Ta亏损不明显。岩浆源区地幔性质从亏损地幔向富集地幔都有分布，流体熔体的交代作用及地壳物质参与可能是造成富集程度不同的主要原因。基性岩体未受到明显的地壳混染，主要经部分熔融形成，成岩过程中发生了橄榄石和单斜辉石的分离结晶作用。构造带对岩浆源区及深部壳幔物质演化发挥重要作用，还控制着岩浆的上升侵入。 3. 赣杭构造带基性脉岩主要为辉绿岩类，在玄武岩-玄武安山岩范围内，碱性-亚碱性范围内都有分布，以亚碱性占大多数。SiO2的范围从44.44-54.73 wt%，MgO的范围从2.74-7.89 wt%，TiO2的范围从0.91-3.39 wt%。微量元素总体富集大离子亲石元素（LILE）（Ba、Rb）和轻稀土元素（LREE），而亏损高场强元素（HFSE）（Ta、Nb、Zr、Hf、Ti）。基性岩脉经不同程度部分熔融作用形成，且成岩过程中经历了橄榄石、单斜辉石及少量斜长石的分离结晶作用。样品没有受到明显的地壳混染现象。基性脉岩的源区性质与流体熔体交代作用及地壳物质参与有关。少量下地壳以拆沉形式加入了原始地幔，进而通过流体熔体交代作用，造成了原始地幔的富集。伸展活动的逐渐加大及软流圈的上涌为拆沉提供了有利条件。赣杭构造带对岩浆源区、深部壳幔物质演化及岩浆上升侵入影响显著。 4. 赣杭构造带岩浆活动发育呈现多元化特点，Sr-Nd-Pb同位素特征显示有EMⅡ的参与。流体交代特征比较复杂，源区存在金云母和金红石的交代，进一步说明下地壳成分参与了壳幔相互作用。同位素模拟表明古老基底通过源区混合也有所参与。结合前人的研究，提出了本区的成岩模式。赣杭构造带地区伴随岩石圈伸展作用的进行，发生了岩石圈减薄及软流圈地幔的上涌作用，少量下地壳物质拆沉到岩石圈地幔参与了岩浆的形成，构造带重新活化及活动对岩浆形成制约明显。新生代岩石圈地幔对中生代岩石圈地幔继承和改造。 5. 根据K-Ar年龄并结合区域内已有同位素年龄，赣杭构造带上的基性岩具有周期性分布特点，初步分为±180 Ma、145-150 Ma、120-140 Ma、95-110 Ma和65-80 Ma五组，且以120-140 Ma和95-110 Ma的峰值最为集中，代表了赣杭构造带岩浆活动最为强烈的期次。据目前研究，145 Ma限定了中国东南岩石圈伸展作用开始作用的下限，随着研究深入，更早能准确指示转换年龄的证据可能会被发现。大于140 Ma的岩浆比较偏向于构造体制转换下的构造-岩浆活动产物，与岩石圈的减薄及软流圈上涌关系密切。整个华南的岩石圈伸展作用对大规模金属成矿意义明显。赣杭构造带在热源、流体来源及驱动机制等方面对区内的以铀为主的金属成矿作用起到了制约。

福建省基性岩的年代学和地球化学：晚中生代以来中国东南部地幔演化

中国东南部地处太平洋板块与欧亚板块的接合部位，其独特的地理位置和构造运动长期以来引起了地质学家的广泛关注。自印支运动以来，板内构造演化复杂而多样。最引人注目的无疑是燕山期广泛而强烈的构造一岩浆热事件。近年来随着研究的深入，逐渐凸显出两个重要的地质问题需要解决：（1）中国东南部晚中生代构造属性的转变时间及地球动力学演化过程；（2）多金属成矿作用与岩石圈伸展减薄及地壳拉张的关系。基于此，本文以中国东南部福建省的基性脉岩、岩体为研究对象，运用系统的矿物学、岩石学、岩石地球化学、同位素地球化学及同位素年代学证据，详细论述了晚中生代中国东南部板块俯冲、地慢演化、壳幔相互作用及岩石圈伸展减薄的地球动力学过程，探讨了地壳拉张期次在福建省区域构造上的响应。本研究主要获得以下几点认识：1、岱前山辉长岩体沿福建长乐一南澳大断裂带分布，侵位于沿海的绿片岩相和角闪岩相的变质岩中及内陆的中生代火山岩中。岩体的微量元素特征表现为与俯冲作用有关的岛弧特点。岱前山岩体由低程度部分熔融形成（约7％），伴有角闪石、单斜辉石的分离结晶作用和斜长石的堆晶作用。