Probable regional geothermal field reconnaissance in the Aegean region from modern multi-temporal night LST imagery

The Hellenic Peninsula and the adjacent Aegean and Ionian seas are segmented into regions on the basis of Terra satellite-MODIS instrument derived land surface temperatures (LST) to test if they can be used in the field reconnaissance for potential geothermal targets, each region representing a different thermal signature. The method has been used successfully to identify hot spot and geothermal activity in the Afar Triangle and in the Red Sea. Night monthly average LST values per pixel, since 2001, are used in this work for geothermal field identification. Average LST seasonal variability is expressed by a common centroid curve of pixel cluster. Clusters were subsequently ranked in increasing LST according to their centroids. Cluster-2 represents by far the Aegean volcanic arc (AVA) which comprises the high enthalpy (320 and 350°C, respectively) geothermal fields of Milos and Nisyros. The interpretation of LST terrain segmentation into sub-clusters of Cluster-2 is consistent with thermal anomalies related to the volcano-islands of the AVA, the occurrence of thermal anomalies related to granodiorite plutons in the Cyclades and to the volcano-related anomalies of the Dodecanese Province. We conclude that the identification of such thermal anomalies obtained by a combination of remote sensing (LST), regional geology and field data (borehole, thermal spring and subsurface hydrothermal reservoir temperatures) can be a particularly useful exploration tool for localizing geothermal anomalies.     

Fracture interaction in the Gregory Rift, East Africa

Vertical fracture is important, and fracture interaction is quite intensive in the Central Gregory Rift. Crack-branching and non-coplanar crack interactions in the rift are characterized for major and minor faults. These two manifestations follow theoretical and experimental angular relationships of fracture reasonably well. Mantle diapirism seems to have been responsible for both tensile (probably unstable) fracture, and block tilting, ultimately resulting in fault dips deviating from the vertical.     

Iterative selective spatial variance reduction of MYD11A2 LST data

The aim of this research effort is to develop a method that will allow to map and evaluate thermal anomalies in SW USA from the MYD11A2 night land surface temperature (LST) imagery being available for the year 2014, that present higher spatial (1 km) and temporal (46 images per year) resolution than the MYD11C3 LST data (12 images per year at 5.6 km spatial resolution). The fact that is MYD11A2 LST imagery is projected to a rectangular grid did not affect the X, Y and elevation (H) spatial decorrelation stretch. Principal component analysis and linear regression models isolated and removed the X, Y, H (spatial) dependent variance included in the data while metrics devised verified the selective spatial variance reduction. The reconstructed 46 LST images represent the amount the LST deviates from the X, Y and H predicted for the year 2014. The thematic information content of the reconstructed LST images is verified by cluster analysis and mapped the spatial extend and the temporal variability of thermal anomalies within the study area. The positive thermal anomaly clusters are spatially arranged mainly west of Sierra Nevada in Great Basin Section where extensional tectonics create a series of titled elongated mountain blocks along the N to S direction in between basins bounded by normal faults, while the negative thermal anomaly clusters are spatially arranged along the coastal region, further north and in the western region far from the tilted mountain tectonic blocks of the Great Basin Section. The spatial maps that define regions with (positive or negative) thermal anomalies and distinct mean land response could assist landcover studies and support urban and rural planning in the context of emerging climatic change.     

Holocene extension direction along the Main Ethiopian Rift, East Africa

Assessment of the extension direction and its spatial and temporal variations is critical for evaluating a rifting process. The extension direction in the East African Rift System is a matter of debate and the NE–SW-trending Ethiopian portion is one of the most controversial areas, for which several extension directions have been proposed. Field analysis was performed along the axis of the Main Ethiopian Rift (MER), aiming at recognizing the opening direction of the NNE–SSW-trending Holocene extension fractures. The matching of pairs of asperities along the sides of these fractures allowed evaluation of the horizontal displacement and, thus, the extension direction. The collected data reveal a consistent Holocene extension direction, with a mean value of N52°W ± 20°. This NW–SE direction is constant along the MER, despite the ∼15° variations observed in its trend and the NNE–SSW trend of the extension fractures, oblique to the NE–SW trend of the MER.     

