active strike slip faulting in el salvador central america several major earthquakes have affected el salvador central america during the past 100 yr as a consequence of oblique subduction of the cocos plate under the caribbean plate which is partitioned between trench orthogonal compression and strike slip deformation parallel to the volcanic arc focal mechanisms and the distribution of the most destructive earthquakes together with geomorphologic evidence suggest that this transcurrent component of motion may be accommodated by a major strike slip fault el salvador fault zone we present field geological structural and geomorphological data collected in central el salvador that allow the constraint of the kinematics and the quaternary activity of this major seismogenic strike slip fault system data suggest that the el salvador fault zone consists of at least two main e w fault segments san vicente and berlin segments with associated secondary synthetic wnw ese and antithetic nnw sse riedel shears and nw se tensional structures the two main fault segments overlap in a dextral en echelon style with the formation of an intervening pull apart basin our original geological and geomorphologic data suggest a late pleistocene holocene slip rate of 11 mm yr along the berlin segment in contrast with low historical seismicity the kinematics and rates of deformation suggested by our new data are consistent with models involving slip partitioning during oblique subduction and support the notion that a trench parallel component of motion between the caribbean and cocos plates is concentrated along e w dextral strike slip faults parallel to the volcanic arc

coal deposits as promising alternative sources for gallium abstract gallium ga which is a rare valuable metal has been found to be anomalously enriched in coal to the extent that it may be considered as an economic resource recovery of ga from coal or coal combustion byproducts offers a promising alternative way to obtain this metal and such techniques could probably lead to economic gains and positive impacts on the environment thus geochemical research and technical investigations of ga bearing coal would be helpful in assessing the potential for economic extraction of the ga the present review of ga in coal focuses on analytical methods that can be used to determine ga concentrations patterns of ga enrichment in coal and formation of economic ga enriched coal deposits modes of occurrence of ga and its origins the behavior of ga during coal combustion and gasification and currently available recovery techniques for ga moreover insufficiencies in previous research are identified and future research needs regarding ga in coal are evaluated and discussed

latest quaternary oceanographic changes in the okhotsk sea based on diatom records abstract the okhotsk sea is a locus of the north pacific intermediate water formation today the formation of the okhotsk intermediate water is linked with seasonal sea ice cover diatom records from the okhotsk sea show the following 1 during the last glacial maximum between 21 000 yr b p and 18 000 yr b p sea ice covered the western side of the sea throughout the whole year but the eastern part was open this permitted more efficient heat exchange with the atmosphere than waters and hence ventilation of the glacial okhotsk sea waters which in turn caused a greater extent of intermediate water formation through the bussol strait 2 the perennial sea ice cover extended northward and sea ice was present throughout the whole year over a great part of the sea except for the eastern part between 18 000 yr b p and 17 000 yr b p 3 the ice free area extended greatly to the south during the interval between 17 000 yr b p and 11 000 yr b p 4 there was no perennial ice cover over the whole sea and the ice free area that appeared as the seasonal ice area began to extend to the western part between 11 000 yr b p and 8 000 yr b p 5 after 8000 yr b p the ice free waters contracted to the present extent

a new estimate for present day cocos caribbean plate motion implications for slip along the central american volcanic arc velocities from 153 continuously operatinggps sites on the caribbean north american and pacic plates arecombinedwith61newlyestimatedpacic cocosseafloor spreading rates and additional marine geophysical data to deriveanewestimate of present daycocos caribbean plate motion acomparisonofthepredictedcocos caribbean di rectiontoslipdirectionsofnumerousshallow thrustsubduc tion earthquakes from the middle america trench between costa rica and guatemala shows the slip directions to be deflected 10 clockwise from the plate convergence direc tion supporting thehypothesisthatfrequentdextralstrike slip earthquakes along the central american volcanic arc result from partitioning of oblique cocos caribbean plate convergence linear velocity analysis for forearc locations in nicaragua and guatemala predicts 14 2m m yr 1 of northwestward trench parallel slip of the forearc relative to thecaribbean plate possibly decreasing inmagnitude inel salvador and guatemala where extension east of the vol canic arc complicates the tectonic setting

the bering and okhotsk seas modern and past paleoceanographic changes and gateway impact abstract the high biological productivity and an efficient biological pumping in the subarctic pacific and adjacent seas make this region important to the modern carbon cycle and both modern and the past climate of the earth knowledge of the northern marginal seas of the pacific however is unsubstantial the bering sea is located between the pacific ocean and the arctic sea and plays an important role in ocean circulation involving balances of heat salt and various chemical properties thus it is necessary to unravel the geologic history of the bering sea as a gateway to the pacific and the arctic atlantic during the last 5 million years and beyond the okhotsk sea is considered a locus of north pacific intermediate water formation today the intermediate water formation is linked with seasonal sea ice cover diatom records from the okhotsk sea demonstrate that sea ice cover was distributed on the western side of the sea and the eastern part was open water during the last glacial maximum this configuration permitted a better ventilation of the glacial okhotsk sea through increased quantity of intermediate water presumably formed there at that time

kinematics of the north american caribbean cocos plates in central america from new gps measurements across the polochic motagua fault system 1 the polochic motagua strike slip fault system in guatemala marks the on land plate boundary between the north american na and the caribbean ca plates gps observations in 1999 and 2003 show that the far field velocity across the system na ca relative velocity is 20 mm yr this is significantly higher than the nuvel 1a velocity but is consistent with the gps based ca na velocity proposed by demets et al 2000 the observations are modeled by a fault centered on the motagua fault locked at a depth of 20 km with a slip rate decreasing from eastern to central guatemala from 20 to 12 mm yr towards the na ca cocos triple junction this decrease is accommodated by 8 mm yr of e w extension in the westernmost part of ca south of the motagua fault about 10 mm yr of dextral slip is observed across the mid american volcanic arc the na ca cocos triple junction is thus a complex 400 km wide wedge shaped area

low vp vs ratios in the crust and upper mantle beneath the sea of okhotsk inferred from teleseismic pmp smp and sms underside reflections from the moho 1 teleseismic ground motion recordings of deep earthquakes often contain clear seismic wave reflections from the free surface above the source pp sp ss with isolated precursors pmp smp and sms produced by underside reflections from the moho the crust mantle boundary below the free surface reflection points the waveforms of the depth phases and their precursors are readily modeled providing constraints for steep angles of incidence on integrated two way crustal travel times and moho shear and compressional impedance contrasts above deep earthquake source regions we model surface reflection waveforms in stacks of three component long period wwssn and digital broadband seismograms for signals traversing the crust and upper mantle beneath the sea of okhotsk which overlies deep earthquakes in the subducted kurile slab the crust beneath most of the sea of okhotsk is 19 25 km thick indicating a submerged continental margin with minor crustal thinning toward the kuril back arc basin where thin oceanic crust is found modeling pmp and sms phases that sample the same subregion provides tight constraints on the vp vs ratio in the crust and uppermost mantle assuming common density structure and consistent crustal thickness for p and s waves the absolute velocities are not constrained by the data we find unusually low vp vs ratios in the range 1 6 1 7 for the uppermost mantle under the sea of okhotsk and comparably low average vp vs ratios for the crust in several regions the presence of fluids and extensive silica enrichment possibly involving low temperature veining are viable explanations for the anomalous vp vs ratios this may represent an important process of continentalization taking place landward from the volcanic arc in subduction zones

geological and seismological analysis of the 13 february 2001 mw 6 6 el salvador earthquake evidence for surface rupture and implications for seismic hazard the el salvador earthquake of 13 february 2001 mw 6 6 caused tectonic rupture on the el salvador fault zone esfz right lateral strike slip surface rupture of the east west trending fault zone had a maximum surface displacement of 0 60 m no vertical component was observed the earthquake resulted in widespread landslides in the epicentral area where bedrock is composed of volcanic sediments tephra and weak ignimbrites in the aftermath of the earthquake widespread damage to houses and roads and the hazards posed by landslides captured the attention of responding agencies and scientists and the presence of surface fault rupture was overlooked additionally the tectonic context in which the earthquake took place had not been clear until mapping of the esfz was completed for the present study we identified several fault segments the distribution of surface ruptures the aftershock pattern and fault rupture scaling considerations that indicate the 21 km long san vicente segment ruptured in the 2001 event static coulomb stress transfer models for the san vicente rupture are consistent with both aftershock activity of the 2001 sequence and ongoing background seismicity in the region at mw 6 6 the 2001 earthquake was of only moderate magnitude yet there was significant damage to the country s infrastructure including buildings and roads and numerous deaths and injuries thus earthquake hazard and risk in the vicinity of the esfz which straddles the city of san salvador with a population of 2 million is high because even moderate magnitude events can result in major damage deaths and injuries in the region