时间上与古太平洋板块低角度一歪斜俯冲、晚中生代的变质事件、平潭一东山变质带抬升和长乐一南澳剪切带运动在时间上基本一致。岩体是受俯冲流体交代的上地慢，经部分熔融沿长乐一南澳断裂一应力转换带侵入。它与中国东南部出露的其它基性岩同源，但未受到地壳的混染作用。2、闽南茅坪一晒鞍角基性侵入体具独特的地球化学属性，表现为高Al2O3、CoO、MnO，低FeOT、MgO、TiO2含量，富集轻稀土元素（LREE）和大离子亲石元素（LILE），并具正的Pb异常和负的Ti异常；Sr-Nd-Pb同位素结果显示，该基性岩有EM2组分的参与。模拟计算表明，该基性岩墙群是尖晶石二辉橄榄岩地慢5-15％部分熔融的产物；微量元素配分模式及理论模拟表明茅坪一晒鞍角基性岩体的地慢源区在熔融前曾受到1％俯冲沉积物熔体的源区混染和5％流体交代作用。基性岩浆在上升过程中还受到10％左右的地壳物质的混染作用，导致该区基性岩富放射成因Sr、Pb同位素。3、福建省晚中生代基性脉岩富Al2O3（14.0-20.4 wt%）、CaO（4.09-12.7wt％）。按地球化学特征可分为两组：第一组脉岩具较低稀土总量（53.8-145.5μg／g）和平缓的稀土配分模式L（La/Yb）n=1.68-4.651，而第二组脉岩的稀土总量较高（63-247μg／g），且轻稀土富集［（La/Yb）n＝4.63-19］。在原始地慢标准化图解上，第一组脉岩显示Pb的正异常和Ti负异常，无Nb、Ta异常，而第二组脉岩显示明显的Nb一Ta一Ti负异常和Pb正异常。两组脉岩经历了不同的源区混合和陆壳混染过程，第一组脉岩显示了以陆壳混染为主的地球化学过程，不具有岛弧特点的微量元素配分模式表明该类基性岩的地慢源区可能未受俯冲作用过程影响，第二组脉岩的岛弧地球化学特点暗示该类基性岩地慢源区是经俯冲作用改造过的富集岩石圈地慢。第一组基性脉岩来源于石榴石一尖晶石二辉橄榄岩地慢，而第二组脉岩来源于尖晶石或尖晶石一斜长石二辉橄榄岩地慢。地球化学数据显示，不同类型的地慢存在不均一性，反映了不同程度的交代作用或不同量俯冲沉积物的加入。福建省晚中生代基性脉岩产生于拉张构造背景，与岩石圈的伸展减薄及软流圈的上涌紧密联系；4、福建省基性脉岩的同位素特征显示，第一组脉岩具较高的143Na／144Nd，第二组脉岩的143Nd／144Nd较低；Th/Nd、Ba/La比值及理论模拟结果表明，第二组脉岩可能受到流体交代和俯冲沉积物的源区混合作用，而第一组脉岩基本未受俯冲组分（沉积物＋流体）的改造。地壳混染对两组脉岩可能起着重要的作用。EC-AFC理论模拟表明，福建省基性脉岩在上升过程中受到前寒武纪变质岩的影响，这种混染作用在一定程度上改变了同位素组成。因此，福建省晚中生代基性脉岩的地球化学特点是太平洋板块俯冲与壳慢相互作用共同作用的结果；5、K-Ar年龄结果表明，出露于福建省的基性脉岩年龄具周期性分布，表现为五个周期：70-75Ma士，85 Ma士，105-110Ma，125Ma士和135-140Ma。这与前人的研究结果基本一致，表明福建省与中国东南部区域上有相似的地壳拉张期次。K-Ar年龄主要集中分布在14OMa→65Ma之间，这表明：①140M。限定了中国东南部岩石圈伸展作用开始的下限，也就是说中国东南部晚中生代的岩石圈伸展至少开始于140Ma左 右，而并非90Ma；②标志着中国东南部大规模拉张作用的开始，表明构造属性由令挤压为主转变为以拉张作用为主。

中国东南部晚中生代以来的基性岩脉（体）的地质地球化学特征及其地球动力学意义初探-以江西省为例