Plume-Lithosphere Interactions in the Generation of the Basalts of the Kenya Rift, East Africa

Major and trace element and Sr–Nd–Pb isotopic datafor mafic volcanic rocks are used to assess the number of mantleplumes contributing to the Tertiary–Holocene magmatismof the Kenya Rift Valley, current estimates of which vary fromnone to three. Rocks ranging in composition from nepheliniteto hypersthene-normative basalt have been sampled from threelithospheric zones: the Tanzanian craton, the craton marginreworked during the late Proterozoic, and the Mozambique mobilebelt. The magmas are interpreted as the products of variabledegrees of partial melting within the spinel–garnet peridotitetransition zone. Trace element and isotopic compositions fromall three zones are broadly similar to those of oceanic islandbasalts, but there is considerable compositional variation,which is related to a strong overprint from the lithosphereon plume-derived melts. Sr and Nd isotopic ratios provide theonly clear distinction between magmatic rocks from the threelithospheric domains. Within each setting, mafic magmatism hastended to become less silica undersaturated with time, and atany one locality magmatism has migrated towards the centre ofthe rift. Magmas may have formed as a result of the infiltrationof plume-derived melts into the base of the lithosphere. Theextent of interaction of inferred plume melts with the lithospherehas not varied systematically in time or space. The plume componentappears to be similar to the source of oceanic island basalts. KEY WORDS: Kenya Rift Valley; mantle plumes; geochemistry; metasomatism     

Mechanism of the Formation of the East African Rift System

正The East African Rift System(EARS)is located in East Africa,separating into two main branches,the eastern branch and the western branch.It is considered as an intracontinental ridge system,which meets the Red Sea and     

东非裂谷Tanganyika地堑石油地质特征和勘探潜力分析

随着东非裂谷乌干达区块的勘探获得重大突破,与之石油地质条件相似的Tanganyika地堑的勘探潜力受到了人们的重视.Tanganyika地堑地处东非,属于东非裂谷西支的中段,是典型陆内裂谷盆地,主要沉积中新世以来的地层,现仍大部分被湖水覆盖,湖盆水体较深.盆地整体分为2个次盆,呈三隆夹两凹的构造格局.盆地目前勘探程度较低,根据现有资料推测,盆地地层埋深较大,深洼区中新统地层发育成熟烃源岩,具有较大的生烃潜力和生烃规模;陆内盆地物源相对充足,储盖组合条件较好;应力复杂,能够形成大量多种类型构造及构造-地层圈闭;各种成藏条件匹配关系较好,有利于油气聚集成藏.综合分析认为,盆地具有较大勘探潜力,其中盆地转换带是最有利的油气勘探区.     

东非裂谷东支肯尼亚裂谷形成演化

东非裂谷东支肯尼亚裂谷包括5个重点凹陷,除South Lokichar凹陷外,其余凹陷均无发现。肯尼亚裂谷的形成演化及动力机制认识不清是制约油气勘探的关键。通过系统分析肯尼亚裂谷不同凹陷形成年代、裂谷类型和动力机制、构造演化和沉积充填过程,得到以下几点认识:(1)South Lokichar凹陷形成时间早,地层年代老。South Lokichar凹陷主要发育晚渐新世-中中新世地层;Turkana、Kerio及North Lokichar凹陷以中中新世-全新世地层为主;Kerio Valley凹陷主要发育中-晚中新世地层;(2)阿法尔地幔柱和肯尼亚地幔柱的隆升控制肯尼亚裂谷的形成演化。South Lokichar凹陷的形成演化主要受阿法尔地幔柱控制;其余4个凹陷主要受肯尼亚地幔柱控制;(3)不同类型的凹陷构造演化和沉积充填差异较大。South Lokichar凹陷与Kerio Valley凹陷为被动型裂谷,构造演化经历初始裂陷期、主裂陷期和裂陷后期三个阶段,在主裂陷期发育优质烃源岩;Turkana、Kerio及North Lokichar凹陷为主动型裂谷,构造演化包括火山事件活动期和间歇...     

