a numerical simulation technique to study fault activation characteristics during mining between fault bundles faults especially fault bundles elevate the difficulties of predicting preventing and controlling water inrush during coal seam mining this paper takes the no 163 mining area at jiangzhuang coal mine of shandong province china as a case study a series of faults form structural patterns consisting of the graben horst and fault terrace in the study area the key technical challenge lies in fault activation which affects sizing of economic and safe coal pillar around the fault bundles an innovative numerical simulation technique was applied to understand the movement law of coal seam roof and floor and fault activation among the fault bundles under different mining plans the results show that reasonable arrangement of mining sequence in the working faces is an effective method to reduce the influence from faults in addition coal seam roof and floor damage and faults activation are different during mining under the graben horst and fault terrace settings moreover the horizontal and vertical displacement values of each point on fault plane of hanging wall and footwall indicate that the maximum displacement is related to roof water conducting fractured zone and floor damage zone which increase the probability of fault activation based on the research results a reasonable coal pillar width was designed beside the fault bundle in the no 16301 working face of the no 163 mining area and the mining was completed safely with significant economic benefits for jiangzhuang coal mine

effective electrode array in mapping karst hazards in electrical resistivity tomography when conducting environmental and engineering investigations in karst terranes engineers and geologists often supplement exploratory borehole results with data gathered from surface geophysics to reduce the site characterization cost and establish the most useful locations for borings or samples when conducting resistivity investigations a frequently occurring problem is the need to determine which of the many existing electrode configurations will respond best to the material changes in karst features each array has its advantages and disadvantages in terms of depth of investigation sensitivity to horizontal or vertical variations and signal strength in the application presented in this paper numerical forward modeling was conducted of dipole dipole schlumberger and wenner arrays and they produced markedly different anomaly shapes for a conceptual model of the development of a cover collapse sinkhole the resolution of the three above mentioned arrays was further evaluated along a section of i 70 near frederick maryland where a sinkhole had occurred in the median of the highway the image from the dipole dipole array appeared to be better than those from the wenner and schlumerger arrays in displaying the sinkhole collapse area however they are all less effective than a mixed array in which apparent resistivities from all the three arrays are combined and processed together in the model because the mixed array requires a significant increase in data collection the dipole dipole array appears to be the most effective and less costly configuration in mapping karst hazards areas this conclusion was then confirmed by two case studies

magnetic properties of variably serpentinized peridotites and their implication for the evolution of oceanic core complexes serpentinization of ultramafic rocks during hydrothermal alteration at mid ocean ridges profoundly changes the physical chemical rheological and magnetic properties of the oceanic lithosphere there is renewed interest in this process following the discovery of widespread exposures of serpentinized mantle on the seafloor in slow spreading oceans unroofing of mantle rocks in these settings is achieved by displacement along oceanic detachment faults which eventually results in structures known as oceanic core complexes occs however we have limited understanding of the mechanisms of serpentinization at the seafloor and in particular their relationship with the evolution of occs since magnetite is a direct product of serpentinization the magnetic properties of variably serpentinized peridotites can provide unique insights into these mechanisms and their evolution in the oceanic lithosphere here we present new results from an integrated rock magnetic paleomagnetic and petrological study of variably serpentinized peridotites from the first fossil occ recognized in an ophiolite integration with existing data from mid ocean ridge related abyssal peridotites recovered from several scientific ocean drilling sites yields the first magnetic database from peridotites extending across the complete range 0 100 of degrees of serpentinization variations in a range of magnetic parameters with serpentinization and associated paleomagnetic data provide i key constraints on the mechanism s of serpentinization at mid ocean ridges ii insights on the potential for serpentinized peridotites to contribute to marine magnetic anomalies and iii evidence that leads to a new conceptual model for the evolution of serpentinization and related remanence acquisition at occs