relations among subduction parameters clues to the dynamics of the subduction process are found in the many measurable parameters of modern subduction zones based on a critical appraisal of the geophysical and geological literature 26 parameters are estimated for each of 39 modern subduction zones to isolate causal relationships among these parameters multivariate analysis is applied to this data set this analysis yields empirical quantitative relations that predict strain regime and strike slip faulting in the overriding plate maximum earthquake magnitude benioff zone length slab dip arc trench gap and maximum trench depth excellent correlation is found between length of the benioff zone and the product of convergence rate and age of the downgoing slab this relationship is consistent with the conductive heating model of molnar et al 1979 if the model is modified in one respect the rate of heating of the slab is not constant it is substantially slower during passage of the slab beneath the accretionary prism and overriding plate the structural style in the overriding plate is determined by its stress state though the stress state of overriding plates cannot be quantified one can classify each individual subduction zone into one of seven semiquantitative strain classes that form a continuum from strongly extensional class 1 back arc spreading to strongly compressional class 7 active folding and thrusting this analysis indicates that strain class is probably determined by a linear combination of convergence rate slab age and shallow slab dip interplate coupling controlled by convergence rate and slab age is an important control on strain regime and the primary control on earthquake magnitude arc parallel strike slip faulting is a common feature of convergent margins forming a forearc sliver between the strike slip fault and trench optimum conditions for the development of forearc slivers are oblique convergence a compressional environment and a continental overriding plate the primary factor controlling presence of strike slip faulting is coupling strongly oblique convergence is not required the rate of strike slip faulting is affected by both convergence obliquity and convergence rate maximum trench depth is a response to flexure of the underthrusting plate the amount of flexural deflection at the trench depends on the vertical component of slab pull force which is very sensitive to slab age and shallow slab dip shallow slab dip conforms to the cross sectional shape of the overriding plate which is controlled by width of the accretionary prism and duration of subduction deep slab dip is affected by the mantle trajectory established at shallow depth but may be modified by mantle flow much of the structural complexity of convergent margins is probably attributable to terrane juxtaposition associated with temporal changes in both forearc strike slip faulting and strain regime empirical equations relating subduction parameters can provide both a focus for future theoretical studies and a conceptual and kinematic link between plate tectonics and the geology of subduction zones

a model for nb zr ree ga enrichment in lopingian altered alkaline volcanic ashes key evidence of h o isotopes abstract clay altered volcanic ash with highly elevated concentrations of nb ta zr hf rare earth elements ree and ga is a new type of critical metal deposit with high commercial prospects that has been discovered in yunnan province southwest china previous studies showed that the volcanic ashes had been subjected to hydrothermal fluids the nature of which however is not clear here we show that the volcanic ashes were originated from alkaline magmatism followed by a continuous hydrothermal weathering process heated meteoric waters which were sourced from acidic rains and mixed with co2 from degassing of the emeishan plume have caused partial but widespread acidic leaching of nb ta zr hf ree and ga into ground water and residual enrichment of these elements along with al and ti in the deeply altered rocks subsequent alteration occurring under cooler neutral or alkaline conditions caused by water rock interaction resulted in precipitation of the leached critical metals in the deposit polymetallic mineralization of similar origin may be found in other continental regions subjected to explosive alkaline volcanism associated with deep weathering in humid conditions

geochemistry of source rock controlled late triassic coal an example from the dabaoding coal mine in panzhihua sichuan province southwestern china abstract the geochemistry of source rock controlled coals from the late triassic daqiaodi formation in the dabaoding coal mine of the southwestern sichuan province was investigated a total of 15 coal samples 6 parting samples and 4 roof and floor rock samples from the d15 3 and d18 coals were subjected to proximate and ultimate analyses for coal quality by using lta xrd with siroquant software for minerals xrf for major element oxides icp ms for trace elements icp cct ms for as and se ise for f and a dma 80 analyzer for hg results indicate that the dabaoding d15 3 and d18 coals are classified as low ash and low volatile bituminous coal minerals in coals are dominated by quartz kaolinite illite and dolomite most trace elements in the dabaoding coals are depleted or at normal levels relative to chinese coals or world hard coals except for cr with slight enrichment the dabaoding coals and host rocks are characterized by weakly positive ce and y anomalies strongly positive gd anomalies and weakly negative eu anomalies based on paleogeographical mineralogical and geochemical evidence the sediment source rocks of the daqiaodi coal bearing strata are identified as the panzhihua trachyte at the top of the kangdian upland which exerted crucial impacts on the dabaoding coals

elemental geochemistry and mineralogy of coals and associated coal mine overburden from makum coalfield northeast india the insufficient research on the nature and mode of occurrence of minerals and other inorganic elements of the northeast indian coal deposits has resulted in lack of proper utilization assessment and mitigation of environmental degradation the mineralogical and geochemical aspects of these coals were studied through the techniques such as optical microscopy low temperature quantitative x ray diffraction lta xrd scanning electron microscopy energy dispersive spectroscopy sem eds inductively coupled mass spectroscopy icp ms and chemical analysis techniques the leaching behavior of the elements including rees in presence of water was studied the high organic sulfur 75 of total sulfur and low ash yields were observed in these coals varying with seam depth the dominance of vitrinite 94 1 94 3 with an r max 0 72 0 78 in these coals along with their dominance within the lean organic fraction in the coal mine overburden ob samples was reported the major oxides present in these coals and their associated overburden samples were studied through xrf analysis various mineral phases were identified in both coal and ob samples such as dawsonite pyrite diaspore marcasite gypsum thenardite berzeliite garnet etc the sem eds analysis indicated the presence of siderite pyrite and kaolinite quartz illite etc in the coal ob and leached samples the distribution of concentrations of the 48 trace and rare earth elements rees varying with seam depth were normalized by upper continental crust ucc and found to be lower in comparison to global chinese and usa coals the statistical analysis on the trace and rare earth elements in the coals was performed to know their mutual correlations

mode of mixture of oceanic fragments and terrigenous trench fill in an accretionary complex example from southern sakhalin abstract four modes of mixture of oceanic materials such as cherts limestones and basalts and terrigenous trench fill sediments are recognized in the cretaceous accretionary complexes in southern sakhalin far eastern pacific margin of the u s s r the first mode is a thin skinned stacking of pelagic bedded cherts with black shale due to duplex formation in association with shallow underplating or off scraping the second mode is a mixture of the uppermost part of the oceanic crust with terrigenous trench fill sediments due to olistostrome formation reconstruction of the original sequence in ascending order suggests that the basement is pillow basalt with overlying pelagic sediments of chert and limestone olistostrome caused by collapse of oceanic crust due to its bending before encountering a trench and finally trenchfill sediments of turbidite this sequence is imbricated by thrusting which appears to have occurred at the time of underplating the third mode is a tectonic mixing of oceanic fragments and terrigenous sediments due to shear which is related to underthrusting of the oceanic plate a reduction in the supply of trench fill sediments causes copious accretion of the upper part of oceanic crust the fourth mode is in situ basalt volcanism at the trench where thick baked margins of terrigenous shale are formed around the injected basalts this mode appears to represent a ridge trench encounter these four different modes of mixing seem to be usual in ancient accretionary complexes in orogenic belts

revisiting the late permian coal from the huayingshan sichuan southwestern china enrichment and occurrence modes of minerals and trace elements abstract the late permian coals from the huayingshan coalfield of southwestern china are significantly enriched in zr 695 g g nb 75 9 g g se 6 99 g g hf 10 1 g g and rare earth elements and y 1423 g g previous studies showed that the sediment source region for these coals was the kangdian upland which was formed at an early stage of the late permian period the source rocks have a basalt composition and those studies attributed the enrichment of the above high field strength elements hfses to derivation from the kangdian upland geochemical and mineralogical data presented in this study show that the dominant sediment source regions for the coal and roof strata of the huayingshan coalfields are the dabashan uplift hannan upland and leshan longnvsi uplift the highly elevated concentrations of hfses in the coals are due to hydrothermal fluids three tonstein layers derived from alkali rhyolite were identified these tonsteins are characterized by highly enriched hfses and by strong negative eu anomalies in the rare earth element distribution patterns the major carriers of the rare earth elements in the coal are rhabdophane and silicorhabdophane the latter of which is also enriched in zr zirconium however mainly occurs in zircon rhabdophane and silicorhabdophane in the coal are mainly distributed along the bedding planes and occur as cell fillings zircon in the coal occurs as cell fillings and is of authigenic origin anatase in the partings and coals contains nb and occurs as fracture filling and colloidal forms the modes of occurrence of the above minerals indicate that they were derived from hydrothermal fluids mercury and se mainly occur in sulfide minerals pyrite and marcasite

neotectonic development of the el salvador fault zone and implications for deformation in the central america volcanic arc insights from 4 d analog modeling experiments the el salvador fault zone esfz is an active approximately 150 km long and 20 km wide segmented dextral strike slip fault zone within the central american volcanic arc striking n100 e although several studies have investigated the surface expression of the esfz little is known about its structure at depth and its kinematic evolution structural field data and mapping suggest a phase of extension at some stage during the evolution of the esfz this phase would explain dip slip movements on structures that are currently associated with the active dominantly strike slip and that do not fit with the current tectonic regime field observations suggest trenchward migration of the arc such an extension and trenchward migration of the volcanic arc could be related to slab rollback of the cocos plate beneath the chortis block during the miocene pliocene we carried out 4 d analog model experiments to test whether an early phase of extension is required to form the present day fault pattern in the esfz our experiments suggest that a two phase tectonic evolution best explains the esfz an early pure extensional phase linked to a segmented volcanic arc is necessary to form the main structures this extensional phase is followed by a strike slip dominated regime which results in intersegment areas with local transtension and segments with almost pure strike slip motion the results of our experiments combined with field data along the central american volcanic arc indicate that the slab rollback intensity beneath the chortis block is greater in nicaragua and decreases westward to guatemala

collisional model for rapid fore arc block rotations arc curvature and episodic back arc rifting in subduction settings 1 we review geophysical and geological data from 23 active and ancient plate boundaries to document a compelling spatial and temporal relationship between collision plate boundary curvature rapid tectonic rotations and the occurrence of back arc rifting our observations support a conceptual model where the change from subduction to collision causes rapid fore arc rotation when viewed in a reference frame relative to the bounding tectonic plates leading to marked plate boundary curvature our global compilation reveals that most active back arc rifts are associated with rapidly rotating fore arcs and nearby collisions thus we propose that collision and rapid fore arc rotations play a major role in the evolution and kinematics of back arc basins we conduct numerical modeling to better understand the physical processes behind these observed rapid tectonic rotations at convergent margins our results suggest that the presence of an indentor or choke point in the subduction system e g collision can generate rapid rotation of the fore arc about a nearby pole and lead to back arc rifting the rate of fore arc rotation and back arc rifting depends on the incoming indentor velocity and can be greatly enhanced by slab rollback and the presence of a low viscosity back arc where viscosity of the back arc is low fore arc rotation dominates where back arc viscosity is high the formation of strike slip faults and tectonic escape dominates our observational and model derived results illustrate that shallow crustal forces produced by the entry of buoyant features into subduction zones are a fundamental mechanism for the generation of fore arc block rotations plate boundary curvature back arc rift evolution and tectonic escape in subduction systems rollback of the subducting slab within the mantle will certainly enhance the processes we describe but it is not the only driving force

