The late Neoarchean tonalite – trondhjemite – granodiorite (TTG) and mafic rocks record essential information regarding the early tectonic evolution of the North China Craton, which is crucial for understanding the onset and development of the plate tectonic regime. In this study, we present a comprehensive analysis of petrography, geochronology, and geochemistry of the Guanghua Mélange from the Tonghua area in NE China. The mélange comprises basalt, gabbro, pyroxene diorite, and trondhjemite, and is classified into three groups: basaltic – gabbroic rocks (Group #1), dioritic rocks (Group #2), and trondhjemites (Group #3). Zircon U-Pb analyses indicate that they formed at 2596–2550 Ma, 2531–2515 Ma, and 2502 Ma, respectively, with metamorphism occurring during ~ 2500–2450 Ma. Meanwhile, geochemical data indicate that the calc – alkaline basaltic rocks (Group #1) exhibit slight depletion of Nb or Ta with weakly negative Eu anomalies, suggesting derivation from the lithospheric mantle and formation within a continental arc environment. The pyroxene diorites (Group #2) display similar geochemical characteristics to Group #1, likely formed by partial melting of depleted mantle that underwent sgignificant metasomatism due to variable amounts of slab-derived fluids or melts. The tholeiitic granitoids (Group #3) exhibit strongly fractionated chondrite-normalized REE patterns with high (La/Yb)N and Sr contents, low Y contents, and depletion of Nb, Ta or Ti, resembling adakites generated in arc setting, indicating likely formation through partial melting of subducted oceanic crust. This process was controlled by the initial plate tectonics under a higher geothermal gradient. Consequently, when combined with previous findings, we conclude that an initial subduction of oceanic plate operated in the northeastern North China Craton during the late Neoarchean (>2.55 Ga). Subsequently, it transformed into modern-type plate tectonics during ~ 2.55–2.53 Ga, eventually followed by the continent-continent collision at ~ 2.50–2.45 Ga, resulting in the formation of the Ji – Liao – Ji (Jilin – Liaoning – Hebei) Collision Orogenic Belt.

The central Inner Mongolia, located at the intersection of the northern margin of the North China Craton (NCC) and the Central Asian Orogenic Belt, is crucial for deciphering the Late Palaeozoic tectonic evolution associated with the subduction and closure of the Palaeo‐Asian Ocean (PAO). Our study focused on petrology, detrital zircon LA–ICP–MS U–Pb geochronology and whole‐rock geochemistry for the Late Carboniferous to Permian sandstones within the Shuanmazhuang, Dahongshan, Naobaogou, and Laowopu formations in Siziwang Banner, central Inner Mongolia. This comprehensive analysis shed light on the dynamic interplay between the NCC and the South Mongolia Block. Detrital zircon U–Pb ages in investigated samples mainly cluster between 250 and 2650 Ma, with significant peaks at 2.4–2.5 Ga, 1.8–2.0 Ga, 400–430 Ma, and 250–320 Ma, respectively. The geochemistry data are characterized by SiO2 contents (56.29–77.95 wt. %), Na2O / K2O ratios (0.45–1.58) and SiO2/Al2O3 ratios between 4.33 and 7.44. Moreover, they exhibit the slight enrichment in large ion lithophile elements (Rb and Ba) and the depletion in high field strength elements (Nb, Ta, Th, and U). These facts indicate that the sedimentary detritus predominantly originates from felsic sources, probably deriving from the Late Carboniferous–Permian continental island arc‐related intermediate‐acid igneous rocks, the Late Ordovician‐Silurian magmatic rocks in the Bainaimiao arc and the basements of the NCC. Furthermore, our present results also suggest that during the Early–Middle Permian, accelerating oceanic crust subduction triggered significant magmatic events in Siziwang Banner, leading to rapid uplift and the erosion of arc magmatic rocks, as well as the abundant corresponding sediments. Subsequently, the gradual convergence and eventual collision between the NCC and the Southern Mongolian Block took place at the end of the Permian, representing final closure of the PAO.

