羌塘盆地东部中生代沉积特征与构造演化

羌塘盆地东部基底由前石炭纪吉塘岩群组成,沉积盖层为晚古生代一白垩纪地层。其中,中生代海相地层在盆地内分布广泛,沉积体系多样,构造古地理转换频繁。中生代盆地包括南羌塘坳陷、唐古拉山隆起带、北羌塘坳陷等3个构造单元,内部又可以划分出不同时期多个次级凹陷和凸起。盆地的发展和演化既受南、北两侧板块结合带控制,又受盆地内部被分划性断裂带围限的各断块差异性活动约束,依次经历了晚三叠世前陆盆地阶段,“北羌塘”早-中侏罗世伸展裂陷盆地发育阶段,多玛侏罗纪-早白垩世早期被动大陆边缘陆表海盆地发展阶段、晚期前陆盆地阶段,晚白垩世南羌塘山间压陷盆地演化阶段。实质上,该盆地是不同时期原型盆地有序叠加而构成的大型叠复式盆地。     

晚中生代—新生代构造体制转换与鄂尔多斯盆地改造

鄂尔多斯盆地是叠加在华北古生代克拉通台地之上的中生代大型陆内盆地。晚中生代—新生代是鄂尔多斯盆地重要的改造阶段,区域构造体制经历了重大转换,在盆地周缘形成不同方向和不同样式的构造带。其中发生在中、晚侏罗世时期的燕山运动主幕,对鄂尔多斯盆地的定型和发展具有划时代意义,这期构造变动导致鄂尔多斯盆地周缘挤压逆冲构造带的形成。早白垩世时期,对区域构造应力体制转换的响应,鄂尔多斯盆地处于弱引张构造环境,引张构造变形主要集中在盆地西南缘地带,六盘山古地堑发育。新生代时期,构造变形主要发生在鄂尔多斯盆地周缘,形成一系列地堑盆地。晚中新世或上新世以来的新构造运动时期,受到青藏高原快速隆升和向东构造挤出作用的影响,鄂尔多斯盆地西南缘六盘山褶皱带快速崛起,而在盆地的其他周边地带则发生引张变形和地块差异性升降。最后,笔者论述了不同构造应力体制下盆地的改造作用,讨论了鄂尔多斯盆地研究中的一些基础地质构造问题。     

雪峰山西麓中生代盆地属性及构造意义

雪峰山西侧发育一系列的中生代盆地,它们的形成与后期变形是华南地区晚三叠世以来板内变形的响应。晚三叠世-早、中侏罗世,雪峰山地区由于桃江-安化-溆浦断裂的左行压剪作用,在雪峰山西北侧形成早期沅麻前陆盆地,而在雪峰山中南段由于走滑作用形成拉分盆地,雪峰山西侧印支期并不存在统一的前陆盆地,其印支期造山规模很有限,为陆内造山。从白垩纪开始,雪峰山西麓盆地进入不同的构造体制环境,总体上经历了三期主要的盆地形成和改造事件。白垩纪早期沅麻盆地进入区域伸展阶段,该期的盆地并不是前人认为的前陆盆地,古水流表明物源为东西两侧的雪峰山和武陵山,而中期沅麻盆地继承早期的伸展体制,生长地层、地堑、地垒结构发育,古水流指示物源依旧是两侧山地,该期伸展可能与整个华南同期的伸展一样受控于同样的机制。进入新生代,雪峰山西麓盆地经历了两期重要的变形改造阶段,早期由于桃江-安化-溆浦的右行走滑,产生了北东向的主压应力,在沅麻盆地中产生了北东走向的张节理,这些节理在后期往往发育成正断层,造成这期变形的原因是由于55～25Ma之间,印度-欧亚板块的碰撞在整个东亚地区产生的一系列右行走滑断裂所致。新生代后期变形体现在北西—南东向挤压,在沅麻盆地以及天柱盆地东缘形成了一系列的逆冲构造,古生界以及元古界逆冲于中生界之上,这期挤压在盆地中形成了稳定分布的一组共轭节理。这期变形与整个东部中新世变形可能有同一的构造背景,其原因与太平洋板块的俯冲无关,而与菲律宾海板块于中新世左右由南向北运移并与华南大陆碰撞有关。     