Magmatism in the Gregory Rift, East Africa: Evidence for Melt Generation by a Plume

The volume and composition of volcanic rocks associated withthe Gregory rift are interpreted in the light of inversionsperformed on the REE concentrations of the most magnesian basalts.When the estimated volume of salic rock ({small tilde}88 000km³) is converted into basalt ({small tilde}792 000 km³) thetotal volume of basaltic melt generated over the last 30 Myis at least 924 000 km³, corresponding to an average rate ofmelt production of {small tilde}0•03 km³/yr and an averagemelt thickness of between 7 and 26 km everywhere beneath therift. The mean compositions of the basaltic magmas erupted withinthe rift and on the rift flanks during the Upper Oligocene andMiocene, the Pliocene, and the Quaternary are taken to be representativeof the average compositions of melts produced by fractionalmelting in the asthenospheric mantle. When the REE concentrationsof the observed average compositions are inverted they suggestthat much of the melt was produced in the depth and temperaturerange of the transition from garnet to spinel peridotite. Fora mantle potential temperature of {small tilde}1500C the topof the melting region predicted from the inversions is at {smalltilde}70 km beneath the rift axis and {small tilde}80 km beneaththe rift flanks. Within the rift zone the predicted thicknessof melt increases from the Upper Oligocene and Miocene to thePliocene and is always greater than that predicted for the riftflanks, and the timeaveraged thickness of melt predicted is0/5 km. To generate the observed volume of melt the asthenosphericmantle must continually upwell through the melting region (extendingfrom 70 to 150 km) with a vertical velocity of between 40 and140 mm/yr. The results suggest that, volumetrically and compositionally,magmatic activity associated with the Gregory rift is quantitativelyconsistent with a model of a mantle plume upwelling beneaththinned continental lithosphere. Predictions made by such amodel are in broad agreement with geophysical observations. ^* Present address/reprint requests to: B.P. Exploration, 4/5 Long Walk, Stockley Park, Uxbridge UB11 1BP, UK     

Tectonic and climatic control on evolution of rift lakes in the Central Kenya Rift, East Africa

The long-term histories of the neighboring Nakuru–Elmenteita and Naivasha lake basins in the Central Kenya Rift illustrate the relative importance of tectonic versus climatic effects on rift-lake evolution and the formation of disparate sedimentary environments. Although modern climate conditions in the Central Kenya Rift are very similar for these basins, hydrology and hydrochemistry of present-day lakes Nakuru, Elmenteita and Naivasha contrast dramatically due to tectonically controlled differences in basin geometries, catchment size, and fluvial processes. In this study, we use eighteen ¹⁴C and ⁴⁰Ar/³⁹Ar dated fluvio-lacustrine sedimentary sections to unravel the spatiotemporal evolution of the lake basins in response to tectonic and climatic influences. We reconstruct paleoclimatic and ecological trends recorded in these basins based on fossil diatom assemblages and geologic field mapping. Our study shows a tendency towards increasing alkalinity and shrinkage of water bodies in both lake basins during the last million years. Ongoing volcano-tectonic segmentation of the lake basins, as well as reorganization of upstream drainage networks have led to contrasting hydrologic regimes with adjacent alkaline and freshwater conditions. During extreme wet periods in the past, such as during the early Holocene climate optimum, lake levels were high and all basins evolved toward freshwater systems. During drier periods some of these lakes revert back to alkaline conditions, while others maintain freshwater characteristics. Our results have important implications for the use and interpretation of lake sediment as climate archives in tectonically active regions and emphasize the need to deconvolve lacustrine records with respect to tectonics versus climatic forcing mechanisms.     