辽西地区位于燕山造山带东段,发育大规模的中生代火山-沉积盆地,是研究中生代燕山运动构造体制转换、岩石圈减薄和克拉通破坏的关键地区之一.报道了辽西寺儿堡-白塔盆地晚侏罗世火山岩岩相学、锆石U-Pb年代学、地球化学和锆石Hf同位素组成等资料,确定了其形成时代、岩石成因及构造背景,探讨了晚中生代期间古太平洋板块对华北克拉通东部俯冲后撤作用时间,为进一步认识燕山运动和燕山期岩浆活动的地球动力学机制提供可靠的地质依据.盆地内大范围出露的流纹岩形成时代为153.8～160.3 Ma,在空间上呈NE向展布,具有较高的SiO2、Al2O3和全碱含量,显示准铝质-过铝质和高钾钙碱性特征.样品相对富集大离子亲石元素(LILEs:Rb、Ba、Pb、K等)和轻稀土元素(LREEs),亏损高场强元素(HFSEs:Nb、Ta、P、Ti等)和重稀土元素(HREEs),具明显的Eu负异常和较低的Cr、Co、Ni含量,结合岩浆成因锆石具有负εHf(t)值(-17.8～-23.2)和相对古老的Hf同位素二阶段模式年龄(TDM2=2334～2697 Ma),暗示初始岩浆可能来自于太古代或元古代的古老下地壳的部分熔融.综合研究表明,辽西地区晚侏罗世岩浆构造活动主要受控于古太平洋板块俯冲和后撤.寺儿堡-白塔盆地中流纹岩形成于古太平洋板块俯冲的NW向挤压构造背景,同时,在辽西地区存在大量与古太平洋板块后撤密切相关的变质核杂岩和伸展盆地,暗示区域上伸展体系的存在.因此,认为燕山-辽西地区构造体制于晚侏罗世发生转变,由挤压体系逐渐过渡为伸展体系,为燕山运动的响应.

Typical ophiolitic rock assemblages such as siliciclastic rocks, basalts and gabbros, together with the subduction-related intermediate-acidic intrusive rocks, are newly discovered in the Tongjiang-Fuyuan area of the Heilongjiang Provence, NE China. To determine the formation age and genesis of the mafic rocks (basalts and gabbros) and intermediate-acidic intrusive rocks (granodiorites) in the area, as well as their geodynamic settings, the whole-rock geochemical analysis and zircon LA-ICP-MS U-Pb dating were carried out. Zircon U-Pb results suggest that the granodiorites are 93-95 Ma and gabbro is 95 Ma, respectively. Geochemical results show that the gabbros and basalts exhibit characteristics of ocean island basalt (OIB) affinity and are typically related to having originated from mantle plumes. While the granodiorites show the nature of the island-arc magmatic rocks and may originate from the lower crust. Based on the coeval igneous rock associations and regional tectonic evolution, we conclude that the late Cretaceous magmatic rocks in the Tongjiang-Fuyuan area are the product of continuous subduction of the Palaeo-Pacific plate and reflect the subduction rollback process of the Palaeo-Pacific plate.

As one of the most representative Paleoproterozoic orogenic belts in the North China Craton, the Jiao-Liao-Ji Belt is of great significance to explore the Paleoproterozoic tectonic evolution of the North China Craton, as well as the convergence process of the Columbia Supercontinent. In this study, we present new geochronological and geochemical data of Paleoproterozoic meta-mafic rocks in the Southern Jilin Province, NE China. Our primary objective is to further constraint the formation and evolution of the Jiao-Liao-Ji Belt. The zircon U–Pb dating reveals that the meta-mafic rocks crystallized at 2.2–2.0 Ga, followed by a metamorphism occurring at 1.9 Ga. Additionally, most of the mafic rocks display moderate fractionation in both light rare earth elements (LREEs) and heavy rare earth elements (HREEs), suggesting their association with an arc setting. Furthermore, the rocks also display an enrichment in large ion lithophile elements (LILEs) such as Cs, Rb, Ba, and Pb, and depletion in high field strength elements (HSFEs) including Nb, Ta, Zr, and Ti. These geochemical characteristics suggest a back-arc setting, indicating that the meta-mafic rocks originated from asthenospheric mantle that was metasomatized by fluids or melts derived from the subducting slab. Notably, a shoshonitic metabasalt exhibits trace element and REEs patterns that resemble those of ocean–island basalts. This suggests that the shoshonitic metabasalt was formed in an oceanic island environment, likely generated from the asthenospheric mantle. Combining these findings with previous studies, we can conclude that the Jiao-Liao-Ji Belt is associated with arc–continental collision, indicating the presence of a modern-type plate tectonic regime in the northeastern North China Craton during the Paleoproterozoic period.

