新疆乌什6.2级地震的中期预测

介绍了利用地倾斜资料和中国地壳运动网络工程GPS复测资料对新疆地区震情进行跟踪研究的基本依据、方法和过程,对2005年2月15日发生的乌什Ms6.2地震给出了较好的年度预测意见。     

渤海南部碎屑石英表面微结构特征等沉积环境

运用扫描电镜研究渤海南部碎屑石英颗粒表面微结构,并根据各种形痕的组合特征,判断沉积物所处的沉积环境,定性分析控制沉积环境的主要因素。     

丽江—攀枝花—者海地带二维地壳结构及其构造意义

本文利用攀西地区通过攀枝花的东西向剖面爆炸地震资料,进行了震相的重新识别和二维射线追踪与理论图计算.结果表明,沿剖面地表附近有4个低速区和若干高速带,它们与地质和构造有很好的对应关系.渡口附近的高速岩体一直延伸到了上地壳的底部,形成一个统一的地垒状构造,该高速体与攀枝花成矿岩体相关,并推断华坪及其以西地带也是找矿的有利地区.中地壳下部有一厚度约9km的低速层,它可能是壳内的韧性剪切带.低速层顶部深度为27.0—29.5km,与研究地区的居里面深度及天然地震震源深度的分布基本符合.剖面东段中地壳顶部还有一层很薄的低速层,反映了构造带两侧运动的不对称性.地壳厚度为53—56km,构造带中部的Moho界面没有明显的上隆.     

赣杭构造带中生代红色碎屑沉积盆地的形成和演化

本文是在继讨论赣杭构造带中生代火山盆地的形成和演化之后,再对赣杭构造带中生代红色碎屑沉积盆地（简称赣杭带红盆）的形成和演化作一探讨。涉及的内容主要有：赣杭构造带中生代红盆结构及演化时代;从晚侏罗世末到整个白垩纪各期主要构造运动及与红盆演化的关系;箕状盆地的几个主要特征;红盆演化的动力学背景;红盆所对应的深部构造以及深断裂活动和盆地演化的实际含义等     

GEOCHEMISTRY

正20141357 Guo Tao(School of Mathematics and Science,Shijiazhuang University of Economics,Shijiazhuang 050031,China);Hu Jiawen Assessment on the New Pressure-Volume-Temperature(PVT) Data of Supercritical Water(Geological Journal of China Universities,ISSN1006-7493,CN32-1440/P,19(3),2013,p.447-455,9 illus.,3 tables,32 refs.)Key words:supercritical fluids     

澜沧江河流沉积物碎屑锆石U-Pb年龄、Hf同位素组成及其地质意义

为研究澜沧江沉积物的物质来源及相邻地块的地壳生长和演化规律,利用LA-MC-ICP-MS分析技术,对澜沧江河流沉积物碎屑锆石进行了U-Pb年龄和Hf同位素研究。结果表明：锆石U-Pb年龄主要有5个年龄段,分别是＜177 Ma、201~418 Ma、428~544 Ma、581~1189 Ma和1406~2533 Ma,主要峰值为260 Ma、788 Ma、1 827 Ma和2 474 Ma。其年龄分布特征与北羌塘地块的年龄分布非常一致,说明澜沧江沉积物主要来源于北羌塘地块;结合Hf同位素分析结果,能够反映源区北羌塘地块的形成与演化历史。新太古代-中元古代是北羌塘地块从亏损地幔物质增生的地壳持续生长阶段,它们构成现今北羌塘地块全部地壳物质的78%以上,此后直到0.64 Ga,北羌塘地块的地壳增生作用基本结束。     

黔中—渝南沉积型铝土矿区域成矿模式及找矿模型

黔中—渝南沉积型铝土矿的区域成矿模式概括如下:志留纪末的广西运动和泥盆纪末的紫云运动等,可能都是在峨眉地幔柱演化的壳幔相互作用阶段,因地幔柱向地壳大量输送物质和辐射能量,从而引发的地壳升降运动,在此期间,全区大面积抬升,形成长期隆起区;泥盆纪末准平原化;早石炭世岩关期气候湿热,暴露地表的早古生代岩石全面红土化、钙红土化,形成的含三水铝石红土风化壳物质,为沉积型铝土矿提供了物源。修文及息烽—遵义沉积区,于早石炭世大塘期早—中期沉积了铝土矿含矿岩系—九架炉组。绥阳—正安—道真沉积区,在晚石炭世的黄龙组石灰岩沉积并钙红土化之后,于马平期沉积了铝土矿含矿岩系的大竹园组。3个沉积区的铝土矿含矿岩系,都是在以陆相为主的环境中沉积形成的。在成岩阶段,铝土矿中的三水铝石逐渐变质为硬水铝石。由于各沉积区形成含三水铝石红土风化壳的母岩不同,由此沉积而成的铝土矿及其含矿岩系,在化学成分和矿物成分上也就有所差异。     