deciphering potential groundwater zone in hard rock through the application of gis remote sensing and geographic information system has become one of the leading tools in the field of hydrogeological science which helps in assessing monitoring and conserving groundwater resources it allows manipulation and analysis of individual layer of spatial data it is used for analysing and modelling the interrelationship between the layers this paper mainly deals with the integrated approach of remote sensing and geographical information system gis to delineate groundwater potential zones in hard rock terrain the remotely sensed data at the scale of 1 50 000 and topographical information from available maps have been used for the preparation of ground water prospective map by integrating geology geomorphology slope drainage density and lineaments map of the study area further the data on yield of aquifer as observed from existing bore wells in the area has been used to validate the groundwater potential map the final result depicts the favourable prospective zones in the study area and can be helpful in better planning and management of groundwater resources especially in hard rock terrains

quantitative evaluation and prediction of water inrush vulnerability from aquifers overlying coal seams in donghuantuo coal mine china the water inrush vulnerability from overlying aquifers is evaluated for a coal seam in the donghuantuo coal mine china the water inrush vulnerability is based on superposition of two zoning maps water abundance map and connectivity map the water abundance zoning map was derived from a comprehensive analysis of six types of geoscience data including 1 lithological changes of the overlying aquifer 2 geological structure 3 pumping test results 4 seepage field of water inrush event 5 geochemistry and 6 loss of drilling mud the connectivity map was constructed based on comparing the numerically calculated height of the induced fracture zone above mining areas with the thickness of formation between the coal seam and the overlying aquifer visual modflow was used to predict the mine discharges at working face 2 284 under both natural and mining conditions based on the water inrush vulnerability map and the modeling results advanced dewatering from the overlying aquifer is proposed as the main prevention and control measure against the overlying aquifer water inrush

remote sensing technology and geographic information system modeling an integrated approach towards the mapping of groundwater potential zones in hardrock terrain mamundiyar basin in this paper remote sensing evaluation of digital elevation models dem geographic information systems gis and fieldwork techniques were combined to study the groundwater conditions in mamundiyar basin tamilnadu several digital image processing techniques including standard color composites intensity hue saturation ihs transformation and decorrelation stretch ds were applied to map rock types remote sensing data were interpreted to produce lithological and lineament maps dem was used for lineament and geomorphologic mapping all thematic layers were integrated and analyzed in a gis the overall results demonstrate that the use of remote sensing and gis provide potentially powerful tools to study groundwater resources and design a suitable exploration plan

origin and granite alteration effects of hydrothermal fluid isotopic evidence from fluorite veins co galway ireland the costelloe murvey granite is a chemically evolved high heat production leucocratic component of the 400 ma old galway granite batholith and is host to hydrothermal fluorite quartz calcite veins a previously reported clinopyroxene 40ar 39ar age of 231 4 ma obtained from a pre mineralization dolerite dyke is reinterpreted as dating this mineralization the hydrothermal fluid extensively altered its granite wallrocks leading to lower sm and nd and higher rb concentrations in altered granite disturbing both its rb sr and sm nd isotopic systems the 87sr 86sr ratio of the hydrothermal fluid from which fluorite and calcite precipitated ranged from 0 7101 to 0 7139 these ratios are very much lower than in the costelloe murvey granite at the time of mineralization precluding the granite as a source for more than 2 of the hydrothermal sr the initial 143nd 144nd ratio varies between fluorite in different veins due to nd derivation from local wallrocks and between fluorite of petrographically distinct growth phases within a single hand specimen highlighting the difficulty of sm nd isochron dating of fluorite in cases where there are multiple sources of hydrothermal nd it is proposed that fluorite and calcite precipitated where hot dilute fluids rising through the granite mixed with cooler more saline fluids of basinal origin migrating through lower carboniferous limestone which then overlay the granite

geophysical and geomorphological approach for locating groundwater potential zones in sukinda chromite mining area the impact of mining causes deterioration of environment and decline of groundwater level in the adjoining mining areas which influences groundwater source for domestic and agriculture purposes this necessitated locating and exploiting of new groundwater source a fast cost effective and economical way of locating and exploration is to study and analyze remote sensing data interpreted remote sensing data were used to select sites for carrying out surface geophysical investigations various geomorphologic units were demarcated and the lineaments were identified by interpretation of false color composite satellite imageries the potential for occurrence of groundwater in the sukinda valley was classified as very good good moderate and poor by interpreting the images sub surface geophysical investigations namely vertical electrical soundings were carried out to delineate and demarcate potential water bearing zones integrated studies of interpretation of geomorphologic lineaments and geophysical data aquifer thickness were used to prepare groundwater potential map the studies reveal that the groundwater potential of shallow aquifers is due to geomorphologic features and the potential of deeper aquifers is determined by lineaments and degree of weathering