The Liaohe Group, which is a significant lithostratigraphic unit within the Paleoproterozoic Jiao-Liao-Ji Belt situated between the Longgang and Liaonan-Nangrim blocks, comprises the Langzishan, Li’eryu, Gaojiayu, Dashiqiao, and Gaixian formations, which are characterized mainly by a clastic-rich sequence with an interlayered bimodal-volcanic sequence, carbonate-rich sequence, and (meta-)pelite-rich sequence. Currently, the tectonic background and evolution of the Liaohe Group remain contentious. Based on the study of detrital zircon geochronology and the zircon trace element characteristics in the Langzishan and Li’eryu formations in the North Liaohe Group in the Lianshanguan area, NE China, this paper reveals the formations’ provenances, depositional ages, and relationships with Paleoproterozoic granitoids (the Liao-Ji granites). The present results, in conjunction with previous studies, indicate that the depositional age of the Langzishan Formation is 2136 Ma and that of the Li’eryu Formation is 1974 Ma. The provenances of the Langzishan Formation and the Li’eryu Formation are mainly characterized by Neoarchean-to-early-Paleoproterozoic basement rocks (~2.6–2.4 Ga) and the Liao-Ji granites (~2.2–2.0 Ga), respectively. Moreover, the coeval mafic and metasedimentary rocks of the Liaohe Group exhibit characteristics of an extensional environment, which is represented by the tectonic setting of a back-arc basin. Notably, the Upper Langzishan Formation records a prominent shift in sedimentary environment from a passive continental margin to an active continental margin. In terms of the tectonic evolution of the North Liaohe Group and the Jiao-Liao-Ji Belt, our proposed model suggests that the Archean basement rocks in the northern part of the continental block, along with a limited contribution from the Paleoproterozoic Liao-Ji granites, served as the primary sources for the Langzishan Formation. Subsequently, the rapid deposition of the Li’eryu Formation was influenced by intense magmatism and subsequent erosion of the subduction-related magmatic arc (the Liao-Ji granites) within a back-arc basin environment. Lastly, the deposition of clastic materials from the Longgang blocks and the Liao-Ji granites resulted in the formation of the Gaojiayu, Dashiqiao, and Gaixian formations.

Closure time of the eastern Paleo-Asian Ocean (PAO) has long been debated, since one important reason is the absence of coeval sedimentation study. Recently, we found well preserved Permian-Triassic (P-T) strata, the Upper Permian Linxi and Lower Triassic Laolongtou formations, at Ar Horchin Banner, Inner Mongolia (China), in southern Great Xing'an Range that can provide detailed record for this process. In this study, the sedimentation and detrital geochronology study of this newly discovered strata are carried out to determine the precise closure time of the eastern PAO. The Upper Permian Linxi Formation is a set of lacustrine sequence, whereas the Lower Triassic Laolongtou Formation a set of fluvial and lacustrine sequence, and the bottom of the later is a conglomerate layer of braided alluvial fan, marking the boundary of the two formations. The sedimentary environment near the P-T boundary were distinct, with warm and humid in ending Permian and hot and arid in earliest Triassic. The accumulation of Linxi Formation occurred at Late Permian Changhsingian Period, while the Laolongtou Formation at Early Triassic Olenekian Period, and they are unconformable contacted with a short sedimentation hiatus between them. The sandstone samples of the Linxi Formation content various kinds of heavy minerals that mainly come from felsic to mafic magmatic rocks, and minor from metamorphic and sedimentary rocks. The heavy minerals from the Laolongtou Formation sandstones are rare, derived from medium-acid magmatic and minor metamorphic rocks. The mean ages of youngest group of the two clastic samples from Linxi Formation are 255 +/- 2Ma and 255 +/- 1Ma, respectively, with epsilon(Hf) (t) values ranging from -22.84 to +13.17. While the two clastic rock samples of Laolongtou Formation have youngest mean ages of 248 +/- 1Ma and 249 +/- 1Ma, respectively, with epsilon(Hf) (t) values of 7.95 similar to 11.28. The heavy minerals, detrital zircon ages and Hf isotopes suggested that the sedimentations of the Linxi Formation have complex provenance that derived mainly from the Xing'an-Mongolia Orogenic Belt, and a small amount of North China Craton (NCC), with long-distance transport and recycling deposit. Whereas the provenance of the Laolongtou Formation is mainly from the Xing'an-Mongolia Orogenic Belt that is characterized by a near source sedimentation with short distance transportation. The comprehensive study of the regional detrital zircon geochronology information of the Linxi and Laolongtou formations indicate that the NCC and Central Asian Orogenic Belt (CAOB) converged and collided along the Xar Moron Suture Zone at ending Permian accompanied with the closure of eastern PAO, and this process lasted at least to Early Triassic. A huge orogenic event due to the collision and amalgamation of NCC and CAOB should have happened during the accumulation of the Laolongtou Formation, which provided right products for this formation.

