The tectonic setting, ore-forming time, metallogenic mechanism of nineteen molybdenum deposits and four gold deposits and their relationship with the Indosinian intrusions, located along the northern margin of Northern China craton (NCC) and adjacent area, have been discussed. Their geographic sites are different, but most of them occur in Precambrian metamorphic rocks and Early Paleozoic volcano-sedimentary rocks, and show intimate spatial and temporal relations with the Indosinian granitoid intrusions. Although the ore-forming process of molybdenum deposits last from Early to Late Trassic, but the large-scale mineralization event occurs from 230 Ma to 220 Ma. The ore-forming process of the gold deposits occurs prior to the “peak time” molybdenum mineralization (230 Ma to 220 Ma). Most of ore-forming age data change from 245 Ma to 239 Ma. Mineralization occurred in Mo and Au deposits locality as dissemination, stockwork, veinlet and vein group as well as replacement along the different fracture zones. Mo deposits can be classified as two types: porphyry and skarn. Au deposits can also be divided into two groups: vein and replacement body. Mineralization was likely formed by filling of ore-bearing fluids or hydrothermal replacement within the reactivated fault or fracture zone. Studies show that the lithospheric and crustal extension prevailed along the northern margin of the NCC following the collision of Xing-Meng amalgamated block and NCC during the period of Latest Permian to Late Trassic period. The post-collisional/post-orogenic extensional activities resulted in the formation of several E-W-trending fault zones, and widespread alkaline or high-K calc-alkaline intrusions. Intensive extension and magmatic activities provide favorable dynamic force and ore-forming material sources for molybdenum and gold mineralization. The identification of Indosinian molybdenum and gold mineralization should encourage renewed mineral exploration aimed at the discovery of blind deposits along the northern margin of the NCC and its adjacent area. The altered and brecciated Indosinian granitoid intrusions may be the favorable exploration targets.

Based upon recent research achievements on polymetallic ore deposits in the eastern section of Central Asian orogenic belt, the authors selectively studied uranium and molybdenum deposits, to explore diversity of the metallogenic sources and the various stages of mineralization in connection with the geochemical behaviors of uranium and molybdenum elements. Because there are many medium massifs, the relationship between mineralization and the medium massifs is also discussed from view of tectonics. These medium massifs have experienced cracking of continental margin, displacement, and collision orogenesis of plates. The ore-forming material was reformed many times and be concentrated. It is indicated that the Indosinian mineralization in the north margin of North China craton of Indo-Chinese epoch and in the Hinggan-Mongolian orogenic belt is related to the extension in the settings of underplating.

Duobaoshan porphyry copper deposit, located in Nenjiang, Heilongjiang Province, is one of the most important porphyry copper deposits in the North China. There are abundant mineral resources in this district, mainly including porphyry copper (molybdenum) deposit, skarn iron-copper deposit and hydrothermal gold deposit.Based on systematic analysis of the previous data, the metallogenetic regularity and prospecting direction in this district are defined. It was thought that the reactive basement structure played an important role in transportation, enrichment and dilution of the copper. The deposit types in weastern, middle and southeastern parts of the district are skarn iron-copper deposit and hydrothermal copper-molybdenum deposit, porphyry copper-molybdenum deposit as well as hydrothermal gold deposit, respectively. Caledonian porphyry copper deposit is the primary type in this district, following Hercynian and Yanshanian tectonic and magmatic process destroyed, preserved and regenerated the deposits in the district. Deposits and their occurrences are controlled strictly by the NW arc structure and hosted in the intermediate and acid volcanic rock of the Duobaoshan Formation and Tongshan Formation. There occurs a low-value copper anomaly field locates outside of the NW arc structure, with area of 228 km², such low-value copper anomaly fields are also defined in andesite around the mineralization zones, upper wall and front area of the ore bodies. Such metallogenic elements as Cu and Au are mainly provided by the country rocks. The S isotopic composition of the copper deposit shows mantle-derived features. From the early to late stage of the metallogenic process, the hydrothermal fluids changes from magmatic to meteoric water. The ore-forming fluid in Zhengguang deposit is mainly a mixture of magmatic water and natural water. It is suggested that special attention should be paid to the hydrothermal gold mineralization in Sankuanggou and Yubaoshan porphyry copper deposits. Porphyry copper deposit is the main prospecting type in Tongshan and Xiaogushan district, while in the Zhengguang district, lead-zinc mineralization is the main prospecting target.

