crustal structure of the western part of the southern granulite terrain of indian peninsular shield derived from gravity data abstract the southern granulite terrain sgt is composed of high grade granulite domain occurring to the south of dharwar craton dc the structural units of sgt show a marked change in the structural trend from the dominant north south in dc to east west trend in sgt and primarily consist of different crustal blocks divided by major shear zones the bouguer anomaly map prepared based on nearly 3900 gravity observations shows that the anomalies are predominantly negative and vary between 125 mgal and 22 mgal the trends of the anomalies follow structural grain of the terrain and exhibit considerable variations within the charnockite bodies two dimensional wavelength filtering as well as zero free air based zfb analysis of the geoid corrected bouguer anomaly map of the region is found to be very useful in preparing regional gravity anomaly map and inversion of this map gave rise to crustal thicknesses of 37 44 km in the sgt crustal density structure along four regional gravity profiles cutting across major shear zones lineaments plateaus and other important geological structures bring out the following structural information the bavali shear zone extending at least up to 10 km depth is manifested as a plane separating two contrasting upper crustal blocks on both sides and the gravity high north of it reveals the presence of a high density mass at the base of the crust below coorg the steepness of the moyar and bhavani shears on either side of nilgiri plateau indicates uplift of the plateau due to block faulting with a high density mass at the crustal base the bhavani shear zone is manifested as a steep southerly dipping plane extending to deeper levels along which alkaline and granite rocks intruded into the top crustal layer the gravity high over palghat gap is due to the upwarping of moho by 1 2 km with the presence of a high density mass at intermediate crustal levels the gravity low in periyar plateau is due to the granite emplacement mid crustal interface and the thicker crust the feeble gravity signature across the achankovil shear characterized by sharp velocity contrast indicates that the shear is not a superficial structure but a crustal scale zone of deformation reaching up to mid crustal level

prediction of inflow from overlying aquifers into coalmines a case study in jinggezhuang coalmine kailuan china aquifers overlying coal seams are common water sources in coalmines the unexpected inflow of water can flood mines and threatens the mine safety mine flooding caused by the overlying aquifers has occurred more frequently in recent years in china proposed in this paper is a new method that involves three basic maps and two predictions to tackle this geo hazard this new approach is based on the water abundance in the overlying aquifer and risk analysis of the roof collapse it couples groundwater flow models with rock mechanics analysis the method was successfully applied to prediction of the water intrusion from the overlying aquifer at jinggezhuang coalmine in kailuan china the areas with high risk of water intrusion were delineated visual modflow version 2 61 was used to simulate the inflows at two active working faces the developed approach can predict the total inflow for a working face and the transient inflow as the working face advances

late cenozoic geodynamic evolution of eastern indonesia this paper presents an internally and globally consistent model of plate evolution in eastern indonesia from middle miocene to present time it is centered on the banda sea region located in the triple junction area between the pacific philippine australia and south east asia plates the geological and geophysical data available from indonesia were until recently insufficient to define a unique plate tectonic model in this paper the new data taken into account clearly restrict the possible interpretations owing to a great number of geological geophysical and geochemical studies the major plate boundaries the sunda banda subduction zone to the south the tarera aiduna fault zone and the seram thrust to the east and the sorong fault zone and molucca sea collision zone to the north are now clearly identified the age of the major tectonic structures is also better known geodetic measurements well constrain the present time plate kinematics we also consider the deformation history within eastern indonesia where numerous short lived microplates and their related microcontinents successively accreted to the asiatic margin moreover magnetic anomalies identification of the north and south banda sea basins allows a precise kinematic reconstruction of the back arc opening we used the plates software to test the coherency of our model presented as a series of 4 plate reconstruction maps from 13 ma to the present finally the origin of oceanic domains restored by our reconstruction is discussed

impacts of karst paleo sinkholes on mining and environment in northern china the karst paleo sinkhole is a special geological structure widely found in the coal measures of northern china some paleo sinkholes have high permeability and connectivity making them excellent connectors between the karst aquifer and the coal seam consequently during coal extraction disastrous water inrushes take place frequently which cause severe loss not only in mine submersions and personnel casualties but also in environmental quality locations and the geological and hydrogeological characteristics of paleo sinkholes in northern china are presented in situ drilling and excavation results show that paleo sinkholes have different hydrogeological behaviors in different regions and in different mines based on observed data mining induced strata failure in the seam floor is analyzed the existence of paleo sinkholes increases the floor strata failure zone numerical simulation then is adopted to model coal mining with the effects of both the paleo sinkholes and the water pressure in the confined aquifer analyses of the simulation conclude that the paleo sinkhole induces the increase in the strata failure and deformation these make water inrushes more likely to happen

karst water control and management in the hanxing mining area of north china the hanxing mining area of north china includes three coalfields fengfeng handan and xingtai six or seven coal seams can be commercially mined in permo carboniferous strata among which the lower three accounting for 37 of the total reserves are threatened with karst water from the underlain ordovician limestone hundreds of water inrush accidents have occurred and over 30 mines have been flooded resulting in heavy economic losses and casualties in order to avoid water inrushes and keep the mines safely operational dewatering in the karst aquifer was considered an essential measure unfortunately this practice has caused serious environmental problems such as surface subsidence sinkhole dry spring and water supply shortage on the basis of a series of investigations and tests in the last 20 years an alternative method mining with water pressure has been proposed and is the main focus of this paper by using this method the karst water in the limestone can be preserved to some extent and the coals can be mined in a relatively safe way

a coupled flow stress damage model for groundwater outbursts from an underlying aquifer into mining excavations abstract uncontrolled groundwater outbursts from underlying limestone aquifers into mining excavations present a significant safety challenge for underground coal mining in china although these mining hazards have been known for decades the mechanism for groundwater outbursts remains elusive a fully coupled flow stress damage model is presented to simulate the progressive development of fractures and the associated groundwater flow under incremental loading conditions resulting from mining processes the model is based on classical theories of porous media flow and damage mechanics and importantly links changes in permeability with the accumulation of damage in following the complete stress strain process this coupled flow stress damage model is applied to examine the influence of mining advance on the initiation extension and evolution of an outburst conduit as it develops adjacent to the mine panel fractures are shown to initiate both from the wings of the excavation in shear and from the center of the floor span in extension the growth of the extensile fractures is stunted by the presence of a high stress abutment but the wing fractures extend with one fracture becoming dominant as the dominant fracture develops into the underlying over pressured zone water pressures transmitted along the now open conduit reduce effective stresses and develop rapid heave displacements within the floor the result is a groundwater outburst the modeling is tuned to the results of laboratory experiments and follows the evolution of a viable outburst path observations corroborate with field measurements of permeability pre and post mining and are strong indicators of the veracity of the approach

geobarometry geothermometry and late archean geotherms from the granulite facies terrain of south india geobarometry and geothermometry of garnet bearing chamockitic and metapelitic assemblages from the high grade terrain from south india indicate three fields of equilibration high pressure granulites p 8 3 pm 1 0 kb t 760 pm 40 circ c are restricted to the charnockites and mafic granulites of the north slopes of the nilgiris these place a minimum constraint of 30 km on the maximum thickness of late archean crust medium pressure granulites p 6 4 pm 1 0 kb t 735 pm 40 circ c characterize the charnockites of the central nilgiris and the madras granulites to the east low pressure granulites p 5 0 pm 1 0 kb t 700 pm 20 circ c characterize the charnockites and metapelites south of the bhavani shear zone although migmatites from the kodaikanal massif may reflect somewhat higher temperatures all three granulite fields lie on a metamorphic geotherm piezothermic array which is strongly convex to the temperature axis and characteristic of convective heat transfer

