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Abstract Most ore‐forming characteristics of the Langshan‐Zha'ertaishan hydrothermal exhalation belt, which consists of the Dongshengmiao, Huogeqi, Tanyaokou and Jiashengpan large‐superlarge Zn‐Pb‐Cu‐Fe sulfide deposits, are most similar to those of Mesoproterozoic SEDEX‐type provinces of the world. The characteristics include: (1) All deposits of this type in the belt occur in third‐order fault‐basins in the Langshan‐Zha'ertaishan aulacogen along the northern margin of the North China Platform; (2) these deposits with all their orebodies hosted in the Mesoproterozoic impure dolomite‐marble and carbonaceous phyllite (or schists) have an apparent stratabound nature; ores display laminated and banded structures, showing clear depositional features; (3) there is some evidence of syn‐sedimentary faulting, which to a certain extent accounts for the temporal and spatial distribution and the size of the orebodies in all deposits and the formation of intrabed conglomerates and breccias; (4) they show lateral and vertical zonation of sulfides; (5) The Cu/(Pb+Zn+Cu) ratio of the large and thick Pb+Zn+Cu orebodies gradually decreases from bottom to top; and (6) barite is interbedded with pyrites and sometimes with sphalerite. However, some characteristics such as the Co/Ni radio of the pyrites, the volcanism, for example, of the Langshan‐Zha'ertaishan metallogenic belt, are different from those of the typical SEDEX deposits of the world. The meta‐basic volcanic rock in Huogeqi, the sodic bimodal volcanic rocks in the Dongshengmiao and potassic bimodal‐volcanic rocks with blastoporphyritic and blasto‐glomeroporphyritic texture as well as blasto‐amygdaloidal structure in the Tanyaokou deposits have been discovered in the only ore‐bearing second formation of the Langshan Group in the past 10 years. The metallogeny of some deposits hosted in the Langshan Group is closely related to syn‐sedimentary volcanism based on the following facts: most of the lead isotopes in sphalerite, galena, pyrite, pyrrhotite and chalcopyrite plot on both sides of the line for the mantle or between the lines for the mantle and lower crust in the lead isotope composition diagram; cobalt content of some pyrites samples is much higher than the nickel content (Co/Ni=11.91‐12.19). Some volcanic blocks and debris have been picked out from some pyritic and pyrrhotitic ores. All Zn‐Pb‐Cu‐Fe sulfide orebodies in these deposits occur in the strata overlying metamorphic volcanic rocks in the only ore‐bearing second formation. In the Jiashengpan deposit that lacks syn‐sedimentary volcanic rocks in the host succession only Pb and Zn ores occur without Cu ore, but in the Dongshengmiao, Tanyaokou and Huogeqi deposits with syn‐sedimentary volcanic rocks in the host succession Cu ores occur. This indicates a relatively higher ore‐forming temperature. The process of syn‐sedimentary volcanic eruption directly supplied some ore‐forming elements, and resulted in secular geothermal anomaly favorable for the circulation of a submarine convective hydrothermal system, which accounts for the precipitation of deep mineralizing fluids exhaling into anoxidic basins along the syn‐sedimentary fault system in the Langshan‐Zha'ertai rift. The Dongshengmiao, Tanyaokou, and Huogeqi deposits hosted in the Langshan Group appear to be a transitional type of mineral deposit between SEDEX and VMS‐types but with a bias towards SEDEX, while the Jiashengpan deposit hosted in the Zha'ertai Group is of a characteristic SEDEX type. This evidence, together with other new discoveries of Mesoproterozoic volcanic rocks and the features of lithogeny and metallogeny of the Bayun Obo deposit in the neighborhood emphasize the diversity, complexity and uniqueness of the Mesoproterozoic Langshan‐Zha'ertai‐Bayun Obo ore belt.