云南兰坪盆地三叠纪沉积作用与古地理演化

根据岩石沉积类型、物源供给、成因机制和沉积序列,结合区域地质特征,将兰坪盆地三叠系划分为陆相火山泥石流、河流相、三角洲相、潮坪相、浅海陆棚相、碳酸盐台地相和深水盆地相7种主要沉积类型。通过对沉积相的详细分析,恢复其古地理格架和面貌,探讨岩相古地理的变迁历史,从而表明三叠纪早期到晚期,其古地理经历了陆相环境※碎屑海盆※碳酸盐海盆到碎屑海盆的转换,即两次海侵-海退旋回。早期的海域分布范围较小,晚期的海域分布范围较宽,并成为统一的海盆。     

A Review of the Bentong-Raub Suture vis-à-vis New Insight of the Tectonic Evolution of Malay Peninsula,South East Asia

Genesis of the so‐called Bentong‐Raub Suture of Malay Peninsula does not fit to the model of subduction‐related collision. It has evolved from transpression tectonics resulting closure and exhumation of the inland basin which underwent extensive back‐arc extension during Triassic. Crust having similar thickness (average ～35 km) below entire Malay Peninsula nagate collision of two separate continental blocks rather supports single continental block that collided with South China continental block during Permo‐Triassic. Westward subduction of intervening sea (Proto South China Sea) below Malay Peninsula resulted in widespread I‐ and S‐Type granitization and volcanism in the back‐arc basins during Triassic. Extensive occurrence of Permo‐Triassic Pahang volcanics of predominantly rhyolitic tuff suggest its derivation from back‐arc extension. Back‐arc extension, basin development and sedimentation of the central belt of the peninsula continued until Cretaceous. A‐Type granite of metaluminous to peraluminous character indicates their emplacement in an intraplate tectonic setting. Malay Peninsula suffered an anticlockwise rotation due to the rifting of Luconia–Dangerous Grounds from the east Asia in the Late Cretaceous–Early Tertiary. Extensive ductile and brittle deformation including crustal segmentation, pull‐apart fracturing and faulting occurred during the closure and exhumation of the basins developed in the peninsula during Late Cretaceous–Early Tertiary. Crustal shortening in the central belt of the peninsula has been accomodated through strike‐slip displacement, shearing and uplift.     

Arc‐nascent back‐arc signature in metabasalts from the Neoarchaean Jonnagiri greenstone terrane,Eastern Dharwar Craton,India

The Neoarchaean Jonnagiri greenstone terrane (JGT) is located at the centre of the arcuate Hutti–Jonnagiri–Kadiri–Kolar composite greenstone belt in the eastern Dharwar Craton. High MgO (MgO = ~14 wt.%; Nb = 0.2 ppm), low Nb (LNB) (MgO = 7.8–12 wt.%; Nb = 0.1–5.1 ppm) and high Nb basalts (HNB) (MgO = 5.6–10.1 wt.%; Nb = 9.0–10.6 ppm) metamorphosed to lower amphibolite facies are identified based on their geochemical compositions. These metabasalts exhibit depleted HFSE (Nb–Ta, Zr–Hf), pronounced LREE and LILE enrichments suggesting contribution from subduction‐related components during their genesis. Th and U enrichment over Nb–Ta indicates influx of fluids dehydrated from subducted oceanic lithosphere. The high MgO basalts with higher Mg# (51) than that of the associated LNB and HNB (Mg# = 34–47) represent early fractionated melts of subduction‐modified mantle peridotite. The LNB were produced by partial melting of mantle wedge metasomatized by slab‐dehydrated fluids, whereas the HNB represents melts of subducted oceanic crust and hybridized mantle wedge. Lower Dy/Yb and variable La/Yb ratios suggest their generation at shallower depth within spinel peridotite stability field. The low Ce–Yb trend of these metabasalts reflects intraoceanic type subduction which straddles the fields of arc and back‐arc basin basalts, resembling the Mariana‐type arc basalts. The Jonnagiri metabasalts were derived in a paired arc‐back‐arc setting marked by nascent back‐arc rift system that developed in the proximity of an intraoceanic arc. Copyright © 2014 John Wiley & Sons, Ltd.     