low density co2 rich fluid inclusions from charnockites of southwestern madurai granulite block southern india implications on graphite mineralization abstract characterization of fluid inclusions in graphite bearing charnockites from the southwestern part of the madurai granulite block in southern india reveals a probable relation with the formation and break down of graphite during the high grade metamorphism the first generation monophase pure co 2 inclusions the composition of which is confirmed by laser raman spectroscopy recorded moderate density 0 77 0 87 g cc corresponding to low tapping pressure around 2 kb than that of the peak granulite facies metamorphism the precipitation of graphite as inferred from graphite inclusions and 13 c values of the graphite from the outcrops is interpreted as the cause of this lowering of fluid density an intermediate generation of pseudosecondary inclusions resulted from the re equilibration or modification of the first generation fluids and the co 2 formed is interpreted to be the oxidation product from graphite the youngest generation of fluids which caused widespread retrogression of the granulites is a low temperature 350 c high saline 32 4 52 0 wt nacl equivalent brine carbon isotope data on the graphite from the charnockites show 13 c values ranging from 11 3 to 19 9 suggesting a possibility of mixing of carbon sources relating to earlier biogenic and later co 2 fluid influx combining the information gathered from petrologic fluid inclusion and carbon stable isotope data we model the fluid evolution in the massive charnockites of the southwestern madurai granulite block

rolling open earth s deepest forearc basin the weber deep a 7 2 km deep forearc basin within the tightly curved banda arc of eastern indonesia is the deepest point of the earth s oceans not within a trench several models have been proposed to explain the tectonic evolution of the banda arc in the context of the ongoing ca 23 ma present australia southeast asia collision but no model explicitly accounts for how the weber deep achieved its anomalous depth here we propose that the weber deep formed by forearc extension driven by eastward subduction rollback substantial lithospheric extension in the upper plate was accommodated by a major previously unidentified low angle normal fault system we name the banda detachment high resolution bathymetry data reveal that the banda detachment is exposed underwater over much of its 120 km down dip and 450 km lateral extent having produced the largest bathymetric expression of any fault discernable in the world s oceans the banda arc is a modern analogue for highly extended terranes preserved in the many regions that may similarly have rolled open behind migrating subduction zones

tectonometamorphic evolution of seram and ambon eastern indonesia insights from 40ar 39ar geochronology the island of seram eastern indonesia experienced a complex neogene history of multiple metamorphic and deformational events driven by australia se asia collision geological mapping and structural and petrographic analysis has identified two main phases in the island s tectonic metamorphic and magmatic evolution 1 an initial episode of extreme extension that exhumed hot lherzolites from the subcontinental lithospheric mantle and drove ultrahigh temperature metamorphism and melting of adjacent continental crust and 2 subsequent episodes of extensional detachment faulting and strike slip faulting that further exhumed granulites and mantle rocks across seram and ambon here we present the results of sixteen 40ar 39ar furnace step heating experiments on white mica biotite and phlogopite for a suite of twelve rocks that were targeted to further unravel seram s tectonic and metamorphic history despite a wide lithological and structural diversity among the samples there is a remarkable degree of correlation between the 40ar 39ar ages recorded by different rock types situated in different structural settings recording thermal events at 16 ma 5 7 ma 4 5 ma and 3 4 ma these frequently measured ages are defined in most instances by two or more 40ar 39ar ages that are identical within error at 16 ma a major kyanite grade metamorphic event affected the tehoru formation across western and central seram coincident with ultrahigh temperature metamorphism and melting of granulite facies rocks comprising the kobipoto complex and the intrusion of lamprophyres later at 5 7 ma kobipoto complex rocks were exhumed beneath extensional detachment faults on the kaibobo peninsula of western seram heating and shearing adjacent tehoru formation schists to form taunusa complex gneisses then at 4 5 ma 40ar 39ar ages record deformation within the kawa shear zone central seram and overprinting of detachment faults in western seram finally at 3 4 ma kobipoto complex migmatites were exhumed on ambon at the same time as deformation within the kawa shear zone and further overprinting of detachments in western seram these ages support there having been multiple synchronised episodes of high temperature extension and strike slip faulting interpreted to be the result of western seram having been ripped off from se sulawesi extended and dragged east by subduction rollback of the banda slab

evidence for a submerged and displaced continental borderland north banda sea indonesia the banda sea is separated into two oceanic fragments the south and north banda basins by a large intervening region of ridges and basins called the banda ridges the north and south banda basins appear to be trapped pieces of pre tertiary oceanic crust whereas the banda ridges are a submerged and displaced continental borderland structurally very similar to the southern california offshore borderland analysis of dredged rocks from the banda ridges suggests an origin from western irian jaya

fine details of the wadati benioff zone under indonesia and its geodynamic implications using about 5200 handpicked p s pp sp pcp and scp phases from digitally recorded seismograms together with international seismological centre reported phases we obtain improved hypocentral locations for 1790 earthquakes 983 of them having 90 confidence limits 50 km in the period 1962 to september 1996 along the indonesian subduction zone we use an improved joint hypocenter determination method in which the solution is more stable than in the original one we show that for deep earthquakes use of the core reflected phases is as good as use of depth phases and since such core phases often have larger amplitudes and sharper onsets than the depth phases their arrival times can be read very accurately the positions of the relocated hypocenters show that 1 a portion of the indonesian arc between 110 e and 123 e longitude and deeper than 500 km is dipping southward at an angle of 75 that is in a direction opposite to the upper part of the north dipping slab and 2 east of about 108 e the seismic zone is wider near 670 km than near the 500 km depth the first suggests southward lateral flow in the mantle relative to the plate motion vector here from the contortion of the seismic zone along the eastern portion of the indonesian arc we can estimate the average lateral shear strain rate in the 300 to 670 km depth range to be of the order of 10 16s 1 over the last 10 20 myr

magnetic lineations constraints for the back arc opening of the late neogene south banda basin eastern indonesia abstract the south banda basin is located within eastern indonesia near the triple junction between the eurasian pacific and indo australian plates it is underlain by oceanic crust but its origin and age were not well established it has been interpreted as a mesozoic trapped piece of indian ocean or as a cretaceous eocene basin related to the celebes and sulu basins but a neogene back arc origin was also considered recent geochemical and geochronological studies strongly support the latter hypothesis in this paper we present a new analysis of the magnetic data from the eastern part of the south banda basin the damar basin we used magnetic field measurements collected during nine oceanographic cruises from various institutions looking for magnetic correlation in the time span given from recent geochronological data the comparison between measured profiles and theoretical profiles deduced from the reversals of earth s magnetic field during neogene time allows us to infer an opening of south banda basin during late miocene early pliocene time from 6 5 to 3 5 ma magnetic lineations 2an 2ar 3n 3r 3an and possibly 3ar are recognized with an extinct spreading centre trending ene wsw at least five segments are identified each segment being separated by inactive transform faults perpendicular to the extinct spreading centre a half spreading rate of about 3 cm yr is calculated based on spacing of magnetic lineations the opening history of the basin is discussed the cause of cessation of spreading is likely the arc continent collision dated at about 3 ma however the onset of opening is less determined we suggest that damar basin began to open at about 6 5 ma during magnetic period 3an as an intra arc basin separating the banda volcanic arc to the south from the incipient lucipara volcanic arc to the north the latter was probably created at the beginning of rifting of damar basin as shown by both magnetic and geochronological data the young age of the south banda sea basin is contradictory with its great depth we discuss this problem in view of thermal and tectonic considerations we finally conclude that our magnetic model allows us to more precisely describe the opening of the basin