Baerzhe alkaline granite is composed of No. 801 and No. 802 plutons, in which the 801 pluton is a superlarge rare earth and REE mineralized alkaline granitic intrusion and the 802 pluton is a non-mineralized pluton in which REE and some rare-elements are also slightly concentrated. A comparative study of major and trace elements and isotopic geochemistry of the mineralized 801 alkaline granite and the associated barren 802 alkaline granite in Baerzhe area was carried out, and the results show that both the mineralized and barren alkaline granites are characterized by enrichment of mantle isotopes, with no significant effect of assimilation. Geochemistry of major and trace elements suggests that the primary magma of the 802 pluton experienced a higher degree of evolution than the 801 pluton, which means that the 802 pluton has further potential for rare metal exploration. Petrographic zonation, pegmatite, miarolitic cavities and fluid-melt inclusions are well developed in the 801 pluton, suggesting that a full differentiation and evolution occurred after the intrusion of the primary magma. On the contrary, the 802 pluton is characterized by a porphyry texture of shallow intrusive rock and a relatively uniform major and trace element abundance, implying rapid cooling and non-differentiation after the emplacement of the primary magma of the 802 pluton. It is obvious that high differentiation and evolution that occurred in a relatively isolated system after the intrusion of the alkaline magma was the dominant factor for the rare-earth and REE mineralization of Baerzhe alkaline granites.

Granitoids and molybdenum ore deposits or ore spots are well developed in the Xilamulun metallogenic belt located on the northern margin of the North China craton. The ore-bearing intrusive rocks include monozogranite, porphyritic granite, granite porphyry and rhyolite porphyry, which belong to the high-K calc-alkaline and shoshonite series. The rock-forming materials were derived from the lower crust and juvenile crust. These granitic intrusive rocks were formed in Early-Middle Triassic, Late Jurassic and Early Cretaceous. The molybdenum deposits are of porphyry, quartz vein, greisen and volcanic-subvolcanic hydrothermal types. The ore-forming ages of the molybdenum deposits are consistent with the ages of the intrusive rocks and can be divided into three stages, i.e., Early-Middle Triassic, Late Jurassic and Early Cretaceous. The Early Cretaceous porphyry molybdenum deposits are extremely well developed in the Xilamulun metallogenic belt. The Early-Middle Triassic, Late Jurassic and Early Cretaceous ore deposits were formed in a syn-collision to post-collision tectonic setting between the Siberian plate and the North China craton. Both the northwestward subduction of the Pacific plate to the East Asia continent in Jurassic period and the lithosphere thinning (extension) in East China in Mesozoic period might have provided geodynamic forces for the ore-forming processes.

Tsav, Jiawula, Chaganbulagen Ag-Pb-Zn deposits as well as Errentaolegai Ag deposit are located at northeastern part of the Northern China-Mongolia block (NCMB), and constitute the most important Ag-polymetalic ore cluster along the China-Mongolia border. The Ag-polymetallic ore deposits occur mainly in the Jurassic volcano-sedimentary rocks as thin veins, veinlets, sulfide-enriched pockets, breccias and lenses. The mineralization can be classified into two types: quartz-sulfide veins and carbonate-sulfide veins. Both of the two type veins have characteristics typical of intermediate sulfidation deposits worldwide. One of the most prominent features for the Ag-polymetallic deposits mentioned above is that they are spatially and temporally associated with Mesozoic Yanshanian alkaline or high-K calc-alkaline intrusive dykes (or sills). It should be pointed out that Jurassic volcanic strata consist of mainly shoshonite, trachyandesite, latite, and high-K, andesite, dacite and rhyolite as well as ignimbrite and tuffaceous rocks, while Yanshanian intrusions include monzonite, monzodiorite, diorite,granodiorite, granite and syenite. All these ore-bearing intrusive rocks are enriched in K,Ba, Th, Rb, Sr, Nb, La, Ag, Zn and Nd, and depleted in Ca, Mg, Co, Ni and Cr. All these geological evidences indicate that the collision of the amalgamated NCMB and  Siberian plate is likely to occur during the time span of Late Middle to Early Late Jurassic. Subsequent, post-collision lithospheric and crustal extension may lead to a large-scale magmatic activity and a great volume of fluid ascent. As a result, a number of Ag-polymetallic deposits and prospects were fromed in Tsav-Jiawula region. Tsav, Jiawula, Chaganbulagen and Errentaolegai deposits have differences on their geographic location, ore body geometry and mineral assemblage, but they have a lot of similarities on geodynamic setting, genetic type, and ore-forming process. Our studies show that most of Ag-polymetallic deposits and prospects are concentrated in jointed part of the Pre-Mesozoic upwelling consisting of Precambrian-Paleozoic strata and Jurassic volcano-sedimentary depression in the studied area. The NW and NS trending tensional fault zones, filled with high-K intrusive dykes would be the potential exploration targets for Ag-polymetallic deposits in  Tsav-Jiawula region at the easternmost part of China-Mongolia border.

