青藏高原新生代三阶段造山隆升模式:火成岩岩石学约束

从岩石从地构造学的角度,分析讨论了青藏高原新生代岩浆作用的特点、差异、成对性及其对高魇隆升深部动力学过程的岩石约束,在此基础上是提出青藏高原是以冈底斯－羌塘造山带为核心,通过三次造山幕事件而形成的高原隆升新模式。     

聚敛型板块边缘岩浆作用及其相关沉积盆地

概括性地介绍了聚敛型板块边缘大地构造环境中的岩浆活动及其所形成的火成岩岩石构造组合类型,并以此为线索,将板块构造、岩石圈运动与沉积盆地的形成有机地结合起来,简要地分析和介绍了聚敛型板块边缘的主要沉积盆地类型及其沉降机理。指出盆地形成是板块构造、岩石圈运动在地壳浅部的一种表现形式,岩石圈板块运动直接受深部作用过程的制约,火山喷发或侵入是上地幔、深部地壳对流在地表或浅部地壳的表现。因此,对火成岩岩石组合或系列的研究,将为沉积盆地的形成与演化提出重要的深部动力学约束。     

岩浆作用的物理过程研究进展

概略地介绍了８０年代以来硅酸盐熔体及硅酸盐晶－液悬浮体的密度、粘度、熔体结构、流全动力学等方面的研究动向,及其对岩浆作用、岩浆运移、岩浆侵位机制的动力学约束条件,硅酸盐熔体的结构是制约熔粘度的主导因素,化学成分对熔体匠控制是通过改变熔体结构而实现的,粘度在一定程度上决定着岩浆的迁移、侵痊和喷发方式。密度和浮力是岩浆上升侵位的重要约束,地壳是岩交涉升的一个密度过滤器岩浆最终由于浮和的消失而停止上升。     

南秦岭勉略带两河弧内裂陷内火山岩组合地球化学

两河火山岩岩片位于秦岭微板块与扬子板块的分界断裂－巴山弧形构造混杂带内。岩石内亚碱性拉班系列玄武质岩石和钙碱性英安岩、流纹岩组成。基性岩和酸性岩均具有高Ｂａ,低Ｔｈ、Ｕ,显著的Ｎｂ、Ｔａ亏损和Ｔｉ的负异常等地球化学特征,玄武岩的Ｔｈ／Ｙｂ－Ｔａ和Ｔｉ／Ｚｒ－Ｔｉ／Ｙ不活动痕量元素组合特征指示这套火山岩可能产于弧间盆地环境。是勉略洋盆在古生代晚期－中生代早期发育期间洋壳俯冲及弧内裂陷的岩浆作用产物。     

北祁连奥陶纪洋脊扩张速率及古洋盆规模的岩石学约束

北祁连奥陶纪期间为一多岛洋，由中间微陆块分隔的三个相对独立的洋盆联合组成。火山岩可区分为洋脊型、洋岛（海山）型及岛弧型三种主要的构造岩石组合类型。根据火山岩化学成分计算获得三个洋盆的扩张速率分别为４．４５ｃｍ／ａ，０．７５ｃｍ／ａ和０．８ｃｍ／ａ；闭合速率分别为４．０５ｃｍ／ａ，３．１０ｃｍ／ａ和４．８７ｃｍ／ａ。奥陶纪末期，三个洋盆相继闭合，形成了下伏的中南祁连陆块—北祁连陆－陆碰撞构造混杂带—上叠的阿拉善陆块三个构造单元叠置的构造构局     

http://www.sciencedirect.com/science/article/pii/S1674987114000607

The Qinling Complex of central China is thought to be the oldest rock unit and the inner core of the North Qinling Orogenic Belt （NQOB）. Therefore, the Qinling Complex is the key to understanding the pre- Paleozoic evolution of the NQOB. The complex, which consists of metagraywackes and marbles, un- derwent regional amphibolite-facies metamorphism. In this study, we constrained the formation age of the Qinling Complex to the period between the late Mesoproterozoic and the early Neoproterozoic （ca. 1062-962 Ma）, rather than the Paleoproterozoic as previously thought. The LA-ICP-MS data show two major metamorphic ages （ca. 499 and ca. 420-400 Ma） for the Qinling Complex. The former age is consistent with the peak metamorphic age of the high- and ultra-high pressure （HP-UHP） rocks in the Qinling Complex, indicating that both the HP-UHP rocks and their country rocks experienced intensive regional metamorphism during the Ordovician. The latter age may constrain the time of partial melting in the NQOB between the late Silurian and early Devonian. The Qinling Complex is mostly affiliated with subduction-accretion processes along an active continental margin, and should contain detritus deposited in a forearc basin.     