the mechanism of great banda sea earthquake of 1 february 1938 applying the method of preliminary determination of focal mechanism to a historical event abstract a moment tensor solution is derived for the great 1938 banda sea earthquake one of the largest events for which no definitive focal geometry has been published we apply the method of preliminary determination of focal mechanism which consists of inverting for a moment tensor using exclusively the spectral amplitudes of mantle rayleigh and love waves while discarding the phase information which can be affected by uncertainties in relative timing between historical records from a dataset of 17 records at seven stations we obtain a robust solution featuring a very large moment of 8 37 10 28 dyn cm the centroid depth being constrained around 60 km by minimizing the rms residual of the inversion the method involves an inherent two fold 180 indeterminacy on the orientations of strike and slip which is lifted by the examination of the polarization of long period body waves read individually on original records resulting in a mostly thrust faulting mechanism strike 276 dip 63 slip 70 this approach coupled with more traditional relocation efforts allows a rare glimpse of this exceptional event confirmed here to rank among the 10 largest moments ever published within the extremely complex regional plate tectonics pattern the 1938 event took place in a region of sparse seismicity and away from the presumed locations of block boundaries the deeper than normal focus of the event agrees well with the generally minor level of reported damage and with the generation of a relatively benign tsunami available modern focal mechanisms in its vicinity are too few and too scattered to allow any meaningful comparison but the 1938 event shares its compressional axis with that of the smaller and deeper 1963 shock to the southwest which probably expresses coherence in the regional contortion of the subducting australian plate lithosphere

geodynamics complex subduction eastern indonesia hosts one of the most complex and fascinating tectonic systems on the planet palaeogeographical reconstructions indicate that subduction and deformation of a single slab of oceanic crust created the complicated configuration

subduction of continental lithosphere in the banda sea region combining evidence from full waveform tomography and isotope ratios article i nfo we provide new insight into the subduction of old continental lithosphere to depths of more than 100 km beneath the banda arc based on a spatial correlation of full waveform tomographic images of its lithosphere with he pb nd and sr isotope signatures in its arc volcanics the thickness of the subducted lithosphere of around 200 km coincides with the thickness of precambrian lithosphere as inferred from surface wave tomography while the deep subduction of continental material in continent continent collisions is widely recognised the analogue process in the arc continent collision of the banda region is currently unique the integrated data suggest that the late jurassic ocean lithosphere north of the north australian craton was capable of entraining large volumes of continental lithosphere the banda arc example demonstrates that continental lithosphere in arc continent collisions is not generally preserved thus increasing the complexity of tectonic reconstructions in the particular case of timor the tomographic images indicate that this island is not located directly above the northern margin of the north australian craton and that decoupled oceanic lithosphere must be located at a considerable distance north of timor possibly as far north as the northern margin of the volcanically extinct arc sector the tomographic images combined with isotope data suggest that subduction of the continental lithosphere did not lead to the delamination of its complete crust a plausible explanation involves delamination within the continental crust separating upper from lower crustal units this interpretation is consistent with the existence of a massive accretionary complex on timor island with evidence from pb isotope analysis for lower crust involvement in arc volcanism and with the approximate gravitational stability of the subducted lithosphere as inferred from the tomographic images the subduction of continental lithosphere including crustal material beneath the banda arc indicates that global injection rates of continental material into the mantle may have been underestimated and that continental subduction in arc continent collisions may have contributed more to isotopic signatures of earth s mantle than previously recognised

geological setting and controls on the development of graphite sillimanite and phosphate mineralization within the jiamusi massif an exotic fragment of gondwanaland located in north eastern china abstract china is the world s biggest producer and exporter of graphite and also possesses the world s largest reserves of crystalline graphite one of the main production areas is in northeastern china around jixi in heilongjiang province where graphite sillimanite and phosphate form in original sedimentary horizons within the mashan group the mashan group is composed of khondalitic metasediments and tectonically interleaved orthogneisses all metamorphosed to granulite facies the peak conditions have been calculated at 800 850 c at 5 3 6 2 kb and the p t t path defines a tight clockwise loop involving simultaneous decrease in temperature and pressure falling to 410 490 c at less than 3 kb this metamorphic event is interpreted as resulting from continent continent collision with emplacement of mantle derived mafic magma and possible delamination at the base of the crust metamorphism has been precisely dated at 500 ma using u pb zircon shrimp techniques it appears likely that this terrane formed part of an originally more extensive orogenic belt of late pan african age rocks of similar age are recorded from east antarctica western australia india and sri lanka suggesting that the mashan group was most likely juxtaposed with these areas within gondwanaland the mechanism by which the mashan group arrived at its present position between the siberian and north china cratons is poorly constrained but it appears likely that along with the north china south china and tarim blocks it underwent a northward drift from an initial location off northern australia to finally dock with the siberian craton in the late permian to late jurassic

gps measurements of crustal deformation within the pacific australia plate boundary zone in irian jaya indonesia abstract global positioning system gps measurements made in 1991 1992 and 1993 provide preliminary estimates of slip distribution between the australian and pacific plates in irian jaya indonesia we interpret the gps results with constraints from earthquake mechanisms and slip vectors recent marine surveys and geology three gps sites in southeastern irian jaya show motions that are within 10 mm yr of the expected motion of australia a coast to coast n s baseline along 140 5 e crosses all known onland regions of active deformation but reveals no more than 15 mm yr of shortening and 20 mm yr of left lateral shear in the 27 month period the remaining 40 mm yr of expected convergence between the pacific and australian plates probably occurs at the new guinea trough gps sites on the island of biak at 136 e and at sorong near the western tip of bird s head at 131 e both move 90 100 mm yr in a wsw direction relative to irian jaya but less than 15 mm yr relative to each other these sites are on either side of the sorong fault and demonstrate that it is not presently the major boundary between the australian and pacific plates instead the plate boundary is now south of the sorong and biak sites earthquakes suggest possible structures that accomodate motion between bird s head and australia but the relative importance of them remains uncertain

the vrancea seismic zone and its analogue in the banda arc eastern indonesia abstract it is now widely although not universally accepted that the carpathian orogen marks the site of an arc continent collision that followed the subduction of a now vanished small ocean basin seismic tomography has defined a high velocity anomaly in the upper mantle similar to those associated with subduction zones worldwide there is however no recognisable wadati benioff zone wbz and intermediate depth seismicity is confined to a relatively small roughly cylindrical and vertically elongated region beneath the extreme southeastern corner of the mountain chain there is no consensus in the published studies as to the origin of this vrancea zone the banda sea region of eastern indonesia has sometimes been cited as an analogue for the pannonian transylvanian basin and the enclosing carpathian orocline but at first sight the patterns of seismicity appear very different intermediate depth seismic activity defines a subducted slab that dips north south and west beneath the banda sea a configuration explained as a consequence of the rapid expansion of the sea during roll back subduction if the similar scenario proposed for the carpathians is correct then it is the absence of a carpathian wbz that is actually anomalous closer examination of banda arc seismicity shows that it can be divided into two parts these being a scoop shaped wbz and an adjacent damar zone of much more intense intermediate depth activity at its eastern end the damar zone merges with the wbz but in the west there is evidence for separation from it a plausible explanation of this pattern is that a lower layer of the downgoing slab is peeling away from the remainder the banda australia collision is now almost complete and the activity in the wbz proper can be expected to decrease damar zone activity on the other hand may persist for a much longer period migrating towards the foreland as the detaching layer separates from the remainder of the subducted lithosphere in a few million years the seismicity of the banda region could well resemble the present day seismicity of the carpathian orogen

a reappraisal of the pressure temperature path of granulites from the kerala khondalite belt southern india abstract the kerala khondalite belt kkb of south india is a pan african ca 600 500 ma regional granulite terrain that is composed of charnockites khondalites and migmatitic leptinitic gneiss peak assemblages in the kkb are characterized by orthopyroxene garnet k feldspar magnetite biotite plagioclase quartz in felsic to intermediate rocks and by orthopyroxene cordierite plagioclase quartz or garnet cordierite sillimanite feldspars quartz in semipelites and pelites postpeak reaction textures in these assemblages often involve the production of cordierite and are consistent with a predominantly decompressional pressure temperature history at temperatures in excess of 700 c pressure temperature estimates based on garnet orthopyroxene thermobarometry are in the range of 6 5 7 5 kbar and 860 920 c for localities close to and within the achankovil shear zone a prominent high grade high strain zone on the northeastern margin of the kkb for this northeastern subarea peak t

