Phylloid algae are the dominant reef-building organisms during the Pennsylvanian, and they have a widespread distribution. However, the construction model and the controlling factors of the phylloid algal reef during this period were not well understood. In this study, a well-developed Kasimovian triple hybrid carbonate reef is reported for the first time from the Houchang area, southern Guizhou Province, South China. The reef is primarily composed of phylloid algal cementstones and phylloid algal-cement-microbial framestones. The reef developed in a platform margin setting within the photic zone under well-circulated marine conditions, likely around the fair-weather water base. Phylloid algae, abiotic cements and microbially mediated cements were dominant contributors to the studied reef. Phylloid algae could build simple frameworks. Early marine cement stabilized the reef framework and filled almost half of primary cavities. Microbial carbonates occurred in the upper part of the reef, as subordinate framework stabilizer. This phylloid algal-cement-microbial reef is classified as a triple hybrid carbonate in the tropical region of eastern Paleo-Tethys. It was controlled by long-term and regionally universal factors throughout the Pennsylvanian, including eustatic fluctuations, atmospheric pCO2 levels, and seawater chemistry (specifically the Mg2+/Ca2+ ratio). The studied reef provides insight for the triple hybrid carbonates in the Late Pennsylvanian.

The Anshan-Benxi greenstone belt (ABGB) in the northeastern North China Craton (NCC) preserves similar to 3.88-2.5 Ga basement rocks, among which the Anshan area has been highly studied due to large number of valuable Neoarchean banded iron formations (BIFs) and thick-bedded metasedimentary rocks. However, few researches focus on the metasedimentary rocks of the Waitoushan-Gongchangling-Benxi (WGB) region in the ABGB. Besides, their provenances still remain puzzled. In this study, we present new whole-rock major and trace element data for metasedimentary rocks in the Waitoushan area and collect 59 previously published geochemical datasets for metasedimentary rocks from across the ABGB, with the aim of determining their provenances, particularly their felsic portions. Collectively, the ABGB metasedimentary rocks consist of chlorite amphibole schists, biotite felsic gneisses/schists, phyllites, biotite amphibole gneisses, garnet biotite gneisses, and two-mica quartz schists. Sixty-eight metasedimentary rocks are geochemically classified into greywacke, shale, and Fe-shale. Greywacke, shale and some Fe-shale samples yield fractioned rare earth element (REE) patterns and high REE abundances that are comparable to those of the average Archean upper continental crust (AUCC), whereas the remaining Fe-shale samples exhibit flat REE patterns and low REE abundances due to the low or absence of Th, U, and LREE-enriched minerals, such as monazite and allanite. According to the chemical index of alteration (CIA), chemical index of weathering (CIW) values and A-CN-K diagram, all metasedimentary rocks exhibit weak to moderate degrees of weathering. Narrow SiO2/Al2O3 ratios and index of compositional variability (ICV) values greater than 1 indicate low recycling and immaturity. The Al2O3/TiO2 ratios, REE patterns and abundances imply that the shale and graywacke were derived from predominantly felsic-related rocks, whereas the Fe-shale sources were hybrid provenances of mafic and felsic-related rocks. We summarize 1612 zircon Lu-Hf isotopes and 129 whole-rock Nd isotopes of sedimentary rocks, volcanic rocks and granitic plutons from the ABGB and surrounding areas to determine where the felsic and mafic provenances of the sedimentary rocks in the ABGB originated. The volcanic rocks in the ABGB provide the dominant mafic sources, whereas felsic provenances may have been supplied from the southern Liaoning granitic plutons and felsic volcanic rocks. In this study, a metavolcanic rock interbedded with sedimentary rocks yielded a metamorphic age of similar to 2512 Ma, limiting the minimum depositional age. Combined with the detrital zircon spectrum from the ABGB sedimentary rocks, the depositional ages of these sedimentary rocks range from similar to 2.53-2.51 Ga. On the basis of arc- and back-arc-related volcanic rocks and the distribution of sedimentary rocks, we propose that these metasedimentary rocks formed under a late Neoarchean arc to back-arc basin tectonic domain.

