assessment of the contribution of in situ combustion of coal to greenhouse gas emission based on a comparison of chinese mining information to previous remote sensing estimates greenhouse gas ghg emission from geological sources such as volcanic activity seabed gas hydrate release hydrocarbon seepage as well as uncontrolled combustion of fossil fuels is erratic and difficult to quantify in this paper we assess the ghg emission due to spontaneous combustion of in situ coal deposits coal fires this problem is aggravated by human intervention mining activities which on the other hand allows better constrained estimations and improved reduction strategies provided modern mining practices are employed in this study we present three case studies on coal fire related ghg emission quantification on provincial scale in china and we propose an integrated quantification aimed at the joint analyses of local knowledge geophysical data and remote sensing data with the objective to retrieve unbiased numbers as a first estimate we conclude that the emissions of ghgs from coal fires in china account for well less than 0 22 of all global fossil fuel related co2 emissions most likely even less than 0 1 this is much less than the previously estimated 2 3

impact of underground coal fire on coal petrographic properties of high volatile bituminous coals a case study from coal fire zone no 3 2 in the wuda coalfield inner mongolia autonomous region north china abstract the wuda coalfield located in the inner mongolia autonomous region north china is known as one of china s major source of prime coking coals and a site of well researched and well documented underground coal fires the underground coal fire at the coal fire zone no 3 2 is situated in the active coal mine of suhai tu located in the north westerly part of the wuda coalfield the present paper investigates the impact of the underground coal fire on the coal seam no 10 by application of coal petrographic methods including detailed characteristic of macerals and other coal components maceral analysis microstructural analysis and vitrinite reflectances performed on 1 coal grains lacking impurities microfractures dark oxidation rims 2 on dark rimmed vitrinite as well as 3 on low temperature semi coke the investigated coal seam no 10 represents a high volatile a bituminous coal and is dominated by vitrinite followed by inertinite with minor amounts of liptinite and by non isotropic low temperature semi coke the microstructure of the oxidatively and thermally altered coals is represented by 1 extensive non tectonic microfissures and non tectonic microfractures i e shrinkage microfractures leading to defragmentation of coal grains 2 dark oxidation rims observed at grain margins non tectonic microfissures and microfractures and by 3 devolatilisation micropores random vitrinite reflectances measured in 1 coal grains lacking impurities microfractures and dark oxidation rims and in 2 dark rimmed vitrinite at non tectonic microfissures and fractures reveal significant lateral variations the presence of low temperature semi coke and its marked lower reflectance values are indicative of thermal alteration induced by the underground coal fire in the coal fire zone no 3 2 the results obtained from the performed analyses of organic matter point to both low temperature oxidation and low temperature pyrolysis processes the applied coal petrological approach revealed characteristic changes to the coal s microstructure its petrographic composition as well as to optical properties induced by the underground coal fire

late cretaceous intraplate silicic volcanic rocks from the lake chad region an extension of the cameroon volcanic line silicic volcanic rocks at hadjer el khamis near lake chad are considered to be an extension of the cameroon volcanic line cvl but their petrogenetic association is uncertain the silicic rocks are divided into peraluminous and peralkaline groups with both rock types chemically similar to within plate granitoids in situ u pb zircon dating yielded a mean 206pb 238u age of 74 4 1 3 ma indicating the magmas erupted 10 million years before the next oldest cvl rocks i e 66 ma the sr isotopes i e isr 0 7021 0 7037 show a relatively wide range but the nd isotopes i e 143nd 144ndi 0 51268 0 51271 are uniform and indicate that the rocks were derived from a moderately depleted mantle source thermodynamic modeling shows that the silicic rocks likely formed by fractional crystallization of a mafic parental magma but that the peraluminous rocks were affected by low temperature alteration processes the silicic rocks are more isotopically similar to late cretaceous basalts identified within the late cretaceous basins i e 143nd 144ndi 0 51245 0 51285 of chad than the uncontaminated cvl rocks i e 143nd 144ndi 0 51270 0 51300 the age and isotopic compositions suggest the silicic volcanic rocks of the lake chad region are related to late cretaceous extensional volcanism in the termit basin it is unlikely that the silicic volcanic rocks are petrogenetically related to the cvl but it is possible that magmatism was structurally controlled by suture zones that formed during the opening of the central atlantic ocean and or the pan african orogeny

geodynamic evolution of the pan african belt in central africa with special reference to cameroon the pan african belt in central africa has benefited from the many petrographic structural and geochronological studies in the recent years that have improved our understanding of the belt however those studies have also produced various and often divergent evolutionary models for the belt some of which do not even involve well defined cratons following a review of the available data in cameroon we propose a model of continent continent collision that involved the congo craton and the north central cameroon active margin showing archean to paleoproterozoic inheritances this model is based among others on i the prominent role of the congo craton as demonstrated by the regional extension of external nappes on its northern edge and the concomitant exhumation of the 620 ma granulitic rocks believed to have formed at the root of the collision zone and ii the late development of a strike slip fault system in central cameroon as the result of horizontal movement following the multistage collision