collision rotation and the initiation of subduction in the evolution of sulawesi indonesia the island of sulawesi indonesia has been shaped and deformed as a result of collision with the sula platform a sliver of continental material from the northern margin of australia new guinea the collision has resulted in rotation of the north volcanic arm of sulawesi and the development of the accretionary wedge of the north sulawesi trench the north sulawesi trench changes laterally from a zone of no active deformation in the eastern part to a wide accretionary wedge in the west early stages of thrusting produce a steep frontal slope 8 16 indicative of relatively high basal shear stress whereas the more advanced western zone of thrusting produces a gentle 2 slope consistent with low basal shear stress reported paleomagnetic data suggest post late eocene counter clockwise rotation of the north arm and the offshore geophysics are explained by a pivot of the north arm with respect to the celebes basin about the eastern end of the arc convergence between the north banda basin and southeast sulawesi is documented by the presence of the tolo thrust its outcrop is strongly arcuate and its accretionary wedge varies in width from a minimum of a few kilometers at each end to a maximum of 30 40 km in the central part the northern end transforms to the leftlateral matano fault with a reported offset of 20 km the southern end of the thrust projects toward the deformed rocks of buton but the structural relations there are not clear the matano fault zone appears to connect westward with the palu fault which forms the western transform of the north sulawesi trench the palu matano fault system acts as a trench trench transform between the north sulawesi trench and the tolo thrust and this system is described by the same rotation pole as that for the sulawesi north arm

sunda banda arc transition incipient continent island arc collision northwest australia the eastern sunda arc represents one of the few regions globally where the early stages of continent arc collision can be studied we studied along the western limit of the collision zone at the sunda banda arc transition where the australian margin collides with the banda island arc causing widespread back arc thrusting we present integrated results of a refraction wide angle reflection tomography gravity modeling and multichannel reflection seismic imaging using data acquired in 2006 southeast of sumba island the composite structural model reveals the previously unresolved deep geometry of the collision zone changes in crustal structure encompass the 10 12 km thick australian basement in the south and the 22 24 kmthick sumba ridge in the north where backthrusting of the 130 km wide accretionary prism is documented the structural diversity along this transect could be characteristic of young collisional systems at the transition from oceanic subduction to continent arc collision citation shulgin a h kopp c mueller e lueschen l planert m engels e r flueh a krabbenhoeft and y djajadihardja 2009 sunda banda arc transition incipient continent island arc collision northwest australia geophys res lett 36 l10304 doi 10 1029 2009gl037533

determining the sula block kinematics in the triple junction area in indonesia by gps summary the point of convergence of the eurasian philippine and australian plates is situated adjacent to the island of sulawesi indonesia the relative plate velocities are estimated by nuvel1 to be 7 to 9 cm yr 1 the complex tectonic mechanism of the triple junction has been studied over a two year period in the course of the geodyssea southeast asian project the gps investigations concentrate on measurements of both the sulawesi eastern indonesia part of the inter regional geodyssea network and a local subnetwork on sulawesi motions derived using data from the subnetwork con rm what the results of the inter regional geodyssea network have suggested that is that current deformation is high and there are distinct deformation domains in the study area on sulawesi the tectonic mechanism of the triple junction has been analysed using a rigid microblock model the triple junction area can best be interpreted as a headland of the australian plate de ected by its collision with the philippine plate thereby identifying the driving forces of the current deformation the northern part is dominated by the sula domain which shows clockwise rotation to the south it is connected to the australian plate by an ensemble of microblocks undergoing counterclockwise rotation in addition to the above our tectonic model permits the determination of the local in uence of two large earthquakes m 7 8 1996 january 1 and m 7 0 1996 july 22 on the motion of the station tomini north sulawesi more observations and a denser gps network are planned in order to study the behaviour of the palu koro fault the main fault on the western limit of the sula block

dehydration melting phenomena in leptynitic gneisses and the generation of leucogranites a case study from the kerala khondalite belt southern india

a note on the depth recurrence and strain release of large vrancea earthquakes the large 1940 vrancea event with body wave magnitude mb 7 3 was investigated in terms of the depth of rupture initiation and extent it was found that the rupture started at 150 km depth and propagated downwards the ruptured zones of the 1977 1986 and 1990 vrancea events were estimated from the distribution of aftershocks located with the joint hypocentre determination method their depth ranges are 90 110 km 130 150 km and 70 90 km respectively because the body wave magnitudes mb were saturated for the last three events and the surface wave magnitudes ms were underestimated not being corrected for depth we chose the moment magnitudes to quantify the four events 7 7 1940 7 4 1977 7 1 1986 and 6 9 1990 respectively the depth interval 110 130 km is found to be unbroken since at least 1838 or 1802 and therefore is expected to accommodate the next large moment release mw 7 0 to 7 4 the strain in the vertical and in the se nw directions is about 0 0003 giving a moderate strain rate of about 10 13 s 1 a correlation between the depth interval of the large events and the year of occurrence in a century is suggested offering a physical basis to the observed quasi cyclicity

carbonic metamorphism of charnockites in the southwestern indian shield a fluid inclusion study abstract forming the southwestern segment of the precambrian granulite facies terrain of the indian shield the kerala region largely comprises charnockites khondalites and migmatitic gneisses fluid inclusions in quartz from the charnockites show distinct distribution patterns consistent with three generations of inclusions the early monophase type records entrapment of high density co2 rich fluid 0 95 1 0 g cm 3 a subsequent monophase type with lower density co2 rich fluid 0 65 0 75 g cm 3 coexists with co2 h2o inclusions having an average degree of filling of 0 2 h2o 20 co2 80 late aqueous biphase inclusions show coexistence with a second category of co2 h2o inclusions showing a degree of filling of 0 6 h2o 60 co2 40 the co2 isochores for early carbonic inclusions yield a pressure range of 4 6 6 1 kbar at granulite facies temperatures of 650 800 c depicting the entrapment of fluids present during or close to the peak metamorphic stage a definite sequence of fluid evolution is traceable for the subsequent stages thus the coexisting co2 and co2 h2o inclusions were entrapped at 510 c and 2 2 kbar marking the waning of carbonic regime and the beginning of aqueous regime at 330 c and 0 4 kbar fluid unmixing occurred leading to the simultaneous entrapment of mixed co2 h2o and h2o inclusions along rehealed microfractures the data presented indicate that the metamorphic fluids evolved from early high density carbonic through mixed carbonic aqueous to late aqueous types the dry granulite mineral assemblage of charnockites is a result of metamorphic equilibration under water deficient and high pco2 conditions

p and s wave travel time tomography of the se asia australia collision zone abstract the southeast se asia australia collision zone is one of the most tectonically active and seismogenic regions in the world here we present new 3 d p and s wave velocity models of the crust and upper mantle by applying regional earthquake travel time tomography to global catalogue data we first re locate earthquakes provided by the standard isc reviewed and isc ehb catalogues using a non linear oct tree scheme a machine learning algorithm that clusters earthquakes depending on their spatiotemporal density was then applied to significantly improve the consistency of travel time picks we used the fast marching tomography software package to retrieve 3 d velocity and interface structures from starting 1 d velocity and moho models synthetic resolution and sensitivity tests demonstrate that the final models are robust with p wave speed variations 130 km horizontal resolution generally recovered more robustly than s wave speed variations 220 km horizontal resolution the retrieved crust and mantle anomalies offer a new perspective on the broad scale tectonic setting and underlying mantle architecture of se asia while we observe clear evidence of subducted slabs as high velocity anomalies penetrating into the mantle along the sunda arc banda arc and halmahera arc we also see evidence for slab gaps or holes in the vicinity of east java in the banda arc we image the slab as a single curved subduction zone furthermore a high velocity region in the mantle lithosphere connects northern australia with timor and west papua the s wave model shows broad scale features similar to those of the p wave model with mantle earthquakes generally distributed within high velocity slabs the high velocity mantle connection between northern australia and the eastern margin of the sunda arc is also present in the s wave model while the s wave model has a lower resolution than the p wave model due to the availability of fewer paths it nonetheless provides new and complementary insights into the structure of the upper mantle beneath southeast asia