The Northern Liaoning terrane locates at the northeastern margin of the North China Craton (NCC). Two debatable tectonic mechanisms, plate tectonic vs. plume/sagduction, were interpreted to dominate the late Neoarchean Northern Liaoning terrane. Besides, similar to 2.57-2.51 Ga supracrustal rocks occur layered or as enclaves within similar to 2.59-2.50 Ga TTG and potassium-rich granitoid gneisses. This is a logical contradiction that 'young' enclaves expose within 'older' wall rocks. In this study, new zircon U-Pb dating results exhibit that protoliths for these meta-volcanic rocks in the Huiyuan area, north of the Northern Liaoning terrane, crystallized at similar to 2.61 Ga and underwent metamorphisms at similar to 2.54-2.48 Ga. The real crystallization ages for reported metavolcanic rocks in the Northern Liaoning terrane were probably highly underestimated. In this contribution, garnet-pyroxene amphibolite, amphibolite and (biotite) amphibole gneiss were interbedded and exhibit geochemical affinities to Nb-enriched basalt (NEB), tholeiite and andesite, respectively. NEB exhibits abnormally high Nb, TiO2 and (Nb/La)(PM) values, fractionated REE patterns, and negligible Nb, Ta and Ti anomalies, which was derived from partial melting of slab melts metasomatized mantle wedge with Nb-bearing minerals (i.e., amphibole). Tholeiites yield flat REE patterns, enrichments of LILEs, and depletions of Nb and Zr, which are comparable to primitive arc basalt and interpreted as partial melting of sub-arc mantle wedge previously metasomatized by limited subducted slab-derived fluids. Andesites give fractionated REE patterns and negative HFSE anomalies, among which several andesites are akin to Phanerozoic high-magnesium andesite (HMA), with high MgO, Mg-#, Cr and Ni values, and were generated by interactions between subducted slab-derived melts and sub-arc mantle wedge. Remained normal andesites were hybrids of crustal melts and mantle-derived basaltic melts. Taken together, similar to 2.61 Ga NEB, andesite (including HMA samples) and primitive arc basalt associations point to a subduction tectonic mechanism developing in the Northern Liaoning terrane. Plume and subduction mechanisms are not mutually exclusive. More precise spatial and temporal distributions effected by plume and subduction, respectively, and how they interact with each other, need to be further studied.

Gongchangling iron deposit is famous for its large amount of high-grade magnetite ore, thus most of the researches focused on Gongchangling mining area Ⅱ due to the bulky high-grade iron ore. In this study, the U-Pb dating of the columbite-group minerals from the hanging wall granite in Gongchangling mining area Ⅰ yields two ages, i.e., 2501 ± 14 Ma and 1845 ± 20 Ma. The chemical compositions of the columbite-group minerals of both ages are always characterized by Nb > Ta, Fe > Mn, low U/Th, and relatively enriched HREEN content, in consideration of the regionally ∼1.85 Ga mono- and multi-mineral uranium mineralization, the rare metal mineralization should be of NYF-type. The ∼2.50 Ga mineralization is coeval with the Lijiapuzi pegmatite Nb-Ta deposit, indicative of the excellent regional late Neoarchean Nb-Ta mineralization potential in eastern Liaoning Province; the ∼1.85 Ga event of Nb-Ta mineralization suggests that the widespread Paleoproterozoic plutons within Jiao-Liao-Ji belt and Trans-North China Orogen should be concerned in the near future. The intimate spatiotemporal relationship implies that the Paleoproterozoic Nb-Ta mineralization and the high-grade iron ores in the Gongchangling deposits were probably the products of the same geologic process, providing critical insights into the ore-forming process of both deposit types.