age migrations of anorogenic ring complexes in northern nigeria forty rb sr isotopic measurements on minerals and whole rock samples from 11 anorogenic complexes in northern nigeria complement the evidence for systematic age variations along a series of en echelon ene wsw and n s lineaments following two major fracture directions of extensional deformation in the precambrian basement the new ages presented in this paper confirm our earlier discoveries of a general southerly age trend but substantiate for the first time that major local migrations of magmatic activity were concentrated along at least two ene wsw zones from the overlap in analytical error the age patterns also suggest that contemporaneous anorogenic magmatism may have been locally derived from several simultaneous high level magma chambers connected to a common deeper source different models that have been proposed for the origin of linear mid plate magmatic activity are critically reviewed in our opinion magma generation was most likely initiated in the asthenosphere lithosphere decoupling zone or

permian alkaline undersaturated and carbonatite province and rifting along the west african craton recent work1 2 carried out in north east mali which showed the pan african orogeny 600 myr to be the result of a collision between the passive margin of the west african craton and the active margin of a continental mass situated to the east has also outlined an entire province of alkaline undersaturated ring complexes and carbonatites the first to be discovered in west africa excluding morocco3 4 fig 1 this province is quite distinct petrologically and structurally from the iforas alkaline younger granite province situated in the pan african domain east of the suture which has yielded rb sr whole rock ages of between 560 and 520 myr ref 5 the undersaturated province is located along a well defined rift on the edge of the west african craton which is totally devoid of pan african magmatism we report here that the permian radiometric age obtained for one of these intrusions shows the existence of a hitherto unsuspected important tectono magmatic event in this part of africa which may have far reaching structural implications as well as economic interest

comparison of methods to estimate the rate of co2 emissions and coal consumption from a coal fire near durango co abstract subsurface fires in coal beds consume coal resources and contribute to the global emissions of co2 and air pollutants many of these fires are found in china india indonesia and the united states combustion product gases at these coal fires exit through surface fissures that form over fires these fissures are created when subsurface subsidence causes preexisting fractures in the area to widen fissures act as both inlets for air and exhaust for combustion gases while remote sensing approaches have been used to quantify the rate of coal consumption and co2 emissions at large scale fires that extend over large distances methods for estimating the coal consumption and co2 emissions values based on surface observations are less well established in this paper a coal fire near durango co is described a combination of fissure mapping thermocouple temperatures and a cesium vapor magnetometer survey was used to delineate the aerial extent of the current combustion zone and previously burned zones three methods were then used to estimate combustion rates at an active region at the site in the first method time lapse high resolution topographic surveys were used to relate surface volumetric losses over the active region to coal consumption and rates of co2 emission in the second method measured temperatures gas compositions and dimensions of an exhaust fissure were used in a simple natural convection chimney model to estimate rate values the third method estimated coal consumption and co2 emission rates by measuring the velocity of exhaust gases gas compositions and exhaust fissure dimensions for the second and third methods 13c isotope signatures were used to determine the fractions of co2 that were emitted from coal and ch4 combustion or from co2 in the native gas in the coal seam a flux accumulation chamber was also used to quantify co2 leakage rates from non fissured regions over an active fire region the three methods produced roughly consistent estimates of coal combustion and co2 emission rates

radiative heat transfer in lithospheric geodynamics implications for asthenospheric partial melting and basin modelling concepts abstract in geodynamic models describing basin formation by stretching the base of the lithosphere is commonly defined by a fixed temperature an alternative definition is proposed where the base of the lithosphere is determined by the solidus of mantle rocks some consequences of this definition are illustrated in a one dimensional model the model applies the finite difference method and approximates the temperature regime in the upper 400 km of the earth the model uses temperature dependent thermal conductivity and includes effects from heat storage by partial melting in the mantle low velocity layer mlv radiative heat transfer contributes significantly at elevated temperatures giving rise to a steepening of the thermal gradient below the lithosphere this change in gradient allows the perturbed geotherm to exceed the mantle solidus in a limited depth interval which accounts for the mlv and thus defines the base of the lithosphere in the model variations in thickness of and degree of partial melting in the mlv results from thinning of the overlying lithospheric plate thus the thickness of the mlv is roughly inversely proportional to the thickness of the lithosphere whereas the base of the mlv is almost flat temperature dependent variations in the carrying capacity of the mlv where the main isostatic compensation occurs is proposed as an epeirogenetic agent this effect may be significant and is expressed as an enhancement of the initial subsidence if no preexisting mlv is available a secondary effect occurs as solidification of the mlv ceases a long time 300 ma after stretching and causes slow uplift

void fraction distribution in overburden disturbed by longwall mining of coal voids in overburden disturbed by coal mining provide channels for transfer of heat methane groundwater oxygen exhaust gas and fire fighting materials in the underground environment based on expressions of strata and ground subsidence a group of void fraction distribution models are proposed including porosity in the caved zone the fracture ratio in the bed separation zone and the fissure ratio in the ground subsidence zone combined with a case study of the antaibao coal mine china theoretical calculation and numerical simulation indicate that porosity distribution in the caved zone is u type and the transverse void fractions in the bed separation zone and ground subsidence zone have m type distributions additionally the longitudinal void fraction distribution changes from type to m type along the strike and dip of the coalbed after the complete subsidence of ground the distribution of fractures in the disturbed overburden of the goaf presents a fractured arch and fracture density gradually decreases from arch foot to crown fire prone zones propagating paths of coalbed fires areas prone to water influx and outlets of boreholes used for fire fighting all usually appear around the perimeter of disturbed overburden the transverse void fractions distribution in the bed separation zone changes from type to m type with an increase in the size of the goaf it is suggested that the inlets of gob vent boreholes should be arranged near the center of the bed separation zone in the early stages of longwall mining and around the perimeter in middle to late stages of mining