中非Melut盆地与我国东部裂谷盆地的类比及意义

Melut盆地为中非地区重要的含油气裂谷盆地,具被动裂谷成盆特征,处于区域构造勘探向"三新领域"勘探的转型阶段,油气富集规律尚不十分清楚,通过开展Melut盆地与我国东部主动裂谷盆地的类比分析,有助于深化盆地成藏认识,推进勘探转型.研究表明,Melut盆地北部具被动裂谷成盆特征,发育大型富油凹陷,形成以古近系跨时代成藏组合为主,近源白垩系成藏组合为辅的油气富集特点,古近系Yabus组上段跨时代岩性油藏与近源白垩系Galhak组断块油藏是北部深化勘探的重要领域;盆地中南部具被动裂谷与主动裂谷的叠加演化过程,与海拉尔盆地相似,具小型断陷沉积充填与成藏特征,近源成藏组合是有利的勘探对象,继承性洼槽内低凸起、凹陷间断裂隆起带及缓坡断层坡折带是有利的成藏构造带.该研究深化了Melut盆地成藏认识,明确了盆地南北具有不同的成盆机制与成藏特征,对推动北部成熟探区深化勘探与中南部低探区勘探突破具有重要意义.     

Hydrothermal hydrocarbon gases: 2, Application in the East African Rift System

Hydrocarbon gases are ubiquitous in the hydrothermal systems of the East African Rift System (EARS), though often found at very low concentrations in the ‘volcanic’ eastern branch as compared to the ‘sedimentary’ western branch. Study of the chemical and isotopic compositions of these hydrocarbons from sites in Kenya, Ethiopia, Djibouti and Uganda reveals considerable homogeneity over hundreds of km of the various rift units. Consideration of C and He isotopic evidence points to a predominantly crustal thermogenic origin for the hydrocarbons, there being no evidence of mantle inputs in either the MORB or ‘hotspot’ sectors of the EARS. Temperature information from geothermal wells has been utilised to investigate the relationship between reservoir temperatures and ratios of CH₄ to C₂H₆. The general C₁/C₂ geothermometric relationship proposed in Part 1 of this study holds reasonably well, and is shown to give results equal to or better than the ‘inorganic’ gas geothermometers presently in use, both in the wellfields and undeveloped high-enthalpy geothermal areas. Results from low-enthalpy hot spring systems are less well correlated with apparent deep temperatures, but consistent with data from similar systems elsewhere in the world.     

Thermal and exhumation history of the central Rwenzori Mountains, Western Rift of the East African Rift System, Uganda

The Rwenzori Mountains (Mtns) in west Uganda are the highest rift mountains on Earth and rise to more than 5,000 m. We apply low-temperature thermochronology (apatite fission-track (AFT) and apatite (U–Th–Sm)/He (AHe) analysis) for tracking the cooling history of the Rwenzori Mtns. Samples from the central and northern Rwenzoris reveal AFT ages between 195.0 (±8.4) Ma and 85.3 (±5.3) Ma, and AHe ages between 210.0 (±6.0) Ma to 24.9 (±0.5) Ma. Modelled time–temperature paths reflect a protracted cooling history with accelerated cooling in Permo-Triassic and Jurassic times, followed by a long period of constant and slow cooling, than succeeded by a renewed accelerated cooling in the Neogene. During the last 10 Ma, differentiated erosion and surface uplift affected the Rwenzori Mtns, with more pronounced uplift along the western flank. The final rock uplift of the Rwenzori Mtns that partly led to the formation of the recent topography must have been fast and in the near past (Pliocene to Pleistocene). Erosion could not compensate for the latest rock uplift, resulting in Oligocene to Miocene AHe ages.     