As an important part of the tectonic m lange belt distributed in the eastern segment of the northern margin of the North China Craton (NCC), the material composition, formation age and tectonic attributes of the "Xia'ertai" tectonic complex still need to be further studied, since it may provide an important scientific basis for exploring the tectonic evolution of the eastern segment of the northern margin of the NCC. We have identified a set of Early-Middle Permian metamorphic volcano-clastic rocks in the "Xia'ertai" tectonic complex which is mainly composed of meta-clastic rocks interbedded with meta-volcanic rocks, and the two mingled in the field. The protoliths of meta-volcanic rocks include rhyolite, dacite, andesite, basaltic andesite. They are a set of calc-alkaline volcanic rocks that are metaluminous-weak peraluminous. According to petrographic and geochemical characteristics, they are divided into metamorphic acid volcanic rocks and metamorphic intermediate-basic volcanic rocks. Both of them were relatively enriched in LREEs and depleted in HREEs, indicating an obvious fractional distillation of light and heavy rare earth elements, while the Eu anomaly was not obvious. The metamorphic acid volcanic rocks are obviously deficient in P and Ti. Combined with the correlation characteristics of high field strength elements, it is considered that they are not the products of the same magma differentiation. The LA-ICP-MS U-Pb ages of zircons from the meta-volcanic rocks range from 272 Ma to 288 Ma, representing their crystallization ages of Early Permian. The original magma of metamorphic acid volcanic rocks came from the partial melting of crustal materials, while the original magma of metamorphic intermediate-basic volcanic rocks came from the lithospheric mantle near the subduction zone and suffered from the mixing of crustal materials. Both of them are formed in a volcanic arc environment at the active continental margin. The protoliths of the meta-clastic rocks are argillo-arenaceous and arenopelitic. In meta-clastic rocks, LREEs are relatively deficient, while HREEs are relatively enriched, indicating a strong fractional distillation, however, the Eu anomaly is not obvious. The zircon LA-ICP-MS U-Pb ages of the two samples are mainly between (267)Ma and (347)Ma, with their lower limits of deposition ages at (267)Ma and 269 Ma respectively, both belonging to the Middle Permian. The argillo-arenaceous rock likely comes from recirculating sedimentary rocks with parent rocks of felsic rocks, while the arenopelitic rock is come from recirculating sedimentary rocks with parent rocks of both felsic and mafic ones. Both of them are formed in the continental island arc and oceanic island arc environments. The Early Middle Permian metamorphic volcano-clastic rocks in Xia'ertai area are important components of " Xia'ertai" tectonic complex, indicating that the eastern segment of the northern margin of the NCC underwent three stages of evolution, i. e., oceanic crust subduction accelerated, new continental arc forming stage in Early Permian, oceanic crust continued subduction, continental arc and oceanic arc collision stage in Middle Permian, and pre-continental collision stage in Late Permian.

The Heilongjiang Complex records the evolution history of the Mudanjiang Ocean, which is of great significance to constrain the amalgamation process of the Jiamusi and Songnen‐Zhangguangcai Range massifs. We carried out petrological, chronological, geochemical, mineral chemical and electron backscatter diffraction (EBSD) fabric analyses on the Heilongjiang Complex in the Yilan area. The latest zircon U–Pb dating results show that the protolith ages of the amphibolite are 261.3 ± 3.0 Ma and 261.8 ± 3.3 Ma, while that of the granodioritic mylonite is 207.8 ± 2.2 Ma. The amphibolites and granodioritic mylonite are enriched in large‐ion lithophile elements (e.g., Rb, Ba, and Sr) and light rare earth elements, with depletion in high‐field‐ strength elements (e.g., Nb, Ta, Zr, and Hf), indicating that the formation of the protoliths of the amphibolites and granodioritic mylonite is related to the subduction of the Mudanjiang oceanic plate under the Songnen‐Zhangguangcai Range Massif. The amphibolites and granodioritic mylonite both experienced two periods of metamorphic and deformation events. The metamorphic degree of the early period of metamorphism is low amphibolite facies, which records a clockwise P–T path from early increased temperature and pressure to a late isothermal depressurization. The P–T path reveals that this period of metamorphism is associated with the collision between two massifs. The later period of metamorphism reaches low greenschist facies, accompanied by deformation, which may be related to the rapid exhumation of the Heilongjiang Complex. This study provides a new perspective for exploring the collision and collage process of the Jiamusi and Songnen‐Zhangguangcai Range massifs.

大兴安岭扎兰屯南部位于中亚造山带东段,兴安地块(XB)与松嫩地块(SB)之间,是探究兴安地块与松嫩地块构造演化过程,乃至中亚造山带东段微地块聚合过程的关键地区.对该地区出露的花岗质糜棱岩进行地质学、地球化学、锆石U-Pb测年分析,以期查明板块俯冲过程中的岩浆作用特征,并尝试限定兴安地块与松嫩地块碰撞拼合时间.LA-ICP-MS锆石U-Pb测年结果表明,花岗质糜棱岩分为两期:Ⅰ期为早泥盆世(～398.8 Ma),Ⅱ期为晚泥盆世末-早石炭世(351.6～365.7 Ma).两期岩石均具有高SiO2(68.20％～77.90％),富碱(K2O+Na2O=6.32％～9.67％),贫镁(MgO=0.22％～0.97％),偏铝质,高钾钙碱性系列的特征.稀土元素分布模式均为右倾[(La/Yb)N=4.33～10.77],Eu负异常(δEu=0.03～0.13),富集LILE,亏损HFSE,具有I型花岗岩的特征.两期花岗质糜棱岩可能为俯冲背景下岛弧岩浆活动形成的I型-分异I型花岗岩.结合区域构造演化和岩石地球化学研究,大兴安岭北段晚古生代早期花岗质岩浆作用与兴安地块与松嫩地块的碰撞拼合作用有关,扎兰屯地区早泥盆世-早石炭世处于古亚洲洋向兴安地块和松嫩地块俯冲的构造背景下,两个地块的最终碰撞拼合时限可能为晚石炭世.