distribution isotopic variation and origin of sulfur in coals in the wuda coalfield inner mongolia china abstract this paper describes coal petrographic characteristics sulfur abundance distribution and isotopic signature in coals in the wuda coalfield inner mongolia northern china petrographic studies suggest that depositional environment influences petrographic composition the no 9 and no 10 coal seams which are thought to have formed on a tidal delta plain have high collodetrinite contents up to 66 1 indicating enhanced gelification and bacteria activity during coal accumulation and also have the highest sulfur content 3 46 and 3 42 both organic and pyritic sulfur isotope values 12 3 to 5 8 and 18 7 to 1 1 respectively are variable and generally tend to be more negative in high sulfur coals than those in low sulfur coals in the wuda coalfield the negative sulfur isotope values indicate that a large portion of sulfur in the high sulfur coals has a bacterial origin sulfur isotopic compositions and variations within the section were used to propose a model to explain the origin of sulfur in these coals the presence of pyritized rod like bacteria cyanophyte s gelatinous sheaths and degraded algae organic matter suggests that bacteria and perhaps algae may play an important role in the formation of these high sulfur coals

numerical modeling for analyzing thermal surface anomalies induced by underground coal fires abstract coal seams burning underneath the surface are recognized all over the world and have drawn increasing public attention in the past years frequently such fires are analyzed by detecting anomalies like increased exhaust gas concentrations and soil temperatures at the surface a proper analysis presumes the understanding of involved processes which determine the spatial distribution and dynamic behavior of the anomalies in this paper we explain the relevance of mechanical and energy transport processes with respect to the occurrence of temperature anomalies at the surface two approaches are presented aiming to obtain insight into the underground coal fire situation in situ temperature mapping and numerical simulation in 2000 to 2005 annual temperature mapping in the wuda inner mongolia pr china coal fire area showed that most thermal anomalies on the surface are closely related to fractures where hot exhaust gases from the coal fire are released those fractures develop due to rock mechanical failure after volume reduction in the seams the measured signals at the surface are therefore strongly affected by mechanical processes more insight into causes and effects of involved energy transport processes is obtained by numerical simulation of the dynamic behavior of coal fires simulations show the inter relation between release and transport of thermal energy in and around underground coal fires our simulation results show a time delay between the coal fire propagation and the observed appearance of the surface temperature signal additionally the overall energy flux away from the burning coal seam into the surrounding bedrock is about 30 times higher than the flux through the surface this is of particular importance for an estimation of the energy released based on surface temperature measurements finally the simulation results also prove that a fire propagation rate estimated from the interpretation of surface anomalies can differ from the actual rate in the seam

risk assessment of underground coal fire development at regional scale abstract underground coal combustion is a phenomenon known worldwide coal fire monitoring and risk assessment provide important input data for the delineation of coal fire zones and planning of extinguishing activities at present research on coal fire risk focuses mainly on the probability assessment of spontaneous combustion at micro scale based on laboratory investigations of coal molecular structure and composition and their impact on the combustion process coal fire risk assessment at a larger scale such as for mines relies on geological factors and aspects of mining engineering and mine management these scales however are insufficient when considering extinguishing activities in larger areas in order to fill these gaps we studied risk assessment of underground coal fire development ucfd at a regional scale the factors impacting on coal fire development were analyzed under three different aspects coal composition and structure which can influence the direction of underground coal combustion topography and geology which determine the burning environment and climatic conditions and human activities which trigger combustion processes based on this analysis a regional underground coal fire risk assessment ucf ra index system was established it is predicated on the assumption that all indices contribute equally to coal fire risk data layers of 1 km 1 km spatial resolution for each index were calculated and overlaid xinjiang uygur autonomous region was selected as a validation area in view of local conditions and the availability of relevant data the index system was modified the applied method however remained unchanged assessment results are generally satisfying and can be used for monitoring and extinguishing of underground coal fires ucfs in xinjiang

late permian mafic rocks identified within the doba basin of southern chad and their relationship to the boundary of the saharan metacraton the doba gabbro was collected from an exploration well through the cretaceous doba basin of southern chad the gabbro is composed mostly of plagioclase clinopyroxene and fe ti oxide minerals and displays cumulus mineral textures whole rock 40 ar 39 ar step heating geochronology yielded a late permian plateau age of 257 1 ma the major and trace elemental geochemistry shows that the gabbro is tholeiitic in composition and has trace element ratios i e la yb n 7 sm yb pm 3 4 nb y 1 zr y 5 indicative of a basaltic melt derived from a garnet bearing mantle source the moderately enriched sr nd isotopes i e i sr 0 70495 to 0 70839 nd t 1 0 to 1 3 fall within the mantle array i e oib like and are similar to other late permian plutonic rocks of north central africa i e i sr 0 7040 to 0 7070 the enriched isotopic composition of the doba gabbro contrasts with the more depleted compositions of the spatially associated neoproterozoic post pan african within plate granites the contrasting nd isotope composition between the older within plate granites and the younger doba gabbro indicates that different mantle sources produced the rocks and thus may mark the southern boundary of the saharan metacraton