seismic response to recent tectonic processes in the banda arc region abstract internal structure and recent tectonics of the geologically complex banda arc region latitude 1 9 s longitude 124 135 e have been studied by means of the analysis of global seismological data relocated hypocentral determinations of the international seismological center ehb data and fault plane solutions of the global centroid moment tensor project have been used together with previously published information on regional geology and dynamics the analysis considered earthquakes in the lithospheric wedges above subducting slabs and earthquakes in the uppermost portions of the wadati benioff zones focal depth

seismic moment release during slab rupture beneath the banda sea summary the highest intermediate depth moment release rates in indonesia occur in the slab beneath the largely submerged segment of the banda arc in the banda sea to the east of roma termed the damar zone the most active western part of this zone is characterized by downdip extension with moment release rates 10 18 nm yr 1 per 50 km strike length implying the slab is stretching at 10 14 s 1 consistent with near complete slab decoupling across the 100 200 km depth range differential vertical stretching along the length of the damar zone is consistent with a slab rupture front at 100 200 km depth beneath roma propagating eastwards at 100 km myr 1 complexities in the slab deformation field are revealed by a narrow zone of anomalous in plane p axis trends beneath damar where subhorizontal constriction suggests extreme stress concentrations 100 km ahead of the slab rupture front such stress concentrations may explain the anomalously deep ocean gateways in this region in which case ongoing slab rupture may have played a key role in modulating the indonesian throughflow in the banda sea over the last few million years

humite and scapolite bearing assemblages in marbles and calcsilicates of dronning maud land antarctica new data for gondwana reconstructions this study investigates marbles and calcsilicates in central dronning maud land cdml east antarctica the paleogeographic positioning of cdml as part of gondwana is still unclear however rock types mineral assemblages textures and p t conditions observed in this study are remarkably similar to the kerala khondalite belt in india the cdml marbles and calcsilicates experienced a pan african granulite facies metamorphism at c 570 ma and an amphibolite facies retrogression at c 520 ma the highest grade assemblage in marbles is forsterite spinel calcite dolomite in calcsilicates the assemblages are diopside spinel diopside garnet scapolite wollastonite clinopyroxene quartz scapolite anorthite calcite clinopyroxene wollastonite these assemblages constrain the peak metamorphic conditions to 830 20 c 6 8 0 5 kbar and xco2 0 46 during retrogression highly fluoric humite group minerals humite clinohumite chondrodite replaced forsterite and garnet rims formed at the expense of scapolite during reactions with wollastonite calcite or clinopyroxene but without involvement of anorthite metamorphic conditions were about 650 c 4 5 0 7 kbar 0 2 xco2fluid 0 36 and the co existence of garnet clinopyroxene wollastonite and quartz constrains fo2 to fmq 1 5 log units mineral textures indicate a very limited influx of h2o rich fluid during amphibolite facies retrogression and point to significant variations of fluid composition in mm sized areas of the rock gypsum was observed in two samples it probably replaced metamorphic anhydrite which appears to have formed under amphibolite facies conditions the observed extensive anorogenic magmatism anorthosites a type granitoids and the character of metamorphism between 610 and 510 ma suggest that the crustal thermal structure was characterized by a long lived 50 100 ma rise of the crustal geotherm probably caused by magmatic underplating

a seismological study of the eastern new guinea and the western solomon sea regions and its tectonic implications summary we use new and pre existing seismological data to study the neotectonics and the state of stress in the seismic zones of eastern papua new guinea and the western solomon sea regions earthquake hypocentres for the period 1964 90 were relocated using the joint hypocentre determination jhd technique we show that the t axes of earthquakes in the 100 250km depth range beneath eastern papua new guinea are aligned parallel to the seismic zone with no seismicity below 250 km this intermediate depth seismic zone forms an inverted u shaped zone with limbs dipping to the north and south and is interpreted to be seismicity along the subducted solomon sea plate the northern and southern limbs of the seismic zone are connected by a flattened zone of seismicity which is marked by predominantly strike slip and a few normal fault mechanisms we suggest that the solomon sea plate at depth beneath the finisterre mountains is no longer influenced by the tectonic forces acting at the surface but breaking up and sinking under its own gravitational forces a significant north dipping seismic zone is imaged above the deeper seismic zone this feature characterized by thrust mechanisms extrapolates to the surface along the ramu markham valley and is attributed to the ramu markham fault rmf the rmf has an average dip of about 40 to the north east but its detailed geometry would appear to be complex the rmf is interpreted to ramp steeply in the uppermost 10 20 km flattening out sharply to a dip of 15 at a depth of about 20km the rmf marks the suture between the finisterre terrane and the australia new guinea plate and may extend to a depth of 90km beneath the western limit of the finisterre mountains there is a clear gap in seismicity between the rmf and the deeper solomon sea plate seismic zone beneath the finisterre mountains which together with the alignment of the t axes of earthquakes along the seismic zone at depths 100km indicates that these are indeed two distinct features the seismicity in the depth range 50 80 km along the new britain arc follows the trend of the 2000m bathymetric contour of the new britain trench and the finsch deep far more closely than it does the trend of the surface plate boundary indicating that the increase in the distance between the solomon sea south bismarck plate boundary and the active volcanos along the new britain arc west of 6 83 150 o e is only a shallow phenomenon and does not reflect the geometry of the solomon sea plate at depths greater than 50 km

rough evaluation of the water inflow discharge in abandoned mining tunnels using a simplified water balance model the case of the cogne iron mine aosta valley nw italy one of the most complex hydrogeological problems in the design and maintenance of drainage systems in abandoned mining sites is quantifying the maximum water infiltration and therefore the amount that is potentially drainable by the tunnels this problem is compounded when water inflow data are limited or lacking the aim of the study was to present a single but reliable model for making this evaluation this model was applied to the case history of the abandoned cogne iron ore mining complex western alps aosta valley region nw italy the study focused on quantifying the amount of water infiltrating into the mine drifts using a water balance model in a geographic information system gis environment in the model five different infiltration scenarios were calculated including a detailed analysis of rainfall data snow density and thickness snow water equivalent calculation and melting periods the maximum water discharge that could affect the mine tunnels was therefore determined under several scenarios of normal precipitation conditions and during heavy rainfall including the case of the cogne valley flood in october 2000 used as a reference for the limit conditions taking into account the various approximations considered the results can be considered a good indication of the magnitude of the total amount of water that should be drained out through abandoned mine drifts and in the drainage network during implementation of final closure of the mine

the formation of sinkholes in karst mining areas in china and some methods of prevention mining of coal lead and zinc gold and iron ore deposits in karst areas has been closely associated with sinkholes in china surface collapse causes an increase in mine water drainage and the possibility of major water inflow from karst aquifers which threatens the environment in mining areas and endangers mine safety the origin of such sinkholes is analyzed quantitatively in this paper and a combination of factors including soil weight buoyancy suffosion process and vacuum suction can contribute to surface subsidence the key measures to prevent sinkholes in mining areas are to control the amount of mine drainage reduce water level fluctuation seal off karst conduits and subsurface cavities in the overlying soil prevent water inflow and to increase gas pressure in the karst conduits