changes in static stress on southern california faults after the 1992 landers earthquake the magnitude 7 5 landers earthquake of 28 june 1992 was the largest earthquake to strike california in 40 years the slip that occurs in such an earthquake would be expected to induce large changes in the static stress on neighbouring faults these changes in stress should in turn affect the likelihood of future earthquakes stress changes that load faults towards failure have been cited as the cause of small1 5 moderate6 and large7 earthquakes conversely those that relax neighbouring faults have been related to a decrease in seismicity5 here we use an elastic half space model8 to estimate the stress changes produced by the landers earthquake on selected southern california faults including the san andreas we find that the estimated stress changes are consistent with the triggering of four out of the five aftershocks with magnitude greater than 4 5 and that the largest changes 1 10 bar occurring on part of the san bernardino segment of the san andreas fault may have decreased the time to the next magnitude 8 earthquake by about 14 years

mineralization of ree y nb ta zr hf in wuchiapingian coals from the liupanshui coalfield guizhou southwestern china geochemical evidence for terrigenous input abstract abundances modes of occurrence enrichment and origin of critical elements in coal and coal bearing sequences have attracted much attention in recent years previous investigations have attributed ree y nb ta zr hf mineralization in coals and in intra and inter seam tuffs in coal bearing sequences to alkali volcanic ash eruptions and subsequent hydrothermal alteration in this study two major minable coal seams d101 and w407 that are located in the lowermost and uppermost wuchiapingian longtan formation in the liupanshui coalfield guizhou southwestern china were investigated in order to better understand the mechanism of ree y nb ta zr hf enrichment in these coals elevated concentrations of ree y nb ta zr hf in the d101 coal are dominantly due to the alkaline volcanic material forming the top of the emeishan large igneous province elip which served as a terrigenous source region for the coal basin and to airborne volcanic ash which occurs as an intra seam tonstein within the coal seam both of the two source materials were subsequently subjected to groundwater leaching resulting in redistribution of the rare earth elements and y rey leading to an uneven distribution of rey and zr along the studied coal seam sections the average rey oxides in the d101 and w407 coals are 2682 and 1260 ppm both on ash basis respectively and the outlook coefficients are 0 79 and 1 15 respectively indicating that both ashes from the two coals are potential raw sources for rey

fault kinematics in northern central america and coupling along the subduction interface of the cocos plate from gps data in chiapas mexico guatemala and el salvador new gps measurements in chiapas mexico guatemala and el salvador are used to constrain the fault kinematics in the north america na caribbean ca and cocos co plates triple junction area the regional gps velocity field is first analysed in terms of strain partitioning across the major volcano tectonic structures using elastic half space modelling then inverted through a block model we show the dominant role of the motagua fault with respect to the polochic fault in the accommodation of the present day deformation associated with the na and ca relative motion the na ca motion decreases from 18 22 mm yr 1 in eastern guatemala to 14 20 mm yr 1 in central guatemala assuming a uniform locking depth of 14 28 km down to a few millimetres per year in western guatemala as a consequence the western tip of the ca plate deforms internally with 9 mm yr 1 of east west extension 5 mm yr 1 across the guatemala city graben alone up to 15 mm yr 1 of dextral motion can be accommodated across the volcanic arc in el salvador and southeastern guatemala the arc seems to mark the northern boundary of an independent forearc sliver ar pinned to the na plate the inversion of the velocity field shows that a four block na ca co and ar model that combines relative block rotations with elastic deformation at the block boundaries can account for most of the gps observations and constrain the overall kinematics of the active structures this regional modelling also evidences lateral variations of coupling at the co subduction interface with a fairly high coupling 0 6 offshore chiapas and low coupling 0 25 offshore guatemala and el salvador

a new evaluation of seismic hazard for the central america region a new evaluation of seismic hazard in central america has been carried out as part of the cooperation project named resis ii under the auspices of the norway cooperation agency norad several seismic hazard experts from costa rica guatemala honduras nicaragua el salvador panama norway and spain participated in the study which was aimed at obtaining results suitable for seismic design purposes the analysis started with a thorough revision of the national seismic catalogs from which a catalog for central america has been compiled and homogenized to moment magnitude m w seismotectonic models proposed for the region were revised and a new regional zonation was proposed taking into account seismotectonic data seismicity focal mechanisms and gps observations besides ground motion prediction equations gmpes for subduction volcanic and crustal zones were revised and the most suitable ones were calibrated with central american strong motion data subsequently a seismic hazard analysis was developed in terms of peak ground acceleration pga and spectral accelerations sa t for periods of 0 1 0 2 0 5 1 and 2 s by means of the probabilistic seismic hazard assessment psha approach as a result different hazard maps were obtained for the quoted parameters together with uniform hazard spectra uhs for six of the capital cities of central america disaggregation was also carried out in these capitals for the target motion given by the pga and sa 1 s and obtained for return periods of 500 years and 2500 years therefore the control earthquakes for motions of short and long periods were derived this is the first study developed in central america at a regional scale after 10 years online material table of the largest central american earthquakes in historical times

enrichment and distribution of elements in the late permian coals from the zhina coalfield guizhou province southwest china abstract this paper investigates the mineralogy and geochemistry of four coal beds wjb 6 wjb 7 fhs 23 and fhs 27 coals of the late permian in the zhina coalfield western guizhou province china the investigated coals reach the semianthracite anthracite coal rank and have super low to low ash yields the sulfur contents vary considerably through coal sections and are mostly in the range of medium high sulfur coal the mineral assemblage present in the fhs 23 and fhs 27 coals is mainly made up of pyrite and rectorite the wjb 6 and wjb 7 coals have different mineralogy with kaolinite and rectorite dominant in the former as well as quartz and rectorite in the latter these coals contain high concentrations of nb and ta but li is only enriched in the wjb 6 coal rectorite and anatase in these coals are important hosting phases of nb and ta while kaolinite and to a lesser extent chamosite in the wjb 6 coal are dominant carriers for the elevated li concentration the terrigenous material input the marine influence and the effect of circulating hydrothermal solution are the pivotal geological factors causing geochemical anomalies in coals investigated the high sulfur coals were subjected to an enhanced marine influence in the depositional environment as well as to a higher terrigenous influx when compared with the medium sulfur and low sulfur coals resulting in higher concentrations of s fe as mo u hg in the former coals than in the latter ones the anomalous enrichment of nb and ta in these coals as well as of li in the wjb 6 coal is the result of the contributions from ascending hydrothermal solutions although source rocks e g high ti basalt may provide relatively high background abundances of nb ta and li

characterization of intrusive rocks and ree geochemistry of coals from the zhuji coal mine huainan coalfield anhui china abstract rare earth element ree concentrations in coals are a source of information relevant to the evolution of source rocks depositional environment and epigenetic tectonic activity as well as the effects of igneous intrusions in this study 186 coal samples 11 intrusion affected coal samples 4 samples representative of the intrusive rocks one coal roof and one parting samples were collected from 29 boreholes at the zhuji coal mine huainan coalfield anhui province china the main objective is to characterize the intrusive rocks in the coal bearing sequence and to investigate the correlation of ree parameters in the coals with the source rocks depositional environment localized faults igneous intrusions and thickness of the coal beds a sequence from base to top of acidic to basic intrusive rocks through the coal bearing strata was identified which possibly corresponds to different intrusive episodes of granite diorite monzonite and gabbro both the ree contents and degree of fractionation of light rare earth elements lree and heavy rare earth elements hree increase from acidic to basic rocks most rocks are slightly depleted in ce but highly depleted in eu the ree concentrations in coals from the zhuiji mine average of 118 g g are nearly identical to recently updated average chinese values but significantly higher than global values the ree content of the intrusion affected coals is not distinctively different from that of the other coals p 0 2 and ree concentrations of the igneous rocks appear to have no clear relationship to those of the intrusion affected coals the depositional environment and source rocks are presumably the main ree contributors to the coal accumulation basin the ree content in coals from fault affected boreholes is higher than that in other boreholes and this trend is stronger in the coal seams of the upper strata the hree tend to be incorporated into thinner coal seams and the degree of fractionation between lree and hree of the coal forming materials increases with coal thickness

mantle flow at a slab edge seismic anisotropy in the kamchatka region the junction of the aleutian island and the kamchatka peninsula defines a sharp turn in the boundary of the pacific and north american plates terminating the subduction zones of the northwest pacific the regional pattern of shear wave birefringence near the junction indicates that trench parallel strain follows the seismogenic benioff zone but rotates to trench normal beyond the slab edge asthenospheric mantle is inferred to flow around and beneath the disrupted slab edge and may influence the shallowing dip of the benioff zone at the aleutian junction