fissure formation and subsurface subsidence in a coalbed fire abstract coalbed fires are uncontrolled subsurface fires that occur around the world these fires are believed to be significant contributors to annual co 2 emissions although many of these fires have been burning for decades researchers have only recently begun to investigate physical mechanisms that control fire behavior one aspect of fire behavior that is poorly characterized is the relationship between subsurface combustion and surface fissures at the surface above many fires long wide fissures are observed at a coalbed fire near durango colorado these fissures form systematic orthogonal patterns that align with regional joints in the upper cretaceous fruitland formation understanding the mechanisms that form these fissures is important as the fissures are believed to play vital roles in sustaining the combustion in the subsurface in some of the coalbed fire simulation models available today these fissures are treated as fixed boundary conditions we argue using data collected field observations and simulation result that there exists a relationship between the location and magnitude of subsidence caused by the fire and the opening of fissures the results presented suggest that fissures are believed to open when subsurface subsidence gives rise to tensile stresses around pre existing joints

mathematical modeling of bituminous coal seams burning contemporaneously with the formation of a variegated beds body partial burning of three bituminous coal seams in the upper silesian coal basin uscb of the czech republic was modeled by the numerical solution of the nonlinear initial boundary value problem for a heat equation it was assumed that a variegated beds body vbb formed around burned out coal seams in addition laboratory results for thermal alteration and oxidation of rocks were considered in addition to thermally altered coal from the vicinity of the variegated beds body models of two variegated beds profiles with three coal seams were derived with femlab using the finite elements method for the discretization in space along with the method of lines maximum temperatures within burned out coal seams ranged from about 350 to 800 c inside the variegated beds body whereas outside the body they were below 350 c it took about 2000 years for all coal seams to burn out the calculated results show very good geologic credibility of the derived model

implications of nb u th u and sm nd in plume magmas for the relationship between continental and oceanic crust formation and the development of the depleted mantle abstract the nb u and th u of the primitive mantle are 34 and 4 04 respectively which compare with 9 7 and 3 96 for the continental crust extraction of continental crust from the mantle therefore has a profound influence on its nb u but little influence on its th u conversely extraction of midocean ridge type basalts lowers the th u of the mantle residue but has little influence on its nb u as a consequence variations in th u and nb u with sm nd can be used to evaluate the relative importance of continental and basaltic crust extraction in the formation of the depleted sm nd enriched mantle reservoir this study evaluates nb u th u and sm nd variations in suites of komatiites picrites and their associated basalts of various ages to determine whether basalt and or continental crust have been extracted from their source region emphasis is placed on komatiites and picrites because they formed at high degrees of partial melting and are expected to have nb u th u and sm nd that are essentially the same as the mantle that melted to produce them the results show that all of the studied suites with the exception of the barberton have had both continental crust and basaltic crust extracted from their mantle source region the high sm nd of the gorgona and munro komatiites require the elevated ratios seen in these suites to be due primarily to extraction of basaltic crust from their source regions whereas basaltic and continental crust extraction are of subequal importance in the source regions of the yilgarn and belingwe komatiites the sm nd of modern midocean ridge basalts lies above the crustal extraction curve on a plot of sm nd against nb u which requires the upper mantle to have had both basaltic and continental crust extracted from it it is suggested that the extraction of the basaltic reservoir from the mantle occurs at midocean ridges and that the basaltic crust together with its complementary depleted mantle residue is subducted to the core mantle boundary when the two components reach thermal equilibrium with their surroundings the lighter depleted component separates from the denser basaltic component both are eventually returned to the upper mantle but the lighter depleted component has a shorter residence time in the lower mantle than the denser basaltic component if the difference in the recycling times for the basaltic and depleted components is 1 0 to 1 5 ga a basaltic reservoir is created in the lower mantle equivalent to the amount of basalt that is subducted in 1 0 to 1 5 ga and that reservoir is isolated from the upper mantle it is this reservoir that is responsible for the sm nd ratio of the upper mantle lying above the trend predicted by extraction of continental crust on the plot of sm nd against nb u

metacraton nature genesis and behavior article i nfo in this paper we show with examples that cratons involved in intercontinental collisions in a lower plate position are often affected by orogenic events leading to the transformation of their margins in some cases craton interiors can also be shaped by intense collisional processes leading to the generation of intra cratonic orogenic belts we propose to call these events metacratonization and the resulting lithospheric tract metacraton metacratons can appear similar to typical orogenic belts i e active margin transformed by collisional processes but are actually sharply different their main distinctive characteristics not all are present in each metacraton are 1 absence of pre collisional events 2 absence of lithospheric thickening high pressure metamorphism being generated by subduction leading to high gradient in strain and meta morphic intensity 3 preservation of allochthonous pre collisional oceanic terranes 4 abundant post collisional magmatism associated with shear zones but not with lithospheric thickening 5 presence of high temperature low pressure metamorphism associated with post collisional magmatism 6 intraconti nental orogenic belts unrelated to subduction and oceanic basin closures reactivation of the rigid but fractured metacratonic lithosphere will cause doming asthenospheric volcanism emplacement and mineral izations due to repetitive mineral enrichments this paper provides several geological cases exemplifying these different metacratonic features in scandinavia sahara central africa and elsewhere a special focus is given to the saharan metacraton because it is where the term metacraton originated and it is a vastly ex panded tract of continental crust 5 000 000 km 2