Baishilazi skarn tungesten deposit is located in the eastern part of Jiamusi-Xingmeng terrain. The major ore body occurs along the contact zone between the Early Yanshanian quartz diorite and the marble of the Late Paleozioc Qinglongcun Group. The host rock of the ore deposit is dominated by the garnet skarn. Using the LA-MC-ICP-MS single-zircon U-Pb dating method, the authors determined the ages of zircon grains separated from the intrusion, which are mainly from 195 Ma to 205 Ma with an average value of (198.27±0.80) Ma. Both the quartz diorite and its associated ore deposit were formed at the beginning of the Jurassic period. Major element geochemistry is characterized by low SiO₂ (58.07％-58.98％) and high alkaline (5.96％-6.41％), sodium (3.65％-4.84%) and aluminum (15.82％-17.89％). The quartz diorite belongs to the high-potassium and calcium system.  Based on the features of low REE content (90.06×10^-6-122.05×10^-6), high LREE and LREE/HREE ratios and low positive or negative Eu anomalies, it can be concluded that the quartz diorite was derived from the deep-crust source. As the quartz diorite has high Sr and low Yb content and its Rb/Sr and Rb/Ba ratios are similar to those of the primary mantle, it is inferred that the rockforming materials were derived from the deep part of the subduction plate or the thickened lower crust (＞40 km). In the light of geochronology and geochemistry of the Baishilazi intrusion in combination with regional tectonic evidence, the authors hold that both the intrusion and the associated tungsten deposit were formed during the transforming period between the Paleo-Asian tectonic belt and the Circum-Pacific accretion belt and related to the collision and collage of the terrain group represented by Jiamusi and Songnen massifs in the eastern Central Asian Paleozoic orogenic belt.

Tungsten mineralization of Wudaogou ore deposit occurs mainly in the Late Indosinian altered granodiorite as parallel scheelite-quartz veins. Compared with the adjacent Yangjingou ore deposit, some of the ore veins in Wudaogou are characterized by large thickness and high ore grade. As the most important ore mineral, the scheelite grains are distributed in massive, coarse-grained disseminated and veinlet forms in quartz veins and altered host rocks. Fluid inclusions are dominated by gas-liquid ones in both scheelite and quartz grains formed at the major ore-forming stage. Moreover, two CO₂-bearing three-phase inclusions are also observed in scheelite grains. Homogenization temperatures and salinities of gas-liquid inclusions in quartz vary mainly from 171.2 to 268.0℃ and from 0.70%NaCl to 10.74%NaCl, respectively, whereas those in scheelite grains vary from 209.6 to 253.3℃ and from 1.39%NaCl to 8.67%NaCl respectively. Homogenization temperatures of two CO₂-bearing three-phase inclusions in the scheelite are 287.2 and 294.7℃. A comprehensive study of compositional and microthermometric analytical results of fluid inclusions has led to the conclusion that the oreforming fluid from Wudaogou ore deposit belongs to the NaCl-H₂O-CO₂ hydrothermal system with medium temperature, low salinity and minor N₂. A comparative study of Wudaogou and Yangjingou scheelite deposits indicates that they were formed in similar geological settings with the same hydrothermal alteration, mineral assemblage, ore textures and structures as well as modes of occurrence of the scheelite. The two ore deposits are genetically related to a common hydrothermal scheelite mineralization event. Since the two ore deposits have different ore-controlling structures, the ore bodies in the two ore deposits have different attitudes, shapes and sizes.

Controlled by NW-trending fractures, the Erdaohezi lead-zinc deposit occurs in volcanic rocks and conglomerate of the Tamulangou Formation in the Hailaer-Genhe Jurassic volcanic fault-depression basin. Its ore bodies are mainly of vein type. Based on geological and geochemical investigation of volcanic rocks and ores as well as dating of volcanic rocks, the authors studied the genesis of the ore deposit. An analysis of major elements, trace elements, rare earth elements and Pb, Sr and Nd isotopes has revealed that the content of SiO2 in the lava is 48.01%-56.44% and that of the lithic crystal tuff is 69.09%-71.73%, and that Pb, Zn and Cu values in the former are much lower than those in the latter. The two kinds of rocks have similar REE patterns, characterized by weak Eu negative anomalies. LILE such as  Rb, U and Th are rich in the volcanic rocks, while Sr and such HFSE as Nb, Ta and Ti are relatively depleted. In the volcanic rocks, I_Sr=0.704 925-0.706 632, ε_Nd(t)=0.5~2.0, ε_Sr(t)=8.5-32.8 and t_DM=619-730 Ma. In addition, the composition of Pb isotopes in volcanic rocks is very close to that in sulfide ores, their ²⁰⁶Pb/²⁰⁴Pb,²⁰⁷Pb/²⁰⁴Pb and ²⁰⁸Pb/²⁰⁴Pb ratios are 18.130-18.475, 15.526-15.567 and 38.078-38.286 respectively, with μ values being 9.32-9.40. With the SHRIMP zircon U-Pb method, the lithic crystal tuff was dated at (164.2±2.3) Ma. These data indicate that the magma that formed the volcanic rocks was derived from the mantle with the mixture of a small amount of crustal materials, and the ore-forming materials came from the magma system. The volcanism had experienced two phases: early magma was mainly intermediate, whereas late magmatism occurred in late Middle Jurassic and formed acid volcanic clastic rocks. Ore-forming material was abundant in the late magma, which might have also formed sub-volcanic rocks related to the mineralization. Ore-forming fluids from late magma differentiation might have formed the ore deposit by filling and metasomatism along the fractures in volcanic rocks and conglomerate, and the mineralization occurred in late Middle Jurassic to Upper Jurassic period.

