Metamorphism of the northern Liaoning Complex:Implications for the tectonic evolution of Neoarchean basement of the Eastern Block,North China Craton

As one of the areas where typical late Archean crust is exposed in the Eastern Block of the North China Craton,the northern Laioning Complex consists principally of tonalitic-trondhjemitic-granodioritic(TTG) gneisses,massive granitoids and supracrustal rocks.The supracrustal rocks,named the Qingyuan Group, consist of interbedded amphibolite,hornblende granulite,biotite granulite and B1F.Petrological evidence indicates that the amphibolites experienced the early prograde(M1),peak(M2) and post-peak(M3) metamorphism.The early prograde assemblage(M1) is preserved as mineral inclusions,represented by actinotite + hornblende + plagioclase + epidote + quartz + sphene,within garnet porphyroblasts.The peak assemblage(M2) is indicated by garnet + clinopyroxene + hornblende + plagioclase + quartz + ilmenite, which occur as major mineral phases in the rock.The post-peak assemblage(M3) is characterized by the garnet + quartz symplectite.The P—T pseudosections in the NCFMASHTO system constructed by using THERMOCALC define the P-T conditions of Ml,M2 and M3 at 490-550℃/<4.5 kbar,780-810℃/7.65- 8.40 kbar and 630-670℃/8.15-9.40 kbar,respectively.As a result,an anticlockwise P-T path involving isobaric cooling is inferred for the metamorphic evolution of the amphibolites.Such a P-T path suggests that the late Archean metamorphism of the northern Liaoning Complex was related to the intrusion and underplating of mantle-derived magmas.The underplating of voluminous mantle-derived magmas leading to metamorphism with an anticlockwise P-T path involving isobaric cooling may have occurred in continental magmatic arc regions,above hot spots driven by mantle plumes,or in continental rift environments. A mantle plume model is favored because this model can reasonably interpret many other geological features of late Archean basement rocks from the northern Liaoning Complex in the Eastern Block of the North China Craton as well as their anticlockwise P—T paths involving isobaric cooling.

U-Pb Zircon Dating of the Granitic Conglomerates of the Hutuo Group:Affinities to the Wutai Granitoids and Significance to the Tectonic Evolution of the Trans-North China Orogen

与在中间的最好、古典的剖面图 Trans 北方 ChinaOrogen 分割的邻近的 Fuping 和 Hengshan Complexesrepresents 联系的 Wutai 建筑群，通常划分了成东方、西方的块。Unconformably overlying Wutai andFuping 建筑群 Hutuo 组在这个区域被看作最年轻的岩石地层单位并且为解释前寒武纪的历史以及 theTrans 北方中国造山带的全面进化重要。在这个组的沉积岩的起源的知识的缺乏妨碍了 depositional 和构造意义的理解。LA-ICP-MS 被使用为花岗石的卵石获得 U-Pb 锆石年龄， Hutuo 组的最低岩石层位学的岩石，它，与结合了以前的岩石层位学， geochronological，结构、变形的数据，在沉积起源和这个区域的构造进化上提供新限制。Hutuo 的顺序从更低的底砾岩 andvolcaniclastic 岩石(Doucun 亚群) 向上组织范围，通过碎屑沉积物，板岩，白云石和云石(Dongye 亚群) ，到在顶(Guojiazhai 亚群) 的沙岩和集团企业。从在 Doucun 亚群底砾岩保存的花岗石的卵石的锆石给加权的mean~( 207 )在 2517 妈和 2566 妈之间的Pb/~( 206 ) Pb 年龄，它与为迟了的 ArcheanWutai Granitoids 的那些一样，显示卵石从 Wutai 花岗石的侵入( 2566-2515 妈)被导出。基于新数据和以前的研究，与在 Hutuo 组为 volcanics 获得的 2087 ±9 妈的火的锆石结晶化年龄结合了， Hutuo 组在在东方块的西方的边缘下面在西方的块的东方指导俯冲期间在 theWutai 弧后面发展了的subduction相关的制动火箭弧低岬盆环境被扔。这盆经历了长寿沉积并且最后在～ 1 期间关上了导致了北方中国古地台的最后的合并的 850 妈 collisional 事件。

What Happened in the Trans-North China Orogen in the Period 2560-1850 Ma?