a type granites from the pan african orogenic belt in south western chad constrained using geochemistry sr nd isotopes and u pb geochronology abstract the zabili granitic pluton sw chad exposed in the mayo kebbi massif is dominated by a coarse grained hornblende biotite granite grading into a fine grained biotite granite along its southern margin petrologic micrographic intergrowth of quartz and alkali feldspars granophyric microstructures the presence of fluorite and bastnaesite as accessory minerals and geochemical data high silica alkalis and fe mg depletions in cao mgo tio 2 high ga nb zr ga al ree depletions in ba sr eu and compatible elements indicate that this pluton consists of a type granites crystallized from hot apatite and zircon saturation temperatures ranging from 744 c to 923 c extremely differentiated magmas u pb zircon geochronology indicates that the magmas crystallized at 567 10 ma and reveals the presence of older neoproterozoic xenocrystic zircons at 668 5 ma in both facies within the fine grained biotite granite discordant zircons with u pb and pb pb ages ranging from neoproterozoic to archaean are also reported the 668 5 ma old zircons are considered to derive from country rocks while discordant zircons characterized by angular shapes internal fractures and inherited cores are likely to represent multi sources detrital crystals that have recorded at least one metamorphic event old pre neoproterozoic zircons are reported for the first time for rocks of the mayo kebbi massif and they attest to the contribution of an old basement likely to be the eastern nigeria basement and or the congo craton involved in a collisional event with a juvenile neoproterozoic crust prior to the emplacement of the zabili granitic pluton initial end values calculated for the zabili pluton range from 2 6 to 7 0 the highest value recorded by one sample from the coarse grained hornblende biotite granite being close to the one of the depleted mantle at 570 ma end 7 4 combining geochronology nd isotopes composition and geochemical modeling leads us to suggest the following model for the origin of the zabili granitic pluton i contribution of juvenile magmas or partial melting of a juvenile basaltic protolith characterized by a short crustal residence time ii interaction of granitic magmas with older continental materials as suggested by the presence of pre neoproterozoic zircons and lower initial end values of the fine grained biotite granite and iii fractional crystallization of feldspars and ferromagnesians to produce the observed geochemical features of sample gab b from which an initial end value of 7 0 has been calculated

looking back at the centralia coal fire a synopsis of its present status abstract centralia is in the anthracite region of eastern pennsylvania the town is part of the western middle field a large synclinorium in columbia and schuylkill counties residents of centralia set fire to a garbage dump in 1962 and in the process ignited the buck mountain coal bed fractured and moderately dipping strata at the site permitted air to circulate into the subsurface thereby promoting combustion and making it difficult to extinguish the centralia fire as the fire advanced during the 1960s 1970s and early 1980s it did so along four fronts however the fire appears to be advancing on only two fronts today the pennsylvania department of environmental protection is currently monitoring the fire fire associated with the first or cemetery front is advancing approximately 20 m year although attempts were made to fight the fire they were unsuccessful for logistical and monetary reasons most residents of centralia relocated with the assistance of funds approved by the u s congress and disbursed by the state of pennsylvania the inexperience of community leaders in working with state bureaucracy contributed to the difficulties of fighting the fire

petroleum geology of cretaceous tertiary rift basins in niger chad and central african republic this overview of the petroleum geology of rift basins in niger chad and central african republic car is based on exploration work by exxon and partners in the years 1969 1991 the work included 50 000 km of modern reflection seismic 53 exploration wells 1 000 000 km2 of aeromagnetic coverage and about 10 500 km of gravity profiles the results outline ten cretaceous and tertiary rift basins which constitute a major part of the west and central african rift system wcars the rift basins derive from a multiphased geologic history dating from the pan african approximately 750 550 ma to the holocene main rifting was probably caused by the stretching and subsidence of african crustal blocks during the breakup of gondwana in the early cretaceous and by r activated plate movements in the early tertiary wcars in the study area is divided into the west african rift subsystem was and the central african rift subsystem cas was basins in niger and chad are chiefly extensional and are filled by up to 13 000 m of lower cretaceous to holocene continental and marine clastics the basins contain five oil 19 43 api and two oil and gas accumulations in upper cretaceous and eocene sandstone reservoirs the hydrocarbons are sourced and sealed by upper cretaceous and eocene marine and lacustrine shales the most common structural styles and hydrocarbon traps usually are associated with normal fault blocks cas rift basins in chad and car are extensional and transtensional and are filled by up to 7500 m of chiefly lower cretaceous continental clastics the basins contain eight oil 15 39 api and one oil and gas discovery in lower and upper cretaceous sandstone reservoirs the hydrocarbons are sourced by lower cretaceous shales and sealed by interbedded lacustrine and flood plain shales structural styles range from simple fault blocks through complex flower structures the main hydrocarbon traps are in contractional anticlines geological conditions favor the discovery of potentially commercial volumes of oil in wcars basins of niger chad and car