Located in eastern Inner Mongolia, the Mengentaolegai silver-polymetallic deposit is one of large-scale deposits. Ore bodies occur as vein-like, and are controlled by the east-west trending fault. Geochronology and geochemistry of the main intrusive rocks occurring in and around the Mengentaolegai silver-polymetallic ore district are studied. In order to constrain the emplacement age of intrusive rocks, the zircons in four samples from the intrusive rocks were dated by the LA-MC-ICP-MS method. Four reliable weighted mean ²⁰⁶Pb/²³⁸U ages of (240.5±1.2) Ma（MSWD=0.48）, (234.3±3.2) Ma (MSWD=0.21), (154.5±0.5) Ma (MSWD=0.41), and (127.5±0.7) Ma (MSWD=1.3) were obtained for the biotite plagioclase granite and muscovite plagioclase granite in Mengentaolegai batholiths, biotite K-feldspar granite in Duerji batholiths and andesite porphyry in southern part of the Mengentaolegai deposit, respectively. It is indicated that there were three times of magmatic emplacement in and around the Mengentaolegai silver-polymetallic ore district, during Middle Triassic, Late Jurassic and Early Cretaceous period, respectively. The geochemical analysis of these intrusive rocks show that the biotite plagioclase granite, muscovite plagioclase granite and biotite K-feldspar granite are characterized by the high SiO₂, enriched alkali, meta-aluminum and calc-alkaline, with LREE differentiation obviously. They are enriched in LILE elements, characterized by relatively depleted Ba, Nb, La, Sr, P and Ti, and enriched Rb, Th, K, Ta, Ce, Nd, Hf, Sm, Y and Yb. Combined with the dating results of the intrusive rocks, it can be concluded that the Mengentaolegai batholiths and Duerji batholiths were formed under collisional and extensional settings, respectively. The reported Ar-Ar age of the muscovite associated the mineralization is (179. 0士1. 5) Ma, which is quite different from the emplacement ages of the intrusive rocks studied. It is suggested that these exposed intrusive rocks are not likely related to the silver-polymetallic mineralization in Mengentaolegai area. The intrusive rocks related to the silver-polymetallic mineralization may be buried in the depth, or have been re-melted due to the intruding of the Duerji batholiths.

Stable (C, H, O and S) and radiogenic (Pb) isotopes of hydrothermal solutions from the Aolunhua Mo-Cu deposit in southern Da Hinggan Mountains were analyzed with the purpose of determining the source of the ore-forming fluids and tracing the ore-forming process. New isotopic data indicate that the hydrothermal solutions were not from a single source. C, H, O and S isotopic compositions of the ore-forming fluids show that the metallogenic complexing agent had a hybrid origin, derived mainly from the mantle and subordinately from the crust. The Pb isotopic compositions of the molybdenite suggest that molybdenum came mainly from the juvenile orogenic belt, with a small amount derived from the mantle. Distinct metallogenic mechanism was identified based on stable isotope compositions and previous fluid inclusion studies. The mineralization at the early stage was caused by a mixing between magmatic fluid and meteoric water. However, mineralization at the prevailing metallogenic stage resulted from the fluid boiling. Distinct from the porphyry deposits formed in arc settings and collisional orogenic settings, the Aolunhua porphyry Mo-Cu deposit was formed in a unique geological setting related to reactivation of a juvenile orogen under an extensional backarc regime during the Late Jurassic and Early Cretaceous period. Interaction between magmas and hydrothermal fluids from the mantle and the crust formed a hybrid system, which created essential conditions for subsequent mineralization. It is thus held that more importance should be attached to this ore-forming process so as to recognize potential fertile intrusions.