Banded iron formations (BIFs) in the Anshan-Benxi region in the North China Craton have made a significant contribution to economic benefits. The Xiaolingzi BIF, south of Anshan, was interpreted as Dayugou Formation, while the Qijiagou BIF, east of Qidashan, was believed to be asynchronous Yingtaoyuan Formation. However, the latest geochronological data for these two BIFs indicate that they deposited simultaneously instead. In this study, we report new geochemical and geochronological data from the Xiaolingzi and Qijiagou BIFs, aiming to decipher their deposition age, origin signatures and depositional setting. Both Xiaolingzi and Qijiagou BIF samples were dominated by alternating iron-rich and quartz-rich microbands, accompanied by lower amounts of hematite, pyrite and silicate phases of cummingtonite and biotite/muscovite. SiO2 and Fe2O3T dominated the major elements in all BIF samples. Most BIF samples yielded nil to low contents of TiO2, Al2O3, Zr, Th, rare earth elements (REE) and +Y; conspicuous positive Eu and Y anomalies; depletions of LREEs; and enrichments of HREEs. This composition represents pure chemical sediments formed by a mixture of high-T hydrothermal fluids and seawater, except one BIF sample with terrigenous detrital involvements. According to zircon U-Pb dating analyses, metamorphosed sedimentary rocks and biotite quartz schists were interbedded in the Xiaolingzi BIF and Qijiagou BIF samples and yielded a maximum depositional age of -2552 Ma. We compile nearly all detrital zircon ages for metasedimentary rocks from the entire Anshan-Benxi region and propose that the maximum depositional age is -2.53 Ga. In light of the accompanying metamorphosed volcanic-sedimentary rocks and VMS Cu-Zn mineralization in northern Liaoning, the Xiaolingzi and Qijiagou BIFs deposited under a typical back-arc basin setting.

How Earth switched from any earlier regimes such as plume-lid tectonics to plate tectonics remains an unresolved issue in Earth sciences. We report early Neoarchean (-2.77-2.68 Ga) metavolcanic rocks, including older calc-alkaline basaltic-andesitic rocks in the southwest but younger tholeiitic rocks in the northeast, from the Jiaobei terrane of North China Craton. Petrogenetic studies and thermodynamic and trace element modeling reveal that the tholeiitic magmas originated mainly from deep and unmodified mantle sources (-1600 degrees C and -3.5 GPa), relative to the shallower and metasomatized depleted mantle sources (-1450 degrees C and -2.2 GPa) of calc-alkaline magmas. Geochemical changes indicate that the mantle sources became isotopically enriched but less metasomatized from southwest to northeast. These data suggest an early Neoarchean plate subductioninduced deep mantle upwelling regime. We further depict a potential geodynamic framework for the early Neoarchean Earth involving active interaction of plate subduction and deep mantle upwelling, which possibly changed the thermal evolutionary trajectory of the Earth and accelerated the arrival of global plate tectonics.

The composition of Archean granitoid rocks changed from predominantly tonalite-trondhjemite-granodiorite (TTG) gneisses in the early Archean (4-3 Ga) to diversified granitoid rock assemblages in the late Archean (3.0-2.5 Ga), marking a crucial transformation in the geodynamic processes of early Earth. However, the reason for this major transition remains enigmatic because the petrogenetic features of different granitoid assemblages and their crust-mantle interactions during different periods are poorly understood. We use variations in the spatial-temporal distribution, lithological association, chemical composition, and petrogenesis of Neoarchean (2.7- 2.5 Ga) granitoids and inferred correlative crust-mantle interactions in the Eastern Liaoning Range (ELR) of the northeastern North China craton to explore this geodynamic transition. The early Neoarchean (ca. 2.7 Ga) ELR granitoids were dominated by TTG gneisses, and the late Neoarchean (2.6-2.5 Ga) ELR granitoid typology and compositions became more complex, changing into TTGs and more K 2 O-rich granitoid rocks. The TTGs can be subdivided into a high-Ca group and a low-Ca group: The 2.71-2.68 Ga high-Ca group TTG magma originated from partial melting of subducted juvenile oceanic crust, and the lowCa group TTG magma was derived from fractionation crystallization of the high-Ca group TTG magma. The chemical composition of the magmatic sources played a dominant role on the 2.60-2.50 Ga TTG magmatism: the high-Ca and low-Ca group TTG magmas came from low-K mafic rocks and tonalites, respectively. The 2.58-2.49 Ga K 2 O-rich granitoids can be divided into three petrogenetic series: (1) The high-CaMg group K 2 O-rich granitoid magma originated from partial melting of high-K mafic rocks, (2) the low-Ca-Mg group K 2 O-rich granitoid magma was derived from partial melting of sedimentary rocks, and (3) the transition group K 2 O-rich granitoid magma was sourced from metagreywackes. The 2.71-2.68 Ga TTGs were generated in an island arc belt, and subducted slab melting and subsequent magmatic differentiation were the dominant mechanisms of the TTG magmatism. The 2.60-2.50 Ga diversified granitoids were formed in the oceanic-continental subduction process under the active continental margin; the complicated oceanic slab subduction and arc-arc and arc-continent collisions contributed to the diversity of late Neoarchean granitoid magmatism.