Geochemistry of Permian Mafic Igneous Rocks from the Napo‐Qinzhou Tectonic Belt in Southwest Guangxi,Southwest China: Implications for Arc‐Back Arc Basin Magmatic Evolution

The Napo-Qinzhou Tectonic Belt (NQTB) lies at the junction of the Yangtze, Cathaysia and Indochina (North Vietnam) Blocks, which is composed of five major lithotectonic subunits: the Qinzhou-Fangcheng Suture Zone (QFSZ), the Shiwandashan Basin (SB), the Pingxiang-Nanning Suture Zone (PNSZ), the Damingshan Block (DB) and the Babu-Lingma Suture Zone (BLSZ). On the basis of geochemical compositions, the Permian mafic igneous rocks can be divided into three distinct groups: (1) mafic igneous rocks (Group 1) from the Longjing region in the PNSZ and Hurun region in the BLSZ, which are characterized by intermediate Ti, P and Zr with low Ni and Cr contents; (2) mafic igneous rocks (Group 2) from the Naxiao and Chongzuo region in the DB, characterized by low-intermediate Ti, P and Zr with high Ni and Cr concentrations; and (3) mafic igneous rocks (Group 3) from the Siming region in the Jingxi carbonate platform of the northwestern margin of the NQTB, with intermediate-high Ti, P and Zr and low Ni and Cr contents. The Group 1 rocks yield a weighted mean 206Pb/238U age of 250.5±2.8 Ma and are geochemically similar to basalts occurring in back-arc basin settings. The Group 2 rocks exhibit geochemical features to those basalts in island arcs, whereas the Group 3 rocks show geochemical similarity to that of ocean island basalts. All three groups are characterized by relatively low εNd(t) values (–2.61 to +1.10) and high initial 87Sr/86Sr isotopic ratios (0.705309–0.707434), indicating that they were derived from a subduction-modified lithospheric mantle and experienced assimilation, fractional crystallization, and crustal contamination or mixing during magmatic evolution. Accordingly, we propose the existence of an arc-back arc basin system that developed along the NQTB at the border of SW Guangxi Province (SW China) and northern Vietnam, and it was formed by continued northwestward subduction of the Cathaysian (or Yunkai) Block under the Yangtze Block, and northeastward subduction of the Indochina Block beneath the Yangtze Block during Permian time.     

南海东南部中生界识别及其构造属性

正确识别南海东南部中生界及其分布,对认识南海形成演化和油气资源潜力具有重要意义。受资料条件约束和地层系统划分差异的影响,南海东南部中生界分布和构造特征一直存在争议。本文在钻井、拖网约束下,通过井震对比、地震反射特征、层速度分析、岩浆岩体与地层接触关系和构造变形特征来综合识别中生界。结果表明,中生界呈平行、连续、低频的反射特征,层速度3400~4200 m/s,随着埋深或（和）变质程度增强,层速度增大（4500~5500 m/s）,反射波组模糊,多数未见明显底界反射。研究区中生代地层发育局限,地震反射波组特征明显,但较难进行区域对比和解释。其中,西北、西南巴拉望盆地、礼乐滩和安渡北盆地中生界呈现低角度掀斜或近水平层状;礼乐滩西南部九章盆地中生界层速度3500~4500 m/s,高于上覆新生界,与钻井层速度吻合,地层呈高角度掀斜或挠曲变形,可能与岩浆活动侵位相关。结合中生代火山弧和识别的岩体分布,推测前者零散分布在弧前盆地靠火山弧一侧,构造活动相对弱,后者分布于岩浆活动强烈的弧间盆地。     