Trans 北方中国造山带(TNCO ) 是东方、西方的块沿着混合了形成一个协调 NorthChina 古地台(NCC ) 的一条 Paleoproterozic continent-continentcollisional 带。最近地质，结构，有在东方块的西方的边缘下面的海洋的岩石圈的东方指导俯冲的 geochemical 和 theorogen 沿着东方块的西方的边缘是大陆人边缘或日本类型弧的同位素的数据表演，由旧海洋与西方的块被分开，。在 2550-2520 妈， deepsubduction 引起了媒介降低的外壳的部分融化，生产被侵入进形成 granitoid plutons 在的外壳的上面的层次的丰富的 granitoid 岩浆低 --tomedium 等级花岗石绿岩岩层。在 2530-2520 妈，海洋的岩石圈的俯冲引起了披风楔的部分融化，它在弧在下地壳和普遍 mafic 和次要的 felsic 火山作用在 mafic 岩浆的 plating 下面导致了，形成绿岩集合的部分。普遍 mafic 驾驶到 felsic 火山作用的扩展在造山带导致了发展 ofback 弧或 intra 弧盆。在 2520-2475 妈，俯冲引起了形成大量 tonalitic-trondhjemitic-granodioritic (TTG ) 的下地壳的进一步偏爱的融化岩浆酌。背弧盆的在这时候后面的进一步的扩展，阵发性的 granitoidmagmatism 发生了，导致 2360 妈，的炮兵阵地～ 2 250 妈 2110-21760 妈和～ 2 在造山带的 050 Magranites。当代的火山沉积的岩石在背弧 orintra 弧盆发展了。在 2150-1920 妈，造山带经历了几前紧张的事件，一条海洋的山脉的可能到期的 tosubduction，导致是的 mafic 女同性恋的炮兵阵地随后变形了到角闪岩和媒介 -- 到高压的 mafic granulites。在 1880-1820 妈，在东方、西方的块之间的海洋被俯冲完全消费，并且关门海洋导致了 continent-arc-continent 碰撞，它引起了大规模推进和等斜褶皱并且搬运了一些岩石进更低的外壳的层次或上地幔形成 granulites 或 eclogites 。山峰变态被 exhumation/uplift 跟随，导致在岩石中的不对称褶皱和 symplectic 质地的普遍开发。

LA-ICP-MS Zircon U-Pb Geochronology of the Fine-grained Granite and Molybdenite Re-Os Dating in the Wurinitu Molybdenum Deposit,Inner Mongolia,China

The Wurinitu molybdenum deposit,located in Honggor,Sonid Left Banner of Inner Mongolia,China,is recently discovered and is considered to be associated with a concealed fine-grained granite impregnated with molybdenite.The wall rocks are composed of Variscan porphyritic-like biotite granite and the Lower Ordovician Wubin'aobao Formation.LA-ICP-MS zircon U-Pb dating of the fine-grained granite reveals two stages of zircons,one were formed at 181.7±7.4 Ma and the other at 133.6±3.3 Ma.The latter age is beli...