The Bairendaba and Weilasituo Ag-Pb-Zn deposits are two large-size deposits in the same orefield, with the prospective reserves of Ag being over 10 000 tons and Pb and Zn about 600 million tons. The magmatism of these two ore deposits was controlled by mantle branch in southern Da Hinggan Mountains. Since Mesozoic, intensive magmatism has generated the channel for the upwelling of deep source materials and resulted in the formation of a series of fracture systems related to igneous activities, which served as important ore-controlling structures for the  migration and concentration of hydrothermal fluids. Studies demonstrate that different scales of structures dominate the mineralization distribution of this ore deposit. The orefield is controlled by the northeast principal detachment zone on the south margin of the mantle branch in southern Da Hinggan Mountains, the deposits are controlled by a series of secondary detachment belts, and the ore bodies are controlled by tensile or tensile-shearing faults. Geochemical studies indicate that ore-forming materials were mainly derived from the depth, with the participation of some crustal materials during the upwelling of hydrothermal fluids.

Chaganhua porphyry molybdenum deposit is a newly discovered large-scale deposit in central Inner Mongolia. Ore bodies are mainly hosted in the greisenizated and silicified granite. Molybdenum mineralization is closely associated with greisenization and silicification and is characterized by quartz-molybdenum-muscovite and quartzmolybdenum stockwork veins. Fluid inclusions in quartz of the major metallogenic stage and late molybdenum mineralization are mainly two-phase vapor-liquid inclusions with small amount of CO₂ phase. The homogenization temperatures and salinities of inclusions in major stage vary from 147℃ to 387℃, 2.6% to 8.6 % NaCl equivalent, and in late molybdenum mineralization vary from 161℃ to 322℃, 0.4% to 6.5% NaCl equivalent, respectively. The oxygen isotopic fractionation temperatures in quartz and muscovite associated with molybdenum mineralization vary from 384℃ to 653℃, which represent the mineralization temperatures and are higher than the homogenization temperatures of fluid inclusions. Studies show that the molybdenum began to deposit at 653℃, 200 MPa (approximately 7.4 km of lithostatic pressure) and mainly deposit from 416℃ to 384℃, 65 MPa to 40 MPa (approximately 6.5 km to 4 km of hydrostatic pressure). The inclusions data, together with H-O isotope data, record an evolution path of the hydrothermal fluid of degassed magma water source from high temperature, pressure and moderately low salinity to low temperature, pressure and salinity, which resulted in Chaganhua porphyry molybdenum deposit.

Located in Qimantage area of Qinghai Province, Hutouya is a typical skarn lead-zinc polymetallic ore district consisting of both orthocontact and exocontact substyles. The basic geological characteristics and ages of petrogenesis and mineralization were studied. The ore-forming elements are quite complex, dominated by Fe, Cu, Sn, Mo, Pb and Zn. Mineralization occurs in the contact zone between the intermediate-acidic intrusive rock and the carbonate-bearing strata, the fault zone or discordant contact between strata of different epochs and the lithologic boundaries, showing obvious zonation of mineralization and alteration from the intrusive rock outwards. U-Pb dating of zircons from granodiorite and adamellite has yielded ages of (235.4±1.8) Ma and (219.2±1.4) Ma, respectively. Re-Os isotopic dating of molybdenite from the skarn Cu-Mo polymetallic ore and skarn molybdenite ore by ICP-MS has yielded isochron ages of (225.0±4.0) Ma and (230.1±4.7) Ma. These new age data, combined with data available, indicate that the ages of ores and related granites should be Middle to Late Triassic. Indosinian magmatism and mineralization occurred at the post-collisional stage of the orogen, corresponding to the late stage of the Late PaleozoicEarly Mesozoic tectonic event in eastern Kunlun orogenic belt.

Located in Qimantage area of southwest Qaidam basin,Kaerqueka copper polymetallic deposit is a characteristic hydrothermal vein-skarn ore deposit controlled by the fractured and altered zone. Two kinds of wall-rock alterations can be recognized in the ore deposit, i.e., skarn and phyllic alteration. The former was formed by intrusion of Indosinian porphyaceous biotite adamellite. Copper polymetallic skarn lenticular bodies are commonly seen in the contact zone of the intrusion, different lithologic interfaces and faulted structural zones of the surrounding rocks. There are some typical calcium skarn minerals, such as diopside, hedenbergite, andradite, hessonite, idocrase, wollastonite, epidote, scapolite and actinolite. The latter forms many parallel NWW-striking chacopyritized hydrothermal alteration zones in porphyaceous biotite adamellite in the northwest part of the ore district, belonging to hydrothermal vein type mineralization controlled by faulted fractured zones. It is concluded that Kaerqueka copper polymetallic deposit is related to Indosinian hypabyssal and high emplacement porphyaceous biotite adamellite. The ages of rocks and ores in the copper polymetallic skarn deposit and the veinlet-disseminated hydrothermal veinlike copper deposit are the same, and the backgrounds of tectono-magmatic activities are identical; nevertheless, they are products of different ore-forming processes that occurred at different stages, different depths and different parts. This ore deposit is a compound one, with the skarn copper polymetallic mineralization as the main body, accompanied by the hydrothermal vein type copper mineralization in well-developed faults of the parent rock.

