Regional metamorphism and hydrothermal alteration related to Miocene submarine volcanism ('green tuff') in the Yurihara oil and gas field, northwest Honshu Island, Japan     

Masahiko  Yagi 《Island Arc》1993,2(4):240-261

Abstract Alteration of reservoir rocks in the Yurihara Oil and Gas Field, hereafter referred to as the ‘Yurihara field’, have been examined by using samples from six wells. These rocks are basalts in the lowermost part of the basin-fills (‘green tuff’ Formation). These basalts were produced in many eruptions in a submarine environment during the early to middle Miocene, and they underwent continuous intensive alteration genetically associated with Miocene submarine volcanism. The alteration of the basalts is of two types: low grade metamorphism and hydrothermal. The former belongs to the type of ocean floor metamorphism and comprises two subgroups: zeolite (zone I) and prehnite-pumpellyite (zones IIa: vein and amygdule occurrence, and IIb: replacing plagioclase). The latter is characterized by potassic metasomatism accompanied by adularia, quartz and calcite veins (zones IIIa: center and IIIb: margin of the metasomatism). This overprints the low grade metamorphic alteration. The central zone of hydrothermal alteration coincides with a major estimated fault, so that fluids probably assent along the fault. The basalts erupted during 16.5-15.5 Ma, determined by planktonic foraminifera assemblages of inter-bedded shales, then underwent successive low grade metamorphism. In time, the hydrothermal alteration that overprints low grade metamorphism occurred. Adularia veins of the altered rocks located in the hydrothermal alteration zones (zone IIIa and IIIb) have been dated as 9 Ma determined by the K-Ar method. This fact indicates that the activity of low grade metamorphism had already crossed the peak before hydrothermal alteration occurred at 9 Ma. The shape of isotherms of fluid inclusion homogenization temperatures (Th) and that of isolines of apparent salinity (Tm) almost coincide with each other, and these also coincide with the distribution of hydrothermal alteration (zones IIIa and IIIb). This indicates that the fluid inclusions formed at the same time as ascending fluids produced the potassic metasomatism. The maximum Th of the fluid inclusions is 222°C and Tm indicates trapped fluids of up to 3.3 wt% equivalent NaCl (i.e. almost the same as seawater). A Th versus Tm plot indicates mixing occurred between hydrothermal fluids and formation water that has low salinity. Corrensite and chlorite form veins, and the temperatures of their formation, estimated by the extent of aluminium substitution into the tetrahedral site of chlorite, ranges between 165 and 245°C in the centre of the hydrothermal alteration zone (zone IIIa). This is consistent with the result of Th analyses. The deposition temperature of chlorite associated with prehnite in veins ranges between 190 and 215°C in zones IIa and IIb.  相似文献   

适用于地质勘探的轻型架空索道运输方法     

李兴中 《铀矿地质》1990,6(4):243-247

本文介绍了3种适用于勘探施工的架空索道运输方法,同时还叙述了索道的线路选择与架设技术及采用火箭布放索道的新方法。  相似文献   

大陆边缘深水区海底滑坡及其不稳定性风险评估   总被引：6，自引：1，他引：5  

吴时国  陈珊珊  王志君  李清平 《现代地质》2008,22(3):430-437

海底滑坡是大陆坡一种常见的沉积作用过程。这种沉积作用包括滑塌和碎屑流等重力流作用过程,它能将沉积物运移数百公里,严重危害深水油气开发平台、油气管线、海底电缆等设施;同时,还可能导致巨大破坏性的海啸。虽然导致海底滑坡的因素很多,但近年来发现海底滑坡的触发机制可能与地震作用和海底天然气水合物的分解关系密切。随着深水油田的开发和深海工程的日益增多,这种地质作用越来越引起学术界和工业界的重视。在介绍大陆边缘深水区海底滑坡的构成、识别和触发机制的基础上,提出海底滑坡的地质风险评估方法。  相似文献   