U-Pb Age and Hf Isotope Study of Detrital Zircons from the Wanzi Supracrustals:Constraints on the Tectonic Setting and Evolution of the Fuping Complex,Trans-North China Orogen

在 Trans 北方中国造山带的中间的片断定位了， FupingComplex 在理解北方 ChinaCraton (NCC ) 的进化历史被看作一个批评区域。建筑群由各种各样的高级、多样地使变形的岩石组成，包括灰色的片麻岩，基本 granulite，角闪岩，有细密纹理的片麻岩和大理石，变形了到上面的角闪岩或 granulite 外形。它能被划分成四个岩石单位：Fuping TTG 片麻岩， Longquanguan augen， Wanzi 在上 crustals，和 Nanying 花岗石的片麻岩。从 FupingComplex 的 Wanzi 在上 crustals 的大约 200 由岩屑形成的锆石的 U-Pb 年龄和 Hfisotope 作文被分析了。边界给的变形锆石上的数据 1.82-1.84 Ga 变老，相应于 NCC 的最后的合并事件为在～ 2 .10 和～ 2 .51 Ga 的火的锆石核心产量二年龄人口的数据，与在第 2.5a 2.9 Ga 之间散布的一些继承年龄。这些结果建议 Wanzi 在上 crustals 从 Fuping TTGgneisses (～ 2 .5 Ga ) 和 Nanying 花岗石的片麻岩(2.0-2.1 Ga ) 被导出并且在 2.10 and1.84 Ga 之间扔了。有～ 2 .51 Ga 年龄的所有锆石有起始的ε _(Hf ) 从 +1.4 珍视到 +10.9 的 positive，建议在通过从披风的少年材料的增加的～ 2 .5 Ga 的一个重要外壳的生长事件。为由岩屑形成的锆石的 Hf 同位素数据进一步暗示 2.8 Ga 岩石是在下地壳的重要部件，它与从为东方块的 Nd 同位素数据的一个建议一致。 2.10 Ga 人口的锆石有起始的ε_( Hf ) -4.9 to+6.1 的价值，作为在 2.1 Ga.These 结果与次要的少年材料贡献外壳的再融化混合解释了为西方的块从那是不同的，支持 Fuping 建筑群是在在东方块的西方的边缘的构造活跃环境的 emplaced 。

Geochemistry and Petrogenesis of Neoarchean Metamorphic Mafic Rocks in the Wutai Complex

Neoarchean metamorphic mafic rocks in the lower and the middle Wutai Complex mainly comprise metamorphic gabbros, amphibolites and chlorite schists. They can be subdivided into three groups according to chondrite normalized REE patterns. Rocks in Group #1 are characterized by nearly flat REE patterns (Lan/Ybn=0.86?1.3), the lowest total REEs (29?52 ppm), and weak negative to positive Eu anomalies (Eun/Eun*=0.84?1.02), nearly flat primitive mantle normalized patterns and strong negative Zr(Hf) anomalies. Their geochemical characteristics in REEs and trace elements are similar to those of ocean plateau tholeiite, which imply that this group of rocks can represent remnants of Archean oceanic crust derived from a mantle plume. Rocks in Group #2 are characterized by moderate total REEs (34?116 ppm), LREE-enriched (Lan/Ybn=1.76?4.34) chondrite normalized REE patterns with weak Eu anomalies (Eun/Eun*=0.76?1.16), and negative Nb, Ta, Zr(Hf), Ti anomalies in the primitive mantle normalized spider diagram. The REE and trace element characteristics indicate that they represent arc magmas originating from a sub-arc mantle wedge metasomatized by slab- derived fluids. Rocks in Group #3 are characterized by the highest total REEs (61?192 ppm), the strongest LREEs enrichment (Lan/Ybn=7.12?16) with slightly negative Eu anomalies (Eun/ Eun*=0.81?0.95) in the chondrite normalized diagram. In the primitive mantle normalized diagram, these rocks are characterized by large negative anomalies in Nb, Ta, Ti, negative to no Zr anomalies. They represent arc magmas originating from a sub-arc mantle wedge enriched in slab-derived melts. The three groups of rocks imply that the formation of the Neoarchean Wutai Complex is related to mantle plumes and island-arc interaction.