The early Neoarchean (similar to 2.8-2.7 Ga) era is the most crucial period of global crustal growth with the emplacement of abundant tonalite-trondhjemite-granodiorite (TTG) series. However, the geodynamic regimes triggering this global event remains controversial. Here, we document two major episodes (similar to 2.78 and similar to 2.71-2.67 Ga) of TTG magmatism in the Northern Liaoning (NL) terrane, the northern margin of the North China Craton (NCC). Based on contrasting spatial and temporal distribution, petrological and geochemical characteristics, the similar to 2.78 Ga TTG gneisses were derived dominantly from partial melting of ancient (similar to 3.6-3.2 Ga) crustal materials under an active continental margin system, whereas the similar to 2.71-2.67 Ga TTG gneisses were generated by juvenile oceanic slabs with significant mantle input under an intra-oceanic warm subduction system. Based on a compilation of published zircon Lu-Hf isotopic data of TTG gneisses throughout the NCC, it is suggested that similar change in the magma sources of similar to 2.8-2.6 Ga TTG gneisses occurred in a craton scale. Furthermore, the tectonic positions of TTG formation might have migrated from the continental margin to the oceanic interior during the early to middle Neoarchean period, providing crucial evidence for large-scale outward continental growth in the NCC.

农村劳动力作为乡村最具能动性的生产要素和乡村振兴战略的最大利益需求者,其年龄结构的变动趋势关系农业劳动生产率的高低和乡村治理的有效性.研究发现,当前农村劳动力老化的绝对水平和相对增速均高于城镇,未来30年农村劳动力供给将继续呈现年龄结构断层的发展轨迹,劳动力老化水平始终超出40％的临界值;在空间特征上呈现出非均衡分布的特点,存在区域和省际差异.农村劳动力老化水平急速提升源于,劳动力乡城转移的年龄选择性带来的农村大龄劳动力相对增多和老龄化城乡倒置现象加剧背景下农村老年人口抚养比大幅上升,而这将逐渐打破原有的农业生产要素分配格局和乡村社会治理结构,势必对农业经济活动和农村社会系统产生深层次影响.基于此,本文提出在全面推进乡村振兴战略背景下有效应对农村劳动力老化的路径选择,以提高乡村人力资本质量和发挥农村社会主体的主动性.