eocene arc continent collision and crustal consolidation in kamchatka russian far east the age and origin of high grade metamorphic rocks of the sredinnyi range kamchatka have been the subject of a long and controversial debate based on geochronologic data and its association with a collage of accreted oceanic terranes leading interpretations argue that the sredinnyi range metamorphic rocks represent an accreted precambrian or mesozoic microcontinent in this contribution we present new data that indicate that these metamorphic rocks were formed from the cretaceous paleocene sedimentary margin of northeast russia when it was overridden during eocene obduction of the olyutorsky arc a far travelled oceanic island arc our data include new mapping and structural observations along the northern and eastern flanks of the sredinnyi range and shrimp zircon and monazite u th pb age data from 15 key samples these new isotopic data demonstrate that paragneissic units were formed from sediments with depositional ages locally no older than late cretaceous to paleocene furthermore the statistical similarity of zircon u pb grain ages from the kamchatka schist with very low grade turbidite sandstones of the ukelayat and khozgon groups indicate that metasediments of the sredinnyi range are upgraded stratigraphic equivalents of northeast russian marginal strata shrimp u pb ages of zircon overgrowths and metamorphic monazite extracted from migmatite and gneiss indicate that peak metamorphism occurred at 52 ma which is synchronous with the onset of the olyutorsky arc continent collision heating and cooling occurred rapidly at rates approaching 80 c m y rapid heating is attributed to syn collisional subduction related magmatism thermochronology and structural observations indicate that exhumation was due to a combination of ductile and brittle thinning of the crust we speculate that this thinning was caused by diapiric ascent of a low density low viscosity continental material beneath a dense structural lid of the obducted island arc

comments on the geochemistry of rare earth elements la ce sm eu tb yb lu with examples from coals of north asia siberia russian far east north china mongolia and kazakhstan abstract the geochemistry of the ree la ce sm eu tb yb and lu is reviewed with supporting data from coals of north asia the 7189 samples from north asia included in this study represent all coal ranks lignites subbituminous coals bituminous coals and anthracites as well as coals formed under different geotectonic regimes and in different sedimentary conditions these coals are characterized by higher contents of the ree as compared to the coal clarke the distribution characteristics and accumulations of the ree have been studied in several coal deposits and basins within some basins with the near background average contents of the ree isolated coal beds enriched in lanthanides have been observed in coal basins and deposits the relative enrichment in the lanthanides are observed in the fields or zones adjacent to the source area of the terrigenous material accumulation of high ree contents in coal deposits can be attributed to the presence of rocks in the source area containing high concentrations of ree and also alkaline or acidic volcanic ash contemporaneous with the peat accumulation in the basin transformation of volcanic ashes under the aggressive hydro environment of a peat bog results in the mobilization and redeposition of the ree adjacent to the altered volcanic ashes tonsteins with the formation of high concentrations of ree in the coal beds the formation of the ree anomalies may also be related to hydrothermal processes the modes of occurrence of the ree change during the coalification process brown coals with a low degree of coalification are dominated by the organic modes of occurrence of the ree whereas in hard coals and anthracites authigenic mineral forms dominate

neotectonics geodesy and seismic hazard in the northern walker lane of western north america thirty kilometers of crustal shear and no strike slip article i nfo roughly 30 km of cumulative right lateral crustal displacement and 5 6 mm yr of the ongoing relative right lateral motion between the pacific and north american plates are observed in the northern walker lane the right lateral shear has been accommodated in large part by the development of a set of discontinuous en echelon normal fault bounded basins and perhaps significant vertical axis rotations of the intervening crust the observations provide an illustrative example of how large amounts of crustal shear may be accom modated in the absence of strike slip faults and point to difficulties attendant to melding geologic and geo detic observations in the analysis of seismic hazard in this particular case the assumption that all geodetically observed shear across the area will be recorded by earthquake displacements may be flawed

occurrence and origin of minerals in a chamosite bearing coal of late permian age zhaotong yunnan china the minerals found in the no 5 coal late permian from the zhaotong coalfield yunnan province southwestern china have been examined and found to consist mainly of kaolinite pyrite chamosite quartz and calcite with trace amounts of illite and mixed layer illite smectite the proportion of chamosite in clay minerals ranges from 32 to 56 wt with an average of 46 wt chamosite is distributed not only in collodetrinite but also occurs as cell fillings in fusinite semifusinite and telinite the high content and mode of occurrence of chamosite in this mine indicate its formation by interaction of kaolinite with fe mg rich fluids during early diagenesis except for a minor amount of terrigenous quartz most quartz is of authigenic origin and formed from kaolinite desilication the calcite content of the no 5 coal is 1 4 6 3 with an average of 3 and is distributed in collodetrinite and as cell fillings of coal forming plants calcite originated from seawater invasion during peat accumulation pyrite occurs in several ways as massive framboidal isolated enhedral anhedral and euhedral forms in addition the presence of a large amount of pyritized red algae provides strong evidence of seawater invasion during peat accumulation the red algae may have played an important role in the enrichment of sulfur in the coal the characteristic assemblage of minerals in this mine resulted from a unique basinal environment in which the mineral matter was derived from a basaltic source region volcanic activity and seawater transgression during coal formation

control of hazard due to seismicity induced by a hot fractured rock geothermal project in 2003 hydraulic stimulations were carried out in a geothermal field in eastern el salvador central america as part of a project to explore the feasibility of commercial hot fractured rock energy generation a key requisite for this environmentally friendly energy source is that the fracturing of the hot rocks at depths of 1 2 km must not produce levels of ground shaking at the surface that would present a serious disturbance or threat to the local population thresholds of tolerable ground motion were inferred from guidelines and regulations on tolerable levels of vibration and from correlations between instrumental strong motion parameters and intensity considering the vulnerability of the exposed housing stock the thresholds were defined in terms of peak ground velocity pgv and incorporated into a traffic light system that also took account of the frequency of occurrence of the induced earthquakes the system was implemented through a dedicated seismograph array and locally derived predictive equations for pgv the traffic light was used as a decision making tool regarding the duration and intensity of pumping levels during the hydraulic stimulations the system was supplemented by a small number of accelerographs and re calibrated using records obtained during the rock fracturing

origin and distribution of tonsteins in late permian coal seams of southwestern china abstract we have surveyed the areal and stratigraphic distribution of tonsteins in late permian coalfields of southwestern china over an area of several hundred thousand square kilometers we studied the relationship between tonstein distribution and sedimentary environment based on mineralogical and petrographic data we have concluded that these tonsteins originated as air fall volcanic ashes following accumulation in the peat swamps in situ alteration of the vitric and lithic components took place under acidic conditions leading to the formation of kaolinite based on petrologic mineralogic and chemical analytical data we have determined that the application of mineralogic and geochemical criteria for tonsteins may be useful in correlating coal beds predicting coal qualities and reconstructing related sedimentary paleoenvironmental conditions

mineralogy and geochemistry of a superhigh organic sulfur coal yanshan coalfield yunnan china evidence for a volcanic ash component and influence by submarine exhalation abstract the mineralogy and geochemistry of a superhigh organic sulfur shos coal of late permian age from the yanshan coalfield yunnan province southwestern china have been studied using optical microscope low temperature ashing plus x ray diffraction analysis scanning electron microscope equipped with energy dispersive x ray spectrometer a sequential chemical extraction procedure and inductively coupled plasma mass spectrometry the m9 coal from the yanshan coalfield is a shos coal that has a total sulfur content of 10 12 11 30 and an organic sulfur content of 8 77 10 30 the minerals in the coal consist mainly of high temperature quartz sanidine albite muscovite illite pyrite and trace amounts of kaolinite plagioclase akermanite rutile and dawsonite as compared with ordinary worldwide bituminous coals and anthracite and chinese coals the m9 coal is remarkably enriched in b 268 g g f 841 g g v 567 g g cr 329 g g ni 73 9 g g mo 204 g g and u 153 g g in addition elements including se 25 2 g g zr 262 g g nb 20 1 g g cd 2 07 g g and tl 2 03 g g are also enriched in the coal occurrence of high temperature quartz sanidine muscovite and illite in the m9 coal is evidence that there is a volcanic ash component in the coal that was derived from acid volcanic ashes fallen into the swamp during peat accumulation occurrence of albite and dawsonite in the coal and strong enrichment of some elements including f s v cr ni mo and u are attributed to the influence by submarine exhalation which invaded along with seawater into the anoxic peat swamp abundances of lithophile elements including rare earth elements nb y zr and tio2 indicate that the silicate minerals in the coal were derived from the northern vietnam upland to the south of the basin

mineralogy and geochemistry of pegmatite hosted sn ta nb and zr hf bearing minerals from the southeastern part of the bastar malkangiri pegmatite belt central india abstract primary tin and rare metal mineralization in the bastar malkangiri pegmatite belt central india is associated with granitic pegmatites hosted by metabasic and metasedimentary rocks the rare metal minerals identified from six mineralized pegmatites at govindpal mundaguda mundval dhuramagurah haladikunda and bacheli include cassiterite columbite tantalite wodginite microlite fersmite and hf zircon ta nb poor cassiterite is ubiquitous and the most abundant ore mineral in all the mineralized pegmatites subtle differences are noted in the ore mineral assemblages and in the compositions of individual minerals in different pegmatites ta nb oxides are represented by microlite wodginite manganotantalite in li f p bearing lct pegmatites govindpal mundaguda and mundval in contrast least evolved members of the lct type pegmatites are characterized by the presence of ferrocolumbite dhuramgurah haladikunda and rare ferrotantalite bacheli the compositional variations of columbite tantalite in terms of ta ta nb and mn mn fe ratios and zircon in terms of hf contents from different pegmatites correlate with the degree of fractionation of the pegmatitic melt in the govindpal pegmatite ta nb poor cassiterite occurs as aggregates of grains small pockets and veinlets in the intermediate and core zone the ta nb oxides are restricted to the core margin texturally and compositionally distinct ta nb rich cassiterite along with ta nb oxides and hf zircon occur as irregular inclusions in ta nb poor cassiterite at the core margin the field evidence textural relations and compositions of the ore minerals suggest that the main mineralizing event was associated with hydrothermal precipitation of ta nb poor cassiterite which postdated precipitation of manganotantalite wodginite microlite hf zircon and ta nb rich cassiterite in the govindpal pegmatite the crystallization of ta nb oxides was facilitated possibly by the removal of li and f from the melt and that of ta nb rich cassiterite by increasing oxygen fugacity calculated higher fe 3 fe 2 in wodginite compared to manganotantalite suggests such a possible increase in oxygen fugacity anastomosing veins of microlite in ta nb poor cassiterite was the last mineralizing event in this pegmatite the consistently high ti contents of this subsolidus vein microlite compared to primary ta nb oxides manganotantalite wodginite and microlite might suggest contamination by ingress of metamorphic fluid during its formation