新识别的"下二台"构造杂岩作为华北板块北缘东段分布的构造混杂岩带重要组成部分,其物质组成、形成时代和构造属性仍需进一步研究,这将为探讨华北板块北缘东段晚古生代构造演化提供重要依据.作者在"下二台"构造杂岩中识别出一套早-中二叠世变质火山-碎屑岩,其以变质碎屑岩为主,并夹变质火山岩,二者在野外产出上混杂在一起.变质火山岩原岩类型包括流纹岩、英安岩、安山岩、玄武安山岩,为一套钙碱性火山岩,属于准铝质-弱过铝质岩石.根据岩相学和地球化学特征,将其分为变质酸性火山岩和变质中-基性火山岩;二者均相对富集轻稀土元素,亏损重稀土元素,轻重稀土元素分馏明显,Eu负异常不明显,但变质酸性火山岩明显亏损P、Ti元素,结合高场强元素相关性特征,认为二者不是同一基性岩浆分异的产物.变质火山岩锆石LA-ICP-MS U-Pb同位素年龄为272～288Ma,代表其原岩结晶年龄,时代为早二叠世;变质酸性火山岩原始岩浆来源于地壳物质的部分熔融,变质中-基性火山岩原始岩浆来源于岩石圈地幔(俯冲带附近),并遭受了地壳物质的混染,二者均形成于活动大陆边缘火山弧环境.变质碎屑岩原岩恢复为泥砂质沉积岩和砂泥质沉积岩,相对亏损轻稀土元素,富集重稀土元素,轻重稀土元素分馏较明显,Eu异常不明显.两件碎屑岩样品锆石LA-ICP-MS U-Pb同位素年龄主要介于267～347 Ma,推断其沉积下限为267 Ma和269 Ma,均为中二叠世;泥砂质沉积岩可能来源于再旋回的以长英质岩石为母岩的沉积岩,砂泥质沉积岩可能来源于再旋回的以长英质和镁铁质岩石为母岩的沉积岩,二者分别形成于活动大陆边缘大陆岛弧和大洋岛弧环境.下二台地区早-中二叠世变质火山-碎屑岩为"下二台"构造杂岩重要组成部分,它表明二叠纪时期华北板块北缘东段经历了三个构造演化阶段:早二叠世古亚洲洋加速俯冲,形成新的大陆弧阶段;中二叠世古亚洲洋持续俯冲,大陆弧和大洋弧碰撞阶段;晚二叠世陆-陆碰撞前阶段.

古亚洲洋东段的具体闭合时限长期以来存在争议,重要原因在于缺乏相应时期的典型沉积剖面研究.近期,笔者在大兴安岭南段阿鲁科尔沁旗地区新发现一套保存较好的二叠-三叠系沉积序列,其详细记录了古亚洲洋闭合过程.本文以此为研究对象,重点对上二叠统林西组和下三叠统老龙头组开展沉积学和碎屑锆石年代学研究.上二叠统林西组上部为一套湖泊相沉积,下三叠统老龙头组为一套河湖相沉积,底部为冲积扇辫状河砾岩层.两套地层界线附近沉积环境发生剧变,气候从温暖湿润转变为炎热干旱,确定研究区林西组沉积时代为晚二叠世长兴期,老龙头组沉积时代为早三叠世奥伦尼克期,两者为平行不整合接触关系,两者之间存在短暂沉积间断.林西组砂岩重矿物含量丰富,类型多样,原岩为中酸性岩浆岩、基性岩浆岩、少部分变质岩及沉积岩;老龙头组砂岩重矿物类型少,原岩为中酸性岩浆岩和少量变质岩.林西组2个碎屑岩样品最年轻峰值年龄分别为255±2Ma和255±1 Ma,εHf(t)=-22.84～+13.17,变化范围较大.老龙头组2个碎屑岩样品最年轻峰值年龄分别为248±1 Ma和249±1 Ma,εHf(t)=7.95～11.28.结合重矿物、碎屑锆石和Hf同位素研究,确定林西组物源主要来自于兴蒙造山带,少量可能来自于华北板块,具有复杂物源、远距离搬运再沉积的特征.老龙头组物源主要来自于兴蒙造山带,具有周缘近距离搬运沉积的特征.通过区域对比上二叠统林西组与下三叠统老龙头组碎屑锆石携带年代学信息,推测古亚洲洋东段沿着西拉木伦河缝合带在晚二叠世发生汇聚碰撞作用,古亚洲洋东段闭合作用至少持续至早三叠世,老龙头组沉积期发生强烈汇聚造山作用,老龙头组是古亚洲洋闭合板块碰撞作用的产物.