Ages and Hf isotopes of detrital zircons from the Permian strata in the engbatu area(Inner Mongolia) and tectonic implications

The Central Asian Orogenic Belt(CAOB) was built up through protracted accretion and collision of a variety of terranes/micro-continents during Neoproterozoice Mesozoic time. To understand potential links among Paleozoic subduction and accretionary processes that were operative during the development of the southeastern CAOB, we conducted a combined U-Pb and Hf-isotope analysis of detrital zircons from previously defined Devonian, Carboniferous and Early Permian strata in the Bengbatu area,Inner Mongolia. Detrital zircons from(meta-) sandstones in these strata commonly yield major Paleozoic age populations at ca. 300-261 Ma, 351-300 Ma and 517-419 Ma, and also give several Precambrian ages that range from 2687 Ma to 544 Ma. The youngest ages redefine the deposition of all these strata to be in the Middle Permian(Wordiane Capitanian) or later, much younger than previously considered.These ages, coupled with regional magmatic records, support an interpretation of most surrounding areas as possible detritus sources, including the Mongolian arcs to the north, the Northern Accretionary Orogen to the south, and the intervening Erenhote Hegenshan Ophiolite Belt. Zircons with magmatic ages of ca. 500-350 Ma and ca. 300-261 Ma display a large range of εHf(t) values(-13.97 to +15.31),whereas ca. 350-300 Ma zircons are dominated by positive εHf(t) values(+0.14 to +16.00). These results support the occurrence of two significant shifts of the zircon εHf(t) values, which has tectonic implications for the understanding of the Carboniferouse Permian evolution of the southeastern CAOB. A marked shift from mixed to positive zircon εHf(t) values at 350 -330 Ma likely manifests the incipient opening of the Hegenshan Ocean, due to the slab rollback of the subducting Paleo-Asian Oceanic lithosphere. Another shift from positive to mixed zircon εHf(t) values at ca. 300 Ma likely corresponds to a tectonic switch from syn-orogenic subduction-related to post-orogenic extensional setting, genetically related to the tectonic collapse of a formerly overthickened crust.

Detrital zircon constraints on late Paleozoic tectonism of the Bogda region(NW China)in the southern Central Asian Orogenic Belt

The Chinese North Tianshan(CNTS)in the southern part of the Central Asian Orogenic Belt(CAOB)has undergone multistage accretion-collision processes during Paleozoic time,which remain controversial.This study addresses this issue by tracing the provenance of Late Paleozoic sedimentary successions from the Bogda Mountain in the eastern CNTS through U-Pb dating and Lu-Hf isotopic analyses of detrital zircons.New detrital zircon U-Pb ages(N=519)from seven samples range from 261±4 Ma to 2827±32 Ma.The most prominent age peak is at 313 Ma and subordinate ages vary from 441 Ma to 601 Ma,with some Precambrian detrital zircon ages(~7%)lasting from 694 Ma to 1024 Ma.The youngest age components in each sample yielded weighted mean ages ranging from 272±9 Ma to 288±5 Ma,representing the maximum depositional ages.These and literature data indicate that some previously-assumed"Carboniferous"strata in the Bogda area were deposited in the Early Permian,including the Qijiaojing,Julideneng,Shaleisaierke,Yangbulake,Shamaershayi,Liushugou,Qijiagou,and Aoertu formations.The low maturity of the sandstones,zircon morphology and provenance analyses indicate a proximal sedimentation probably sourced from the East Junggar Arc and the Harlik-Dananhu Arc in the CNTS.The minor Precambrian detrital zircons are interpreted as recycled materials from the older strata in the Harlik-Dananhu Arc.Zircon EHf(t)values have increased since^408 Ma,probably reflecting a tectonic transition from regional compression to extension.This event might correspond to the opening of the Bogda intraarc/back arc rift basin,possibly resulting from a slab rollback during the northward subduction of the North Tianshan Ocean.A decrease of zirconεHf(t)values at^300 Ma was likely caused by the cessation of oceanic subduction and subsequent collision,which implies that the North Tianshan Ocean closed at the end of the Late Carboniferous.