asymmetric deformation in the backarc region of the kuril arc northwest pacific new insights from analogue modeling 1 the eocene to middle late miocene tectonic evolution of the kuril arc and backarc region has been simulated with analogue experiments the experiments simulate asymmetric deformation in the overriding plate due to anticlockwise rollback of the subducting pacific plate the results show the formation of a n s to ne sw oriented dextral shear zone near the far edge of the retreating boundary analogous to the sakhalin hokkaido dextral shear zone contemporaneously normal faults and grabens form striking parallel to the retreating boundary near the far edge but striking more oblique near the hinge point and away from the retreating boundary this is similar to extensional structures observed in the kuril basin and the sea of okhotsk furthermore the model shows that the amount of extension progressively decreases away from the retreating boundary this appears to have also happened in the kuril okhotsk region as evidenced by crustal thickness variation in the region finally the model results show that extension is increasingly accommodated by the region close to the retreating boundary with progressive deformation this can account for the eocene early miocene extension in the sea of okhotsk followed by miocene spreading in the kuril basin

mineralogical and geochemical compositions of late permian coals and host rocks from the guxu coalfield sichuan province china with emphasis on enrichment of rare metals abstract this paper reports the geochemical and mineralogical compositions of the late permian no 25 coal semi anthracite and its host rocks roof and floor strata from the guxu gulin xuyong coalfield sichuan province china the coal is characterized by medium sulfur content average 2 73 and has an average ash yield of 20 95 in contrast to other late permian coals from southwestern china that are enriched in sc v cr co ni and cu the no 25 coal does not contain an abundance of these transition elements but is rich in lithophile elements be y nb zr hf and u the elevated concentrations of trace elements in the no 25 coal were probably derived from the felsic intermediate rocks at the top of the emeishan basalt sequence rather than from the emeishan mafic basalts the floor strata of the no 25 coal can be divided into two sub sections the upper sub section of the sequence immediately below the no 25 coal consists of material with a felsic intermediate composition probably derived from terrigenous sources and the lower sub section is composed of mafic tuff the terrigenous mineral matter in the no 25 coal appears to have the same sediment source region as the upper sub section of the floor strata based on their similar geochemical compositions the roof strata of the no 25 coal are more quartzose and were probably derived from a different sediment source region the mineral matter in the coal is dominated by kaolinite and to a lesser extent calcite and pyrite the roof and floor strata each have quite different mineralogy with kaolinite dominant in the latter and illite kaolinite and quartz in the former pyrite contents are variable both in the coal and in the host rocks the floor strata and the coal have been affected by hydrothermal solutions leading to the enrichment of rare earth elements and yttrium rey nb ta zr hf and u the rey in the coal and floor strata as well as the nb ta zr hf and u in the floor strata represent potentially economic rare metal resources

the latest cretaceous early paleogene rapid growth of accretionary complex and exhumation of high pressure series metamorphic rocks in northwestern pacific margin episodic growth of accretionary complexes along the northwestern pacific margin is well documented from detailed biostratigraphy and radiometric dating of metamorphic rocks the latest cretaceous to early paleogene rapid growth of the accretionary complexes observed in hokkaido and sakhalin islands was caused by the supply of a large amount of terrigenous sediments from an intracontinent collision zone the mongolia okhotsk zone in the northern asian continent rapid growth of the accretionary prism resulted in episodic tectonic events in the forearc and magmatic arc rapid underplating caused uplift and exhumation of previously accreted complexes along with high pressure series metamorphic rocks now exposed as the kamuikotan complex in hokkaido and the susunai complex in sakhalin the forearc basin shallowed as a result of the uplift the uplift collapsed the old accretionary complex and supplied olistoliths onto the forearc region magmatic activity along the continental margin was also active at the same time subduction of a large amount of terrigenous sediments into the mantle may have contributed to active magmatism at that time a large supply of water trapped in the subducted sediments entered the mantle and increased partial melting of the mantle wedge

the tectonics of the okhotsk sea abstract the northern and central parts of the okhotsk sea form an epimesozoic platform the hetero aged acoustic basement is represented by deformed geosynclinal rocks from cretaceous to precambrian in age the slightly deformed sedimentary cover levelled the uneven surface of the acoustic basement and this upper paleogene neogene cover filled up the system of the structural basins the general nw se and w e extensions of the taphrogenic horsts and grabens of the acoustic basement were formed due to extension and subsidence of the earth s crust during the late paleogene neogene

mineralogical and compositional characteristics of late permian coals from an area of high lung cancer rate in xuan wei yunnan china occurrence and origin of quartz and chamosite abstract some townships in xuan wei county yunnan province have one of the highest lung cancer mortality rates in china and the epidemic disease in the area has generally been attributed to the polycyclic aromatic hydrocarbons pahs released from domestic coal burning however the cancer causing culprit is not settled as tian tian l 2005 coal combustion emissions and lung cancer in xuan wei china ph d thesis university of california berkeley found nanometer quartz in these coals soot emissions and lung cancer tissues we have conducted mineralogical and geochemical studies of the coals from xuan wei for the purpose of shedding light on the minerals which may be related to the epidemic lung cancer in this paper abundances modes of occurrence and origins of minerals and elements in the coals from two mines in xuan wei have been studied using optical microscope low temperature ashing x ray diffraction analysis scanning electron microscope equipped with energy dispersive x ray spectrometer and inductively coupled plasma mass spectrometry the minerals in the coals are mainly composed of quartz chamosite kaolinite and calcite the particle size of quartz is rather small mostly less than 20 m and it is of authigenic origin chamosite occurs mainly as cell fillings the occurrence of quartz and chamosite indicates that they were derived from the hydrothermal fluids epigenetic calcite is derived from calcic fluids kaolinite is derived mainly from sediment source region of kangdian oldland to the west of coal basin the composition of xuan wei coal is high in sio2 fe2o3 tio2 cao mno v co ni cu and zn the high sio2 content is attributed to quartz and the fe2o3 content to chamosite the high mn and low mg contents in the coal indicate the inputs of hydrothermal fluids cao occurs mainly in epigenetic calcite elements ti co ni cu zn and rare earth elements were derived from the basaltic rocks at sediment source region

coal deposits as potential alternative sources for lanthanides and yttrium abstract this paper presents data on widespread abnormal accumulations of lanthanides and yttrium rey in many coal deposits worldwide high rey contents 0 1 have been found in coal seams and coal ashes as well as in the host and basement rocks of some coal basins for a preliminary evaluation of coal ashes as an rey raw material not only the abundance but also the individual rey compositions were taken into account in this paper three rey distribution patterns for high rey coal ashes are fixed with lrey lan lun 1 mrey lan smn 1 and hrey lan lun

new data on geology and germanium mineralization in the hunchun basin northeastern china abstract the geochemistry and mineralogy of palaeogene coals from the hunchun coalfield jilin province northeastern china have been studied using x ray fluorescence spectrometry inductively coupled plasma mass spectrometry scanning electron microscopy in combination with energy dispersive x ray spectrometry and x ray diffraction analysis of the low temperature ash the 22a coal from the banshi mine is of subbituminous a to high volatile bituminous rank 0 53 0 56 ro ran and has a low sulfur content 0 74 on average the 22a coal consists mainly of kaolinite quartz illite and to a lesser extent plagioclase siderite and pyrite as compared with the average world low rank coals the 22a coal is enriched in as sb ge cs and w combined with the geochemical features of six other coal seams from the hunchun coalfield the terrigenous materials of the hunchun coals were dominantly from mesozoic mostly lower cretaceous volcanic rocks and paleozoic granites and associated metamorphic rocks surrounding the coal basin a minor source was the paleogene volcaniclastics including some adakitic rocks which are characterized by higher sr y and la yb ratios the ge enrichments that are detected in some individual coal benches from the hunchun coalfield were related to tectonic uplift of the crystalline rocks surrounding the basin and their following denudation the oxidized meteoric waters episodically influenced by volcanic related hot springs might extract ge from the source rocks and then precipitate it as a result of bio chemical reduction forming the mineralization disseminated in the coals