The high-grade granulite-phase metamorphic and anatectic rocks are widespread in the Daqingshan area, which is an archetypical of the Early Paleoproterozoic Orogenic Belt (POB) in the North China Carton (NCC), providing an ideal object to delineate the rheology of partially molten lower crust. The multiple approaches of SEM-EBSD fabric analysis, electron probe microanalyses (EPMA) and LA-ICP-MS zircon U-Pb geochronology have been carried out on the metamorphic and anatectic rocks from the Shijiaqu-Xuehaigou area in the Daqingshan. The results of zircon U-Pb dating show that the anatexis process in the POB took place more or less prior to ca. 1920 Ma, subsequently, the main plastic deformation event occurred at ca. 1915-1870 Ma. The macro- and microscopic structures suggest that the Xuehaigou and Shijiaqu areas show the characteristics of the diatexite and metatexite zones, respectively. In the diatexite zone, appearance of abundant melts tends to form schollen and schlieren structures in the high-grade metamorphic and anatectic rocks. The deformation mechanism of plagioclase is mainly represented by diffusion creep and particle flow. In contrast, in the metatexite zone, the deformation pattern is represented by stromatic structure with light-colored bands paralleling to the main gneissosity, and the deformation mechanism of plagioclase is characterized by dislocation creep. Besides, the deformation mechanism of amphibole in the lower crustal rocks from both zones is mostly dominated by dislocation creep. Significantly, the presence of melts in the high-grade metamorphic and anatectic rocks probably weaken their strength, and may have aided to form the sub-horizontal channel, contributing significantly to the subsequent exhumation of the lower crustal rocks in the orogenic belt.

The Western Liaoning area, where a large number of Jurassic-Cretaceous volcanic rocks are exposed, is one of the typical areas for studying the Mesozoic Paleo-Pacific and Mongolia-Okhotsk subduction process, and lithospheric destruction of North China Craton. The identification and investigation of Early Jurassic adakitic volcanic rocks in the Xintaimen area of Western Liaoning is of particular significance for exploring the volcanic magma source and its composition evolution, tracking the crust-mantle interaction, and revealing the craton destruction and the subduction of oceanic plates. Detailed petrography, zircon U–Pb dating, geochemistry, and zircon Hf isotope studies indicate that the Early Jurassic intermediate-acidic volcanic rocks are mainly composed of trachydacites and a few rhyolites with the formation ages of 178.6–181.9 Ma. Geochemical characteristics show that they have a high content of SiO2, MgO, Al2O3, and total-alkali, typical of the high-K calc-alkaline series. They also show enrichment of light rare earth elements (LREEs) and large ion lithophile elements (LILEs), depletion of heavy rare earth elements (HREEs) and high field strength elements (HFSEs), and have a high content of Sr and low content of Y and Yb, suggesting that they were derived from the partial melting of the lower crust. The εHf(t) values of dated zircons and two-stage model ages (TDM2) vary from −11.6 to −7.4 and from 1692 to 1958 Ma, respectively. During the Early Jurassic, the study area was under long-range tectonic effects with the closure of the Mongolia-Okhotsk Ocean and the subduction of the Paleo-Pacific plate, which caused the basaltic magma to invade the lower crust of the North China Craton. The mantle-derived magma was separated and crystallized while heating the Proterozoic lower crust, and part of the thickened crust melted to form these intermediate-acidic adakitic volcanic rocks.

Cone-producing gymnosperms are important elements of the Mesozoic floras. Studying their cone organizations can potentially help us understand the evolutionary trends of seed plants through time and the origin of angiosperms. In this paper, we present a new and an undetermined species of Ixostrobus Raciborski, a fossil genus representing male cones of the Czekanowskiales from the Middle Jurassic Daohugou locality in Inner Mongolia, China. The holotype specimen of the new species was studied using the neutron tomography (NT) technique. The cone shows higher neutron attenuation than the surrounding matrix. To detect the different organic compounds, a volume rendering of tomographic reconstruction with false colour spectrum of relative neutron attenuation is presented. The highest concentration of organic material is in the axis and some parts of the sacs, the rest of the cone has lower concentration, and the surrounding matrix has the lowest concentration. It seems that the remnant organic materials are regularly differentiated in different parts of the cone probably because of the preservation and different taphonomic process of different type of cells. In addition to revealing more detailed morphological features of the cone by NT reconstruction, the application of NT is potentially important for detecting remnant organic materials preserved in fossil plants.