The Daheishan supergiant porphyry molybdenum deposit (also referred to as the Daheishan deposit) is the second largest molybdenum deposit in Asia and ranks fifth among the top seven molybdenum deposits globally with total molybdenum reserves of 1.65 billion tons, an average molybdenum ore grade of 0.081%, and molybdenum resources of 1.09 million tons. The main ore body is housed in the granodiorite porphyry plutons and their surrounding inequigranular granodiorite plutons, with high-grade ores largely located in the ore-bearing granodiorite porphyries in the middle-upper part of the porphyry plutons. Specifically, it appears as an ore pipe with a large upper part and a small lower part, measuring about 1700 m in length and width, extending for about 500 m vertically, and covering an area of 2.3 km(2). Mineralogically, the main ore body consists of molybdenite, chalcopyrite, and sphalerite horizontally from its center outward and exhibits molybdenite, azurite, and pyrite vertically from top to bottom. The primary ore minerals include pyrite and molybdenite, and the secondary ore minerals include sphalerite, chalcopyrite, tetrahedrite, and scheelite, with average grades of molybdenum, copper, sulfur, gallium, and rhenium being 0.081%, 0.033%, 1.67%, 0.001%, and 0.0012%, respectively. The ore-forming fluids of the Daheishan deposit originated as the CO2-H2O-NaCl multiphase magmatic fluid system, rich in CO2 and bearing minor amounts of CH4, N-2, and H2S, and later mixed with meteoric precipitation. In various mineralization stages, the ore-forming fluids had homogenization temperatures of > 420 degrees C-400 degrees C, 360 degrees C-350 degrees C, 340 degrees C-230 degrees C, 220 degrees C-210 degrees C, and 180 degrees C-160 degrees C and salinities of > 41.05%-9.8% NaCleqv, 38.16%-4.48% NaCleqv, 35.78%-4.49% NaCleqv, 7.43% NaCleqv, and 7.8%-9.5% NaCleqv, respectively. The mineralization of the Daheishan deposit occurred at 186-167 Ma. The granites closely related to the mineralization include granodiorites (granodiorite porphyries) and monzogranites (monzogranite porphyries), which were mineralized after magmatic evolution (189-167 Ma). Moreover, these mineralization-related granites exhibit low initial strontium content and high initial neodymium content, indicating that these granites underwent crust-mantle mixing. The Daheishan deposit formed during the Early-Middle Jurassic, during which basaltic magma underplating induced the lower-crust melting, leading to the formation of magma chambers. After the fractional crystallization of magmas, ore-bearing fluids formed. As the temperature and pressure decreased, the ore-bearing fluids boiled drops while ascending, leading to massive unloading of metal elements. Consequently, brecciated and veinlet-disseminated ore bodies formed.(c) 2023 China Geology Editorial Office.

The Central Asian Orogenic Belt (CAOB) contains many microblocks, and their Precambrian basement origin and crustal evolution are disputed. This study focuses on the geochronology of metamorphic complexes from the Shuangsheng area, southeastern Inner Mongolia. Combined with regional geological data, we discuss the tectonic attribution of the metamorphic complexes and provide geochronological evidence for regional crustal evolution and tectonic affinity. From the Shuangsheng area, the Pingandi metamorphic complex and Baolige metamorphic complex are composed of greenschist-amphibolite facies metamorphic intrusive rocks and metamorphic supracrustal rocks, mainly including tremolite rock, chlorite rock, actinolitite (gneissic) plagioamphibolite, actinolitite schist, marble, and feldspar quartzite. Zircon U-Pb geochronology analysis of actinolitite and plagioamphibolite suggests that there were two intermediate-acid magmatic events (2500-2400 Ma and 2050-1980 Ma), one basic magmatic event (1860 Ma), and three metamorphic events (1930-1890 Ma, 1815-1785 Ma and 1740-1730 Ma). Based on comparisons with the regional Precambrian chronological spectrum, geotectonically, Precambrian geological records from the Shuangsheng area should belong to the basement of the Bainaimiao Arc Terrane (BAT). Each segment of the BAT shows consistent Precambrian chronological frameworks, which indicates that the BAT has a unitive Precambrian basement. The basement underwent crustal growth during 3.0-2.4 Ga and 2.1-1.4 Ga and multistage crustal reconstruction between 2.75 and 0.55 Ga, which is different from the crustal evolution of the North China Craton, northeast Gondwana continent, and Tarim Craton. In the early Palaeozoic, the Precambrian material provided varying source contributions to the arc crust of the BAT through crust-mantle interaction.

在老龄社会新形态格局下,老年人积极参与生产性经济活动对于实施积极应对人口老龄化国家战略有着重要的现实意义.基于2018年CHARLS调查数据,研究分析了老年人参与生产性经济活动的劳动供给状况及其个体特征差异.通过构建生活满意度综合指数,发现劳动供给降低了老年人的满意度指数,但该负面影响随家庭消费支出增加、享有优质的居家社区养老服务等个体资源禀赋的优化而有所减弱;同时延长劳动时间显著提升了生活满意度指数.基于积极老龄观视角,从存量提质、挖掘增量两方面对促进老年人劳动供给和提升生活满意度提出可干预举措.