Screening of Sapindus germplasm resources in China based on agro-morphological traits

Sapindus L.species are widely cultivated for biodiesel,biomedical,and biochemical raw materials in southern China.However,yields fuctuate widely due to the lack of high-yielding,high-quality,stable cultivars.Therefore,the objectives of this study were to evaluate three species and one variety among 149 nationwide Sapindus species and screen for elite accessions which would serve as Sapindus breeding materials.Accessions were evaluated on 19 agro-morphological traits by correlation analysis and principal component analysis.These displayed substantial diversity and a broad range of economic traits.In particular,accessions of Sapindus mukorossi and Sapindus rarak had more variation in economic traits than Sapindus delavayi and Sapindus rarak var.velutinus.Increased saponin accumulation may be achieved at the cost of seed oil production.Thirty elite accessions for oil and saponin production,and for comprehensive utilization were screened and accessions no.80,110,and 112 had significant potential to produce high yields.These elite accessions will facilitate the identification of genetic determinants of valuable traits and the effective utilization of trait variability in Sapindus breeding.

Biogeographic divergence in leaf traits of Sapindus mukorossi and Sapindus delavayi and its relation to climate

To explore differences in leaf morphology between Sapindus mukorossi and Sapindus delavayi,and how the environment might drive these differences,80 germplasm samples from the Sapindus germplasm nursery in Fujian Province were selected.The study revealed a wide variation and diversity in 16 germplasm traits,both within and between species grown under the same conditions.On average,the relative contribution of intraspecific variability to total variability was more important(83%) than the relative contribution of interspecific variability(17%).PERMANOVA analysis showed differences in leaflet thickness,length,perimeter,length to width ratio,and leaf hairs or trichome density.Correlation analyses between leaf morphological traits and environmental variables indicated that leaves tended to be larger,longer,and thicker in wetter,warmer,and low-altitude conditions.Our analysis of the relationship between climate and leaf morphology revealed that S.mukorossi had a greater sensitivity to climate variation,particularly in response to mean temperatures of the coldest and warmest seasons,which led to differences in leaf traits and the distribution of the two species.These findings contribute to the understanding of leaf morphology variations in S.mukorossi and S.delavayi,and provide a basis for the collection of Sapindus germplasm resources,their cultivation and use to help address climate change.

前板块构造与大陆起源研究进展及关键科学问题

本文总结了现阶段前板块构造与大陆起源研究的三大重要进展:(1)提出了地幔柱构造、重力凹沉构造和热管构造的前板块构造模式;(2)揭示了非板块构造与板块构造的标志;(3)发现了地球早期层圈演化地质记录.但是,现有的前板块构造并不能完美解释太古宙大陆的起源,板块构造在解释大陆起源与演化方面也遇到重大挑战.此外,阐述了我国开展前板块构造与大陆起源研究的必要性、研究优势及风险,并凝练了目前前板块构造与大陆起源研究的关键科学问题:(1)地球是先有陆还是先有板块构造;(2)海陆的形成是否同步;(3)冥古宙陆壳和英云闪长岩-奥长花岗岩-花岗闪长岩(tonalite-trondhjemite-granodiorite,TTG)的起源.基于学科发展,提出动力学热模拟和比较行星学在前板块构造与大陆起源研究中的重要性.在此基础上,认为未来5~10年前板块构造与大陆起源的研究重点领域为:(1)大陆的起源及其对早期地球环境和生命的影响;(2)前板块构造样式及其形成机制;(3)太古宙的构造热体制及热演化;(4)前板块构造与类地行星演化.