Mineralogy,Sulfur Isotope and Fluid Inclusion Studies of Hydrothermal Ore at the Hakurei Deposit,Bayonnaise Knoll,Izu‐Bonin Arc

Sulfide and sulfate ore samples collected from the Hakurei deposit of the Bayonnaise knoll were examined for the occurrence and chemical composition of minerals, including the sulfur isotopes and the microthermometry of fluid inclusions. Massive sulfide ore, mineralized volcanic rock, and anhydrite ore occur in descending order, from the seafloor to the bottom of the cored sample. The massive sulfide ore is dominated by sphalerite and accompanied by tennantite, chalcopyrite, and pyrite with lesser amounts of galena, enargite, and covellite. Amorphous silica is commonly precipitated on the surface of the sulfide minerals. As‐bearing minerals such as tennantite, enargite, and luzonite are common, while galena and Sb‐rich tetrahedrite are scarce. The mineral abundance and chemical composition of the minerals differs from that found in chimneys of the deposit. The sulfur isotope compositions in the minerals are +3.1–5.2‰ for sulfides and +19.6–21.8‰ for sulfate minerals. The homogeneous nature of the sulfur isotopes suggests that sulfur incorporated in the Hakurei deposit came from the reduction of aqueous sulfate in seawater.     

Chemical and Isotopic Characteristics of the Kuroko‐Forming Volcanism

The Miocene northeast Honshu magmatic arc, Japan, formed at a terrestrial continental margin via a stage of spreading in a back‐arc basin (23–17 Ma) followed by multiple stages of submarine rifting (19–13 Ma). The Kuroko deposits formed during this period, with most forming during the youngest rifting stage. The mode of magma eruption changed from submarine basalt lava flows during back‐arc basin spreading to submarine bimodal basalt lava flows and abundant rhyolitic effusive rocks during the rifting stage. The basalts produced during the stage of back‐arc basin spreading are geochemically similar to mid‐ocean ridge basalt, with a depleted Sr–Nd mantle source, whereas those produced during the rifting stage possess arc signatures with an enriched mantle source. The Nb/Zr ratios of the volcanic rocks show an increase over time, indicating a temporal increase in the fertility of the source. The Nb/Zr ratios are similar in basalts and rhyolites from a given rift zone, whereas the Nd isotopic compositions of the rhyolites are less radiogenic than those of the basalts. These data suggest that the rhyolites were derived from a basaltic magma via crystal fractionation and crustal assimilation. The rhyolites associated with the Kuroko deposits are aphyric and have higher concentrations of incompatible elements than do post‐Kuroko quartz‐phyric rhyolites. These observations suggest that the aphyric rhyolite magma was derived from a relatively deep magma chamber with strong fractional crystallization. Almost all of the Kuroko deposits formed in close temporal relation to the aphyric rhyolite indicating a genetic link between the Kuroko deposits and highly differentiated rhyolitic magma.     

Geochemical characterization of Archaean amphibolites from the eastern part of Anshan–Benxi iron producing area,northeastern China: implication for tectonic setting of BIFs

The Anshan–Benxi iron producing area, which is located at the northeastern margin of the North China Craton, is the main distribution area of Archaean BIFs in China. In their eastern part, including the Gongchangling and Waitoushan deposits, BIFs mainly are hosted in the Archaean middle Anshan Group. Amphibolites are widely distributed in the iron‐bearing rock series, reflecting the tectonic setting of BIFs. Amphibolites not only have MORB‐like compositional characteristics, but also have island arc‐like ones, and they are consistent with back‐arc basin basalts (BABB). In the study area, the protolith of amphibolites belongs to Okinawa‐type BABB; it indicates that tectonic setting of BIFs is the intra‐continental back‐arc basin. In the study area, the formation of sedimentary basins for BIFs had been associated with oceanic plate subduction. Amphibolites from Gongchangling deposit are characterized by relative enrichments in LILE and LREE, and depletions in HFSE. This indicates that they had a relatively large influence of subduction in their formation. Amphibolites from Waitoushan deposit are characterized by relative enrichments in LILE without conspicuous depletions in HFSE, indicating relatively low subduction rates. Copyright © 2015 John Wiley & Sons, Ltd.     