新时代青年成长于重大社会历史变迁时期并形塑了独特的群体特征.本研究以"社会代"概念和"生命历程理论"搭建分析框架,强调宏观社会路线约束和个体生命历程间的互动作用,具体包括新时代青年群体共同经历了两大发展奇迹、教育扩张大潮、人口迁徙浪潮、互联网全覆盖等重大历史事件,并形塑了独特的人口和社会文化特征.基于此,本文提出新时代青年群体研究应重点聚焦低生育社会下青年婚恋观和生育意愿研究、高社会流动下青年城市化路径与社会融入研究、数字化背景下网络青年亚文化现象及其影响研究等议题,并提出了研究展望.

Carrying forward the traditional virtues of filial piety and respect for the elderly plays a positive role in supporting the effective operation of the family pension security mechanism and improving the welfare of the elderly. It is also an active exploration to effectively carry forward the traditional virtues and strengthen the family construction and family education in the report of 20thCPC National Congress. The research finds that filial piety held by the offspring can be further divided into four potential categories of“high identification type”,“differentiation type”,“contradiction type”and“low identification type”on the basis of the dual orientation of“Reciprocity Filial Piety”and“Authoritarian Filial Piety”. The“filial piety-welfare promotion effect”is stable. When the degree of identity of offspring Reciprocity Filial Piety is higher,the the parental welfare is better. And the effect is heterogeneous among the parental groups. Parents with less elderly care resources can benefit more from the positive effect of filial piety on welfare. Later policy orientation should strengthen the institutional guarantee of family values in the New Era,and further exert the effective force of the construction of family education and the development of family virtues to realize the close emotional connection and high degree of responsibility identity between generations.

关于积极老龄观的学理性研究和政策实践因应推动老龄事业高质量发展和满足老年群体日益增长的美好生活需求的现实需要.通过梳理分析新时代践行积极老龄观的政策脉络与理论探索发现,积极老龄观的政策演进路径表现为:积极看待老年人的社会观念—部署老龄工作的政策理念—有效应对老龄社会的治理信念.将积极老龄观融入经济社会发展全过程已具备"两种生产"理论的有力支撑,并结合了我国老龄工作的丰富经验.据此提出践行积极老龄观的三个基本遵循,即:将确定老年的标准同时根植人的生理属性和社会属性;强化将家庭作为福利资源的输入单位;重视新媒体的积极老龄化话语传播.与之相对应的政策路径表现为:建构系统、标准的人口老龄化指标体系;综合运用发展性和救助性福利工具,强化家庭的养老功能;将传播学视角引入老年学研究.

The reserves of the Duobaoshan porphyry Cu-Au-Mo-Ag deposit (also referred to as the Duobaoshan porphyry Cu deposit) ranks first among the copper deposits in China and 33rd among the porphyry copper deposits in the world. It has proven resources of copper (Cu), molybdenum (Mo), gold (Au), and silver (Ag) of 2.28x10(6) t, 80x10(3) t, 73 t, and 1046 t, respectively. The major characteristics of the Duobaoshan porphyry Cu deposit are as follows. It is located in a zone sandwiched by the Siberian, North China, and paleo-Pacific plates in an island arc tectonic setting and was formed by the Paleozoic mineralization and the Mesozoic mineralization induced by superposition and transformation. The metallogenic porphyries are the Middle Hercynian granodiorite porphyries. The alterations of surrounding rocks are distributed in a ring form. With silicified porphyries at the center, the alteration zones of K-feldspar, biotite, sericite, and propylite occur from inside to outside. This deposit is composed of 215 ore bodies (including 14 major ore bodies) in four mineralized zones. Ore body No. X in the No. 3 mineralized zone has the largest resource reserves, accounting for more than 78% of the total reserves of the deposit. Major ore components include Cu, Mo, Au, Ag, Se, and Ga, which have an average content of 0.46%, 0.015%, 0.16 g/t, 1.22 g/t, 0.0003%, and 0.001% -0.003%, respectively. The ore minerals of this deposit primarily include pyrite, chalcopyrite, bornite, and molybdenite, followed by magnetite, hematite, rutile, gelenite, and sphalerite. The ore-forming fluids of this deposit were magmatic water in the early metallogenic stage and then the mixture of meteoric water and magmatic water at the late metallogenic stage. The ore-forming fluids experienced three stages. The ore-forming fluids of stage I had a hydrochemical type of H2O-CO2-NaCl, an ore-forming temperature of 375 -650 degrees C, and ore-forming pressure of 110-160 MPa. The ore-forming fluids of stage II had a hydrochemical type of H2O-CO2-NaCl, an ore-forming temperature of 310 -350 degrees C, and ore-forming pressure of 58-80 MPa. The ore-forming fluids of stage III had a hydrochemical type of NaCl-H2O, an ore-forming temperature of 210 -290 degrees C, and ore-forming pressure of 5-12 MPa. The Cu-Au-Mo-Ag mineralization mainly occurred at stages I and II, with the ore-forming materials having a mixed crust-mantle source. The Duobaoshan porphyry Cu deposit was formed in the initial subduction environment of the Paleo-Asian Ocean Plate during the Early Ordovician. Then, due to the closure of the Mongol-Okhotsk Ocean and the subduction and compression of the Paleo-Pacific Ocean, a composite orogenic metallogenic model of the deposit was formed. In other words, it is a porphyry -epithermal copper-gold polymetallic mineralization system of composite orogeny consisting of Paleozoic island arcs and Mesozoic orogeny and extension. (c) 2023 China Geology Editorial Office.