Abstract The North China Craton (NCC) is one of the largest blocks composing the continent. Different types of continental margins well developed around the NCC, along with lots of metallogenic systems of different metals and different times. Based on the study on the structural evolution of the NCC, the authors made a new division of tectonic units of the NCC. Through an analysis of the data of 1:25000 geochemical survey on stream sediments, regional geochemical features of main ore‐forming elements including Au, Ag, Cu, Pb, Zn, W, Ni, Co and Mo of the NCC are discussed in the paper. Then different metallogenic systems and their forming processes and geodynamics are discussed in detail. At last, temporal and spatial distribution regularities are summarized and ten favorable ore‐control factors on the paleocontinental margins are put forward, including (1) abundance of ore sources; (2) rendezvous of ore‐forming fluids; (3) high thermo‐dynamic anomaly; (4) remarkable Earth crust‐mantle interaction; (5) cluster of macroscopic structures and their long activities; (6) diversity of ore‐forming environments; (7) long geohistory; (8) multiforms of critical transitional ore‐forming mechanisms; (9) multi‐staged and superimposed ore‐formation; and (10) suitable preservation condition.

The mobility of the rare-earth elements (REE) during hydrothermal activities is increasingly documented. Geological and experimental evidence suggests that REE may be mobile in solutions rich in F-, Cl-, HCO3-, CO32-, HPO42-, PO43-, or in combinations of the above ligands, even though little has been known about which ligand or which combination is most effective in mobilizing REE. The fractionation of REE resulting from hydrothermal activities is inconsistent. One set of field data implies the preferential mobility of the light rare-earth elements (LREE), whereas another set of field observations indicates the dominant mobilization of the heavy rare-earth elements (HREE), and some theoretical prediction is contradictory to the field evidence. The Eu anomalies due to hydrothermal activities are complex and plausible explanation is not available. The existing experimental approaches dealing with REE are not adequate for explanation of REE behaviour in aqueous solutions. Systematic experimental approaches are suggested.

The190Pt-186Os system should be a unique tracer for mantle processes because both Pt and Os are concentrated in the mantle. The190Pt-186Os system will also be a good supplement to the187Re-187Os system for dating and tracing mantle processes because the190Pt-186Os system is not so easily contaminated by crustal materials as the187Re-187Os system. In turn, the application of the187Re-187Os system to Ptenriched materials uncontaminated by crustal materials will indirectly refine the half life of190Pt. The190Pt-186Os system will be a promising tracer and chronometer when the decay constant of190Pt is refined. In the coupled187Re-187Os and190Pt-186Os systematics, an186Os*/190Pt-187Os*/187Re concordia diagram similar to the206Pb*/238U-208Pb*/232Th concordia can be constructed. In such a concordia diagram, a date will be obtained so long as the190Pt-186Os system remains closed even if the187Re-187Os system is contaminated by crustal materials. In addition, for the coupled190Pt-186Os and187Re-187Os systematics, the mantle processes and the interactions between the mantle and the crust will be described by two ratios:186Os/188Os and187Os/187Os. The coupled187Re-187Os and190Pt-186Os systematics will be a powerful tool in the investigation of the geodynamic history of the Earth because the187Re-187Os system is sensitive to the interactions between the mantle and the crust, while the190Pt-186Os system is a good tracer for mantle processes.

The North China Continental Block (NCB) is the oldest craton in China. Its complex tectonic framework and geological evolution have resulted in a series of petro-tectonic assemblages with associated mineral deposits. The NCB and other blocks were sutured together along orogenic belts at different geological times. Frequent tectonic-magmatic activity along these belts provided favorable geological environments for the differentiation and concentration of ore-forming components. As a result, major mineral deposits in the NCB mainly occur along its margins. Archean rocks in the NCB are mostly metamorphosed and are covered by Phanerozoic sediments. The oldest isotopic age for Archean basement rocks is 3.8 Ga (Lin et al., 1994). Mineral deposits of Archean age are few, and only the BIF of Algoma type, such as the Anshan Fe orefield in Liaoning Province has important economic significance (Yao, 1994). Different from some other cratons in the world, Archean Ni(Cu, Au) deposits in komatite series rocks have not been found in the NCB. During the Early Proterozoic, aulacogens and rifts were developed in the interior parts and along some margins of the NCB. In these environments, Cu deposits of VMS-type and banded Pb-Zn deposits hosted by carbonate rocks were formed (Song, 1992). Giant mineral deposits include the Hongtoushan Cu-Zn deposit (2566 Ma), Kuandian boron deposit (2167 Ma), Dashiqiao magnesite deposit (> 1900 Ma) and Qinchengzi Pb-Zn deposit, all situated in the Central Liaoning Early Proterozoic Aulacogen of the NCB. About at the same time, the Hujiayu and Tongkuanyu Cu deposits (2300-1800 Ma) were formed in the Zongtiao rift valley along the southern margin of the NCB.