Phreatomagmatic volcanic hazards where rift-systems meet the sea, a study from Ambae Island, Vanuatu

Ambae Island is a mafic stratovolcano located in the northern Vanuatu volcanic arc and has a NE–SW rift-controlled elongated shape. Several hundred scoria cones and fissure-fed lava fields occur along its long axis. After many decades of quiescence, Ambae Island erupted on the 28th of November 2005, disrupting the lives of its 10,000 inhabitants. Its activity remained focused at the central (crater-lake filled) vent and this is where hazard-assessments were focused. These assessments initially neglected that maars, tephra cones and rings occur at each tip of the island where the eruptive activity occurred < 500 and < 300 yr B.P. The products of this explosive phreatomagmatic activity are located where the rift axis meets the sea. At the NE edge of the island five tephra rings occur, each comparable in size to those on the summit of Ambae. Along the NE coastline, a near-continuous cliff section exposes an up to 25 m thick succession of near-vent phreatomagmatic tephra units derived from closely spaced vents. This can be subdivided into two major lithofacies associations. The first association represents when the locus of explosions was below sea level and comprises matrix-supported, massive to weakly stratified beds of coarse ash and lapilli. These are dominant in the lowermost part of the sequence and commonly contain coral fragments, indicating that the loci of explosion were located within a reef or coral sediment near the syn-eruptive shoreline. The second type indicate more stable vent conditions and rapidly repeating explosions of high intensity, producing fine-grained tephra with undulatory bedding and cross-lamination as well as megaripple bedforms. These surge and fall beds are more common in the uppermost part of the succession and form a few-m-thick pile. An older tephra succession of similar character occurs below, and buried trees in growth position, as well as those flattened within base surge beds. This implies that the centre of this eruption was very near the coastline. The processes implied by these deposits are amongst the most violent forms of volcanism on this island. In addition, the lowland and coastal areas affected by these events are the most heavily populated. This circumstance is mirrored on many similar volcanic islands, including the nearby SW Pacific examples of Taveuni (Fiji), Upolu and Savai'i (Samoa), and Ambrym (Vanuatu). These locations are paradoxically often considered safe areas during summit/central-vent eruptions, simply because they are farthest from the central sources of ash-fall and lahar hazard. The observations presented here necessitate a revision of this view.     

The architecture, eruptive history, and evolution of the Table Rock Complex, Oregon: From a Surtseyan to an energetic maar eruption

The Table Rock Complex (TRC; Pliocene–Pleistocene), first documented and described by Heiken [Heiken, G.H., 1971. Tuff rings; examples from the Fort Rock-Christmas Lake valley basin, south-central Oregon. J. Geophy. Res. 76, 5615-5626.], is a large and well-exposed mafic phreatomagmatic complex in the Fort Rock–Christmas Lake Valley Basin, south-central Oregon. It spans an area of approximately 40 km², and consists of a large tuff cone in the south (TRC1), and a large tuff ring in the northeast (TRC2). At least seven additional, smaller explosion craters were formed along the flanks of the complex in the time between the two main eruptions. The first period of activity, TRC1, initiated with a Surtseyan-style eruption through a 60–70 m deep lake. The TRC1 deposits are dominated by multiple, 1-2 m thick, fining upward sequences of massive to diffusely-stratified lapilli tuff with intermittent zones of reverse grading, followed by a finely-laminated cap of fine-grained sediment. The massive deposits are interpreted as the result of eruption-fed, subaqueous turbidity current deposits; whereas, the finely laminated cap likely resulted from fallout of suspended fine-grained material through a water column. Other common features are erosive channel scour-and-fill deposits, massive tuff breccias, and abundant soft sediment deformation due to rapid sediment loading. Subaerial TRC1 deposits are exposed only proximal to the edifice, and consist of cross-stratified base-surge deposits. The eruption built a large tuff cone above the lake surface ending with an effusive stage, which produced a lava lake in the crater (365 m above the lake floor). A significant repose period occurred between the TRC1 and TRC2 eruptions, evidenced by up to 50 cm of diatomitic lake sediments at the contact between the two tuff sequences. The TRC2 eruption was the last and most energetic in the complex. General edifice morphology and a high percentage of accidental material suggest eruption through saturated TRC1 deposits and/or playa lake sediments. TRC2 deposits are dominated by three-dimensional dune features with wavelengths 200–500 m perpendicular to the flow, and 20–200 m parallel to the direction of flow depending on distance from source. Large U-shaped channels (10–32 m deep), run-up features over obstacles tens of meters high, and a large (13 m) chute-and-pool feature are also identified. The TRC2 deposits are interpreted as the products of multiple, erosive, highly-inflated pyroclastic surges resulting from collapse of an unusually high eruption column relative to previously documented mafic phreatomagmatic eruptions.     

怀来地震台伸缩仪EW向改进试验

对怀来台伸缩仪EW向基线固定端、传感器进行布设改进试验,将原有28m长基线改为两段短基线（东段：14．6m,西段：13．4m）。改进后,两条短基线取得了较好的观测成果,其中东段基线改造效果非常明显,观测曲线干扰减少,光滑度显著提高,观测数据精度明显优于改造前的观测数据。这次改造试验解决了困扰怀来台多年的难题。     

基于GIS矿产勘查靶区优选技术

靶区优选是矿产勘查中的一个关键环节, 它既是矿产资源预测成果的直接体现形式, 同时又是联系矿产资源预测与勘查工作部署的桥梁.然而, 由于人们认识上的不完备性和缺乏相应的技术手段支撑, 使得靶区优选常被忽视或简化.探讨了靶区优选的地质基础原则, 建立了靶区优选的技术流程, 研发了基于GIS支持下靶区优选计算机辅助决策模块, 并以云南省个旧地区与岩浆活动有关的锡铜多金属矿靶区为例进行了示范研究.结果表明靶区优选技术及相应的软件能够客观地反映不同靶区的特征, 提高靶区优选的智能化程度和工作效率.      