timing and significance of crosscourse mineralization in sw england rb sr isotope analyses of inclusion fluids from quartz have demonstrated a triassic age 236 3 ma for n s trendmg pb zn f vein mineralization in the tamar valley district of the cornubian orefield consideration of the stratigaphy and structure of the permo triassic basins both onshore and in the english channel suggest that this mineralization results from the formation of fractures during regional extension driven subsidence and the subsequent ingress of basinal brines to the variscan basement

indium mineralisation in sw england host parageneses and mineralogical relations abstract the sw england ore region contains significant amounts of indium in in early permian granite related skarn and lode parageneses and to a lesser extent triassic epithermal crosscourse veins ore parageneses that predate granite emplacement devonian and lower carboniferous sedimentary exhalative and vein parageneses are largely devoid of in cadmium cd and gallium ga occur widely in all sulphide bearing parageneses across the region with sphalerite concentrations locally reaching 1 74 wt cd and 1750 ppm ga indium displays a strong affinity to sulphide bearing magmatic hydrothermal parageneses it occurs in silicate sulphide skarns polymetallic sulphide lodes and sulphide bearing portions of greisen bordered sheeted vein systems and quartz tourmaline lodes across the region magnetite silicate skarns and quartz tourmaline lodes that are devoid of sulphide in contrast were comparatively unfavourable for in precipitation the highest in concentrations are found in mineral lodes associated with the carnmenellis and st agnes granites which are the districts that had the highest historical production of sn total in concentrations in these areas locally exceed 430 ppm while concentrations elsewhere are systematically below 200 ppm the principal in hosts are chalcopyrite sphalerite and stannite group minerals with local concentrations within cassiterite and tennantite surprisingly chalcopyrite accounts for the majority of the in budget throughout the region although concentrations are highest in sphalerite and stannite group minerals sphalerite locally contains up to 1 42 wt in chalcopyrite has up to 2200 ppm and stannite group minerals up to 6800 ppm no in was detected in lollingite arsenopyrite rutile haematite magnetite tourmaline biotite chlorite galena bornite chalcocite or pyrrhotite scattered concentrations in pyrite relate to impurities rather than incorporation by solid solution roquesite and possibly dzhalindite or native in formed locally where in bearing chalcopyrite or sphalerite has been replaced by bornite and quartz the in partitioning between sphalerite and chalcopyrite varies broadly between 1 1 and 10 1 sporadic in was included in triassic crosscourse veins as a result of interactions between migrating cacl2 rich basinal brines and earlier formed granite related parageneses the interactions involved at least two distinct components 1 incorporation of clasts of magmatic hydrothermal veins in crosscourse veins during faulting and 2 dissolution and re precipitation of magmatic hydrothermal vein minerals in crosscourse fluids local concentrations reach 140 ppm in the magmatic hydrothermal parageneses in sw england are comparable to the south china tin belt mount pleasant as well as erzgebirge krusne hory magmatic hydrothermal fluids associated with peraluminous granites have developed a variety of skarn greisen lode and veins parageneses by interactions with their host rocks and contained fluids crosscourse epithermal mineralisation occurred as in was transported by cacl2 rich basinal brines in a similar manner as in bearing veins in the west shropshire ore field