an application of hydraulic tomography to a deep coal mine combining traditional pumping tests with water inrush incidents abstract water inrush incidents threaten the safety of coal mining understanding of hydrogeologic parameter distributions is critical for preventing water related hazards in coal mines during the deep mining 1000 m under the north china plain water from water bearing strata discharges into coal seams through geologic conduits i e water inrush due to the fractured zone under the floor of working faces in this study a water inrush incident was exploited as an active stimulus a 3d groundwater flow model was built for the eighth member of the middle ordovician system in xingdong coal mine using this model and an inverse approach we first checked if the data from the incident and an independent pumping test carry non redundant information about the heterogeneity of the mine afterward we combined these datasets to conduct a large scale approximately 10 km hydraulic tomography ht analysis the estimated hydraulic conductivity distribution from the ht analysis is found consistent with the distribution of known geologic faults that is a cluster of faults is characterized as a high conductivity zone a high conductivity zone is identified at locations close to the water inrush location which is the high cement consumption zone during the grouting project finally results of this study promote exploiting the water inrush events as a ht survey for mapping geologic structures over a large area

stratigraphic constraints on suture models for eastern indonesia abstract although collision in eastern indonesia is now accreting the australian continent to southeast asia the small north and south banda oceanic basins within the suture zone are interpreted as late cenozoic extensional features stratigraphic columns from the surrounding islands conform to one of three generalised patterns two of which can be related to the margins of se asia sundaland and the australian continent respectively the third system which is dominant in the outer banda arc and eastern sulawesi is associated with a microcontinent that was rifted from australia in the jurassic drifted northwards ahead of australia in the cretaceous and collided with the sundaland margin in the paleogene subsequent collapse of the resulting collision orogen led to rapid extension and the formation of the banda sea behind the outer banda arc thrust belt eastern indonesia thus duplicates a pattern familiar in the mediterranean the tertiary compressional structures of the region cannot be explained solely in terms of the most recent collision which began only in the pliocene

tertiary tectonic and magmatic evolution of western sulawesi and the makassar strait indonesia evidence for a miocene continent continent collision

global trench migration velocities and slab migration induced upper mantle volume fluxes constraints to find an earth reference frame based on minimizing viscous dissipation sincetheadventofplatetectonicsdifferentglobalreferenceframeshavebeenusedtodescribethemotionofplatesandtrenches thedifferencein plate motion and trench migration between different reference frames can be substantial up to 4 cm yr this study presents an overview of trench migration velocities for all the mature and incipient subduction zones on earth as calculated in eight different global reference frames calculations show that irrespective of the reference frame 1 trench retreat always dominates over trench advance with 62 78 of the 244 trench segments retreating 2 the mean and median trench velocity are always positive retreating and within the range 1 3 1 5 cm yr and 0 9 1 3 cm yr respectively 3 rapid trench retreat is only observed close to lateral slab edges b1500 km and 4 trench retreat is always slow far from slab edges n2000km thesecalculationsarepredictedbygeodynamicmodelswithavaryingslabwidth inwhichplatemotion trenchmotionandmantleflow result from subduction ofdense slabs suggesting that trenchmotion is indeedprimarily drivenby slab buoyancyforces andthat proximity to alateral slab edge exerts a dominant control on the trench migration velocity despite these four general conclusions significant differences in velocities between such reference frames remain it is therefore important to determine which reference frame most likely describes the true absolute velocities togetanunderstandingoftheforcesdrivingplatetectonicsandmantleconvection itishereproposedthat basedonfluiddynamicconsiderationsand predictions from geodynamic modelling the best candidate is the one which optimises the number of trench segments that retreat minimizes the trench perpendicular trench migration velocity vt in the centre of wide n4000 km subduction zones maximizes the number of retreating trench segments located within 2000 km of the closest lateral slab edge minimizes the average of the absolute of the trench perpendicular trench migration velocity vt forallsubductionzonesonearth andminimizestheglobaluppermantletoroidalvolumeflux to thatresultsfromtrenchmigration and associated lateral slab migration i e slab rollback or slab roll forward calculations show that these conditions are best met in one particular indo atlantic hotspot reference frame where 75 of the subduction zones retreat vt in the centre of wide subduction zones ranges between 3 5 and 1 8 cm yr 83 of the trench segments located within 2000 km of the closest lateral slab edge retreat the average of vt is 2 1 cm yr and to 456 km 3 yr lower limit and 539 km 3 yr upper limit inclusion of all the incipient subduction zones on earth results in slightly greater fluxes of 465 km 3 yr lower limit and 569 km 3 yr upper limit it is also found that this reference frame is close to minimizing the total sub lithospheric uppermantlevolumeflux k associatedwithmotionofcontinentalkeelslocatedbelowthemajorcratons itisstressed however that kisanorder of magnitude smaller than to and thus of subordinate importance in conclusion the indo atlantic hotspot reference frame appears preferable for calculating plate velocities and plate boundary velocities

fluid evolution characteristics and piezothermic array of south indian charnockites the precambrian granulite fades metamorphism that gave rise to the charnockites of south india involved the activity of chemically distinct fluids that evolved progressively from early high density carbonic 1 0 0 95 g cm3 through moderate density carbonic 0 75 0 65 g cm3 and mixed carbonic aqueous to low salinity and moderate density aqueous 0 88 0 65 g cm3 types the pressure temperature conditions recorded by fluid inclusions define a piezothermic array that is characterized by higher convexity toward the temperature axis than the array defined by the locus of metamorphic geotherms obtained from mineral assemblages the convexity depicts a fast rate of uplift that exceeded the rate of heat transfer the carbonic metamorphism resulting in the formation of charnockites was achieved under high pco2 conditions by the transfer of juvenile co2 from the upper mantle

nature and evolution of metamorphic fluids in the precambrian khondalites of kerala south india abstract the precambrian charnockite khondalite groups of rocks in the kerala region constitute a significant part of the granulite facies terrain of south india the khondalites comprise interlayered garnet biotite and garnet sillimanite gneisses analyses of coexisting mineral pairs from these rocks give temperatures of 869 50 c garnet biotite and 862 75 c garnet cordierite a garnet orthopyroxene thermometer records 644 c for charnockite intercalated with the khondalites fluid inclusion studies show that the early fluids were high density co 2 rich type 0 97 g cm 3 the graphite bearing garnet sillimanite gneisses show traces of ch 4 also the early high density regime was followed by moderate density co 2 0 73 0 75 g cm 3 and mixed co 2 h 2 o 0 70 g cm 3 fluids a dominant aqueous regime with h 2 o densities in the range 0 79 0 57 g cm 3 manifested during the waning stage a combination of data from solid and fluid phases denote that the high density co 2 rich inclusions entrapped at a pressure of 6 1 kbar represent the fluid phase present at or near the peak of metamorphism the delineated fluid evolution path corresponds to the piezothermic array of khondalites and is similar in form to that of the charnockites the array is characterised by high convexity towards the temperature axis which depicts a fast rate of uplift that exceeds the rate of heat transfer

melting of albite and dehydration of brucite in h 2 o nacl fluids to 9 kbars and 700 900 c implications for partial melting and water activities during high pressure metamorphism the melting reaction albite solid h2o fluid albite h2o melt has been determined in the presence of h2o nacl fluids at 5 and 9 2 kbar and results compared with those obtained in presence of h2o co2 fluids to a good approximation albite melts congruently at 9 kbar indicating that the melting temperature at constant pressure is principally determined by water activity at 5 kbar the temperature t mole fraction x h2o melting relations in the two systems are almost coincident by contrast h2o nacl mixing at 9 kbar is quite non ideal albite melts 70 c higher in h2o nacl brines than in h2o co2 fluids for x h2o 0 8 and 100 c higher for x h2o 0 5 the melting temperature of albite in h2o nacl fluids of x h2o 0 8 is 100 c higher than in pure water the p t curves for albite melting at constant h2o nacl show a temperature minimum at about 5 kbar water activities in h2o nacl fluids calculated from these results from new experimental data on the dehydration of brucite in presence of h2o nacl fluid at 9 kbar and from previously published experimental data indicate a large decrease with increasing fluid pressure at pressures up to 10 kbar aqueous brines with dissolved chloride salt contents comparable to those of real crustal fluids provide a mechanism for reducing water activities buffering and limiting crustal melting and generating anhydrous mineral assemblages during deep crustal metamorphism in the granulite facies and in subduction related metamorphism low water activity in high pressure temperature metamorphic mineral assemblages is not necessarily a criterion of fluid absence or melting but may be due to the presence of low a h2o brines