mineralogical and geochemical compositions of the coal in the guanbanwusu mine inner mongolia china further evidence for the existence of an al ga and ree ore deposit in the jungar coalfield abstract aluminum hydroxide boehmite and diaspore ga rey rare earth elements and y and al rich pennsylvanian taiyuan formation coals have previously been found in the jungar and daqingshan coalfields inner mongolia china gallium rey and al are potentially extractable and usable elements in combustion residues derived from these coals this paper reports new results on 50 bench samples of the no 6 coal from the guanbanwusu mine jungar coalfield inner mongolia and provides new data and evidence for the existence of an al ga rey ore deposit in the unique jungar coalfield the no 6 coal in the guanbanwusu mine has a low rank ro ran 0 56 and a low sulfur content st d 0 58 the proportion of inertinite in the coal 56 7 mineral free basis is higher than that of vitrinite 31 the minerals in the coal are mainly represented by kaolinite boehmite and chlorite along with variable proportions in some samples of calcite ankerite siderite and goyazite boehmite goyazite and part of the kaolinite were derived from bauxite in the weathered surface of the sediment source region ankerite calcite and siderite in the coal are of authigenic origin the chlorite in the guanbanwusu coals appears to have a chemical composition intermediate between cookeite and chamosite this mineral mainly occurs as cell fillings also indicating an authigenic origin and was probably derived from hydrothermal fluids a new mineral phase mainly composed of ti cl and fe is probably a ti bearing oxychloride or hydroxychloride compared to other chinese coals and to world hard coals the coal from the guanbanwusu mine is enriched in al2o3 9 34 p2o5 0 126 li 175 g g f 434 g g cl 1542 g g ga 12 9 g g sr 703 g g and th 12 9 g g but has a lower sio2 al2o3 ratio 0 74 due to the higher proportions of boehmite and goyazite in the coal the major carrier of p2o5 and sr is goyazite lithium mainly occurs in the chlorite cf cookeite kaolinite and possibly to a lesser extent illite fluorine in the coal has a major boehmite affinity but a small proportion may also occur in the organic matter and chlorite gallium in the coal largely occurs in goyazite chlorine is independent of other elements in the coal associated neither with moisture nor with organic matter but possibly occurring in molecular form cl2 and in the ti bearing oxychloride or hydroxychloride thorium in the coal occurs in the clay and accessory minerals and was mainly derived from detrital materials of the source region rare earth elements and y have a mixed organic and inorganic affinity largely occurring in goyazite group minerals and to a lesser extent boehmite and organic matter most coal benches and partings have either an l type or h type of rey enrichment owing respectively to the weathered bauxite source region and groundwater effects the al2o3 ga rey and possibly li in the guanbanwusu coals like those in coals from the jungar and adjacent daqingshan coalfields are industrially useful metals that could potentially be recovered from the relevant coal combustion residues it is suggested that if ga in ash 50 g g rey 800 900 g g sio2 al2o3 40 in ash and coal thickness 5 m the coal combustion residues would be expected to be suitably enriched in al2o3 and can be considered for al2o3 ga and rey recovery

continent elevation mountains and erosion freeboard implications 1 to the simplest approximation earth s continental crust is a floating aggregate on the planet s surface that is first attracted to subduction zones and upon arrival thickened by mountain building then producing some extension thickened regions are thinned again by erosion a comparison between 65 ma and the present shows that the modern state is significantly more mountainous an estimated average continental elevation increase relative to average ocean floor depth of about 54 m and sea level decrease relative to the ocean floor of about 102 m add up to a 156 m increase of continent elevation over sea level since 65 ma both are affected most strongly by the roughly 1 7 continent surface area decrease caused by cenozoic mountain building this includes contributions from erosion volumes of sediments in deltas and submarine fans indicate an average thickness of 371 m deposited globally in the ocean basins since 65 ma this relatively large change of continent area over a short span of earth history has significant consequences extrapolating if continent area change exceeded 5 in the past either severe erosion or flooded continents occurred if continent elevation freeboard remains at the present value of a few hundred meters the past continent ocean area ratio might have been quite different depending on earlier volumes of continental crust and water we conclude that along with the ages of ocean basins continental crustal thickening exerts a first order control on the global sea level over hundreds of million years

large magnitude crustal seismic sources in el salvador and deterministic hazard scenarios abstract during the last years several crustal seismic sources have been proposed in el salvador however the actual destructive potential of these proposals has not been revealed yet here we present several seismic scenarios related with the main crustal faults in the country we have characterized the corresponding hazard scenarios in a deterministic way estimating the peak ground accelerations pga including local site effects in addition we present a list of 29 sources that can be considered potentially dangerous with their main features when they are available and four seismic scenarios that we consider to be more probable we have resorted to the february 13th 2001 mw 6 6 destructive earthquake the only earthquake occurred in a known crustal source in el salvador and recorded by the strong motion network in order to test the methodological approach and the reliability of the pga results predicted by two available ground motion prediction equations gmpes including the site effect the consistence between the values given by the models and the ones recorded during the event provides reliability to our results this approach allowed us to conclude that faults within the volcanic arc can produce accelerations up to 1 g in the most conservator case mw 7 0 while accelerations up to 0 6 g are usual results related with specific faults within the salvadoran volcanic arc besides the reported damage distribution of the 8th june 1917 earthquakes and its similarity with one of the proposed scenarios allowed us to infer the possible source of this event the guaycume fault

the 13 january 2001 el salvador earthquake a multidata analysis 1 on 13 january 2001 a large normal faulting intermediate depth event mw 7 7 occurred 40 km off the el salvadorian coast central america we analyze this earthquake using teleseismic regional and local data we first build a kinematic source model by simultaneously inverting p and sh displacement waveforms and source time functions derived from surface waves using an empirical green s function analysis in an attempt to discriminate between the two nodal planes 30 trenchward dipping and 60 landward dipping we perform identical inversions using both possible fault planes after relocating the hypocentral depth at 54 km we retrieve the kinematic features of the rupture using a combination of the neighborhood algorithm of sambridge 1999 and the simplex method allowing for variable rupture velocity and slip we find updip rupture propagation yielding a centroid depth around 47 km for both assumed fault planes with a larger variance reduction obtained using the 60 landward dipping nodal plane we test the two possible fault models using regional broadband data and near field accelerograms provided by universidad centro americana 2001 near field data confirm that the steeper landward dipping nodal plane is preferred rupture propagated mostly updip and to the northwest resulting in a main moment release zone of approximately 25 km 50 km with an average slip of 3 5 m the large slip occurs near the interplate interface at a location where the slab steepens dip significantly the occurrence of this event is well explained by bending of the subducting plate

chemical characteristics and genesis of the quartz feldspathic rocks in the archean crust of greenland a total of 108 samples of meta tonalites metagranodiorites granites and meta tholeiites representing groups of early to late archean age and different metamorphic history from sw and se greenland have been analyzed for ca k and 28 trace elements there is no systematic change of the chemical composition with age observable the results support petrologic experiments which suggest that tonalites and granodiorites the most abundant rocks of the archean crust are partial melting products of a mafic lower crust modelling suggest that this crust consisted of garnet amphibolite derived from a source with a bulk composition resembling a slightly enriched rather than depleted mantle the cen ybn ratio is above 10 in the majority of tonalites most samples have no eu anomaly because of a balanced contribution from the minerals of a mafic rock or a plagioclase free source the positive eu anomaly of some granodiorites and of a minor proportion of tonalites can be explained as being caused by plagioclase accumulation during differentiation or by partial melting of plagioclase rich fractions modelling with zn excludes an origin of tonalitic melts by differentiation of basaltic to dioritic magmas the archean meta diorites meta tonalites and meta granodiorites from greenland have generally lost some k and s relative to their suggested magmatic protoliths loss of rb tl pb and k and relative gain of ca sr ba and sc connected with granulitization of meta tonalites can be explained in the majority of cases by separation of about 25 percent granitic partial melt high k rb k pb zn cd and nb th ratios of granulites plus low ratios of granites are almost in balance with intermediate ratios of amphibolite facies tonalites retrogression of granulites into amphibolites was accompanied by introduction of pb tl rb ba sr and k from na cl rich brines circulating on fractures a comparison of the abundance of 24 elements characterized by different compatibility in the archean crust of greenland with the present bulk crust reflects only minor changes th nb if at all in the chemical composition of the continental crust since the archean

palynological constraints on the provenance and stratigraphic range of a lopingian late permian inter extinction floral lagerstatte from the xuanwei formation guizhou province china abstract late permian lopingian volcanoclastic lithologies from the huopu mine near fuyuan guzihou province sw china have yielded konservat lagerstatte grade plant macrofossils these fossils derive from a stratigraphic interval bounded by the mid capitanian extinction below and the end permian extinction above and globally few anatomically preserved floras are known from this age due to practical constraints of active mining at the site to date this konservat lagerstatte is only known from ex situ mine spoil however through the use of combined petrographic and palynologic analyses it has been possible to constrain the stratigraphic position provenance and taphonomic history of these fossils such that they are now known to have been deposited in in a shallow marine setting as part of the lower member of the xuanwei formation during the wuchiapingian the palynological assemblage is of low abundance and diversity and is dominated by fern spores with less common lycopsid and sphenopsid spores and gymnosperm pollen and rare marine acritarchs and is suggestive of an ecologically pioneering rather than established flora given the wuchiapingian age of the lagerstatte this flora has broader potential significance in that affords insights into pre adaption and resilience to the profound environmental perturbations associated with the mid capitanian and end permian extinctions which were key to long term survival into the triassic