Moerdaoga district is situated in the northern Eerguna block. There occur a lot of Precambrian intrusive and metamorphic rocks, including Fengshuishan complex, intermediate and mafic complex, macrophenocryst syenogranite, adamelite, etc. The authors collected a series of intrusive rock thought to form in Neoprotozoic period, and separated the zircons from the rocs for U-Pb dating by LA-ICP-MS method. The obtained ages suggested that the majority of rocks, which were thought to form in Neoprotozoic period, emplaced in Early Mesozoic period, except the migmatic syenogranite formed in Neoprozoic. It can be conclude that there took place intensive tectonic and magmatic activities in Moerdaoga and adjacent areas during the Early Mesozoic period. According their ages, the Early Mesozoic intrusive and metamorphic complexes in Eerguna and northern Daxinganling Mountain could be divided into such three groups as 243-246 Ma, 210-229 Ma, 200-205 Ma, and the 200-205 Ma group is the most extensive. The 243-246 Ma group is dominated by the intermediate and mafic intrusive complex, maybe related to the extension occurred in after the Late Permian orogensis of Xing’an-Mongol collision. The rocks formed from 200 Ma  to 229 Ma are dominated by granite and metamorphic complexes which have such characteristics formed in continental collision setting as calc-alkaline, per aluminous, S-type granite, migmatites, biotite, muscovite and horbenlende as well as lacking associated volcanic rocks. The geology and geochemistry of the Early Mesozoic granites and metamorphic complex indicate that the middle part of Mongol-Okhotsk Ocean (Transbaikal) might be closed at the end of Middle Triassic to the beginning of Late Triassic period when the collisional orogeny might start. The peak collision might took place at the end of Triassic period (200 Ma±). The confirmation of the Early Mesozoic granite and its geodynamic setting in Eerguna and northern Daxing’anling is also important to reconsider the geological evolution of the area.

The volcanic rocks of  Tamulangou Formation in southern Manchuria are composed mainly of olivine basalt, pyroxene basalt and basaltic andesite. LA-ICP-MS zircon U-Pb dating results show that the volcanic rocks formed at the end of Middle Jurassic, ranged from 164 Ma to 161 Ma. Geochemical data show that the volcanic rocks belong to high-K calc-alkaline series, have low contents of MgO(1.64%-9.59%) and small Mg^# (0.26-0.66); The chondrite-normalized rare earth element (REE) patterns indicate that the volcanic rocks are enriched in light rare earth elements(LREE) with significant fractionation of HREE and LREE ((La/Yb)_N=6.86-22.29) and weak Eu anoalies(δEu=0.70-0.93); The trace element geochemistry are characterized by enrichment in large ionic lithophile elements(e.g. Rb, Ba, K) and LREEs, depletion in high field strength elements(e.g. Nb, Ta, P, Ti) and compatible elements (Cr, Co, Ni); The initial ¹⁷⁶Hf/¹⁷⁷Hf ratios of the magmatic zircons from volcanic rocks vary from 0.282 691 to 0.282 740, and the corresponding ε_Hf(t) values range from 0.67 to 2.30. The geochemical data suggest that the magma could be derived from partial melting of lithosphere mantle which had been metasomatized by subduction fluids, and probably experienced fractional crystallization of olivine and clinopyroxene,and insignificant crustal contamination. Combined with the regional research results, we suggest that the metasomatic fluids could be originated from the oceanic crust of Mongol-Okhotsk Ocean, and these volcanic rocks formed under a lithospheric extension after the closure of Mongol-Okhotsk Ocean.

Zircon U-Pb ages of four granitoids in Xinkailing region, Northwestern Xiao Hinggan Mountain, are reported in this paper. They are (187.7±1.4) Ma for the Datoushan quartz diorite, (170.7±1.3) Ma for the Dapingshan biotite monzogranites, (128.0±1.1) Ma for the East Fudiyingzi biotite monzogranite porphyry and (120.6±0.6) Ma for biotite granite porphyry dyke, respectively. Combined with previous zircon age datas, the Mesozoic granitic magmatism in this area can be divided into two stages, Early-Middle Jurassic (188-164 Ma) and Early Cretaceous (128-106 Ma), which are comparable with NE China and Far East Russia. From Jurassic to Cretaceous, the granitoids show clear evolution characteristics, from metaluminousweakly peraluminous, high-K calc-alkaline (or over with calc-alkaline type) I-type granitoids to weakly peraluminous, high-K calc-alkaline to shoshonitic highly differentiated I-type granitoids, Sr/Y ratios become significantly lower and zircon ε_Hf (t) values increased slightly. These suggest that the early high Sr/Y granitoids probably melted from the lower crust of compressional and thicken crust transferred into the late highly fractionated I-type granitoids formed in a relative extensional and thinning setting and evolved by mantle-derived materials. Evolution characteristics of granitoid magmatisms, combined with the regional tectonic evolution on the periods, indcates that the crust in the region experienced a transition from compaction and thickening setting to a relative extension and thinning setting during ca. 160 Ma.