coal fires in indonesia abstract indonesia s fire and haze problem is increasingly being ascribed to large scale forest conversion and land clearing activities making way for pulpwood rubber and oil palm plantations fire is the cheapest tool available to small holders and plantation owners to reduce vegetation cover and prepare and fertilize extremely poor soils fires that escaped from agricultural burns have ravaged east kalimantan forests on the island of borneo during extreme drought periods in 1982 1983 1987 1991 1994 and 1997 1998 estimates based on satellite data and ground observations are that more than five million hectares were burned in east kalimantan during the 1997 1998 dry season not only were the economic losses and ecological damage from these surface fires enormous they ignited coal seams exposed at the ground surface along their outcrops coal fires now threaten indonesia s shrinking ecological resources in kutai national park and sungai wain nature reserve sungai wain has one of the last areas of unburned primary rainforest in the balikpapan samarinda area with an extremely rich biodiversity although fires in 1997 1998 damaged nearly 50 of this reserve and ignited 76 coal fires it remains the most valuable water catchment area in the region and it has been used as a reintroduction site for the endangered orangutan the office of surface mining provided indonesia with the capability to take quick action on coal fires that presented threats to public health and safety infrastructure or the environment the us department of state s southeast asia environmental protection initiative through the us agency for international development funded the project technical assistance and training transferred skills in coal fire management through the ministry of energy and mineral resource s training agency to the regional offices giving the regions the long term capability to manage coal fires funding was also included to extinguish coal fires as demonstrations to the indonesian government successful demonstrations obtained visible benefits for a large number of local interests and received overwhelmingly favorable public response this built the public and political support needed to continue this work these successes encouraged the ministry to officially assume the responsibility for coal fire management by decree 1539 20 mpe 1999 the ministry reallocated internal funds to support portions of the immediate suppression projects and committed a portion of the coal royalty fund to provide long term support for coal fire suppression activities coal fires continue to present a serious risk to indonesia s ecosystems population and forest resources the ministry and local governments in east kalimantan are still working on the coal fire inventory it presently contains 164 coal fires but it is far from complete unless these coal fires are managed or extinguished they will add to the already catastrophic cycle of anthropogenic forest fires that further reduce indonesia s forest resources and endangered species while contributing unnecessarily to global carbon emissions

coal fires revisited the wuda coal field in the aftermath of extensive coal fire research and accelerating extinguishing activities abstract the wuda coal mining area in inner mongolia autonomous region china is one of the largest coal fire areas world wide at the same time it is also one of the most extensively researched ones the sub surface coal fires raging in the underground coal seams of the syncline are located directly west of the town of wuda the fires have been mapped in situ based on remote sensing data as well as based on geo physical survey all throughout the years 2001 to 2005 numerous publications depict the situation during that time in the present study we assess the current situation in wuda coal field five years after the last field campaigns under nowadays on going and accelerating extinguishing activities we present the results of coal fire dynamics assessment based on in situ mappings between 2004 and 2010 the analyses of changes in mining infrastructure between 2005 and 2012 as well as land cover change in the area from 2005 to 2012 newest high resolution multispectral and panchromatic quickbird data as well as time series of quickbird data supported this endeavor we furthermore present the result of semi structured interviews undertaken with members of the local mine directorate of the wuda syncline all jointly analyzed data indicate that the wuda coal fires tend to move eastwards within the syncline meaning that they move along the dip of the coal seams to greater depths furthermore mining related infrastructure is clearly moving from the west to the east as well despite large funds spent on fire extinguishing only few fires remain permanently extinct while other fire areas increase in size the former land cover structure in the arid syncline does not exist anymore extinguishing activities have led to a complete turn over of all material in the region the coal fire problem in wuda area remains a pressing one

mineralogical and magnetic characterisation of iron titanium oxides in soils developed on two various basaltic rocks under temperate climate abstract the objective of this study was to characterize alteration processes of iron titanium oxides in andic soils developed on basaltic rocks under temperate climate among the magnetic minerals titanomagnetites are the most abundant and represent the major spinel in basalts in order to understand processes involved in the alteration of iron titanium oxides from basaltic rocks associated to soils two pedons developed on tertiary massive basaltic formations submitted to temperate climate were considered the magnetic minerals have been characterized by studying rock and soil magnetic parameters i e magnetic susceptibility and curie temperature chemical composition was investigated by optical and electron microscopy empa sem eds and by micro proton induced x ray emission pixe because mineralogy of the parent rocks controls those of the soils we have first studied the rocks the thermomagnetic curves obtained on the two studied rocks show that initial titanomagnetite is preserved in one sample mc rock while the other pc rock contains near pure magnetite possibly issued from exsolution process microscopic observations confirm the exsolution lamellae on titanomagnetites and show a cr content gradient in chromian spinel partially enclosed in olivine these observations suggest a deuteric alteration the two profiles exhibit increasing curie temperature between the rocks and soil horizons indicating a transformation of magnetic minerals results emphasize the maghemitization of iron titanium oxides in andic soils in a temperate climate

phase relations in transitional and alkali basaltic glasses from iceland basaltic glasses from the three alkalic areas of iceland snaefellsnes volcanic zone sudurland volcanic zone and vestmannaeyjar volcanic area contain plagioclase olivine clinopyroxene chromian spinel and titanomagnetite as phenocryst phases the glasses are hypersthene to nepheline normative alkali basaltic with feo mgo ratios between 1 4 4 7 olivine ranges in composition from fo90 to fo55 plagioclase from an90 to an50 and clinopyroxene from en45fs10wo45 to en40fs17wo43 clinopyroxene reveals systematic ti al metastable crystallization trends related to the composition of the enclosing glass two types of phenocryst are present in most glasses and show a bimodality in size and composition microphenocryst phases are those most likely to have crystallized from the enclosing glass while macrophenocrysts may have crystallized from a liquid of slightly less evolved composition the glasses show complex phenocryst glass relations which can be related to a polybaric effect the normative glass compositions are related to 2 phase cotectic surfaces in the basalt tetrahedron and define the position of the 3 phase cotectic line in general with increasing feo mgo in the glass the phenocryst assemblages vary from clinopyroxene olivine and plagioclase along a clinopyroxene olivine surface to olivine and plagioclase along an olivine plagioclase surface the normative glass compositions show a deflection from clinopyroxene bearing to clinopyroxene free glasses the appearance of plagioclase together with clinopyroxene and olivine can be explained in the light of experimental investigations of the effect of pressure on phase relations the major element variation of the glasses is interpreted as representing mantle derived magma batches of primary liquids modified to some degree by high 6 kbar and intermediate to low pressure below 3 kbar crystal fractionation towards equilibrium phase relations during ascent and residence in crustal magma chambers the observed deflection in normative compositions of the glasses marks the position of the high pressure 3 phase cotectic line the bimodality in size and composition of plagioclase and olivine phenocrysts can be related to high pressure crystal fractionation in the melt the fe ti basalt glasses from sudurland are believed to be quenched high pressure compositions