geochemistry of trace elements in chinese coals a review of abundances genetic types impacts on human health and industrial utilization abstract china will continue to be one of the largest coal producers and users in the world the high volume of coal use in china has focused attention on the amounts of toxic trace elements released from coal combustions and also the valuable trace elements extracted or potentially utilized from coal ash compared to world coals chinese coals have normal background values for most trace elements with the exception of higher li 31 8 g g zr 89 5 g g nb 9 44 g g ta 0 62 g g hf 3 71 g g th 5 84 g g and rare earth elements la lu y 136 g g this is not only due to the higher ash yields of chinese coals but also to alkali volcanic ashes found in some southwestern coals the background values of toxic elements of hg 0 163 g g as 3 79 g g and f 130 g g in chinese coals are comparable to coals from most other countries the genetic types for trace element enrichment of chinese coals include source rock controlled marine environment controlled hydrothermal fluid controlled including magmatic low temperature hydrothermal fluid and submarine exhalation controlled subtypes groundwater controlled and volcanic ash controlled the background values of trace elements were dominated by sediment source regions low temperature hydrothermal fluid was one of the major factors for the local enrichment of trace elements in southwestern china serious human health problems caused by indoor combustion of coal in china include endemic fluorosis arsenosis selenosis and lung cancer endemic fluorosis mainly occurring in western guizhou was mostly attributed to the high fluorine in clay that was used as a briquette binder for fine coals in addition to a small quantity of fluorine from coal fluorine in the coal from endemic fluorosis areas of western guizhou is within the usual range found in china and the world endemic arsenosis in southwestern guizhou is attributed to indoor combustion of high as coal endemic selenosis in enshi of hubei was due to high se in carbonaceous siliceous rocks and carbonaceous shales fine particles of quartz released into air during coal combustion are hypothesized as a possible cause for the lung cancer epidemic in xuanwei yunnan china valuable elements including ge ga u ree rare earth element nb zr and re are concentrated to levels comparable to conventional economic deposits in several coals or coal bearing strata in china the ge deposits at lincang yunnan province and wulantuga inner mongolia have been exploited and industrially utilized the enrichment of ge in the two deposits was caused by hydrothermal fluids associated with adjacent granitoids the ga al ore deposit in the jungar coalfield inner mongolia was derived from the neighboring weathered and oxidized bauxite of the benxi formation pennsylvanian the nb ta zr hf ree ga deposits in the late permian coal bearing strata of eastern yunnan and chongqing of southwestern china were attributed to ashes of the alkali volcanic eruptions

triggering of destructive earthquakes in el salvador we investigate the existence of a mechanism of static stress triggering driven by the interaction of normal faults in the middle american subduction zone and strike slip faults in the el salvador volcanic arc the local geology points to a large strike slip fault zone the el salvador fault zone as the source of several destructive earthquakes in el salvador along the volcanic arc we modeled the coulomb failure stress cfs change produced by the june 1982 and january 2001 subduction events on planes parallel to the el salvador fault zone the results have broad implications for future risk management in the region as they suggest a causative relationship between the position of the normal slip events in the subduction zone and the strike slip events in the volcanic arc after the february 2001 event an important area of the el salvador fault zone was loaded with a positive change in coulomb failure stress 0 15 mpa this scenario must be considered in the seismic hazard assessment studies that will be carried out in this area

mineralogy and geochemistry of the late permian coals in the huayingshan coal bearing area sichuan province china abstract the mineralogical and geochemical characteristics of the late permian huayingshan coals partings roof and floor strata as well as lutitic rocks from the longtan formation in sichuan province southwestern china were investigated in this study the huayingshan low volatile bituminous coals are characterized by relatively high mineral contents mainly kaolinite quartz pyrite and calcite the concentrations of most trace elements are relatively high compared with other chinese and world coals the coals and associated strata show similar element affinities al ti li ta th ga u sn sc cr cu rb co and se probably have an aluminosilicate affinity zr nb hf y rees and u probably result from the occurrence of heavy minerals such as zircon s fe w and rb mainly have a sulfide affinity ca sr and mn mainly have an carbonate affinity the high enrichment in the huayingshan coal of zr nb hf rees ta ga and th is caused by a geochemical anomaly in the source of this coal s detrital material and probably also by input of volcanic ash which is influenced by the alkaline volcanic magmas of the emeishan basalt the zr hf zr nb zr la and zr th ratios support the volcanic origin of such a geochemical anomaly

constraints from finite element modeling on the active tectonics of northern central america and the middle america trench 1 we have developed an elastic finite element model in order to study the role of the different forces acting on the northwestern part of the central american volcanic arc and the chortis block we present synthetic focal mechanisms maps of tectonic regime and strain crosses to analyze the results the models show that to achieve the observed state of stress on the volcanic arc the arc must be modeled as a lithospheric weak zone also the forces related to the eastward drift of the caribbean plate must be higher than those related to the subduction of the cocos plate the coupling on the subduction interface must be low with or without slip partitioning due to the obliquity of the subduction at the trench at guatemala the western edge of the chortis block is pinned against north america even with low trench normal forces making the triple junction between the cocos north american and caribbean plates a zone of diffuse deformation the extension in the western part of the chortis block from guatemala to the honduras depression is explained by the geometry of the north american caribbean plate boundary and the direction of motion of the caribbean plate with respect to north america the direction of extension in the chortis block is always e w regardless of the magnitude of the applied forces and the main part of the deformation is absorbed between the ipala graben and the honduras depression both features being consistent with our models

collision rotation and back arc spreading in the region of the okhotsk and japan seas the india eurasia collision caused extensive deformation in the eurasia continent since late eocene time we propose that back arc spreading in the okhotsk and japan seas was related to the movement of microplates relevant to the india eurasia collision the kuril basin of the okhotsk sea and the basins of the japan sea were formed as back arc basins simultaneously their late oligocene to middle miocene age is constrained by sediment stratigraphy basement depth and heat flow data the movements of two microplates the okhotsk and amuria plates are significant for the tectonics of the okhotsk and japan seas simultaneous retreat of both microplates from trench hinge lines caused back arc spreading in the kuril basin and the japan sea the amuria plate moved north northeastward due to the india eurasia collision this caused pull apart opening of the baikal rift along a transform boundary between the siberia and amuria plates and a collision along the stanovoy range at its northern margin this movement triggered a clockwise rotation of the okhotsk plate with a component of dextral collision between the okhotsk and amuria plates which is well observed along the central zone of the sakhalin hokkaido islands between the two back arc plates the clockwise rotation of the okhotsk plate is suggested by the southwestward fan shaped opening of the kuril basin the kuril basin narrows to the northeast and terminates south of the kamchatka peninsula where a relative rotation pole between the okhotsk and kuril forearc plates is located the kamchatka peninsula was a zone of collision on the other side of the clockwise rotating okhotsk plate during the opening of the kuril basin the sredinny range in the kamchatka peninsula is one of the results of the collision between the okhotsk plate and the forearc plate of the kuril arc the bending of the japanese islands occurred in association with the back arc spreading of the yamato basin of the japan sea

trace element geochemistry of altered volcanic ash layers tonsteins in late permian coal bearing formations of eastern yunnan and western guizhou provinces china trace element compositions were determined by instrumental neutron activation analysis inaa in 30 samples of synsedimentary volcanic ash derived tonsteins and detrital claystones from coal seams within the late permian coal bearing formation of eastern yunnan and western guizhou provinces china the characteristics of trace element geochemistry in the tonsteins can be distinguished from those of detrital claystones because of the former s unique volcanic ash origin the detrital claystones are characterized by their relatively high content of v ti sc cr co and ni relatively low content of th and u th u ratio and small negative eu anomaly eu eu 0 63 0 93 overall these trace element characteristics are consistent with a mafic source similar to the composition of basalt rocks in the erosional region on the western edge of the study area in contrast the tonsteins are low in v ti sc cr co and ni contents and have a high th u ratio with a distinct negative eu anomaly eu eu normally in the range of 0 2 0 4 consistent with a silicic magmatic source within the group of tonsteins those from the lower section p2 1 of the coal bearing formation are relatively high in ti zr hf nb ta and rare earth elements ree as compared to those from the middle and upper sections p2 2 3 in trace element discrimination diagrams scatter plots of hf ta ti ta ti v hf sc lu hf and lu th tonsteins from the p2 1 horizon always fall in isolated distribution areas separate from the tonsteins of the p2 2 3 horizon these results suggest that the source materials of tonsteins from the two separate horizons were probably derived from volcanic ash falls of two distinctly different natures based on a comparison of the concentrations and assemblages of trace elements between various magmatic rocks the source materials of tonsteins from p2 1 horizon were mostly composed of calc alkalic silica poor volcanic ash similar to rhyodacitic magma whereas those from p2 2 3 were apparently more siliceous and k rich rhyolitic magma thus tonsteins from the two different horizons are characterized by unique geochemical properties which remain constant over a wide lateral extent integration of trace elemental compositions with mineralogical and textural observations makes possible the establishment of tonstein stratigraphy thus facilitating more precise and reliable coal seam correlations

scandium sc geochemistry in coals siberia russian far east mongolia kazakhstan and iran abstract this research discusses new original data on the geochemistry of scandium sc in the coals of the asian region of russia mongolia kazakhstan and iran in general the studied coals are enriched in sc compared with the mean value for coals throughout the world in different regions of the studied territory coal deposits with anomalous sc concentrations up to commercially important concentrations were found and the factors that control the sc contents in those coals were revealed the composition of the rock types that surround the coal forming basins and the hydro geochemical conditions of these basins and deposits determine the levels of sc accumulation in the coals it was found that sc was redistributed and partially lost from the seams during coal metamorphism studies of the modes of sc occurrence in the coals showed the predominance of an organic mode in addition the peculiarities of the sc distribution in the deposits and coal seams indicate a predominantly hydrogenous mechanism for the accumulation of anomalous sc concentrations in coal and peat scandium in coal and peat accumulates by leaching from coal bearing strata and re deposition in coal peat beds with the participation of soil and ground water enriched with organic acids specific conditions for the formation of coal containing sc enriched rocks and for the sc leaching and transportation into coal seams are necessary for the accumulation of high sc concentrations in the coals such conditions that occur in the contemporary mire ecosystems of western siberia could also have occurred in ancient basins of peat coal accumulation

constraints for the recent tectonics of the el salvador fault zone central america volcanic arc from morphotectonic analysis abstract we have used hypsometric analysis to improve our understanding of the current tectonic deformation and structure of el salvador fault zone a n90 e oriented strike slip fault zone that extends 150 km through el salvador central america our results indicate an important amount of transtensive strain along this fault zone providing new data to understand the tectonic evolution of the salvadorian volcanic arc we have defined kilometric scale tectonic blocks and its relative vertical movements length of segments with homogeneous vertical motions and lateral relay of active structures we have identified and quantified slip rate variations along strike of the el triunfo fault within el salvador fault zone ranging from 4 6 mm year in its central parts to 1 mm year towards the tips of the fault this study supports the hypothesis of a recent rotation in the maximum shortening direction and the accommodation of the current deformation through the reactivation of pre existing structures inherited from a previous tectonic regime