大兴安岭北段裸河组物源及其构造环境:来自地球化学和碎屑锆石年代学的证据

为探讨大兴安岭北段罕达气地区出露的裸河组形成的大地构造背景,对研究区裸河组泥质粉砂岩中的碎屑锆石进行LA—ICP—IMS U—Pb年代学分析和地球化学分析等工作。定年结果显示:本区裸河组1 000 Ma的年龄主要可分为两组,444～550 Ma:峰值年龄460 Ma; 700～1 000 Ma,峰值年龄为780 Ma,反应物源区岩浆事件的年龄,其中最小的年龄限定裸河组形成时代下限为晚奥陶世。主量元素及稀土元素特征显示碎屑岩特征与长英质岩石一致,轻稀土富集,重稀土亏损,弱Eu负异常,指示裸河组物源区具有活动大陆边缘构造背景。结合样品岩相学、稀土元素特征及前人资料,推断在早古生代时期研究区受嫩江洋俯冲影响,其沉积环境可能与弧后盆地沉积有关。     

准噶尔南缘前陆盆地白垩纪—新近纪构造挤压作用与储层关系的新表征:镜质体反射率与颗粒填集密度

镜质体反射率Ro是构造挤压作用对砂砾岩储集体产生热效应的重要反映,颗粒填集密度则是二者关系的具体体现。通过对准噶尔南缘白垩系—古近系样品镜质体反射率Ro的分析,结合白垩系—新近系霍001井等14口井76块样品统计颗粒填集密度分布规律与储层微观镜下研究,认为构造挤压作用对砂砾岩储集性的影响具有如下演化特征:白垩纪Ro值具有东部高、中西部低的特点,颗粒填集密度平面分布规律与其相近,表明位于前陆冲断带东部呼图壁地区储集层受构造侧向挤压影响较为强烈,西段的西湖—独山子地区储集层受构造影响弱,晚侏罗世—早白垩世博格达山隆升造成了这一结果。古近纪镜质体反射率Ro与颗粒填集密度展布与白垩纪显著不同,具有由冲断带中远端(第二、三排构造)安集海—玛纳斯—吐谷鲁背斜区向冲断带近端(第一排构造)与前渊带南北两方向降低趋势,表明古近纪储集层受构造侧向挤压影响弱,转变为主要受地层埋藏热效应影响。由于中新世以来的北天山强烈隆升,颗粒填集密度与古地温展布特点反映了储集层由古近纪主要受埋藏热效应影响,转变为受构造侧向挤压的影响。白垩系砂砾岩孔隙度与镜质体反射率Ro、颗粒填集密度呈明显负相关关系,也与成岩作用强度呈负相关关系;古近系镜质体反射率Ro、颗粒填集密度与砂砾岩孔隙度呈正相关关系,由此预测了准噶尔南缘较有利储层的分布。     

The Eocene corundum-bearing rocks in the Gangdese arc,south Tibet:Implications for tectonic evolution of the Himalayan orogen

The genesis of Liangguo corundum deposit in the southern Gangdese magmatic arc, east-central Himalaya, remains unknown. The present study shows that the corundum-bearing rocks occur as lenses with variable sizes in the Eocene gabbro that intruded into marble. These corundum-bearing rocks have highly variable mineral assemblage and mode. The corundum-rich rocks are characterized by containing abundant corundum, and minor spinel, ilmenite and magnetite, whereas the corundum-poor and corundum-free rocks have variable contents of spinel, plagioclase, sillimanite, cordierite, ilmenite and magnetite. The host gabbro shows variable degrees of hydration and carbonization. The corundum grains are mostly black, and rarely blue, and have minor Fe O and TiO_2. The spinel is hercynite, with high Fe O and low Mg O contents. The corundum-bearing rocks have variable but high Al_2O_3, FeO and TiO_2, and low SiO_2 contents. Inherited magmatic and altered zircons of the corundum-bearing rocks have similar U e Pb ages(~47 Ma) to the magmatic zircons of the host gabbro, indicating corundum-bearing rock formation immediately after the gabbro intrusion. We considered that emplacement of gabbro induced the contact metamorphism of the country-rock marble and the formation of silica-poor fluid. The channeled infiltration of generated fluid in turn resulted in the hydrothermal metasomatism of the gabbro, which characterized by considerable loss of Si from the gabbro and strong residual enrichment of Al. The metasomatic alteration probably formed under Pe T conditions of ~2.2 -2.8 kbar and ~650 -700℃. We speculate that SiO_2, CaO and Na_2O were mobile, and Al_2O_3, FeO, TiO_2 and high field strength elements remained immobile during the metasomatic process of the gabbro. The Liangguo corundum deposit, together with metamorphic corundum deposits in Central and Southeast Asia, were related to the Cenozoic Himalayan orogeny, and therefore are plate tectonic indicators.     