Zircon SHRIMP U-Pb age (225.6±1.1) Ma of alkaline syenite from the Sungezhuang alkaline complex in Jixian County of Tianjin is reported  for the first time, which suggests that the complex is a product of Late Triassic alkaline magmatism. A systematic study on the composition of major element, trace element, REE of the alkaline syenite and ortho-pyroxenite from the complex reveals their lithogeochemical feature, source material, tectonic setting and geological significance. According to the bulk compositions, the syenite has high Al, low Ca, Fe and Mg content with aluminum over-saturation, and the ortho-pyroxenite has high Ca, Fe and Mg content. Both are characterized by enrichment in alkaline with K₂O/Na₂O>1. It is suggested that the Sungezhuang alkaline complex is resulted from the magmatism in a postorogenic setting. These rocks are all of high REE content, LREE enrichment, HREE depletion and no obviously Eu anomaly. In the PM-normalized diagram, trace element diagram exhibits LILE (Sr, Ba) and LREE(La, Ce, Pr, Nd, Sm) enrichment, relative depletion in HFSE (Nb, Ta, Hf and Th) with negative U, Nb, Ce and Ti anomalies. Furthermore, transitional element (Cr, Ni and Co) contents in the ortho-pyroxenite are relatively low, which implies that the Sungezhuang alkaline complex has a deep magma source related to enriched mantle. The comprehensive research on Indosinian alkaline intrusive belt in northern margin of the North China craton shows that the emplacement ages of these alkaline complexes range from 238 Ma to 220 Ma. It can speculate that the geodynamic setting of large-scale Early Mesozoic alkaline magmatism in northern margin of the North China craton and destruction of the North China craton, specially lithospheric thinning in North China, are basically the same. The Early Mesozoic alkaline rocks (238-200 Ma) is possible to represent the beginning of lithospheric thinning in North China. Moreover, the lithospheric extension and thinning in northern margin of the North China craton may start from the western section.

The Shadegai granite is located in Hadamengou large gold-molybdemum orefield, in the north margin of North China craton. The SHRIMP U-Pb weighted average age of 15 zircon grains from the Shadegai granites is (221.6±2.1) Ma（MSWD=1.6），which indicates the granite emplaced in the medium Indosinian epoch. Geochemical characteristics show that the granite is characterized by high silicon(SiO2=71.21%Northern margin of North China craton； Shadegai granite； geochronology； geochemistry； Triassic 73.67%), potassium-rich (K₂O/Na₂O=1.01-1.37), rich alkaline(K₂O+Na₂O=8.23%-9.96%), weakly peraluminous（Al₂O₃=13.11%-14.31%）. The Rittmann index (σ) of granite varies from 2.43 to 3.52, which means that the rock samples are calc-alkaline to alkaline. The ∑REE varies from 185.70×10^-6 to 96×10^-6, the ratios of LREE/HREE and La_N/Yb_N are 17.68-14.92 and 22.85-16.58, respectively, and δEu is weakly negative anomalies. Trace elements composition exhibit such characteristics of A-type granite, as depletion of Nb, Ta, P, Ti, Sr，and enrichment of K, La, Ce, Hf. The values of (⁸⁷Sr/⁸⁶Sr)i is from 0.705 31 to 0.702 29， (¹⁴³Nd/¹⁴⁴Nd)i from 0.511 682 to 0.511 620，and ε_Nd(t) from -13.1 to -14.3, indicating that the magma source of Shadegai granite should have been mainly of crust-derivation. Nd isotope two-stage model ages(T_2DM) are 2 061-2 160 Ma. In the tectonic model diagram of lead isotopic compositions, the granite samples are plotted between the mantle and lower crust curves. The comprehensive analysis suggests that the Shadegai granite formed under the tectonic setting of transformation from syn-collision to post-collision. Statistics indicate that the magmatism and mineralization took place extensively in the northern margin of North China craton during the Indosinian epoch.