investigations of water inrushes from aquifers under coal seams in many coal mines limestone confined aquifers underlie coal seams during coal extraction from these mines water inrushes occur frequently with disastrous consequences this paper introduces the hydrogeological conditions of the coal mines and the potential water inrush disasters from aquifers under coal seams it then presents the water inrush mechanism the main factors which control water inrushes include strata pressure mining size geologic structures and the water pressure in the underlying aquifer analysis shows that reduction of confinement due to mining is the major cause of the water conducting failure in the floor strata the depth of the failure zone is strongly dependent on the mining width this paper also presents field observation results of the water conducting failure in the floor strata and applies the finite element method coupled with stress dependent permeability to analyze hydraulic conductivity enhancement due to coal extraction finally theoretical and empirical methods to predict water inrushes are given and technical measures for improving mine design and safety for coal extraction over aquifers are presented these measures include fault and fracture grouting and mining method modification such as changing long wall to short wall mining

subduction in eastern indonesia how many slabs abstract seismicity associated with arc continent collision in eastern indonesia testifies to past north directed subduction of indian ocean lithosphere beneath the banda sea the complex patterns of deep seismicity have been cited as evidence for simultaneous south directed subduction at the northern margin of the sea but this interpretation has not been universally accepted recently available recomputations of hypocentre locations have provided increased resolution of eastern indonesian wadati benioff zones wbzs shallow to intermediate depth seismic activity around the banda arc appears to support models involving subduction of two separate and distinct lithospheric slabs but between 150 and 500 km the wbz has a continuous shoehorn shape this shape confirms the presence of subducted lithosphere beneath seram in the north as well as beneath timor in the south is incompatible with independent subduction of two unconnected plates and implies rapid eastwards retreat of the subduction trace across a now vanished northern spur of the indian ocean this roll back is unlikely to have been driven by local gravitational forces alone and may have been sustained by injection behind the banda slab of asthenospheric material escaping from the molucca sea arc arc collision

southeast asia new views of the geology of the malay archipelago southeast se asia is surrounded by subduction zones causing intense seismicity and volcanic activity subduction has been the principal tectonic driver of collisions that caused the growth of continental se asia and most recently the collision of australia with se asia the western part of se asia sundaland is a heterogeneous and weak region reflecting processes that can be observed today in the east where there are subduction zones in different stages of development a close relationship between subduction rollback and extension has caused dramatic elevation of land exhumation of deep crust and spectacular subsidence of basins observable with remotely acquired images and seismic and multibeam data obtained from oil exploration new dating indicates that subsidence and uplift occurred at high rates during short time intervals laboratory studies modeling and reconstructions provide valuable insights but field based studies continue to present surprises and new discoveries essential for interp

hydrogeological analysis and salvage of a deep coalmine after a groundwater inrush this paper presents a case history of the permanent salvage of the sanhejian coalmine in china after a sudden groundwater inrush which includes emergency responses hydrogeological analyses and design and performance of bulkheads the inrush accident occurred in october 2002 in the mined out area with a high water pressure of 7 6 mpa and a high water temperature of 51 c the emergency response quickly followed up to provide the time required to perform a detailed hydrogeological analysis to identify the source and pathway of groundwater the sanhejian coalmine is geologically located in the tengxian anticline hydrogeological setting the sunshidian fault the northern boundary of the mine was assumed impermeable in the original hydrogeological report after the accident and hydrogeological analysis this assessment was revised and the fault was considered to be permeable the sunshidian fault connects the strata in the mine and the excellent water productive middle ordovician majiagou formation in the core of the tengxian anticline it was concluded that the water inrush was from the underlying ordovician karst aquifer and the pathway was a hidden tectonic structure in the strata overlying the aquifer this assessment served as the guideline for salvaging the mine in this project after a detailed technical and economic analysis a concrete bulkhead design was selected from several alternatives including dewatering and surface grouting the performance of the bulkheads has been sufficient for the last 6 years since their construction this case history shows that the hydrogeological analysis plays an essential role in successfully salvaging the coalmine from the water inrush by identifying the source and pathway of groundwater

orogeny in arc continent collision the banda arc and western new guinea eastern indonesia contains a modern continent island arc collision that demonstrates how a complex juxtaposition of continental and oceanic elements can occur in an orogenic belt shallow earthquakes show that strike slip faulting transports large crustal blocks into out of and along the collision zone while crustal shortening and thickening occur by steep angle thrust faulting near the strike slip faulting whereas strike slip faulting is paramount in positioning australian continental rocks so as to enclose the oceanic and island arc rocks of eastern indonesia its role may be overshadowed by the contemporaneous thrusting and may confuse geologic interpretations of the resulting orogenic belt

mineral thermobarometry and fluid inclusion studies on the closepet granite eastern dharwar craton south india implications to emplacement and evolution of late stage fluid the closepet granite cpg a spectacularly exposed magmatic body along with other intrusive bodies to the east of it typifies the late archean granitic activity in the eastern dharwar craton edc south india in the present study the p t fo2 conditions of emplacement and physico chemical environment of the associated magmatic hydrothermal regime of cpg have been retrieved on the basis of mineral chemical and fluid inclusion studies amphibole plagioclase ti in amphibole and ti in biotite geothermometers along with al in amphibole geobarometer have been used to reconstruct the emplacement temperature and pressure conditions in the majority of the pluton estimated temperatures of emplacement of cpg vary from to 740 to 540 c a variation of pressure from 4 8 to 4 1 kilo bars corresponding to this temperature range was obtained while there is a faint south to north negative gradient in temperature the variation of pressure does not seem to follow this trend and indicates more or less same crustal level of emplacement for the body between ramanagaram kalyandurga segment extending for about 230 km mineral chemistry of biotite indicates crystallization of cpg under high oxygen fugacity conditions mostly above qfm buffer with no clear spatial variation in the fugacity of halogen species in the late stage magmatic fluid it may be surmised that barring the southernmost part of cpg there is no perceptible variation in the physicochemical environment of emplacement fluid inclusion studies in the granitic matrix quartz and pegmatite vein quartz show dominance of h2o and h2o co2 fluids respectively in them the difference in the fluid characteristics is interpreted in terms of the initial loss of co2 rich fluid from granitic magma and aqueous rich nature during the later stages of crystallization of quartz the exsolved co2 rich fluid was responsible in formation of the later quartz and pegmatitic veins at different crustal levels and also possibly was responsible in co2 induced metamorphism charnockitization preserved in the kabbaldurga area in the southernmost part the fluid characteristics in the vast tract of cpg revealed from mineral chemical and fluid inclusion studies make a case for its involvement in gold mineralization in the schist belts in edc