geochemistry of metal rich brines from central mississippi salt dome basin u s a abstract oil field brines are the most favored ore forming solutions for the sediment hosted mississippi valley type ore deposits detailed inorganic and organic chemical and isotope analyses of water and gas samples from six oil fields in central mississippi one of the very few areas with high metal brines were conducted to study the inorganic and organic complexes responsible for the high concentrations of these metals the samples were obtained from production zones consisting of sandstone and limestone that range in depth from 1900 to 4000 m 70 120 c and in age from late cretaceous to late jurassic results show that the waters are dominantly bittern brines related to the louann salt the brines have extremely high salinities that range from 160 000 to 320 000 mg l total dissolved solids and are na ca cl type waters with very high concentrations of ca up to 48 000 mg l and other alkaline earth metals but with low concentrations of aliphatic acid anions the concentrations of metals in many water samples are very high reaching values of 70 mg l for pb 245 mg l for zn 465 mg l for fe and 210 mg l for mn the samples with high metal contents have extremely low concentrations 2 s samples obtained from the smackover formation limestone have low metal contents that are more typical of oil field waters but have very high concentrations up to 85 mg l of h 2 s computations with the geochemical code solmineq 87 give the following results 1 both pb and zn are present predominantly as aqueous chloride complexes mainly as pbcl 4 2 and zncl 4 2 respectively 2 the concentrations of metals complexed with short chained aliphatic acid anions and reduced s species are minor 3 organic acid anions are important in controlling the concentrations of metals because they affect the ph and buffer capacity of the waters at subsurface conditions and 4 galena and sphalerite solubilities control the concentrations of pb and zn in these waters

prediction model of water yield property based on gra fahp and topsis methods for ordovician top aquifer in the xinwen coalfield of china

40ar 39ar phlogopite geochronology of lamprophyre dykes in cornwall uk new age constraints on early permian post collisional magmatism in the rhenohercynian zone sw england the spatial and temporal association of post collisional granites and lamprophyre dykes is a common but enigmatic relationship in many orogenic belts including the variscan orogenic belt of sw england the geology of sw england has long been interpreted to reflect orogenic processes associated with the closure of the rheic ocean and the formation of pangaea the sw england peninsula is composed largely of early devonian to carboniferous volcano sedimentary successions deposited in synrift and subsequent syncollisional basins that underwent deformation and low grade regional metamorphism during the variscan orogeny voluminous early permian granitic magmatism cornubian batholith is considered to be broadly coeval with the emplacement of lamprophyric dykes and lamprophyric and basaltic lava flows largely on the basis of geochronological data from lamprophyric lavas in devon although published geochronological data for cornish lamprophyre dykes are consistent with this interpretation these data are limited largely to imprecise k ar whole rock and biotite analyses hindering the understanding of the processes responsible for their genesis and their relationship to granitic magmatism and regional variscan tectonics 40 ar 39 ar geochronological data for four previously undated lamprophyre dykes from cornwall combined with published data suggest that lamprophyre magmatism occurred between c 293 6 and c 285 4 ma supporting previous inferences that their emplacement was coeval with the cornubian batholith these data provide insights into 1 the relative timing between the lamprophyres and basalts the cornubian batholith and post collisional magmatism elsewhere in the european variscides and 2 the post collisional processes responsible for the generation and emplacement of lamprophyres basalts and granitoids supplementary data complete datasets photomicrographs and photographs of sample locations are available online at http www geolsoc org uk sup18838

the origin and evolution of base metal mineralising brines and hydrothermal fluids south cornwall uk abstract a fluid inclusion geochemical study has been carried out on quartz from post variscan quartz carbonate base metal sulphide anhydrite fluorite veins hosted by palaeozoic basement porthleven menheniot cornwall and permo triassic sediments western approaches data indicate that the base metal mineralising fluids have a similar bulk chemical composition to the saline fluids found in the permo triassic basinal sequence and support the hypothesis that these basins are the source of the mineralising fluids cl and br systematics suggest that the brines were formed either by the evaporation of seawater or a seawater meteoric water mixture past the point of halite precipitation the major cation composition na ca k mg of the brines is not consistent solely with evaporation processes but may be explained by dolomitisation processes albitisation processes or both which are recognised in the basinal sequences the presence of seawater in the base metal mineralised veins suggests that the first marine incursions late triassic into the region must act as a lower age limit for the mineralisation the halogen chemistry of a second hotter 200 c more dilute 0 5 wt fluid identified in fault hosted e w trending veins in the porthleven area suggests that the chlorinity of these fluids has a magmatic origin circulation of these fluids in post variscan extensional structures was driven by the local high heat producing cornubian batholith the local high heat producing granites provided fracture permeability and a heat source that heated the base metal mineralising fluids as they entered the horst block and the dilute fluids circulating around the granites petrographic evidence suggests that both palaeohydrologic systems were active contemporaneously however each flow system was isolated in differently orientated structures and there is little evidence for fluid mixing