铌(Nb)、钽(Ta)广泛应用于全球高新科技领域,是不可替代的稀有金属资源,在中国,铌钽属于紧缺战略性矿产. 铌钽成矿主要与内生作用有关,国内外目前发现的铌钽矿床几乎都产于过铝质花岗岩、花岗伟晶岩、碱性花岗岩、碳酸岩等侵入体中.

The Anshan-Benxi greenstone belt in the northeastern North China Craton preserves -3.88 Ga to -2.5 Ga lithologies that exhibit based secular trends in their geological signatures and hosts large amounts of valuable Neoarchean banded iron formations. However, whether plume or subduction mechanism responsible for those iron deposits remains confusing. This contribution focuses on the metamorphosed volcanic rocks and aims to constrain their geodynamic regime, based on temporal and spatial distributions, petrogenesises and tectonic characteristics. The late Neoarchean metamorphosed volcanic rocks of the Anshan-Benxi greenstone belt are prominently exposed in the Waitoushan-Gongchangling-Benxi area and consist of plagioclase amphibolites, amphibole/mica plagioclase gneisses and amphibole/mica two-feldspar gneisses. All 107 metamorphosed volcanic rock samples may be geochemically and petrographically classified as tholeiites, tholeiitic to calc-alkaline basalts, andesite, and dacite-rhyolite. The tholeiites are characterized by approximately flat REE patterns with negligible Eu anomalies and show negative Nb anomalies on primitive normalized multiple element diagrams, consistent with a back-arc basin basalt origin. The tholeiitic to calc-alkaline basalts have slightly heavy REEdepleted patterns and obvious negative Nb anomalies, which were likely produced by partial melting of mantle peridotites that were metasomatized by subducted slab-released fluids and melts. They may be comparable to island arc basalts. The andesites exhibit notably high MgO, Mg# and transition metal element contents, low FeOT/MgO ratios, fractionated REE patterns and evident negative Nb, Ta and Ti anomalies, which are akin to Phanerozoic high magnesian andesites and are melts of mantle peridotites that were previously metasomatized by subducted slab melts/fluids. The dacite-rhyolites have the highest SiO2 and lowest MgO, Cr and Ni contents and were derived from intracrustal remelting. The zircon U-Pb dating results reveal that the arc tholeiitic to calc-alkaline basalt-andesite-dacite-rhyolite assemblages erupted at -2.57 Ga --2.52 Ga and back-arc basin basalt lithological association at -2.55-2.52 Ga. Furthermore, both the arc basalt-andesite-dacite-rhyolite and back-arc basin basalt associations are predominantly exposed within the Waitoushan-Gongchangling-Benxi range of the northeastern Anshan-Benxi greenstone belt. Therefore, we suggest that the Waitoushan-Gongchangling-Benxi area represents a rear-arc to back-arc zone, which was subsequently subjected to consistent NE-SW compression (sigma(1)) and top-to-northeast kinematic features during back arc closure and underwent up to high amphibolite facies metamorphism. However, the Anshan area in the southwestern range of the Anshan-Benxi greenstone belt preserves large amounts of thick-bedded metasedimentary rocks instead of back-arc and arc volcanic rocks, which indicates a stable depositional environment in a typical back arc basin depositional zone. The supracrustal rocks within the back arc basin depositional domain underwent NE-SW compression (sigma(1)) and top-to-southwest kinematic features and mostly experienced greenschist facies metamorphism. These crust-mantle interaction features inferred by metamorphosed volcanic rocks in the Anshan-Benxi greenstone belt, spatial and temporal variations in the lithological assemblages, together with the style of structural deformations, indicate a late Neoarchaean geodynamic evolution from SW-dipping subduction to arc back-arc development and collisions between ancient continental blocks and arcs.

