缅甸中部抹谷早白垩世构造岩浆作用及对特提斯演化的启示

本文系统报道了缅甸抹谷变质带中部Yinmabin花岗闪长岩体及其基性岩墙的主量元素、微量元素及锆石U-Pb年龄和Lu-Hf同位素组成,重点讨论了花岗闪长岩和基性岩墙的岩石成因、物质来源及其地质意义。抹谷Yinmabin花岗闪长岩体主量元素显示富钠(N2O/K2O=1.5~1.75)、准铝(ACNK=0.94~0.97)和钙碱性岩石系列的地球化学特征。样品富集轻稀土(LREE)元素、大离子亲石元素(LILE),相对亏损高场强元素(HFSE)。岩体的主、微量元素地球化学特征均显示其具有活动陆缘I型花岗岩的地球化学属性。抹谷Yinmabin花岗闪长岩的锆石U-Pb年龄为131~135 Ma,其εHf(t)值在-15.66~-2.99之间,平均值为-8.77,单阶段模式年龄(tDM)为795~1569 Ma;而后期侵位的辉绿岩的锆石U-Pb年龄为120~118 Ma,其εHf(t)值在-13.72~+5.82之间,平均值为-2.72,单阶段模式年龄(tDM)为570~1341 Ma,表明这些岩石可能主要来源于古老下地壳部分熔融但同时也受到地幔物质的加入混染。与滇西以及北拉萨岩浆带的Lu-Hf同位素特征十分相近,暗示抹谷-毛淡棉地块早白垩世岩浆岩带与波密-察隅-高黎贡-拉萨岩浆岩带形成环境相似,可能是腾冲岩浆岩带向南延伸的一部分。结合岩石成因、源区性质和区域构造演化,认为抹谷花岗闪长岩体及基性岩墙的形成与中特提斯洋板块的俯冲作用密切相关,同时俯冲-碰撞转换的时限应该在120 Ma左右。这对于研究抹谷地体在中生代期间中特提斯洋俯冲碰撞过程具有重要的地质意义。     

沿海滩涂软弱地基上轻质硬壳堤坝的构筑

为了能在各种不同地质的滩涂上快速、经济、高效地建造堤坝,实施水产养殖业,提出了轻质硬壳堤坝在滩涂软弱地基上的应用结构体系,阐述了硬壳轻质堤坝的构造和选材、设计思路及施工方法.与软弱地基上传统堤坝相比,轻质硬壳堤坝具有施工快、稳定性好、防冲蚀、防渗性好等特点.以竹胶合板为硬壳材料,以稻草等作轻质垫层,以螺栓等作连接的竹胶合板轻质硬壳堤坝的应用,提高了在软弱地基和砂土地基滩涂上的水产养殖效益.     

轻质硬壳海堤断面设计初探

从海堤本身角度看，坝体过重与填料松散是影响其稳定性的主要因素，因此轻质硬壳堤坝是一种很好的选择。该结构采用高强度材料作为外壳，以松散材料填充坝体。根据受力特性、构造要求、施工条件及抗滑稳定条件拟解决结构断面设计的一些基本问题，并结合实例通过对比计算分析，说明轻质硬壳海堤比传统海堤具有更高的整体稳定性。     

Early Paleozoic lithospheric extension law,dynamic mechanism,origin of mafic dykes in Ziyang,South Qinling Block,ChinaSCIEI北大核心CSCD

南秦岭地块紫阳地区广泛出露早古生代基性岩墙群,其研究具有重要的地球动力学意义。虽然如此,已有相关研究目前主要集中于志留纪基性岩墙群方面,而对早古生代(如,寒武纪、奥陶纪)基性岩墙群的研究仍相对薄弱。从而制约了对南秦岭早古生代岩石圈伸展过程相关问题(如,时空分布规律、地幔性质、动力学机制和相关成矿作用)的总体把握。鉴于尚存的科学问题,本研究选取康家坪、梨树梁、大竹坪、清明寨、苟家山、庙梁上、曾家山和毛坝村的基性岩墙群为研究对象,开展了矿物学、岩石学、锆石U-Pb年代学、地球化学和Sr-Nd-Hf同位素方面的研究,对其精细时代格局、成因及成岩动力学背景进行了系统探讨。研究结果显示,紫阳早古生代基性岩墙以辉绿岩和辉绿玢岩为主,形成时代为奥陶纪(478.8-486Ma),属碱性系列岩石(K_(2)O+Na_(2)O变化范围为4.10%-5.14%)。另外,基性岩墙群具有富集LREE、Rb、Ba、Sr、Nb、Ta、Zr、Hf和Eu(Eu/Eu*=1.13-1.35),亏损HREE、U、Pb和Ti的典型地球化学特征。(87Sr/86Sr)i=0.7044-0.7050、εNd(t)=3.1-3.6、εHf(t)=4.4-12.1,176Hf/177Hf=0.282634-0.282846,暗示基性岩墙为地幔柱作用过程亏损岩石圈或软流圈地幔部分熔融作用的产物。另外,在辉绿岩成岩过程经历了橄榄石和单斜辉石的分离结晶,但地壳混染的影响不明显。     