基性岩脉具有特殊的地球动力学意义，一直是近十年来国际上研究的热点和重点。至今共举办过四次关于岩脉的国际专题大会，掀起了基性岩脉的研究高潮，分别从其分布、形态、古地磁、岩石学、地球化学、年代学和构造演化等方面进行了系统的研究。由于出露面积的关系，岩脉或岩脉群往往容易被人忽略，直到最近五年来中国东部中新生代基性岩脉的地球动力学意义才引起地质学者的关注，甚至有些学者指出中国东部中生代基性岩脉的研究可以填补国际上对此方面的空白。对中国东南部中生代基性岩脉的系统研究主要集中在粤北地区，琼南、福建沿海一带、湘东南、某些热液矿床的矿区的基性岩脉得到零星的研究，缺少对中国东南部更大范围的和系统的研究。另外，中国东南部晚中生代部分基性岩体与地壳拉张有关，但研究多集中于沿海一带，对于内陆基性岩体的构造应力体制是否与基性岩脉类似。本论文选择了江西省晚中生代以来的基性岩脉（体）为研究对象，运用矿物学、元素和同位素地球化学及K-Ar测年等研究方法，首次较为系统地研究了江西省晚中生代以来的基性岩脉、与地壳拉张有关的基性侵入岩体的地质地球化学特征，并利用对其形成时代、源区性质的研究来探讨中国东南部地壳拉张期次、地幔性质等地球动力学背景中的关键性问题。通过研究取得了以下几点初步认识：1系统地进行野外地质考察和采样，并收集前人的研究资料，发现江西省的基性岩脉的岩石类型主要为煌斑岩、辉-长辉绿岩、辉绿岩、辉绿（珍）岩等，相对较多，主要呈三条北北东向带状分布，分别为星子-上高-萍乡、德兴-余江-相山-吉安-上犹、草桃背-岩背-大吉山。2对江西省的基性岩脉和部分与地壳拉张有关的墓性岩体进行全岩K-Ar定年，结果表明，基性岩脉的形成时代为140-50Ma，再结合中国东南部发育的富碱侵入岩（包括A型花岗岩）和已发表的基性岩脉的年代学资料，作者认为中国东南部地壳拉张可能共有六期，分别为50-6OMa、90士Ma、100-11OMa、125士Ma、140士Ma、165～180 Ma。3对赣南车步辉长岩类的地质特征、矿物学和地球化学特征进行了研究，着重讨论它与沿海辉长岩类构造环境和源区性质的不同，研究表明它可能是中国东南部中侏罗世软流圈上涌、岩石圈伸展和地壳裂解的产物，而沿海白至纪辉长宕类的构造环境是弧后拉张盆地；车步辉味岩类的源区可能是未受到明显俯冲组分影响的富集地幔，而沿海白翌纪辉长岩类的源区可能包含较多俯冲组分。4对赣南大吉山地区和赣北地区早白圣世基性岩脉的地质地球化学特征进行了系统的研究，表明它们可能代表中国东南部早白至世初存在一次重要的岩石圈伸展和地壳拉张事件。但两者在岩石序列、微量元素、同位素方面存在明显不同，结合区域地质背景，认为造成赣南和赣北地区早白坐世的基性岩脉源区不同的可能原因是岩石圈地慢组成不同和／或形成基性岩脉的岩浆深度不同。5通过对江西省早白至世欧特里夫期（125士Ma）基性岩脉的地质、矿物学和地球化学特征进行研究，发现中国东南部的确存在早白至世欧特里夫期（125士Ma）基性岩脉，代表一次重要地壳拉张事件，其源区可能由亏损地幔、EMI和EMII地幔组成，后面两种类型地幔可能是先前受俯冲流体影响的成分不均一的富集岩石圈地幔。6通过对江西省早白至世未期（100-11oMa）和晚白至世（90士Ma）的基性岩脉（体）的地质地球化学特征进行研究，强有力的表明江西省存在100-110Ma、90士Ma两期地壳拉张，与粤北地区类似。本论文研究表明晚白至世的地壳拉张除了形成基性岩脉外，还形成同时代的基性岩体。这两期的基性岩脉（体）的源区可能由亏损地幔、EMI和EMll地幔组分组成，与（125士Ma）基性岩脉类似，但早白至世未期（100-110Ma）基性岩脉的源区可能含有相对较高的亏损地幔组分。7通过对江西省中部古新世的基性岩脉（体）的地质地球化学特征进行研究，发现了江西省中部的确存在50-60Ma地壳拉张事件。本期的基性岩脉（体）微量元素含量、MORB标准化模式和同位素与前面白至纪的基性岩脉（体）明显不同，软流圈参与其源区明显增多。8通过对中侏罗世以来基性岩脉（体）地质地球化学的系统研究，表明中国东南部晚中生代以来地幔性质发生了明显变化，总体变化趋势为亏损地幔代替富集地幔，这种过程与软流圈上涌、岩石圈伸展和地壳拉张有关：主要机制可能为岩石圈减薄，当然不排除其他机制。