The Dantazi Complex in the North Hebei Terrane is located in the middle segment of the northern North China Craton, and plays a crucial role for understanding the early Precambrian crustal evolution of the craton. The Dantazi Complex is composed mainly of late Neoarchean tonalites-trondhjemites-granodiorites, potassic granites, sanukitoid granodiorites-monzodiorites and quartz syenites, which were emplaced by Paleoproterozoic gabbroic stocks. SHRIMP and LA-ICP-MS zircon dating analyses have revealed that the Neoarchean diversified granitoids of the Dantazi Complex were formed in-2.52-2.47 Ga, and preserved-2.60-2.53 Ga inherited/captured zircon ages. All these rocks experienced early metamorphism and deformation at-2.40 Ga, later granulite facies metamorphism at-1.80 Ga, and alterations at-1.73 Ga. Whole-rock chemical characteristics and Sm-Nd-Lu-Hf isotopes indicate that (1) The-2.52 Ga tonalites-trondhjemites-granodiorites were derived from partial melting of juvenile mafic crust; (2) the-2.51 Ga sanukitoid monzodiorite-granodiorite series came from slab-mantle interaction with different melt/rock ratios; (3) The-2.50-2.47 Ga potassic granites were generated by intracrustal recycling of metagreywacks that sourced from the mixture between juvenile and ancient crustal materials; and (4) The-2.50 Ga quartz syenites were originated from fractional crystallization of mantle-derived magmas. These petrogenetic processes reveal that the subduction-related crust-mantle interaction is the key reason for the diversity of late Neoarchean granitoids in the Dantazi Complex. Regional comparison indicates that the Precambrian North Hebei Terrane show distinct structure in the chronology and lithological assemblages from other basement terranes in the trans-North China Orogen and Western Block, implying that they were formed in different crust-mantle dynamic systems. Therefore, the Precambrian North Hebei Terrane was prob-ably an independent micro-continental block at least until the early Paleoproterozoic. In the Archean crystalline basement range of the North Hebei-West Liaoning-East Hebei, from NW to SE, the magmatic crystallization ages gradually became older, and the granitoid assemblages transformed from sodium-rich to potassium-rich, the spatio-temporal evolution of chemical composition and lithological assemblages further indicates that the North Hebei Terrane was most likely developed in an arc environment with continuous retreat subduction caused by the slab roll-back.

首次于鞍本地区发现晚太古宙晚期变质高镁安山岩,其主要矿物组合为角闪石+斜长石+云母+石英+少量辉石,并与～2.55～2.52 Ga BIF和变质表壳岩互层产出.全岩主微量元素地球化学结果显示,鞍本地区高镁安山岩发育钙碱性,高MgO,Cr和Ni含量,以及低FeOT/MgO比值等原始岩浆特征,并呈现强分异REE模式和明显Nb,Ta,Ti亏损等典型岛弧岩浆特征,与～2.7 Ga Wawa绿岩带高镁安山岩和显生宙Setouchi地区赞岐质高镁安山岩具有相近的地球化学特征,将鞍本地区晚太古宙高镁安山岩解释为受到俯冲板片熔体交代的地幔橄榄岩部分熔融形成,为鞍本地区晚太古宙晚期存在俯冲机制提供了佐证.