The combined NE China blocks are the major component of the Central Asian Orogenic Belt ( CAOB). There has been a continued debate on the derivation of the old Precambrian crustal basements and Paleozoic tectonic division and evolutions of this orogen. Due to the absence of the Precambrian tectono-magmatic events, the Ordovician strata and magmatism play a key role in the reconstruction of the tectonic evolution of the Xing'an accretionary Terrane located in the west of the combined NE China blocks. In this study, we conducted U-Pb dating, geochemical analyses and Lu-Hf isotope analysis for the detrital zircon grains from metasandstone and tuff samples in the Duobaoshan Formation. The youngest ages of 481 5Ma ( D9088), 462 5Ma (296NJ-1) and 473 11Ma ( HDG06) and similar to the youngest weighted mean 206Pb/238U ages of 482 3Ma ( n =12), 475 6Ma ( n =10) and 483 8Ma ( n = 7), and thus give the lower limit age of sediments, indicating the Duobaoshan Formation developed in the Early -Middle Ordovician. The ages of detrital zircons from the Duobaoshan Formation range ( <1. OGa) are mainly concentrated in 462 520Ma ( with peaks at ca. 516Ma, 497Ma and 482Ma), and 790 980Ma ( peaks at ca. 969Ma, 830Ma, 788Ma and 760Ma). The ages of detrital zircons ( >1. OGa) have a minor population of 1321.2410Ma, with the peaks at ca. 1882Ma and 2410Ma. All the peaks are consistent with the contemporaneous magmatism of the Erguna Block, which reveal that the provenance of the metasandstone and tuff samples is mainly derived from the Erguna Block. By comparing the detrital zircon Hf isotopes of the Duobaoshan Formation in different areas, a rule can be observed that the farther the Duobaoshan Formation are away from the Erguna Block, the smaller e Hf (t) values and the older Hf model ages ( tD,2) of the detrital zircons in it will be, which suggests that there are more older crustal source from the Erguna Block from east to west. Together with the geochemical characteristics of the Ordovician strata, the Duobaoshan Formation was deposited in an environment related to an active continental margin.

The Jiamusi Block, located in the eastern part of the Central Asian Orogenic Belt ( CAOB) , is one of the important tectonic units in Northeast China ( NE China). It has experienced a complicated evolutional history corresponding to the overprinting processes of multiple tectonic regimes since Paleozoic. By systematically reviewing of the previous works in the past two decades, and combining with our recent work, this paper discusses the basement properties and origin of the Jiamusi Block, and reconstructs the tectonic model of amalgamation process in the western margin of the Jiamusi Block, as well as the subduction-accretion event developed in its eastern margin. The results presented here, show that the Jiamusi Block was likely a part of the Gondwana Super-continent and drifted a long distance to the north after dispersion of the Gondwana. The Jiamusi Block probably had been docked to the Songliao Block in the Mid-Silurian ( ca. 425Ma) , but broken apart from the Songliao Block in the Late-Permian ( ca. 250Ma) , forming a new narrow ocean basin ( so-called Mudanjiang Ocean) , and finally collided back again in the Jurassic (185 similar to 145Ma) along the Mudanjiang-Yilan suture zone, linking to the formation of the high-P/T metamorphic Heilongjiang Complex. In addition, the eastern margin of the Jiamusi Block involved two subduction-accretion processes, that are the Panthalassa Plate subduction occurred in the Late-Carboniferous to Late-Triassic (305 similar to 250Ma) , forming the Yuejinshan accretionary complex, and followed by the Paleo-Pacific Plate subduction in the Mid-Jurassic to Early Cretaceous (165 similar to 128Ma) , forming the Raohe accretionary complex. In summary, the tectonic evolution of the Jiamusi Block is not only related to the extinction of the Paleozoic Paleo-Asian tectonic domain, but also related to the superposition of the Mesozoic Paleo-Pacific tectonic domain. More significantly, the formation of the Heilongjiang Complex possibly reveals that the transformation of the Paleo-Pacific tectonic system and the Paleo-Asian tectonic system took place in the Late-Triassic ( ca. 210Ma).