a fluid inclusion and stable isotope study of 200 ma of fluid evolution in the galway granite connemara ireland fluid inclusions in granite quartz and three generations of veins indicate that three fluids have affected the caledonian galway granite these fluids were examined by petrography microthermometry chlorite thermometry fluid chemistry and stable isotope studies the earliest fluid was a h2o co2 nacl fluid of moderate salinity 4 10 wt nacl eq that deposited late magmatic molybdenite mineralised quartz veins v1 and formed the earliest secondary inclusions in granite quartz this fluid is more abundant in the west of the batholith corresponding to a decrease in emplacement depth within veins and to the east this fluid was trapped homogeneously but in granite quartz in the west it unmixed at 305 390 c and 0 7 1 8 kbar homogeneous quartz 18o across the batholith 9 5 0 4 n 12 suggests v1 precipitation at high temperatures perhaps 600 c and pressures 1 3 kbar from magmatic fluids microthermometric data for v1 indicate lower temperatures suggesting inclusion volumes re equilibrated during cooling the second fluid was a h2o nacl kcl low moderate salinity 0 10 wt nacl eq moderate temperature 270 340 c high d 18 2 low 18o 0 5 2 0 fluid of meteoric origin this fluid penetrated the batholith via quartz veins v2 which infill faults active during post consolidation uplift of the batholith it forms the most common inclusion type in granite quartz throughout the batholith and is responsible for widespread retrograde alteration involving chloritization of biotite and hornblende sericitization and saussuritization of plagioclase and reddening of k feldspar the salinity was generated by fluid rock interactions within the granite within granite quartz this fluid was trapped at 0 5 2 3 kbar having become overpressured this fluid probably infiltrated the granite in a meteoric convection system during cooling after intrusion but a later age cannot be ruled out the final fluid to enter the granite and its host rocks was a h2o nacl cacl2 kcl fluid with variable salinity 8 28 wt nacl eq temperature 125 205 c d 17 to 45 18o 3 to 1 2 13cco2 19 to 0 and 34ssulphate 13 23 that deposited veins containing quartz fluorite calcite barite galena chalcopyrite sphalerite and pyrite v3 correlations of salinity temperature d and 18o are interpreted as the result of mixing of two fluid end members one a high d 17 to 8 moderate 18o 1 2 2 5 high 13cco2 4 low 34ssulphate 13 high temperature 205 230 c moderate salinity 8 12 wt nacl eq fluid the other a low d 61 to 45 low 18o 5 4 to 3 low 13c 10 high 34ssulphate 20 23 low temperature 80 125 c high salinity 21 28 wt nacl eq fluid geochronological evidence suggests v3 veins are late triassic the high d end member is interpreted as a contemporaneous surface fluid probably mixed meteoric water and evaporated seawater and or dissolved evaporites whereas the low d end member is interpreted as a basinal brine derived from the adjacent carboniferous sequence this study demonstrates that the galway granite was a locus for repeated fluid events for a variety of reasons from expulsion of magmatic fluids during the final stages of crystallisation through a meteoric convection system probably driven by waning magmatic heat to much later mineralisation concentrated in its vicinity due to thermal tectonic and compositional properties of granite batholiths which encourage mineralisation long after magmatic heat has abated

samarium neodymium direct dating of fluorite mineralization the direct dating of many styles of hydrothermal mineralization has proved difficult limiting understanding of the geological processes that lead to crustal fluid flow and the formation of major ore deposits the hydrothermal mineral fluorite caf2 displays large variations in rare earth element ree abundance and samarium neodymium ratios within a single vein samarium neodymium dating of fluorite from the classic granite hosted tin deposits of southwest england demonstrates its use as a precise chronometer of mineralization the concentrations of light rare earth elements lrees in the fluorites are highly variable and suggest the coeval precipitation of an lree rich phase as the most likely cause of the extreme variation in samarium neodymium ratios