Pre-Cryogenian integrative stratigraphy,biotas,and paleogeographical evolution of the Qinghai-Tibetan Plateau and its surrounding areas

The composition and geological evolution of pre-Cryogenian material in the Tibetan Plateau and its surrounding areas have played an important role in studying the formation and evolution of early supercontinents on Earth.This paper systematically summarizes the characteristics of pre-Cryogenian sedimentation,paleontology,magmatism,and metamorphism in the Tibetan Plateau and its surrounding areas.Based on existing data,the records of pre-Cryogenian sedimentation and paleontology are mainly concentrated in the Meso-Neoproterozoic,with relatively few records from the Paleoproterozoic or earlier.The oldest geological record is the Hadean detrital zircons in the metamorphosed sedimentary rocks of the Himalaya and Qamdo areas(ca.4.0 Ga).The Tibetan Plateau and surrounding areas preserve records related to the formation and evolution of the Kenor supercraton,and the Columbia,Rodinia,and Gondwana supercontinents.Pre-Cryogenian basements can be divided into three types:Tarim-,Yangtze-,and Lhasa-type.The Tarim-type basement has a paleogeographic affinity with the northern margins of the Australian and Indian continents and lacks detrital zircon age peaks and magmatic-metamorphic records related to the Rodinia assembly(ca.1.3-0.9 Ga).The Yangtze-type basement records volcanic activity related to global cooling in the latest pre-Cryogenian period and contains Meso-Neoproterozoic stromatolite and micropaleoflora fossils,as well as magmaticmetamorphic records related to Rodinia assembly(ca.1.1-1.0 Ga).The Lhasa-type basement is characterized by Neoproterozoic rift-related sediment records(ca.900 Ma)and high-pressure metamorphic events(ca.650 Ma),with a prominent peak of detrital zircon ages of ca.1.2-1.1 Ga.It is likely to have a paleogeographic affinity with the African continent.

前板块构造与大陆起源

建立于20世纪60年代并被誉为地球科学史上一场革命的板块构造理论能圆满地解释显生宙至元古宙几乎所有地质现象、过程和事件,但却无法解释太古宙大陆克拉通基本特征,包括绿岩带内高温(~1600°C)科马提岩的成因和缺乏岩浆弧安山岩的双峰式火山岩组合,占太古宙陆壳总面积70%以上、几乎同时侵位的英云闪长岩-奥长花岗岩-花岗闪长岩岩石成因,反映垂向运动的片麻岩穹窿构造样式,缺失典型的蛇绿岩、蓝片岩、榴辉岩和双变质带等板块构造特征标志.所有这些都说明,太古宙大陆可能不是起源于板块构造体制,而是起源于某种前板块构造体制,但目前已提出的前板块构造模式(如地幔柱构造、重力凹沉构造、热管构造、滞留盖构造等)同样皆不能圆满解释太古宙大陆的岩石组合、构造样式和变质作用演化等特征.正因如此,目前世界各国有若干研究团队正在攻克这一科学难题.我国学者虽无缘参与20世纪60年代板块构造理论的创立,但在过去40年里,在早期地球动力学体制和大陆起源与演化方面开展了大量工作,并取得令人瞩目的研究成果,积累了大量资料数据,有望在构建前板块构造理论方面率先取得突破.

关注前寒武纪大陆形成演化研究

“前寒武纪地质学”研究的是寒武纪(5.4亿年)之前地质时代的地质问题,核心是大陆形成演化及相关环境资源效应.前寒武纪时间跨度约40亿年,占地球形成以来的90%,对理解地球的历史、现在以及未来具有重要意义.相关的重要科学问题包括圈层分异、大陆形成和演化,以及伴随的构造、物质(包括矿产)、环境和早期生命演化.地球是太阳系中唯一的具有花岗岩质陆壳以及出现板块构造的星球,前寒武纪地质的研究,对了解地球的形成演化、生命宜居环境,以至地球的未来命运都至关重要.地球早期历史中有3个重大的地质事件:大陆地壳的巨量生长和稳定化、构造体制的演化、地球环境的剧变,它们涵盖了地球的物质(资源)、构造和环境(灾害)科学的所有内容.