The Xinlin ophiolite, located in the Great Xing’an Range domain of the Central Asian Orogenic Belt (CAOB), is considered to represent a fragment of an oceanic plate. The ophiolite consists of several discontinuous blocks composed dominantly of serpentinized ultramafic rocks with subordinate cumulate gabbros, basalts, and diabase dikes, which are intruded by younger leucogranite dikes. Here we characterize the geochemical features and formation age of the ophiolite. The ultramafic rocks are dominated by harzburgite with minor dunite, and are enriched in large-ion lithophile elements (LILEs) and light rare earth elements (LREEs), consistent with remnants of oceanic mantle. The mafic rocks show depletion in some high-field-strength elements (HFSEs) and have relatively low TiO2 and MgO contents, and likely originated from an E-MORB-like source in a back-arc setting. This suggests that the ophiolite is of supra-subduction zone (SSZ) origin. The cross-cutting leucogranite dikes, most of which are trondhjemitic, have high Al2O3 contents, low K2O/Na2O ratios, and negative zircon εHf(t) values (-8.5 to -3.8; average = -5.8), which are features distinct to other granites (e.g., fractionation-, shear-, and subduction-types) within the ophiolite and to coeval granitoids in the northern Great Xing’an Range. Zircon U-Pb dating on samples of gabbro and a leucogranite dike yielded ages of ca. 480 and 324 ± 1 Ma, respectively, suggesting that the ophiolite formed in the Early Ordovician and was emplaced at ca. 320 Ma. Together with the ages of ca. 480 Ma for the Duobaoshan arc and ca. 340 Ma for subduction-related high-Mg diorites, we suggest that ophiolite formation was probably related to the opening of an Ordovician back-arc basin, whereas formation of the younger leucogranite dikes was probably related to closure of the back-arc basin.

The tectonic pattern of Archean crust is a key issue for the current geology, and rising two classical tectonic models, i.e. horizontal and vertical tectonics. The studied Anshan area, eastern Liaoning Province, located in the northeastern part of North China Craton (NCC), and widely exposed Archean tonalite, trondhjemite and granodiorite (TTGs), greenschist-facies metamorphosed mafic-mid acid volcanic clastic rocks and BIF-bearing siliceous rocks, composing the typical Archean granite-greenstone belt. Additionally, the abundant deformation developed in the belt provide important evidences to better understanding the tectonic evolution of the early earth crust. In this study, the detailed macro-structural analysis reveals that the steep-dipping-slip ductile shear zones exist around the boundary between the TTGs and greenstones in the Qidashan and Baijiafen districts, respectively, revealing a Neoarchean vertical dome and keel structure tectonic pattern. Moreover, the I2VIS finite difference and mark-in-cell technique, simulates the process of the vertical Archean tectonics in the Anshan area, and suggests the evolutional process:firstly, the large volumes of magmatic activities took place in the Late Neoarchean, resulting in the re-activation of TTG upper crust rocks and the decrease of viscosity and density; subsequently greenstone sagduction happened, caused by the density difference between the greenstone layers and TTGs basement. Meanwhile, the numerical simulation results also show that the Archean vertical tectonic system may be an important mechanism of crust-mantle material exchange cycle in the early earth's evolution.

The glaucophanic rocks, including the garnet‐barroisite schist (09YL10) and glaucophane aegirine‐augite schist (09YL12) from the Heilongjiang Complex exposed in the Yilan area, have been petrographically investigated, in order to contribute to the discussion on the high‐P/T metamorphism that took place in the suture zone between the Jiamusi and Songliao blocks, NE China. The mineral assemblages of peak metamorphic stage are characterized by garnet (100XCa < 26) + epidote + barroisite/katophorite + phengite (Si < 6.84 pfu) + chlorite + quartz + rutile + haematite and barroisite/katophorite + glaucophane + aegirine‐augite (Jd < 30) + epidote + phengite (Si < 6.84 pfu) + haematite ± quartz ± chlorite for the investigated samples 09YL10 and 09YL12, respectively. By applying P–T pseudosection modelling in the NCKFMASHTO system, the peak metamorphic conditions yield 550–580°C/1.1–1.3 GPa and 500–550°C/1.1–1.3 GPa, for sample 09YL10 and 09YL12, respectively, indicating the epidote‐amphibolite facies metamorphism. Furthermore, the equilibrium mineral assemblages and the estimated P–T conditions define the Alpine‐type clockwise P–T paths for the Heilongjiang glaucophanic rocks, suggesting isothermal decompression (ITD) and/or slight heating during the beginning of the exhumation process. These P–T paths significantly match to the warm subduction trajectory, indicating the tectonic regimes similar to those of young oceanic slabs subduction zones and subsequent continental orogenic belts. Taking available regional geochronological data into account, we propose that the final subduction/collision between the Jiamusi and Songliao blocks took place in the Jurassic, effected by the Palaeo‐Pacific subduction system, leading to formation of the Heilongjiang glaucophanic rocks and their high‐P/T metamorphosed pelitic country rocks.