曹妃甸海底深槽斜坡稳定性分析与评价     

褚宏宪  方中华  史慧杰  高小惠 《海洋工程》2016,34(3):114-122

海底斜坡稳定性受风暴潮、海底地震等诸多不确定因素影响,易发生失稳破坏,产生较大的海洋地质灾害。简要介绍海底斜坡稳定性分析方法,建立曹妃甸深槽典型斜坡计算模型,确定了模型计算的海底地形参数、地层结构参数、土体物理力学参数等指标,利用GEO-SLOPE斜坡分析软件进行海底斜坡稳定性定量计算,分析了工程建设前自然状态下以及在大规模工程建设后海底斜坡稳定性,并模拟分析了在大风浪和地震等极端条件下斜坡的稳定性,确定了海底斜坡失稳空间特征。首次采用数值计算对曹妃甸海底斜坡稳定性进行定量分析评价,可以为类似近海建设工程提供重要的参考作用。  相似文献   

Mechanism of Salt Contamination of Karstic Springs Related to the Messinian Deep Stage. The Speleological Model of Port Miou (France)     

《Geodinamica Acta》2013,26(1-3):15-28

Submarine karstic springs are frequent on the Mediterranean shore but most of them are brackish which prohibits their use. The numerous attempts to catch these springs ended in failure. Recent studies on the development of karst systems and the paleogeography of the Mediterranean sea explain these failures. Studies on the shores of south-eastern France have enabled us to propose an operating model that explains the mechanism of salt contamination.

The Port Miou system (Cassis, France) is a two kilometers long submarine gallery developped in the limestone series of Calanques (Marseille, France). The average discharge is between 2 to 5 m3/s but the water is brackish. In the 70's a dam was built to prevent sea intrusion in the cave but the water remained brackish upstream of the dam. The use of helium, and then rebreathers by cave divers, made it possible to explore a vertical pit down to -179 m below the sea level at the end of the cave. At that depth, the water is still brackish.

Important quantity of titanium was observed at the surface of the cave sediment upstream of the dam and at the end of the cave. The titanium comes from the residual product of a factory of alumina that is discharged in the Cassidaigne submarine canyon, at a depth of 300 m b.s.l., a few kilometers south to the spring. This residual product locally called «red mud» is very rich in titanium. This supports the model of a sea water aspiration in a deep gallery connected to the canyon. The Cassidaigne canyon that cuts a limestone plateau with dolines and caves is probably a pocket valley. Its presence is related to the several stages of lowering of the Mediterranean sea at the Messinian Deep Stage that allowed the existence of cave networks up to several hundreds of meters below the present sea level. The sea water is now sucked into the system.

A similar example exists in Kefalonia island (Greece) where a sea intrusion is observed in coastal sinkholes. This model explains why the different attempts to diminish the salinity of these brackish springs, by construction of dams close to the outlets, have failed.  相似文献   

中心通缆钻杆及其在煤矿井下定向钻进中的应用          下载免费PDF全文

刘睿全 《探矿工程》2013,40(5):44-47

针对煤矿井下定向钻技术对钻杆的随钻测量通讯和强度要求,钻杆采用中心通缆方式,可实时传输钻孔随钻测量信号。采用高强度管材、特种螺纹丝扣结构、摩擦焊技术,可提高钻杆抗拉、压、弯、扭强度。并根据现场使用中存在的问题给出了解决方法。大佛寺煤矿随钻测量应用实例说明中心通缆钻杆满足最大孔深1200 m的随钻测量通讯和钻杆强度要求,朱仙庄梳状孔应用实例说明中心通缆钻杆满足最小弯曲半径54 m定向孔施工,哈沙图煤矿定向钻孔应用实例说明中心通缆钻杆满足急倾斜58?煤层定向孔施工。  相似文献   

Can liquefied debris flows deposit clean sand over large areas of sea floor? Field evidence from the Marnoso‐arenacea Formation,Italian Apennines     

PETER J. TALLING  GIUSEPPE MALGESINI  FABRIZIO FELLETTI 《Sedimentology》2013,60(3):720-762