Clay Minerals in an Active Hydrothermal Field at Iheya‐North‐Knoll,Okinawa Trough

Iheya‐North‐Knoll is one of the small knolls covered with thick sediments in the Okinawa Trough back‐arc basin. At the east slope of Iheya‐North‐Knoll, nine hydrothermal vents with sulfide mounds are present. The Integrated Ocean Drilling Program (IODP) Expedition 331 studied Iheya‐North‐Knoll in September 2010. The expedition provided us with the opportunity to study clay minerals in deep sediments in Iheya‐North‐Knoll. To reveal characteristics of clay minerals in the deep sediments, samples from the drilling cores at three sites close to the most active hydrothermal vent were analyzed by X‐ray diffraction, scanning electron microscope and transmission electron microscope. The sediments are classified into Layer 0 (shallow), Layer 1 (deep), Layer 2 (deeper) and Layer 3 (deepest) on the basis of the assemblage of clay minerals. Layer 0 contains no clay minerals. Layer 1 contains smectite, kaolinite and illite/smectite mixed‐layer mineral. Layer 2 contains chlorite, corrensite and chlorite/smectite mixed‐layer mineral. Layer 3 is grouped into three sub‐layers, 3A, 3B and 3C; Sub‐layer 3A contains chlorite and illite/smectite mixed‐layer mineral, sub‐layer 3B contains chlorite/smectite and illite/smectite mixed‐layer minerals, and sub‐layer 3C contains chlorite and illite. Large amounts of di‐octahedral clay minerals such as smectite, kaolinite, illite and illite/smectite mixed‐layer mineral are found in Iheya‐North‐Knoll, which is rarely observed in hydrothermal fields in mid‐ocean ridges. Tri‐octahedral clay minerals such as chlorite, corrensite and chlorite/smectite mixed‐layer mineral in Iheya‐North‐Knoll have low Fe/(Fe + Mg) ratios compared with those in mid‐ocean ridges. In conclusion, the characteristics of clay minerals in Iheya‐North‐Knoll differ from those in mid‐ocean ridges; di‐octahedral clay minerals and Fe‐poor tri‐octahedral clay minerals occur in Iheya‐North‐Knoll but not in mid‐ocean ridges.     

Discovery of the Early Paleozoic Boin Sum‐Ordor Sum Island Arc in the Hadamiao Gold Ore District,Inner Mongolia and its Significance to the Evolution of the Paleo‐Asian Ocean