Continental rift evolution: From rift initiation to incipient break-up in the Main Ethiopian Rift, East Africa

The Main Ethiopian Rift is a key sector of the East African Rift System that connects the Afar depression, at Red Sea–Gulf of Aden junction, with the Turkana depression and Kenya Rift to the South. It is a magmatic rift that records all the different stages of rift evolution from rift initiation to break-up and incipient oceanic spreading: it is thus an ideal place to analyse the evolution of continental extension, the rupture of lithospheric plates and the dynamics by which distributed continental deformation is progressively focused at oceanic spreading centres.The first tectono-magmatic event related to the Tertiary rifting was the eruption of voluminous flood basalts that apparently occurred in a rather short time interval at around 30 Ma; strong plateau uplift, which resulted in the development of the Ethiopian and Somalian plateaus now surrounding the rift valley, has been suggested to have initiated contemporaneously or shortly after the extensive flood-basalt volcanism, although its exact timing remains controversial. Voluminous volcanism and uplift started prior to the main rifting phases, suggesting a mantle plume influence on the Tertiary deformation in East Africa. Different plume hypothesis have been suggested, with recent models indicating the existence of deep superplume originating at the core-mantle boundary beneath southern Africa, rising in a north–northeastward direction toward eastern Africa, and feeding multiple plume stems in the upper mantle. However, the existence of this whole-mantle feature and its possible connection with Tertiary rifting are highly debated.The main rifting phases started diachronously along the MER in the Mio-Pliocene; rift propagation was not a smooth process but rather a process with punctuated episodes of extension and relative quiescence. Rift location was most probably controlled by the reactivation of a lithospheric-scale pre-Cambrian weakness; the orientation of this weakness (roughly NE–SW) and the Late Pliocene (post 3.2 Ma)-recent extensional stress field generated by relative motion between Nubia and Somalia plates (roughly ESE–WNW) suggest that oblique rifting conditions have controlled rift evolution. However, it is still unclear if these kinematical boundary conditions have remained steady since the initial stages of rifting or the kinematics has changed during the Late Pliocene or at the Pliocene–Pleistocene boundary.Analysis of geological–geophysical data suggests that continental rifting in the MER evolved in two different phases. An early (Mio-Pliocene) continental rifting stage was characterised by displacement along large boundary faults, subsidence of rift depression with local development of deep (up to 5 km) asymmetric basins and diffuse magmatic activity. In this initial phase, magmatism encompassed the whole rift, with volcanic activity affecting the rift depression, the major boundary faults and limited portions of the rift shoulders (off-axis volcanism). Progressive extension led to the second (Pleistocene) rifting stage, characterised by a riftward narrowing of the volcano-tectonic activity. In this phase, the main boundary faults were deactivated and extensional deformation was accommodated by dense swarms of faults (Wonji segments) in the thinned rift depression. The progressive thinning of the continental lithosphere under constant, prolonged oblique rifting conditions controlled this migration of deformation, possibly in tandem with the weakening related to magmatic processes and/or a change in rift kinematics. Owing to the oblique rifting conditions, the fault swarms obliquely cut the rift floor and were characterised by a typical right-stepping arrangement. Ascending magmas were focused by the Wonji segments, with eruption of magmas at surface preferentially occurring along the oblique faults. As soon as the volcano-tectonic activity was localised within Wonji segments, a strong feedback between deformation and magmatism developed: the thinned lithosphere was strongly modified by the extensive magma intrusion and extension was facilitated and accommodated by a combination of magmatic intrusion, dyking and faulting. In these conditions, focused melt intrusion allows the rupture of the thick continental lithosphere and the magmatic segments act as incipient slow-spreading mid-ocean spreading centres sandwiched by continental lithosphere.Overall the above-described evolution of the MER (at least in its northernmost sector) documents a transition from fault-dominated rift morphology in the early stages of extension toward magma-assisted rifting during the final stages of continental break-up. A strong increase in coupling between deformation and magmatism with extension is documented, with magma intrusion and dyking playing a larger role than faulting in strain accommodation as rifting progresses to seafloor spreading.     