The Marnoso‐arenacea Formation in the Italian Apennines is the only ancient rock sequence where individual submarine sediment density flow deposits have been mapped out in detail for over 100 km. Bed correlations provide new insight into how submarine flows deposit sand, because bed architecture and sandstone shape provide an independent test of depositional process models. This test is important because it can be difficult or impossible to infer depositional process unambiguously from characteristics seen at just one outcrop, especially for massive clean‐sandstone intervals whose origin has been controversial. Beds have three different types of geometries (facies tracts) in downflow oriented transects. Facies tracts 1 and 2 contain clean graded and ungraded massive sandstone deposited incrementally by turbidity currents, and these intervals taper relatively gradually downflow. Mud‐rich sand deposited by cohesive debris flow occurs in the distal part of Facies tract 2. Facies tract 3 contains clean sandstone with a distinctive swirly fabric formed by patches of coarser and better‐sorted grains that most likely records pervasive liquefaction. This type of clean sandstone can extend for up to 30 km before pinching out relatively abruptly. This abrupt pinch out suggests that this clean sand was deposited by debris flow. In some beds there are downflow transitions from turbidite sandstone into clean debrite sandstone, suggesting that debris flows formed by transformation from high‐density turbidity currents. However, outsize clasts in one particular debrite are too large and dense to have been carried by an initial turbidity current, suggesting that this debris flow ran out for at least 15 km. Field data indicate that liquefied debris flows can sometimes deposit clean sand over large (10 to 30 km) expanses of sea floor, and that these clean debrite sand layers can terminate abruptly.  相似文献   

珠江口盆地白云凹陷中新统珠江组物源及其研究意义     

李云  郑荣才  杨宝泉  朱国金  胡晓庆 《地质论评》2013,59(1):41-51

南海北部陆坡深水区3Ma以来碎屑物质来源具多样性、复杂性和变化性.利用砂岩和异源生屑灰岩岩石学及泥岩稀土元素地球化学特征研究了珠江口盆地白云凹陷中新统珠江组深水扇的物源.结果表明,珠江组砂岩岩屑主要为变质岩屑和火山岩屑,并含较多深成岩屑.阴极射线下,石英以发蓝紫色-褐色光为主,长石主要发亮蓝色光.异源生屑灰岩为陆坡钙屑碎屑流沉积,来自于神狐暗沙隆起中新统碳酸盐台地.泥岩∑REE与燕山褶皱带燕山期中酸性火山岩较接近,分配模式与上地壳基本一致,并与燕山中酸性火山岩和花岗岩较接近.渐新世末,南海运动使南海海盆第二次海底扩张,并使陆架坡折带由白云凹陷南侧跳跃到凹陷北侧.该构造事件在青藏高原邻近盆地和中国东部盆地都有反映,反映可能发生了青藏高原隆升事件,使珠江组物源向西拓展.珠江期虽然存在活跃的深水牵引流,但珠江组原始物质仍应源自古珠江携带的华南沿海燕山褶皱带的中酸性火山岩、花岗岩和内陆古老的沉积-变质岩.  相似文献   

Spatial distribution of some groups of microzooplankton in relation to oceanographic processes in the vicinity of a submarine canyon in the north-western Mediterranean Sea   总被引：2，自引：2，他引：0  

Sanchez-Velasco  L.; Shirasago  B. 《ICES Journal of Marine Science》1999,56(1):1-14

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Separation of up-going and down-going wave fields of vertical cable data     

ChuanwenSun JohnStratton JohnAnderson PhilipRabinowitz 《中国海洋湖沼学报》2005,23(3):259-268

The vertical cable method for acquiring and processing pre-stack 3-D marine seismic data is based on the technology developed by the US Navy for antisubmarine warfare. In order to achieve the maximum utilization of vertical cable field data, a new separation method of the up-going and down-going wave fields of the vertical cable data processing was developed in this paper, which is different from the separation of the down-going and up-going wave fields of normal VSP data processing. In tests with synthetic modeling data andactual field data, this newly developed method performs well and is also computationally simpler without pre-assumption conditions.  相似文献