Ophiolites from the Mianlüe Suture in the Southern Qinling and Their Relationship with the Eastern Paleotethys Evolution

Abstract The Mianlüe suture extends from Derni‐Nanping‐Pipasi‐Kangxian to the Lüeyang‐Mianxian area, then traverses the Bashan arcuate structure eastward to the Huashan region, and finally to the Qingshuihe area of the southern Dabie Mountains. From east to west, with a length of over 1500 km, the ophiolitic melangé associations are distributed discontinuously along the suture. The rock assemblages include ophiolite, island‐arc and oceanic island rock series, indicating that there existed a suture zone and a vanished paleo‐ocean basin. The Mianlüe paleo‐ocean basin experienced its main expansion and formation process during the Carboniferous‐Permian and closed totally in the Triassic. It belongs to the northern branch of the eastern paleotethys, separated from the northern margin of the Yangtze block under the paleotethys mantle dynamic system.     

黔南坳陷下寒武统牛蹄塘组泥页岩埋藏史与热史研究——以贵都地1井为例

下寒武统牛蹄塘组是黔南坳陷最重要的页岩气目标层之一.为探究牛蹄塘组泥页岩的生烃演化史,文章以黔南坳陷贵都地1井为研究对象,通过对该区油气地质、地球化学分析,运用盆地模拟技术等方法,对贵都地1井牛蹄塘组埋藏史与热史进行重建.结果表明:牛蹄塘组泥页岩具有较高的有机质丰度,有机质类型为I型,已达到过成熟阶段,整体具有一定的生...     

Granitic Magmatism in Eastern Tethys Domain (Western China) and their Geodynamic Implications

Western China locates in the eastern section of the Tethys domain, granitic rocks in this region with variable formation ages and geochemistry record key information about the crust-mantle structure and thermal evolution during the convergent process of Tethys. In this study, we focus on some crucial granitic magmatism in the western Yangtze, Qinling orogen, and western Sanjiang tectonic belt, where magma sequence in the convergent orogenic belt can provide important information about the crust-mantle structure, thermal condition and melting regime that related to the evolution processes from Pre- to Neo-Tethys. At first, we show some features of Pre-Tethyan magmatism, such as Neoproterozoic magmatism (ca. 870–740 Ma) in the western margin of the Yangtze Block were induced by the assembly and breakup of the Rodinia supercontinent. The complication of voluminous Neoproterozoic igneous rocks indicated that the western Yangtze Block underwent the thermodynamic evolution from hot mantle-cold crust stage (ca. 870–850 Ma) to hot mantle and crust stage (ca. 850–740 Ma). The Neoproterozoic mantle sources beneath the western Yangtze Block were progressively metasomatized by subduction-related compositions from slab fluids (initial at ca. 870 Ma), sediment melts (initial at ca. 850 Ma), to oceanic slab melts (initial at ca. 825–820 Ma) during the persistent subduction process. Secondly, the early Paleozoic magmatism can be well related to three distinctive stages (variable interaction of mantle-crust to crustal melting to variable sources) from an Andeans-type continental margin to collision to extension in response to the evolution of Proto-Tethys and final assembly of Gondwana continent. Thirdly, the Paleo-Tethys magmatism, Triassic granites in the Qinling orogenic display identical formation ages and Lu-Hf isotopic compositions with the related mafic enclaves, indicate a coeval melting event of lower continental crust and mantle lithosphere in the Triassic convergent process and a continued hot mantle and crust thermal condition through the interaction of subducted continental crust and upwelling asthenosphere. Finally, the Meso- and Neo-Tethyan magmatism: Early Cretaceous magmatism in the Tengchong Block are well responding to the subduction and closure of Bangong-Nujiang Meso-Tethys, recycled sediments metasomatized mantle by subduction since 130 Ma and subsequently upwelling asthenosphere since ca. 122 Ma that causes melting of heterogeneous continental crust until the final convergence, this process well recorded the changing thermal condition from hot mantle-cold crust to hot mantle and crust; The Late Cretaceous to Early Cenozoic magmatism well recorded the processes from Neo-Tethyan ocean slab flat subduction, steep subduction, to initial collision of India-Asia, it resulted in a series of continental arc magmatism with enriched mantle to crustal materials at Late Cretaceous, increasing depleted and/or juvenile materials at the beginning of early Cenozoic, and increasing evolved crustal materials in the final stage, implying a continued hot mantle and crust condition during that time. Then we can better understand the magmatic processes and variable melting from the mantle to crust during the evolution of Tethys, from Pre-, Paleo-, Meso-, to Neo-, both they show notably intensive interaction of crust-mantle and extensive melting of the heterogeneous continent during the final closure of Tethys and convergence of blocks, and thermal perturbation by a dynamic process in the depth could be the first mechanism to control the thermal condition of mantle and crust and associated composition of magmatism.     

水汽对大气重力和倾斜格林函数的影响

建立用相对湿度表示的大气比气体常数模型，利用地面温度和空间垂直温度梯度与压力变化的规律估算大气水汽组分变化对比气体常数的影响。结果表明：在自然温度条件下，水汽变化对大气比气体常数影响不大。进一步将此结果应用于大气重力和倾斜格林函数，得到了水汽对大气重力和倾斜格林函数的影响估计。