华北南缘古元古代末岩墙群侵位的磁组构证据

华北克拉通南缘的中条山及邻区广泛发育元古宙放射状基性岩墙群,与五台山-恒山和大同地区的北北西向基性岩墙群以及熊耳中条拗拉谷的火山岩在时空分布和地球化学方面均具有密切的相关性。中条山及邻区放射状基性岩墙群的宏观和微观流动构造(包括捕虏体、冲痕构造、矿物线理和定向斑晶)指示岩墙群以一定的仰角向北西侵位。通过该区岩墙群磁化率各向异性(AMS)测量得到磁组构的最大磁化率长轴优势方位分布图和磁组构各向异性特征分析进一步指示华北南缘古元古代末岩墙群从熊耳中条拗拉谷的底部向北西侵位。岩墙群的流动构造和磁组构的统计成果夯实了华北克拉通古元古代末基性岩墙群与熊耳中条拗拉谷的成生联系。     

Extensional deformation along the late Precambrian-Cambrian Baltoscandian passive margin: the Sarektjåkkå Nappe,Swedish Caledonides

The structural evolution of a part of the late Precambrian Baltoscandian passive margin just before the inception of seafloor spreading is described, recording the change from deformation by faulting to dominantly magmatic extension of the crust. The allochthon of the Scandinavian Caledonides contains the imbricated passive margin of continental Baltica overlain by various exotic terranes. The Sarektjåkkå Nappe in the Seve Nappe Complex, which contains the outer parts of Baltica's passive margin, consists of sedimentary rocks, occurring as screens between Vendian (573±74 Ma) diabase dykes. These dykes constitute 70–80% of the nappe and locally form sheeted dyke complexes. The Sarektjåkkå Nappe largely escaped penetrative Caledonian deformation and preserves igneous, metamorphic and structural elements that are linked to the evolution of a pre-Caledonian rift to a passive continental margin. Extensional deformation before dyke emplacement is recorded by normal faults, pull-apart structures and folds. Unconformities, dykes affected by brittle deformation, and fluidization of sediments during dyke emplacement indicate close relations between the deposition of sediments, extensional deformation and dyke emplacement. The Sarektjåkkå Nappe is compared with other parts of the Baltica's passive margin and its tectonic evolution is discussed.     

脉岩与脉状金矿：一个简要的评述

在综述了脉岩与热液型脉状金矿关系的基础上，认为中基性脉岩、煌斑岩脉不仅在空间上与脉状金矿相伴生，形成时间祁近，而且在物源和成因上有着密切的关联。脉岩是脉状金矿床成因系列的组成部分。据此提出中基性岩浆在某种动力作用下，诱导上覆花岗质岩石（包括古老变质岩）熔融，并发生混染，在地壳脉动作用下，脉岩与含矿流体多期次多阶段侵位，在相应的部位形成脉岩与矿脉共存的金矿区带。     

堤防工程及穿堤建筑物土石接合部安全监测技术发展

堤防工程及穿堤建筑物的渗流破坏多数是沿基土或侧向、顶部填土与建筑物接触面等薄弱部位或存在隐患的部位产生。由穿堤建筑物渗透破坏引起馈堤的事例很多,教训极为深刻。概述了堤防安全监测技术的现状、内容、方法及监测技术的发展,监测目标的选择等;并提出利用先进监测技术对工程运行状态进行实时监测和控制。超前预测到险情及险情变化,为堤防工程现代化管理和防汛抢险提供科学依据。     

屿塘山东侧滑坡成因分析与治理措施

详细分析了温州市永嘉县屿塘山东侧滑坡产生的原因，并列举各影响因素的作用机理。治理措施采用截排水沟与抗滑桩相结合，并介绍了施工中应注意的几个关键事项。     

Occurrence and Dispersal of Magmas in the Jurassic Ferrar Large Igneous Province, Antarctica

Tholeiitic rocks of the Ferrar Large Igneous Province (FLIP) occur in a linear belt from the Theron Mountains to Horn Bluff in the Transantarctic Mountains and extend into southeastern Australasia. The FLIP was emplaced during the initial stages of Gondwana break-up from a source suggested to be in the proto-Weddell Sea region. Magma transport from its source (Weddell triple junction) was controlled by an Early Jurassic zone of extension. The FLIP comprises the Dufek intrusion, Ferrar Dolerite sills and dykes (sheet intrusions), and extrusive rocks consisting of pyroclastic strata overlain by Kirkpatrick Basalt lavas. The Dufek intrusion occurs in deformed supracrustal rocks of the foldbelt along the paleo-Pacific Gondwana margin. A few sills were emplaced in basement rocks, but the majority of the sheet intrusions occur in flat-lying Devonian to Triassic Beacon strata. Only in the central Transantarctic Mountains (CTM) and south and north Victoria Land (SVL, NVL) are extrusive rocks preserved overlying Beacon strata. The greatest cumulative thicknesses of magmatic rocks (ca. 2 km) occur in areas where lavas are preserved (CTM and SVL). Sheet intrusions have complex relationships. Dyke swarms (sensu stricto) are unknown and dykes cutting basement rocks are uncommon. Nevertheless, these dykes, including a 30-m-wide dyke in SVL, suggest that some magmas locally migrated up through basement rocks. In CTM and NVL the outcrop belt has a width of about 160 km. Sills originally extended farther toward the plate margin but have been cut out by erosion and Cenozoic faulting, most clearly in CTM; geophysical data suggest extension under the East Antarctic ice sheet for at least 100 km. Although Early Jurassic extension is documented in CTM, major rift-bounding faults have not been observed. Models for magma emplacement include transport along the axis of the Transantarctic Mountains and off-axis transport from major rift-bounding faults. Contrasts in geochemistry between lavas of NVL (MgO=67%) and CTM (MgO=24%) and the presence of massive dolerite bodies (CTM, SVL) suggest discrete episodes and locations of magma emplacement, and that there was no long range interconnection along the mountain range in supracrustal rocks.