groundwater favorability map using gis multicriteria data analysis on crystalline terrain sao paulo state brazil summary this paper presents the groundwater favorability mapping on a fractured terrain in the eastern portion of sao paulo state brazil remote sensing airborne geophysical data photogeologic interpretation geologic and geomorphologic maps and geographic information system gis techniques have been used the results of cross tabulation between these maps and well yield data allowed groundwater prospective parameters in a fractured bedrock aquifer these prospective parameters are the base for the favorability analysis whose principle is based on the knowledge driven method the multicriteria analysis weighted linear combination was carried out to give a groundwater favorability map because the prospective parameters have different weights of importance and different classes of each parameter the groundwater favorability map was tested by cross tabulation with new well yield data and spring occurrence the wells with the highest values of productivity as well as all the springs occurrence are situated in the excellent and good favorability mapped areas it shows good coherence between the prospective parameters and the well yield and the importance of gis techniques for definition of target areas for detail study and wells location

dynamic control on serpentine crystallization in veins constraints on hydration processes in oceanic peridotites deformation and hydration processes are intimately linked in the oceanic lithosphere but the feedbacks between them are still poorly understood especially in ultramafic rocks where serpentinization results in a decrease of rock density that implies a volume increase and or mass transfer serpentinization is accompanied by abundant veining marked by different generations of vein filling serpentines with a high variety of morphologies and textures that correspond to different mechanisms and conditions of formation we use these veins to constrain the role of deformation and mass transfer processes during hydration of oceanic peridotites at slow spreading ridges we have selected a representative set of veins from ocean floor serpentinites of the mid atlantic ridge near kane transform fault 23 n and characterized these in detail for their microstructures and chemistry by coupling optical and electron microscopy sem tem with electron microprobe analyses four main veining episodes v1 to v4 accompany the serpentinization the first episode identified as vein generation v1 is interpreted as the tectonically controlled penetration of early seawater dominated fluid within peridotites enhancing thermal cracking and mesh texture initiation at 3 4 km up to 8 km depth and at t 300 350 c the two following vein stages v2 and v3 formed in a closed diffusive system and accommodate volume expansion required to reach almost 50 serpentinization of the protolith the cracks exploited by these veins were caused by the progressive unroofing at depths of 4 to 2 km along a detachment fault degree and rate of serpentinization seem to be controlled by the capacity of the system to create space and to drive the mass transfer needed for ongoing serpentinization and this capacity is in turn linked to the exhumation rate and local tectonics during this period water consumed by hydration may prevent the establishment of convective hydrothermal cells the onset of an open hydrothermal system in the shallow lithosphere 2 km where brittle fracturing and advective transfer dominate and enable the completion of serpentinization is marked by the last vein generation v4 these results show a complete history of alteration with the crystallization of different types of serpentine recording different tectonic events chemical conditions and modes of hydrothermal alteration of the lithosphere

late carboniferous to triassic reactivation of variscan basement in the western english channel evidence from onshore exposures in south cornwall south cornwall represents the westernmost part of the variscan basement massif in sw england field based investigations into the distribution geometry kinematics and relative chronology of post variscan deformation have been accompanied by preliminary palaeostress analyses these indicate three episodes of basement reactivation 1 stephanian to early permian nnw sse extension 2 early to late permian strike slip deformation and 3 late permian to triassic ene wsw extension these data have been used to test and refine previously published models based upon seismic and well data of late carboniferous to triassic basement reactivation and sedimentary basin development within the western approaches trough we confirm that nnw sse regional extension and reactivation of ene striking variscan thrusts had initiated by the latest carboniferous and that ene wsw regional extension and dip slip reactivation of nnw striking high angle faults occurred during the triassic permian strike slip deformation recognized onshore may have contributed to the development of widespread unconformities within the ovshore basins

the nature and significance of rift related near surface fissure fill networks in fractured carbonates below regional unconformities fissure fill networks are a widely recognized but relatively little described near surface phenomenon supplementary material appendix a is available at https doi org 10 6084 m9 figshare c 5023103