Early Paleozoic granodiorite has been identified on the northern margin of the North China craton in the east section of the central-Asian orogenic belt, which was previously known as early Indosinian in age. By using the LA-ICP-MS method, the obtained zircon U-Pb age is 445.6±2.7 Ma, which represents the crystallization age of the granodiorite. The granodiorite near the east of the large-sized Bilihe gold deposit is of the tholeiite series with low potassium. It is quasi-aluminous I-type granite, enriched in sodium (Na2O/K2O=7.29-9.77) and magnesium (Mg#=0.51-0.67). The ΣREE value is relatively low, obvious differentiation is shown between LREE and HREE and within LREE, and the Eu anomaly is low and negative (δEu=0.74-0.91). In the primitive-mantle normalized spider diagrams of trace elements, the granodiorite is relatively rich in LREE and LILE (Ba, Sr, Th), and strongly depleted in HFSE (Nb, Ta, Ti and P), which shows features of subduction zone components (SZC). In the discrimination diagrams of tectonic settings of granite for Rb vs. (Nb+Y), Rb vs. (Ya+Ta), La/Nb vs. Ba/Nb and Th/Nb vs. Ba/Nb, the granodiorite exhibits typical features of island arc granite. The normalized values of K and Rb are extremely low, while the values of Sr and Eu are very high, which are similar to those of island arc magma that has undergone metasomatism of fluid from the oceanic crust. The granodiorite is relatively depleted in εHf(t) (5.1-7.1) and low in εHf(t) model ages (1089-921 Ma). In the εHf(t) vs. age (T) diagram, the distribution area of the granodiorite is accordant with the field of the Xing’anling-Mongolia orogenic belt, which indicates that the magmatic sources are mainly the mixture of partial melting of wedged mantle subjected to metasomatism of fluid from the oceanic crust and young substance from the crust. The granodiorite is similar to the felsic arc magma in the Damao Banner, Bate Obon, Boin Sum and Ordor Sum regions, and they altogether constitute an early Paleozoic accretionary island arc magmatic belt on the northern margin of the North China craton. A number of early Paleozoic zircons trapped in late Paleozoic intrusions in the Hadamiao and Bilihe regions and the discovery of the early Paleozoic island arc magmatic belt near the east of the Bilihe gold deposit suggest that the late Paleozoic volcanic-intrusive rocks have a basement of early Paleozoic arc accretionary complexes. This is just the evident of the multiphase subduction and accretion model of the Paleo-Asian Ocean (PAO). Paleozoic structures and magmas on the northern margin of the North China craton are shown from south to north as the late Paleozoic Andes-type arc magmatic belt in the Inner Mongolia plateau, the Chifeng-Bayan Obo fault and the late and early Paleozoic arc magmatic belt, which shows that after the early Paleozoic arc-continent collisional orogeny and at the stage of the late Paleozoic accretionary orogeny, the PAO plate was likely to continuously pulsate and underthrust beneath the early Paleozoic island arc accretionary complex belt and its front, i.e. the North China craton. During the early Paleozoic collisional orogeny, the PAO plate might not experience large-scale breakup or delamination. The characteristics of the early Paleozoic island arc accretionary complex basement have a significant control on late Paleozoic diagenesis and metallization in the Hadamiao and Bilihe gold concentrated areas.     

东北亚晚古生代—中生代岩浆时空演化:多重板块构造体制范围及叠合的鉴别证据

东北亚大地构造发展经历了古亚洲洋、蒙古—鄂霍茨克洋和古太平洋的俯冲-碰撞作用。如何鉴别和厘定这三种构造体制的时空影响范围和叠合过程一直是一个难题。本文通过巨型岩浆岩带的建库编图,揭示了该地区晚古生代—中生代岩浆岩的时空迁移规律;据此,探讨和厘定了这三大板块构造体制的时空分布范围和构造叠合过程。二叠纪到三叠纪早期间,古亚洲洋体制经历了俯冲到碰撞,主要作用于阿拉善—华北北缘—大兴安岭一带;期间,鄂霍茨克洋主要为陆缘环境,影响范围限于中北部蒙古—外贝加尔一带,并在侏罗纪逐渐向蒙古—鄂霍茨克主缝合带迁移,到白垩纪,其造山带伸展垮塌阶段,影响范围增大,远程效应波及阿拉善—华北北缘—大兴安岭一带,叠加于古亚洲洋体制产物之上。古太平洋构造体制主要发育于三叠纪—侏罗纪时期,其平板俯冲影响范围抵达大兴安岭—太行山,在白垩纪,俯冲板片后撤,影响范围迁移至东亚大陆最东缘。这些作用叠加于古亚洲洋体制产物之上;并与蒙古—鄂霍茨克洋体制同时叠合于大兴安岭一带。     