The southern extension of the East African Rift System and related igneous activity

New details of the late- and post-Karroo fracture pattern in eastern southern Africa are shown on a map together with associated igneous rocks. The pattern is remarkably like that of the East African Rift Valleys with which it is continuous.There is a close parallelism between the Rift fractures and intracratonic orogenic belts, and also locally between the fractures and foliation trends of the gneisses in the belts. Relief differences across the faults range up to 2000 feet; many of the Rifts are asymmetrical with displacement only along one side.Although earth movements were intermittent over a long period of time, two main episodes occurred during post-Karroo to Cretaceous and Tertiary to recent times. Forty-nine isotopic ages of igneous material are taken from the literature and indicate eruptive activity over a 100 m. y. period.

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Zusammenfassung Neue Einzelheiten über das Bruchmuster in der Spät- und Post-Karroo im Osten des südlichen Afrikas sowie über die damit verbundenen Magmagesteine sind auf einer Karte angegeben. Das Bruchmuster hat eine außerordentliche Ähnlichkeit mit dem Ostafrikanischen Graben, welcher eine Fortsetzung davon ist.Ein enger Parallelismus besteht zwischen den Brüchen des tektonischen Grabens und den intrakratonischen, orogenetischen Zonen sowie auch örtlich innerhalb der Zonen zwischen den Brüchen und dem Schieferungsstreichen der Gneise. Der Unterschied im Relief über die Verwerfungen hin ist bis zu 2000 feet; viele dieser tektonischen Gräben sind asymmetrisch, und Verschiebungen geschehen nur entlang einer Seite.Obgleich Erdbewegungen durch lange Zeiträume unterbrochen waren, konnten jedoch zwei Hauptepisoden von der Post-Karroo bis zur Kreide und von dem Tertiär bis zur heutigen Zeit festgestellt werden. Neunundvierzig isotopische Alter für Magmagestein sind in der Literatur zitiert und deuten auf eine eruptive Tätigkeit von über 100 M. J. hin.

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Résumé Nouveaux détails concernant le dessin de fracture pendant le Karroo Supérieur et le Post-Karroo dans l'est de l'Afrique méridionale ainsi que les roches ignées associées sont indiqués sur une carte. On y observe une similarité très remarquable entre le dessin de fracture de l'Afrique méridionale et celui du fossé tectonique de l'Afrique-Est, du quel il est un prolongement.Il y a un parallélisme étroit entre les fractures de fossé tectonique et les zones orogéniques ainsi que localement entre les fractures et la direction de foliation des gneisses dans les zones orogéniques. La différence en relief à travers les failles se range près de 2000 feet; beaucoup de fossés tectoniques sont asymmétriques; ils montrent un déplacement sur un côté seulement.Les mouvements de terre étaient intermittents pendant une longue période de temps; mais deux épisodes principaux se présentaient pendant le Karroo Supérieur jusqu'au Crétacé et pendant le Tertiaire jusqu'au Quaranteneuf âges isotopiques de roches ignées sont cités de la littérature consultée et les âges indiquent une activité eruptive plus de 100 m. a.

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Crustal structure of the East African Rift zone

A review of seismological data on the crustal structure of the East African Rift zone is presented. The only refraction line is that along the Gregory Rift, which indicates a 7.5 km/sec refractor which is presumed to be the Moho. The bulk of data is provided by surface-wave dispersion studies. Some preliminary measurements of crustal and sub-Moho velocities using the University of Durham array at Kaptagat in Kenya are included.

There is now a growing body of evidence that the crust is generally of shield type over the whole rift zone. The exception is along the axis of the Gregory Rift, where a low-velocity Moho and some crustal modification is apparent. This is presumably the result of magma intrusions and suggests some crustal separation along this section of the rift. Sub-Moho velocities are probably normal outside the rifts themselves, though anomalously low upper-mantle velocities are to be associated with rifting. There is firm evidence for thinning of the lithosphere along the eastern branch of the rift. A cross-section of the Gregory Rift which is consistent with the current data is presented.     