protracted construction of gabbroic crust at a slow spreading ridge constraints from 206pb 238u zircon ages from atlantis massif and iodp hole u1309d 30 n mar sensitive high resolution ion microprobe shrimp u pb zircon ages of 24 samples from oceanic crust recovered in integrated ocean drilling program iodp hole u1309d and from the surface of atlantis massif mid atlantic ridge mar 30 n document a protracted history of accretion in the footwall to an oceanic detachment fault ages for 18 samples of evolved fe ti oxide gabbro and felsic dikes collected 40 1415 m below seafloor in u1309d yield a weighted mean of 1 20 0 03 ma mean square of weighted deviates 7 1 however the ages range from 1 08 0 07 ma and 1 28 0 05 ma indicating crustal construction occurred over a minimum of 100 200 ka the zircon ages along with petrologic observations indicate at least 2 major periods of intrusive activity with age peaks separated by 70 ka the oldest ages are observed below 600 mbsf an observation inconsistent with models requiring constant depth melt intrusion beneath a detachment fault the data are most consistent with a multiple sill model whereby sills intrude at random depths below the ridge axis over a length scale greater than 1 4 km zircon ages from broadly spaced samples collected along the southern ridge of atlantis massif yield a detachment fault slip rate of 28 7 6 7 mm a and imply significant asymmetric plate spreading up to 100 on the north american plate for at least 200 ka during core complex formation

a gis based model of potential groundwater yield zonation for a sandstone aquifer in the juye coalfield shangdong china abstract resolving the potential groundwater yield zonation of sandstone aquifers occurring at depths of several hundred meters has been an important and challenging objective of the hydrogeological research focused on preventing flood hazards in coal mines using accessible geological exploration data we put forward a method of predicting the spatial distribution of groundwater storage potential in sandstone aquifers from permian age coal deposits in juye coalfield shangdong china a geological tectonic and lithological composition index gtlci model was created using the following parameters sandstone depth and thickness faults length density fald faults density fad fault frequency density fafd fault scale density fasd variation coefficient of the slope vcs of the coal seam intensity index of folds in horizontal direction iifoh and lithological composition index lci each of these factors was subsequently divided into 5 classes the analytic hierarchy process ahp and trapezoidal fuzzy number tfn method was applied to calculate the weight of the conditioning factor and their respective sub classes groundwater yield potential contour map which was initially constructed using the gtlci values revealed four groundwater abundance zones the map was further refined by taking into account hydrogeologic data collected during mining activities the gtlci model predictive success rate of 80 was explained by the limited number of boreholes available for validation it is considered that the gtlci model is effective at predicting zonation of groundwater yield in the sandstone aquifers from permian age coal deposits in juye coalfield china

spreading rate spreading obliquity and melt supply at the ultraslow spreading southwest indian ridge we use bathymetry gravimetry and basalt composition to examine the relationship between spreading rate spreading obliquity and the melt supply at the ultraslow spreading southwest indian ridge swir we find that at regional scales more than 200 km melt supply reflects variations in mantle melting that are primarily controlled by large scale heterogeneities in mantle temperature and or composition focusing on adjacent swir regions with contrasted obliquity we find that the effect of obliquity on melt production is significant about 1 5 km less melt produced for a decrease of 7 mm a to 4 mm a in effective spreading rates esr but not enough to produce near amagmatic spreading in the most oblique regions of the ridge unless associated with an anomalously cold and or depleted mantle source our observations lead us to support models in which mantle upwelling beneath slow and ultraslow ridges is somewhat focused and accelerated thereby reducing the effect of spreading rate and obliquity on upper mantle cooling and melt supply to explain why very oblique swir regions nonetheless have large outcrops of mantle derived ultramafic rocks and in many cases no evidence for axial volcanism cannat et al 2006 dick et al 2003 we develop a model which combines melt migration along axis to more volcanically robust areas melt trapping in the lithospheric mantle and melt transport in dikes that may only form where enough melt has gathered to build sufficient overpressure these dikes would open perpendicularly to the direction of the least compressive stress and favor the formation of orthogonal ridge sections the resulting segmentation pattern with prominent orthogonal volcanic centers and long intervening avolcanic or nearly avolcanic ridge sections is not specific to oblique ridge regions it is also observed along the swir and the arctic gakkel ridge in orthogonal regions underlain by cold and or depleted mantle