the permo jurassic alkaline province of tadhak mali geology geochronology and tectonic significance the tadhak alkaline complexes located along the eastern edge of the west african craton in northeastern mali intrude the 2 ga old basement or the overlying pan african nappes and are covered by cretaceous sediments this magmatic activity was accompanied by doming and rifting northnortheast trending normal faults define two crustal segments exhibiting variously sized 1 km to 17 km intrusive complexes these comprise eroded undersaturated ring complexes with occasional carbonatites in the west and high level phonolitic plugs with shallow intrusive nepheline syenites in the east new rb sr isotopic data indicate 100 ma of within plate magmatic activity in the area without any obvious age progression in addition to the adrar tadhak complex 262 7 ma the following intrusions have been dated tirkine 215 11 ma anezrouf 184 14 ma and tidjerazraze in imanal 161 5 ma a clear break thus exists with the cambrian alkaline granite province of the iforas located on the opposite side of the pan african suture 87sr 86sr initial ratios are similar throughout between 0 7044 and 0 7049 which indicates a bulk earth isotopic composition the conclusion of exclusively mantle origin dupal composition previously demonstrated for the adrar tadhak complex can now be extended to the other complexes this implies repeated tapping of a single mantle source throughout the life of the province the described magmatic and tectonic permo jurassic activity has been triggered by intraplate stresses focussed along the pre existing pan african suture zone together with similar features in europe and africa the permo jurassic tadhak alkaline province heralds the progressive break up of pangaea and the opening of the atlantic ocean

proterozoic basalt dikes in the nain anorthosite complex labrador two sets of proterozoic between 1290 and 1042 ma alkali to transitional basaltic dikes occur sparsely in an area of at least 5000 km2 within the nain anorthosite complex both are compositionally similar in terms of major elements but the set that trends roughly north south hp dikes contains much higher concentrations of incompatible elements than the more abundant dikes that trend roughly east northeast west southwest lp dikes both types have low normative clinopyroxene relative to olivine a characteristic shared with widespread troctolitic rocks in the nain complex low mg numbers and low ni contents suggest that the magmas producing these dikes have undergone extensive fractional crystallization the low normative di content of these dikes suggests that this fractional crystallization occurred at depths equivalent to at least 10 kbar 1000 mpa high equilibration temperatures for coexisting fe ti oxides in the matrices of these dikes indicate that the dikes cooled rapidly and were emplaced near

three fe ti oxide ore bearing gabbro granitoid complexes in the panxi region of the permian emeishan large igneous province sw china the permian 260 ma emeishan large igneous province of sw china contains three nearly identical gabbro granitoid complexes that host giant fe ti oxide deposits the fe ti oxide deposits are within the lower portions of evolved layered gabbroic intrusions and are spatially and temporally associated with a type granitic plutons the 264 3 ma taihe layered gabbroic intrusion hosts a large magmatic fe ti oxide deposit and is coeval with the taihe peralkaline a type granitic pluton which is dated at 261 2 ma within the a type granitic pluton are microgranular enclaves which have compositions intermediate between the gabbro and host granite primitive mantle normalized incompatible element plots show corresponding reciprocal patterns between the mafic and felsic rocks the chondrite normalized ree patterns show eu anomalies changing from positive eu eu 1 5 to 5 9 in the gabbroic intrusion to negative in the enclaves eu eu 0 4 to 0 6 and granites eu eu 0 2 to 0 5 whole rock end t values of the gabbroic intrusion end t 2 5 to 3 3 are similar to those of the enclaves end t 1 0 to 2 0 and granite end t 1 5 to 1 9 whereas the zircon ehf t values of the gabbro ehf t 8 1 0 8 are indistinguishable from those of the granites ehf t 9 2 1 0 suggesting that the parent magmas for all rock types originated from the same mantle source geochemical modeling indicates that the gabbros and granites can be generated by fractional crystallization of a common parental magma similar to high ti emeishan flood basalt the compositional jump from the gabbro to the enclaves is attributed to the crystallization of fe ti oxide minerals the results of this study and other studies suggest that the magmatic conditions for example pressure composition fo2 which led to the formation of at least three fe ti oxide bearing gabbro granitoid complexes were relatively common during the development of the emeishan large igneous province