Using recent research results and previously published data of chronology and petrogenesis, the authors have divided the Indosinian granitoid magmatism into three stages in the middle segment of the Qinling orogen. The early stage of the magmatism is attributed to the northward subduction of oceanic slab coupled with the closure of the Mianxian-Lueyang ocean during 248-216 Ma. The middle stage of the magmatism occurred in the period from the collision between the northern margin of the Yangtze Craton and the North Qiling arc complex zone to the collapse of the orogen during 215-200 Ma. The late stage of the magmatism is considered to have resulted from the delamination of the orogenic root in the post-collision period during 200-195 Ma. Therefore, the Indosinian granitoid magmatism perfectly registered the evolutionary processes of the Qinling orogenic belt.

Based on a study of the regional tectonic evolution, regional geology, geophysics and geochemistry of the Da Hinggan Mountains, the authors hold that this region has gone through intense mantle plume evolution since the Yanshanian movement, as obviously evidenced by intense structural movement and large-scale magmatism. The most prominent representation is the formation of the mountain-basin structural pattern and the extensive metallogenesis. The middle to southern region of the Da Hinggan Mountains is a typical mantle branch. It consists of magmatic-metamorphic core complex, surrounding detachment zones and overlapped fault basin, constituting an important ore-forming and ore-controlling tectonic unit. In Da Hinggan Mountain region, sulfur isotope values of 103 samples from six polymetallic deposits range from -4‰ to 3‰, suggesting high uniformity. Lead isotope values of 24 samples from four polymetallic deposits indicate that ²⁰⁶Pb/²⁰⁴Pb ratios range from 18.441 4 to 17.666 7,²⁰⁷Pb/²⁰⁴Pb range from 15.665 1 to 15.488 3, and  ²⁰⁸Pb/²⁰⁴Pb range from 38.642 6 to 37.710 9. The mantle helium ratios of 12 deposits range from 37.25% to 76.96%, with the average being 55.90%. The helium-argon isotopes of hydrothermal fluids are mainly concentrated in the mantle fluid domain. All geochemical analyses indicate that metallogenic materials and hydrothermal fluids mainly came from the depth of the earth, even from the core-mantle boundary. They passed through mantle plume, sub-mantle plume, mantle branch and crustal expanding structure zones and eventually moved to favorable structural positions and precipitated to form ore deposits.

Due to much covering by sand and grass, there is less mineralization information on the ground in Daolangheduge tungsten-polymetallic mine. Geological and geochemical studies show that the Early Cretaceous K-feldspar granite closely correlates to tungsten mineralization, while the orehosting rock is chiefly the Permian augite diorite. According to the difference of physical property between host rock and ore body, the geological mapping, magnetic and gravity survey at scale of 1∶10 000 have been completed in the deposit. By integrated gravity-magnetic inversions of data, three NE-trending important structural alteration zones are identified in augite diorite occurring in the northwestern part of the deposit, which correspond to negative magnetic anomalies, respectively. Parallel to the boundary between augite diorite and K-feldspar granite, the three zones have the length of 800-3 000 m and the width of 50-100 m. As a result, six integrated geophysical anomalies are predicted in augite diorite. The depth of anomalies does not exceed 1 000 m and the area of a single anomaly is usually 500 800 m². Through drilling, three blinded fractured-zone type tungsten-polymetallic exploration targets are discovered.  Tungsten-polymetallic  ore bodies are sited in the depth of 150-650 m. The thickness of the ore body is 2-4 m. The combination method of regional metallogenic condition analysis and integrated gravity-magnetic inversions is confirmed to be effective for forecasting tungsten deposit in covered area and worth to being applied in other region.

The skarn polymetallic deposit, an important deposit type in southeastern Inner Mongolia, is mainly distributed in southwest section of Huanggang-Wulanhot polymetallic metallogenic belt. Baiyinnuo Pb-Zn deposit, Haobugao Pb-Zn-Cu-Sn deposit and Huanggang Fe-Sn deposit are representative skarn deposits in the area, and they are also important producing area for lead, zinc and tin in Northern China. The authors summarized and analyzed the effectiveness of geophysical and geochemical exploration method, and established comprehensive geological, geophysical and geochemical ore-prospecting models for skarn polymetallic deposit in the region. The ore bodies in these skarn deposits often are located in interlayer of Permian crystalline limestone or marble. The collapse part of compound anticline axis is favorable position for ore-forming materials precipitating by the tectonic movement. The mineralization, especially lead-zinc, has close relationship with manganese and calcium pyroxene skarn. The Cu, Pb, Zn, Ag, Sn contents in the strata and acid intrusive rocks near the ore district are much higher than the background value. In addition, the alteration zone associated with the mineralization and ore bodies exposed appear the geochemical anomalies with high-intensity, high-contrast and good-clear zoning. The element zoning shows that the geochemical halo in the front ore body are characterized by As, Sb, Hg, Pb and F, while the halo in the tail ore body by Sn, W and Mo. The ore bodies and mineralized skarn often display high polarization, high magnetic, high gravity and low resistivity (three high and one low) combination of anomalies.