quantitative constraint on footwall rotations at the 15 45 n oceanic core complex mid atlantic ridge implications for oceanic detachment fault processes the subsurface geometry of detachment faults at slow spreading mid ocean ridges is debated are they planar features that form and slip at low angles as often inferred for their continental equivalents or do they initiate at steep angles and then flatten in response to flexural unloading as displacement proceeds as predicted in rolling hinge conceptual models an essential difference is that significant rotation of the footwall should occur in the rolling hinge but not the planar fault model this can be tested using paleomagnetism previous attempts to address this question have relied upon data from azimuthally unoriented drill cores although results are consistent with large rotations having occurred these interpretations are very nonunique and other solutions that require minimal rotations are equally permissible we here present a rigorous analysis of paleomagnetic and structural data from a unique set of azimuthally oriented cores collected using a seabed rock drill from the 15 45 n oceanic core complex on the mid atlantic ridge by considering the full paleomagnetic remanence vector in combination with kinematic data from the detachment fault shear zone we are able to quantitatively constrain the geometrically permissible axes and magnitudes of rotation of the detachment fault footwall for the first time without having to make a priori assumptions about the orientation of the axis we show that significant rotations 64 16 have indeed occurred about a gently plunging near ridge parallel axis robustly supporting the rolling hinge models we further discuss the geological implications of this result for oceanic detachment fault processes

a new approach for predicting bedding separation of roof strata in underground coalmines abstract in order to avoid the influence of monitoring location to measured vertical bedding separation a new estimating approach for vertical bedding separation which uses the ratio between current and average vertical bedding separation k has been proposed in situ investigations showed there exists a threshold value of k t for any kind of roof stratum and the sedimentation has a great influence on it in the eastern deep coal mines which are subjected to intense sedimentation in shandong province china k t ranges from 1 48 to 1 73 in the western shallow coalmines which are subjected to weak sedimentation inner mongolia china k t ranges from 1 32 to 1 37 k t is related to t the lower layer thickness and separation position when separation occurs in the anchored range k t increases with t but in a downward gradient and slightly decreases with the lower layer thickness when separation occurs outside the anchored range k t increases with t in an upward gradient and increases with the lower layer thickness to combine monitoring the technique for k and the borehole camera scanning technique is a more reliable for estimating roof safety in a roadway

coupled mineral fluid evolution of a basin and high kaolinization in the sw england granites in relation to the development of the plymouth basin

magnetic effects of maghemitization of oceanic crust both theoretical considerations and available experimental results indicate that magnetic effects of maghemitization are strongly dependent on the grain size of the originally unoxidized titanomagnetite maghemitization of single domain titanomagnetite results in a decrease in coercivity an increase in susceptibility and a large decrease in q ratio maghemitization of multidomain titanomagnetite results in an increase in coercivity a decrease in susceptibility and no large changes in q ratio single domain titanomagnetite is probably resistant to the development of a chemical remanent magnetization crm whereas multidomain titanomagnetite can acquire a crm during maghemitization the behavior of pseudo single domain titanomagnetite which is the main carrier of remanence in submarine extrusive rocks is investigated by comparing the magnetic properties of the french american mid ocean undersea study famous less than 0 1 m y old and the leg 37 3 5 m y old pillow basalts recovered from the mid atlantic ridge near 37 n combining electron microprobe analyses curie temperature measurements and cell edge determinations we find that the famous rocks are already oxidized z 0 38 possibly as a result of some high temperature maghemitization during cooling of the magma comparison with the more highly oxidized z 0 7 leg 37 pillow basalts indicates that low temperature maghemitization of such rocks does not result in appreciable changes of coercivity and susceptibility although the q ratio does decrease and crm seems to be acquired such a crm could account for the anomalously low magnetic inclinations observed at most of the leg 37 sites