The Quebradagrande Complex: A Lower Cretaceous ensialic marginal basin in the Central Cordillera of the Colombian Andes

The Quebradagrande Complex of Western Colombia consists of volcanic and Albian–Aptian sedimentary rocks of oceanic affinity and outcrops in a highly deformed zone where spatial relationships are difficult to unravel. Berriasian–Aptian sediments that display continental to shallow marine sedimentary facies and mafic and ultramafic plutonic rocks are associated with the Quebradagrande Complex. Geochemically, the basalts and andesites of the Quebradagrande Complex mostly display calc-alkaline affinities, are enriched in large-ion lithophile elements relative to high field strength elements, and thus are typical of volcanic rocks generated in supra-subduction zone mantle wedges. The Quebradagrande Complex parallels the western margin of the Colombian Andes’ Central Cordillera, forming a narrow, discontinuous strip fault-bounded on both sides by metamorphic rocks. The age of the metamorphic rocks east of the Quebradagrande Complex is well established as Neoproterozoic. However, the age of the metamorphics to the west – the Arquía Complex – is poorly constrained; they may have formed during either the Neoproterozoic or Lower Cretaceous. A Neoproterozoic age for the Arquía Complex is favored by both its close proximity to sedimentary rocks mapped as Paleozoic and its intrusion by Triassic plutons. Thus, the Quebradagrande Complex could represent an intracratonic marginal basin produced by spreading-subsidence, where the progressive thinning of the lithosphere generated gradually deeper sedimentary environments, eventually resulting in the generation of oceanic crust. This phenomenon was common in the Peruvian and Chilean Andes during the Uppermost Jurassic and Lower Cretaceous. The marginal basin was trapped during the collision of the Caribbean–Colombian Cretaceous oceanic plateau, which accreted west of the Arquía Complex in the Early Eocene. Differences in the geochemical characteristics of basalts of the oceanic plateau and those of the Quebradagrande Complex indicate these units were generated in very different tectonic settings.     

甘孜-理塘蛇绿混杂岩带晚三叠世构造演化——来自理塘地区勇杰岩体地球化学、年代学的制约

甘孜-理塘蛇绿混杂岩带是西南三江构造带的重要组成部分,经历了古特提斯构造体系的演化,形成完整的沟-弧-盆体系。义敦岛弧属甘孜-理塘弧盆系范畴,位于甘孜-理塘缝合带西侧。对义敦岛弧勇杰岩体开展详细的岩石学、地球化学、年代学研究,为甘孜-理塘洋盆晚三叠世构造演化研究提供新的证据。义敦勇杰岩体黑云母二长花岗岩和花岗质细晶岩的锆石UPb年龄分别为214.2±1.4Ma和206.2±1.8Ma,整体属高钾钙碱性弱过铝质花岗岩;稀土元素配分曲线具轻稀土元素相对富集、重稀土元素相对平坦的特征,负Eu异常明显;微量元素表现为大离子亲石元素Rb、Ba、Th、U、K相对富集,高场强元素Nb、Ta、P、Ti亏损的特征,显示勇杰岩体黑云母二长花岗岩明显具俯冲型花岗岩的特征,而花岗质细晶岩具有碰撞型花岗岩的特征。总体反映晚三叠世甘孜-理塘洋盆从俯冲至碰撞的地球动力学背景,应属理塘蛇绿混杂岩带碰撞造山过程的产物。     

鄂尔多斯盆地西南缘中生代中晚期构造体制转化过程及其动力学背景

逆冲推覆构造对含油气盆地有效圈闭形成、源储体系配置影响明显,且其形成时限及演化过程对油气勘探意义重要.鄂尔多斯盆地西南缘中生代中晚期曾发生过强烈的逆冲推覆作用,但其构造体制转化过程一直缺乏年代学的约束.热年代学是揭示构造带隆升剥露和相邻盆地演化过程的有效手段.本文通过对祁连山东缘钻井基岩的磷灰石裂变径迹分析,结合鄂尔多...