magmatic evolution of sulawesi indonesia constraints on the cenozoic geodynamic history of the sundaland active margin abstract tertiary and quaternary magmatic rocks from west sulawesi record the complex history of part of the sundaland margin where subduction and collision have been and are still active the present study based on petrographic data major and trace element chemistry and 40 k 40 ar dating aims to document the age and chemical characteristics of the magmatic formations from west sulawesi and to determine the corresponding constraints on the geodynamic evolution of the sundaland border the west sulawesi magmatic province includes the south arm of sulawesi ujung pandang area the western part of central sulawesi with the toraja and palu areas and finally the north arm extending from palu to manado which includes the tolitoli and manado areas paleocene magmatic activity seems to be restricted to an episode of calc alkaline magmatism in the ujung pandang area 61 59 ma the major eocene 50 40 ma magmatic event is tholeiitic and is documented in all areas except in ujung pandang it led to the emplacement of tholeiitic pillow lavas and basaltic dykes of back arc basin bab affinity these rocks are potential equivalents to the celebes sea basaltic basement from oligocene to miocene magmatic eruptions produced successively island arc tholeiitic iat and calc alkaline ca rock series the youngest iat activity occurred around 18 ma in the central part palu area and around 14 ma in the north arm tolitoli area while ca magmas were emplaced in the north arm at ca 18 ma tolitoli and manado areas typical calc alkaline activity resumed only in the north arm tolitoli and manado areas during the late miocene 9 ma and is still active in the manado region in other areas palu toraja and ujung pandang areas an important and widespread magmatic event occurred between 13 and 10 ma and emplaced k rich magmas either silica undersaturated alkali potassic basalts ak ultrapotassic basanites uk or shoshonites sh k rich activity continued in the south until the pleistocene 0 77 ma with alkali potassic ultrapotassic and shoshonitic magmas in central sulawesi toraja and palu areas the most recent magmatic event occurred between 6 5 and 0 6 ma the corresponding products are granitic rocks and widely distributed rhyolitic pyroclastic flow deposits all these rocks are acidic in character sio 2 60 with trace element and isotopic signatures sr nd pb typical of a strong continental imprint the most striking tectonic implication of this magmatic evolution is that west sulawesi can no longer be considered as a typical magmatic arc as previously assumed with the exception of the manado area beneath which subduction is still active calc alkaline and island arc tholeiitic lavas and plutonics are volumetrically minor with respect to k rich magmas their occurrence through time is also fairly restricted mostly to the period between 30 and 15 ma another important feature is the occurrence of island arc tholeiitic and calc alkaline magmas crosscutting an older terrane of bab affinity the tinombo formation manado tolitoli and palu areas as this formation is being regarded as an equivalent to the celebes sea floor the most likely explanation for this feature is the hypothesis of tectonic erosion linked to the nw dipping subduction beneath the north arm the late miocene high k magmatic activity in central and south sulawesi reflects the prevalence of a post collisional tectonic regime following the docking of microcontinents of australian origin to central sulawesi during neogene times the incompatible element enriched character of these high k rocks might reflect their derivation from a mantle source enriched through metasomatism related to a previous subduction event such a model cannot account for the plio pleistocene cak magmatism of central sulawesi the acidic composition of which does not support a derivation from an ultrabasic source the trace element patterns of the cak rocks are very similar to those of the high grade metamorphics of central sulawesi suggesting that the latter might represent their possible source such an anatectic model implies a collisional to post collisional tectonic regime limited to central sulawesi while a post subduction regime prevailed in the south

coupled simulation optimization model for draining confined aquifer via underground boreholes to prevent water inrush of coal mines in north china groundwater drainage is commonly applied by coal mines to prevent water inrush from confined aquifers underlying coal seams which can also cause environmental problems the previous research has proposed dual factor and triple factor models to manage water resources in coal mines however three features of draining confined water via underground boreholes have not been sufficiently considered the geological heterogeneity workface relocation and draining principle of underground boreholes this paper aims to incorporate the three features into an optimization model for underground borehole draining a novel mathematical model was proposed that included the three features a workflow framework was proposed to conduct the optimization based on gis and a coupled simulation optimization approach an algorithm was designed and a c program was developed to couple feflow with a modified genetic algorithm to search for the optimal solution the application to the liangbei coal mine indicates that the aquifer has been over drained about 69 and 36 of the water could be saved in the first two stages the total draining rate significantly changes with the workface relocation the boreholes located at the headwaters and closer to the workface that are mined now or in the next stage usually have higher rates than other boreholes the distribution of the draining rates is also related to the workface geometry and the aquifer anisotropy the optimization should be repeated as new monitoring data are acquired

structural styles and tectonic evolution of the seram trough indonesia abstract the seram trough is located in the northern part of the banda arc australian collision zone in eastern indonesia and is currently the site of contraction between the bird s head of new guinea and seram island it has been interpreted as a subduction trench an intra continental thrust zone and foredeep and a zone of strike slip faulting recently acquired 2d seismic lines clarify its tectonic evolution and relationship to the bird s head folding in the early pliocene formed an anticlinorium running from misool to the onin peninsula of irian jaya and produced a newly recognised angular unconformity the unconformity truncates sediments as old as middle jurassic and is an ancient topographic surface with significant relief it was later folded and now dips south towards the trough where it is covered by up to 3 km of sediments initial tilting of the unconformity surface was accompanied by deposition of a transgressive sequence which can be traced into the trough this is overlain by two sequences which prograde towards the trough these sequences show progressive rotation of the unconformity surface gravitational displacement of sediments into the trough and thrusting which continues to the present day contraction occurred in the trough after the early pliocene and is younger than the previously suggested late miocene age thrust faults in the trough deform sediments deposited above the unconformity and detach at the unconformity surface on seram thrust faults repeat mesozoic miocene sequences and probably detach at their contact with metamorphic basement the detachment surface must cut through the mesozoic miocene sequence between seram and the trough this work suggests the seram trough is not a subduction trench but a foredeep produced in response to loading by the developing fold and thrust belt of seram with an associated peripheral bulge to the north the seram trough is interpreted to be a very young zone of thrusting within the australian continental margin

mantle structure beneath indonesia inferred from high resolution tomographic imaging we investigated mantle structure beneath the indonesian region by means of tomographic inversions of traveltime residuals of direct p and the surface reflected depth phases pp and pwp the hypocentres and phase data used in the inversions were derived from the reprocessing of data reported to international data centres which include data from the australian skippy project we used more than 6 0 10 data from more than 50 000 globally distributed earthquakes recorded at a subset of nearly 3000 seismological stations worldwide the use of depth phases improved the sampling of the upper mantle structure in particular beneath the back arc regions the mapping of distant aspherical mantle structure into the study region was minimized by combining a high resolution regional with a low resolution global inversion the inversion was linearized around the ak135 reference velocity model and a combination of minimum norm and gradient damping was applied to constrain the solution inversion of different subsets of the data and test inversions of synthetic data indicate that resolution is sufficient to substantiate the conclusions pertinent to the complex large scale structure of the subducted slab beneath the indonesian archipelago the tomographic images confirm previous evidence for regional slab penetration into the upper part of the lower mantle but suggest a more complex trajectory of mantle flow beneath indonesia the implied lateral variation in the shape of the upper mantle slab is generally in good agreement with inferences from seismicity the data reveal a seismic anomaly beneath the sunda arc which is detected to at least 1500 km in depth and forms the eastern end of a deep anomaly associated with the past subduction of lithosphere of the mesozoic tethys ocean below java the lithospheric slab is probably continuous from the earth s surface to the lower mantle but beneath sumatra the deep slab seems to be detached from the seismogenic slab the high resolution images suggest that the subducted slab is deflected in the transition zone beneath the banda arc and that the descending slabs form a spoon shaped structure north of the banda sea we detect the two opposing subducted slabs of the molucca sea plate this is consistent with previous studies but our images suggest that the westward subduction has a significantly steeper dip than the eastward subduction slab structure beneath the banda and molucca seas is explained in the context of the continent arc collision between australia and the southeast indonesian island arc and the arc arc collision between sangihe and halmahera inversion of traveltime residuals of direct s phases a novelty for this region largely confirms the inferences from the p wave data even though less detail is resolved