阿尔金南缘阿克提山岩体锆石U- Pb定年、Hf同位素特征及构造意义

阿克提山花岗岩体位于阿尔金断裂南缘,其形成时代与区域内其他花岗岩体差异较大,该岩体走向明显地受阿尔金断裂带分支断裂控制。锆石LA-ICP-MS U-Pb年代学分析表明,该岩体结晶年龄约为262Ma,其形成可能与南阿尔金地区在华力西期-印支期发生的大规模线性构造运动有关。岩体的岩性主要为石英闪长岩、花岗闪长岩,其暗色矿物以角闪石、黑云母为主,岩石A/CNK值均小于1.1,显示准铝质—弱过铝质特征,属于高钾钙碱性系列;大离子亲石元素Rb、Th、K相对富集,高场强元素Nb、Ta、P、Sr、Ti明显呈负异常;稀土元素配分曲线具有中等负Eu异常,δEu的平均值为0.73,(La/Yb)_N平均值为14.57,说明该花岗岩体岩浆部分熔融程度较高。根据岩石学及地球化学特征可判断该岩体为I型花岗岩。锆石Lu-Hf同位素分析表明,锆石ε_(Hf)(t)值为+1.46～+9.14,均为正值,二阶段模式年龄的峰值平均为943Ma,表明其源岩主要为新元古代新生地壳物质的部分熔融。阿尔金断裂在印支期的走滑运动是从地壳深部的韧性变形开始的,随后在浅地表发生脆性断裂形成大规模走滑断裂带。阿克提山岩体的形成与地壳深部减压熔融有关。     

Paleoproterozoic accretion in the Northeast Siberian craton: Isotopic dating of the Anabar collision system

Geochronological database considered in the work and characterizing the Anabar collision system in the Northeast Siberian craton includes coordinated results of Sm-Nd and Rb-Sr dating of samples from crustal xenoliths in kimberlites, deep drill holes, and bedrock outcrops. As is inferred, collision developed in three stages dated at 2200–2100, 1940–1760, and 1710–1630 Ma. The age of 2000–1960 Ma is established for substratum of mafic rocks, which probably originated during the lower crust interaction with asthenosphere due to the local collapse of the collision prism. Comparison of Sm-Nd and Rb-Sr isochron dates shows that the system cooling from ≈700 to ≈300°C lasted approximately 300 m.y. with a substantial lag relative to collision metamorphism and granite formation. It is assumed that accretion of the Siberian craton resulted in formation of a giant collision mountainous structure of the Himalayan type that was eroded by 1.65 Ga ago, when accumulation of gently dipping Meso-to Neoproterozoic (Riphean) platform cover commenced.     

Early Miocene adakite-like volcanism in the Balkuyumcu region, central Anatolia, Turkey: Petrology and geochemistry

The Balkuyumcu region, located in the southwestern part of Ankara in the Izmir-Ankara suture zone (central Anatolia, Turkey), consists of basic andesitic, andesitic, dacitic and rhyolitic rocks extruded during the Early Miocene (20–22 Ma) as a result of post-collisional volcanism. Balkuyumcu volcanic rocks can be divided into two groups on the basis of their mineralogy and composition: The basic andesitic (BA) and andesitic, dacitic and rhyolitic (ADR) groups. The ADR and BA group of rocks have adakite-like and calc-alkaline characteristics, respectively. The ADR group has higher SiO₂ content, Sr/Y and La/Yb ratios and low MgO, Mg#, Y and Yb contents than the BA group. Both groups have nearly the same Sr, Nd isotopic compositions and display similar normalized multi-element patterns with enrichments in LILE and LREE, depletions in Nb, Ti, Zr, P and a lack of Eu anomalies. Major, trace element and Sr, Nd isotopic data indicate that both groups of rocks were derived from the same source but affected by different magmatic processes during ascent. The adakite-like rocks may have been produced by partial melting of thickened lower continental crust. Fractional crystallization also played a major role in their formation. However, the BA group rocks were derived from partial melting of lower continental crust that was probably delaminated. These rocks appear to have had limited interaction with mantle peridodite during ascent to the surface.