青海贵德县扎仓温泉特征及其开发利用

扎仓温泉位于青海省贵德县扎仓寺村,其开发利用至今已有600多年的历史。温泉出露于断裂带交汇部位,地下热水矿化度为1 310~1 390 mg/L, 水化学类型属于SO₄·Cl-Na型。研究结果表明,温泉的补给来源为大气降水,温泉水年龄约165 a。利用SiO₂温标法计算出热储温度为136 ℃,估算热水循环深度为1 385 m。温泉的天然放热量大于1.23×10¹⁴J/a,扎仓沟地区的地热资源量达2.07×10¹⁴J以上。热水宜直接用于供暖、洗浴、温室种植和养殖等。该地热田深部尚有地热能潜力。     

中俄蒙跨边界次区域矿产资源合作开发机制与模式研究

本文以区域经济地理学为理论基础．采用实证分析的方法．结合东北经济区现实发展条件,通过分析中俄蒙三国毗邻地区矿产资源合作的区位条件、贸易条件、资源互补条件及开发现状,探讨区域合作深入发展的制约机制与优化机制,并结合实证研究总结出政府主导型、大型国有企业合作型和民营企业境外拓展型三种中俄蒙跨边界矿产资源合作开发模式。     

高分辨率层序地层学应用中的问题探析

高分辨率层序地层学自诞生以来, 由于其基本原理和分析技术的广泛适用性、可行性、高精度和可预测性, 得到了广大石油地质工作者的认可并在油气勘探与开发研究中得到了广泛的应用,对中国油气勘探与油田开发挖潜起着至关重要的作用。但在应用过程中,还存在一些对概念理解的偏差以及模糊不清的认识,须要更深入的探讨以加深认识。作者主要从概念和方法上分析探讨了高分辨率层序地层学在储集层规模的地层划分与对比中存在的一些问题,包括基准面旋回与准层序概念的差异性;基准面旋回的级次划分;基准面旋回的界面识别与基准面旋回对比等,旨在通过对这些问题的分析,与运用该理论和方法的学者达成一定的共识并提供一些思考。     

中国煤层气技术可采资源潜力

煤层气原地资源量和技术可采资源量的计算结果,可为国家制定煤层气开发战略提供决策依据,也可为煤层气开发的相关部门或单位提供参考依据,对推动我国煤层气产业发展具有重要意义。通过对我国褐煤分布区的煤层气资源量的计算,弥补了我国长期缺少褐煤煤层气资源量的缺陷,使我国煤层气资源量数据更加完整,我国陆上煤层埋深2 000 m以浅的煤层气原地资源量为32.86×1012m3,其中,褐煤主要分布区为1.40×1012m3,非褐煤地区为31.46×1012m3。利用已建立的煤层气技术可采资源量评价方法体系,并基于目前的开发技术,对我国煤层气技术可采资源量进行计算,结果为13.90×1012m3,占原地资源量的42%。      

北京市朝阳区多目标水量优化配置模型

进行了北京市朝阳区水资源经济优化模型的实例研究。提出了地表水、地下水、自来水、中水4种水源类型。考虑生活用水（城镇生活用水、农村生活用水）、工业用水（电子及通讯制造业用水,一般工业用水,石油化工用水,电力、蒸汽、热水的生产和供应业用水）、农业用水（种植业、渔业、林业、畜牧业）和生态环境用水等4大用水部门、十几个小用水部门,建立了多目标水资源规划模型,并运用单纯形法求解模型,计算了2010年、2020年的水资源量最佳分配。     

南海海域新生代沉积盆地的油气资源

南海新生代经历过大陆张裂与分离、海底扩张和地块碰撞等构造演化历史,南海北部为被动大陆边缘,南部是碰撞挤压边缘,东部为俯冲聚敛边缘,西部是走滑边缘。在这种构造体制下,形成了许多沉积盆地。北部和西部边缘上发育着张性沉积盆地和走滑拉张盆地;在南部边缘上,其北部发育着张性盆地,南部为挤压环境下形成的盆地,如前陆盆地、前孤盆地;东部边缘上发育着前孤盆地。目前油气勘探实践证明,南海南部的油气资源比北部丰富。究其原因,南海北部为被动大陆边缘,张性沉积盆地的烃源岩体积较小,而南部挤压环境下形成的沉积盆地的烃源岩体积大;北部的地热流较南部小,因此地温梯度也较小,故南部边缘烃源岩的成熟度比北部高;由于南部边缘处于挤压构造环境,在沉积盆地中形成了许多挤压构造,而北部边缘一直处于张性构造环境,形成的构造较少且较小;同时,南部边缘沉积盆地中,烃源岩生烃与构造形成在时间上搭配较好。因此,在南海南部边缘沉积盆地中形成了许多大型油气田,而南海北部边缘沉积盆地中,大型油气田较少,中小型油气田较多。