geomorphology of coal seam fires abstract coal fires occur in underground natural coal seams in exposed surface seams and in coal storage or waste piles the fires ignite through spontaneous combustion or natural or anthropogenic causes they are reported from china india usa south africa australia and russia as well as many other countries coal fires lead to loss of a valuable resource coal the emission of greenhouse relevant and toxic gases and vegetation deterioration a dangerous aspect of the fires is the threat to local mines industries and settlements through the volume loss underground surface collapse in coal fire areas is common thus coal fires are significantly affecting the evolution of the landscape based on more than a decade of experience with in situ mapping of coal fire areas worldwide a general classification system for coal fires is presented furthermore coal seam fire geomorphology is explained in detail the major landforms associated with and induced by these fires are presented the landforms include manifestations resulting from bedrock surface fracturing such as fissures cracks funnels vents and sponges further manifestations resulting from surface bedrock subsidence include sinkholes trenches depressions partial surface subsidence large surface subsidence and slides additional geomorphologic coal fire manifestations include exposed ash layers pyrometamorphic rocks and fumarolic minerals the origin evolution and possible future development of these features are explained and examples from in situ surveys as well as from high resolution satellite data analyses are presented the geomorphology of coal fires has not been presented in a systematic manner knowledge of coal fire geomorphology enables the detection of underground coal fires based on distinct surface manifestations furthermore it allows judgments about the safety of coal fire affected terrain additionally geomorphologic features are indicators of the burning stage of fires finally coal fire geomorphology helps to explain landscape features whose occurrence would otherwise not be understood although coal fire induced thermal anomalies and gas release are also indications of coal fire activity as addressed by many investigators no assessment is complete without sound geomorphologic mapping of the fire induced geomorphologic features

integrating satellite remote sensing techniques for detection and analysis of uncontrolled coal seam fires in north china abstract china is the biggest producer of coal in the world and mines about 1000 mt of raw coal per year approximately 70 of china s energy consumption is covered by coal at the same time it is estimated that about 20 mt of coal are being burnt in uncontrolled coal fires in china each year because these coal fires are spread out over the whole northern part of the country stretching from xinjiang province in the west to the pacific coast in the east it is extremely difficult to keep an overview of the development of known fires as well as of newly developing ones satellite remote sensing offers a powerful tool to observe and monitor such large regions however special methods and techniques have to be derived to accurately detect and monitor near surface coal seam fires in this paper an integrated satellite remote sensing approach is described allowing detection and monitoring of near surface coal seam fires by observing subtle land surface changes induced by the fires these changes include thermal surface anomalies changes in spectral surface characteristics as well as land subsidence caused by the fires the methods comprise the radar interferometric generation of digital elevation models dems for geometric referencing and orthorectification of satellite imagery dedicated analysis of thermal satellite data daytime and nighttime and multispectral analysis of land surface properties as well as the mapping of small scale land subsidence by means of differential radar interferometry it is shown how different satellite remote sensing methods can be synergistically combined to detect analyze and monitor near surface coal seam fires in arid or semiarid areas of north china first results show the successful application of the methods and furthermore a comparison with ground measurements is given while thermal and optical analysis of the fires can be considered robust methods the assessment of coal seam fires using differential radar interferometry still has to be further developed in order to serve as a reliable analysis and monitoring tool within this work a special focus is given to aspects of automation of the coal fire detection and analysis by means of satellite remote sensing in order to allow fire mapping in large areas with only minimal operator interaction

origin of the cameroon line of volcano capped swells abstract swells of the cameroon line a 1000 km long line of 10 volcano capped swells resemble other volcano capped topographic and bathymetric swells on the african plate however individual swells of the cameroon line are about 10 times smaller in area and distinct in being arranged in a straight line half on the continent and half on the ocean floor these peculiarities are here interpreted as related to an underlying mantle plume the 711 plume at lat 7 n long 11 5 e and to the location of this plume area on the bisector of a right angled bend in the continental margin i suggest that circumstances that led to the development of the cameroon line included 1 the stress field in the neighborhood of the right angled bend in the continental margin which favored extension normal to the bisector and 2 formation of a zone of extension aligned with the bisector that joined a point in the lithosphere over the 711 plume to the continental margin the right angled bend in the continental margin h

investigating dynamic underground coal fires by means of numerical simulation summary uncontrolled burning or smoldering of coal seams otherwise known as coal fires represents a worldwide natural hazard efficient application of fire fighting strategies and prevention of mining hazards require that the temporal evolution of fire propagation can be sufficiently precise predicted a promising approach for the investigation of the temporal evolution is the numerical simulation of involved physical and chemical processes in the context of the sino german research initiative innovative technologies for detection extinction and prevention of coal fires in north china a numerical model has been developed for simulating underground coal fires at large scales the objective of such modelling is to investigate observables like the fire propagation rate with respect to the thermal and hydraulic parameters of adjacent rock in the model hydraulic thermal and chemical processes are accounted for with the last process complemented by laboratory experiments numerically one key challenge in modelling coal fires is to circumvent the small time steps resulting from the resolution of fast reaction kinetics at high temperatures in our model this problem is solved by means of an operator splitting approach in which transport and reactive processes of oxygen are independently calculated at high temperatures operatorsplitting has the decisive advantage of allowing the global time step to be chosen according to oxygen transport so that time consuming simulation through the calculation of fast reaction kinetics is avoided also in this model because oxygen distribution within a coal fire has been shown to remain constant over long periods an additional extrapolation algorithm for the coal concentration has been applied in this paper we demonstrate that the operator splitting approach is particularly suitable for investigating the influence of hydraulic parameters of adjacent rocks on coal fire propagation a study shows that dynamic propagation strongly depends on permeability variations for the assumed model no fire exists for permeabilities k 10 10 m 2 whereas the fire propagation velocity ranges between 340 m a 1 for k 10 8 m 2 and drops to lower than 3 m a 1 for k 5 10 10 m 2 additionally strong temperature variations are observed for the permeability range 5 10 10 m 2 k 10 8 m 2