Early Cambrian high pressure/low temperature metamorphism in the southeastern Tarim craton in response to circum-Gondwana cold subduction

The circum-Gondwana subduction initiated by the early Cambrian has been suggested to reflect the establishment of the modern plate tectonics.The metamorphic rocks with low thermobaric(T/P)ratios indicative of cold subduction in the present tectonic regime have not been well investigated.To better understand the circum-Gondwana subduction and to test its possible link with the emergence of the modern plate tectonics,this study focused on blueschist-facies metamorphic rocks in the Altyn Tagh of the southeastern Tarim craton.Mineral assemblage and chemistry,phase equilibrium modelling,and quartz-in-garnet Raman elastic geobarometry reveal that the zoisite blueschist and glaucophane(Gln)-bearing quartz schist in northern Altyn Tagh were metamorphosed to lawsonite to epidote blueschistfacies at 520–545℃ and 16–19 kbar.It reflects high-pressure(HP)/low temperature(LT)metamorphism with low T/P ratios of<300℃/GPa and thermal gradients of<10℃/km.These blueschist-facies metamorphic rocks underwent rapid decompression starting at P-T conditions of<495℃ and<9.6 kbar during exhumation.Ar-Ar geochronology records paragonite Ar-Ar plateau ages of 520–506 Ma for the zoisite blueschist samples and phengite Ar-Ar plateau ages of 522–516 Ma for the Gln-bearing quartz schist samples,suggesting that the peak HP/LT metamorphism occurred prior to ca.522 Ma.Based on new results and available data from the major Gondwana blocks,cold subduction was suggested to profoundly operate along circum-Gondwana in the early Cambrian after the amalgamation of Gondwana.The extensive circum-Gondwana subduction represents the earliest global cold subduction in Earth’s history associated with the establishment of the modern plate tectonics,as directly recorded by the studied early Cambrian blueschist-facies metamorphic rocks and a dramatic drop in the mean T/P of metamorphism since the early Paleozoic.

Newly discovered youngest UHT metamorphism on Earth,Western Sulawesi,Indonesia

Ultrahigh-temperature(UHT)metamorphism represents an extreme crustal thermal event with peak conditions exceeding 900C at 7–13 kbar.In the modern-style plate tectonic system,records of the UHT metamorphism are relatively rare due to the secular cooling of Earth.In the Palu region of Western Sulawesi,we newly discovered a series of HT-UHT metamorphic rocks including amphibolite,granulite,eclogites and gneiss.Of them,two granulite samples(18CS14-2,18CS14-4)with high garnet content(>50 mol%)are chosen for petrographic observation,phase equilibrium modelling,and zircon U-Pb dating.These rocks are characterized by a relic M1 assemblage of Grt+Ky+Bt+Rt and a M2 assemblage of Grt+Sil+Pl+Spl+Crd±Qtz+Ilm+melt.Phase equilibrium modelling based on effective bulk compositions yields UHT conditions of 7.2–8.5 kbar/940–1080C(18CS14-2)and 7.0–7.3 kbar/1000–1040C(18CS14-4).U-Pb analysis reveals two generations of metamorphic zircon with evolving REE content that is intimately related to garnet growth and decomposition.Zircon age of 36–5.3 Ma is ascribed to syn-to post-M1 metamorphism,whereas the young zircon age of 5.1–3.8 Ma is linked to syn-and post-M2 stage.The UHT metamorphism was probably the consequence of the upwelling of asthenospheric mantle triggered by post-collisional delamination of lithosphere in the MiocenePliocene(ca.5 Ma).It could represent the youngest known UHT metamorphism on Earth.

地质学科未来5~10年发展战略:趋势与对策

当代地球科学的内涵和外延已经拓展到涵盖整个固体地球内部及外部层圈形成演化及与资源能源富集、生态环境变迁、地球宜居性和社会可持续发展相关的地球系统科学问题.随着人类社会经济高速发展,与地球相关的资源能源、气候环境、地质灾害等问题日益突出.为了适应新时代地球科学发展形势,在地球系统科学理论框架下,准确分析我国地球科学未来5~10年的发展趋势、明确战略目标和优先发展领域,不仅能够大力促进和强化我国地球科学的发展、赶超世界领先水平、早日实现从地质大国到地质强国的转变,而且对于保障国家矿产能源安全、助推国家经济建设和人类社会可持续发展具有重大意义.