Spatial and temporal geochemical variability in lacustrine sedimentation in the East African Rift System: Evidence from the Kenya Rift and regional analyses

Many previous studies on lacustrine basins in the East African Rift System have directed their attention to climatic controls on contemporary sedimentation or climate change as part of palaeoenvironmental reconstruction. In contrast, this research focuses on the impact of tectonism and volcanism on rift deposition and develops models that help to explain their roles and relative importance. The study focuses on the spatial and temporal variability in bulk sediment geochemistry from a diverse range of modern and ancient rift sediments through an analysis of 519 samples and 50 major and trace elements. The basins examined variously include, or have contained, wetlands and/or shallow to deep, fresh to hypersaline lakes. Substantial spatial variability is documented for Holocene to modern deposits in lakes Turkana, Baringo, Bogoria, Magadi and Malawi. Mio‐Pleistocene sediments in the Central Kenya Rift and Quaternary deposits of the southern Kenya Rift illustrate temporal variability. Tectonic and volcanic controls on geochemical variability are explained in terms of: (i) primary controlling factors (faulting, subsidence, uplift, volcanism, magma evolution and antecedent lithologies and landscapes); (ii) secondary controls (bedrock types, rift shoulder and axis elevations, accommodation space, meteoric and hydrothermal fluids and mantle CO ₂); and (iii) response factors (catchment area size, orographic rains, rain shadows, vegetation densities, erosion and weathering rates, and spring/runoff ratios). The models developed have, in turn, important implications for palaeoenvironmental interpretation in other depositional basins.     

东非裂谷Kerio盆地石油地质特征与勘探潜力

东非裂谷东支的South Lokichar盆地于2012年获得勘探突破,成为研究和勘探的热点地区.但近年来周边盆地勘探效果不佳,有待深入分析.Kerio盆地紧邻South Lokichar盆地,勘探程度低,国内在此地的研究处于空白区.基于最新地震地质综合研究成果,阐述其石油地质特征和勘探潜力.结果表明:Kerio盆地为主动裂谷,呈西陡东缓的半地堑结构;发育渐新世以来的5套沉积地层,最大沉积厚度可达6500 m;存在一套被证实的烃源岩,生烃指标好,但厚度仅20 m;发育河流和三角洲相砂岩,孔渗物性好.盆地可划分为4个凹陷和5个构造圈闭带.中部缓坡带和东部反转构造带为盆地的有利勘探区带,可能存在2种成藏模式.盆地具有一定勘探潜力,烃源岩是最主要的地质风险.     

根据多时相夜间MODIS LST推断的腾冲地区新生代火山岩岩浆囊分布与活动特征

腾冲火山地热区位于印度板块与欧亚板块俯冲-碰撞带的弧后活动区,是我国新生代火山-地热最为活动的地区之一.本文利用MODIS夜间月平均地表温度(Land Surface Temperature,LST)数据,计算了研究区2001～2011年132个月的月平均地表温度,圈定了地温异常区;分析了异常区年内及年际间的平均地表温度变化趋势,推测了可能的地下岩浆囊分布位置及活动特征.研究结果表明,腾冲地区现今地下可能存在3个岩浆囊:第1个位于五合-新华-蒲川-团田一带,面积约为537km2,地温异常最明显;第2个位于朗蒲-热海-马鞍山地区,面积约为226km2,地温异常次之;第3个位于马站-曲石之间,面积约为28km2,地温异常较为明显.3个地温异常区在年内的地表温度变化趋势基本一致,而且周期性明显,均在5～6月份和8～9月份出现2个温度峰.其中朗蒲-热海-马鞍山异常区的地温变化波动最大,可能反映地下岩浆囊地热系统与地表地下水系统的对流交换活动性更强.MODIS夜间月平均地表温度数据得出的结果与测震、GPS形变、He同位素比值及最大相对地热梯度等方法推测的地温异常区范围具有很好的一致性,特别是地温异常区年内温度周期性变化的发现,表明卫星热红外遥感技术应用于地热异常实时监测与研究的巨大潜力.