地球历史上两种范式的板块构造

板块构造在地球上开始出现的时间及其如何随着时间而演化,是地球科学中的最基本问题.尽管重力驱动的俯冲作用已经被看成是地球上板块构造运作的关键条件,但是地球历史上俯冲带动力机制和热状态变化如何影响板块构造范式这个问题依然值得探讨.沿汇聚板块边界分布的区域变质岩记录了地壳岩石在岩石圈深度通过脱水和熔融作用发生的再造.区域变质作用的性质受控于板块边缘热状态,在变质相系全球分布上随时间推移所发生的变化就记录了板块边缘动力体制随时间的演化.现代板块构造开始于新元古代,这时板块边缘具备了足够的刚性得以冷俯冲;远古板块构造则开始于太古代,那时板块边缘因具有足够的韧性而进行暖俯冲.这种差异主要是由于太古代地幔比显生宙地幔具有显著较高的温度,在冷和暖两种状态下的板块俯冲属性主要受控于板块边缘的流变学.因此,本文建立了地球历史上不同时期板块构造范式的功能性整体模型.

Genesis of the Xinfang Gold Deposit,Liaodong Peninsula:In-sights from Fluid Inclusions and S-Sr Isotopic Constraints

The North China Craton(NCC)has been continuously reactivated since the Mesozoic and this decratonization is responsible for its economically important gold mineralization in the Meso-zoic.The Early Cretaceous(110-130 Ma)gold mineralization in the NCC has been well-studied due to its significance,but little attention has been given to other episodes of gold mineralization related to polyphased reactivation of the NCC.The Xinfang mesozonal gold deposit(143 Ma)in the Liaodong Peninsula is related to the one of the episodes of the Yanshanian orogeny.The orebodies of the Xin-fang gold deposit were controlled by the low angle transpressive fault systems and hosted by the Neoarchean monzogranitic gneiss.Fluid inclusion microthermometry reveals that the mineralizing temperatures range from 220 to 280℃,with salinities from 6 wt.%NaCl eqv.to 15 wt.%NaCl eqv.,pressures from 199 to 321 Ma.The S isotopic characteristics of sulfides not only record a heterogene-ous source including magmatic or gneissic sulfur but also record inter-mineral isotope fractionation.The initial^(87)Sr/^(86)Sr values of pyrite(0.713480-0.729031)indicate a radiogenic crustal origin for the sources.The metamorphic dehydration of the underlying basement resulted in the genesis of the Xin-fang gold deposit.We summarize three episodes of gold mineralization in the Liaodong Peninsula re-lated to continuous reactivation of the NCC,which indicates a great exploration potential of this area.

中亚造山带南缘末次大规模侧向增生的机制

中亚造山带是世界上最大的显生宙增生造山带.其古生代形成了巨量的年轻弧地壳物质,然而形成的构造机制和结束时限尚不清楚.南蒙古拼合体系是中亚造山带晚古生代典型的增生造山区,为研究中亚造山带晚期侧向增生提供了理想的窗口.通过对南蒙古东部Khan-Bogd地区的石炭纪火山岩-火山碎屑岩进行精细的岩石学和锆石的U-Pb-Hf和全岩Sr-Nd同位素研究,得出南蒙古石炭纪弧岩浆作用经历了由北向南的迁移,是俯冲板片后撤的产物.结合前人对整个中亚造山带南缘同时期及稍晚的岩浆岩、沉积岩和大地构造的研究,认为该期弧岩浆作用发生在弧后洋盆,并代表了中亚造山带南缘最后一次大规模侧向增生.