forecasting the evolution of seismicity in southern california animations built on earthquake stress transfer 1 we develop a forecast model to reproduce the distribution of main shocks aftershocks and surrounding seismicity observed during 1986 2003 in a 300 310 km area centered on the 1992 m 7 3 landers earthquake to parse the catalog into frames with equal numbers of aftershocks we animate seismicity in log time increments that lengthen after each main shock this reveals aftershock zone migration expansion and densification we implement a rate state algorithm that incorporates the static stress transferred by each m 6 shock and then evolves coulomb stress changes amplify the background seismicity so small stress changes produce large changes in seismicity rate in areas of high background seismicity similarly seismicity rate declines in the stress shadows are evident only in areas with previously high seismicity rates thus a key constituent of the model is the background seismicity rate which we smooth from 1981 to 1986 seismicity the mean correlation coefficient between observed and predicted m 1 4 shocks the minimum magnitude of completeness is 0 52 for 1986 2003 and 0 63 for 1992 2003 a control standard aftershock model yields 0 54 and 0 52 for the same periods four m 6 0 shocks struck during the test period three are located at sites where the expected seismicity rate falls above the 92 percentile and one is located above the 75 percentile the model thus reproduces much but certainly not all of the observed spatial and temporal seismicity from which we infer that the decaying effect of stress transferred by successive main shocks influences seismicity for decades finally we offer a m 5 earthquake forecast for 2005 2015 assigning probabilities to 324 10 10 km cells

a dislocation model of strain accumulation and release at a subduction zone strain accumulation and release at a subduction zone are attributed to stick slip on the main thrust zone and steady aseismic slip on the remainder of the plate interface this process can be described as a superposition of steady state subduction and a repetitive cycle of slip on the main thrust zone consisting of steady normal slip at the plate convergence rate plus occasional thrust events that recover the accumulated normal slip because steady state subduction does not contribute to the deformation at the free surface deformation observed there is completely equivalent to that produced by the slip cycle alone the response to that slip is simply the response of a particular earth model to embedded dislocations for a purely elastic earth model the deformation cycle consists of a coseismic offset followed by a linear in time recovery to the initial value during the interval between earthquakes for an elastic viscoelastic earth model elastic lithosphere over a viscoelastic asthenosphere the postearthquake recovery is not linear in time records of local uplift as a function of time indicate that the long term postseimic recovery is approximately linear suggesting that elastic earth models are adequate to describe the deformation cycle however the deformation predicted for amore simple elastic half space earth does not reproduce the deformation observed along the subduction zones in japna at all well if stick slip is restricted to the main thrust zone as recognized earlier by shimazaki seno and kato the uplift profiles could be explained if stick slips were postulated to extend along the plate interface beyond the main thrust zone to a depth of perhaps 100 km but independent evidence suggests that stick slip at such depths if unlikely less

observations and modeling of the august 27 2012 earthquake and tsunami affecting el salvador and nicaragua on 27 august 2012 04 37 utc 26 august 10 37 p m local time a magnitude mw 7 3 earthquake occurred off the coast of el salvador and generated surprisingly large local tsunami following the event local and international tsunami teams surveyed the tsunami effects in el salvador and northern nicaragua the tsunami reached a maximum height of 6 m with inundation of up to 340 m inland along a 25 km section of coastline in eastern el salvador less severe inundation was reported in northern nicaragua in the far field the tsunami was recorded by a dart buoy and tide gauges in several locations of the eastern pacific ocean but did not cause any damage the field measurements and recordings are compared to numerical modeling results using initial conditions of tsunami generation based on finite fault earthquake and tsunami inversions and a uniform slip model

review and update of the applications of organic petrology part 2 geological and multidisciplinary applications abstract the present paper is focused on organic petrology applied to unconventional and multidisciplinary investigations and is the second part of a two part review that describes the geological applications and uses of this branch of earth sciences therefore this paper reviews the use of organic petrology in investigations of i ore genesis when organic matter occurs associated with mineralization ii the behavior of organic matter in coal fires self heating and self combustion iii environmental and anthropogenic impacts associated with the management and industrial utilization of coal iv archeology and the nature and geographical provenance of objects of organic nature such as jet amber other artifacts and coal from archeological sites and v forensic science connected with criminal behavior or disasters this second part of the review outlines the most recent research and applications of organic petrology in those fields

tertiary tectonics of the sea of okhotsk russia far field effects of the india eurasia collision a new structural map of the western sea of okhotsk based on grids of multichannel seismic data provides several new insights into the tertiary deformation of asia especially in regard to the extension of extrusion tectonics linked to the india eurasia collision into northeastern asia the sedimentary basins in this offshore region are the result of two regional shear systems in the west the north trending sakhalin hokkaido dextral fault system transects sakhalin island accessory structures closely related to its dextral shear include northeast trending normal faults as well as northwest trending en echelon folds and thrusts the accessory normal faults are predominantly eocene to lower miocene and indicate transtensional shear whereas the folds and thrusts are mostly younger and indicate late miocene and pliocene transpression in the north an east west trending sinistral shear zone enters the sea at its northwest corner this sinistral shear system links farther west to extensional faults of the early tertiary baikal rift extending northeastward from the terminus of this sinistral shear zone are a series of long predominantly northwest dipping listric normal faults that form a large lazy s shaped pull apart basin the shantar liziansky basin slb normal faults in this 500 140 km basin accommodate 15 to 20 extension extension and related sinistral shear appear to be largely eocene to oligocene in age with lesser later activity to the northeast of slb a further extension of the sinistral shear zone appears to bend northeastward transecting pustorets and penzhina basins and following the course of the older mesozoic mongol okhotsk chukotsk active margin and suture it possibly reaches as far as the arctic as suggested by previous workers the baikal rift and its associated sinistral shear zone may be interpreted as by products of the india eurasia collision in eocene time mapping results included here show that this diffuse sinistral shear system extends much farther to the northeast the sinistral shear zone is transected by the dextral sakhalin hokkaido fault zone in the kashevarov region of central slb where a fan of north to northwest striking late tertiary transpressional fault splays marks the northern termination of the dextral fault zone older slb normal faults are locally deformed and half grabens are partly inverted by the slightly younger dextral splays the two regional fault systems are essentially conjugate and the pattern of intersection closely resembles that predicted by recent modelling studies of india eurasia collision tectonics

mineral and chemical composition of some claystones from the troyanovo 3 mine maritsa east lignite basin bulgaria abstract this paper presents the results of a detailed mineralogical and geochemical study on five types of claystones from the maritsa east lignite basin in bulgaria the studied samples of each claystone type are composite taken from outcrops at the operated pre stripping and stripping horizon of the mine most of the minerals in claystones such as quartz illite montmorillonite kaolinite plagioclase feldspar zircon and mica have terrigenous origin pyrite arsenopyrite barite calcite apatite gypsum and goethite are authigenic a total of 66 elements were analyzed in samples based on coefficient of enrichment of elements compared to clarke values for clays the samples can be arranged as follows yellow claystone 43 elements black claystone 1 42 elements blue claystone 25 elements black claystone 2 20 elements and white claystone 17 elements the black and yellow claystone have highest content of rare earth elements and yttrium rey gold ag pt and pd are highly and unusually enriched in some samples the dominant mode of occurrence of elements is mineral matter as sorbed on clay minerals illite montmorillonite and kaolinite structurally bound in other silicates plagioclase feldspar apatite and goethite a portion of the studied elements also show affinity to organic matter ca sr mg p s mo sc cr cu cd hg tl as ag and hree y mercury also has clear relation to kaolinite as does u to calcite the la lu sm lu and gd lu refer the claystones to mix l m type yellow blue and black claystones and h type white claystone the rey in claystones is as follows black claystone 1 400 ppm yellow claystone 366 ppm blue claystones 188 ppm black claystone 2 162 ppm and white claystone 146 ppm these concentrations do not imply that the claystones would be a possible source for extraction of rey

gas induced erosion features in the north sea pockmarks are prominent features on the seafloor at two main regions of the north sea the south fladen area and the norwegian trench the pockmarks vary in size from 5 m across to about 150 m and in depth from 1 m to about 20 m some of the features consist of several very small unit pockmarks these are probably gas induced erosion features and found only in soft finegrained marine and glaciomarine sediments they are probably caused by shallow or deep seated gas or fluid release through the seabed whereby the finest particles are thrown into suspension and redistributed by nearbottom currents on the north sea plateau a small pockmarked area has recently been found a close relationship exists here between mobile gas in the upper sediments faulting in the soft sediments and the morphology of the seabed other morphological features in the north sea such as coast parallel depressions and elongated depressions or terraces are also interpreted here as gas induced erosion products this applies yet again to the mottled seabed features which appear as patches of high reflectivity on side scan sonar records from the north sea plateau they correspond to shallow seabed depressions on the deep towed boomer records judging from reported observations from several shallow seas world wide volatile transport through the seabed is probably quite common and several morphological features are undoubtably induced by this process several erosion features of similar origin are probably common also in deep ocean basins

estimations of clarkes for carbonaceous biolithes world averages for trace element contents in black shales and coals abstract black shale and coal clarke values are the average trace element contents in the world black shales and coals these calculations are made in russian geochemistry but up to now are poorly known in the west modern tables of black shale and coal clarkes are presented based on comprehensive calculations using very large amount of information thousands analyses of black shales coals and coal ashes for trace elements in black shale geochemistry three figures were calculated for each main lithologies terrigenous tuff chert and carbonate two clarke estimations are presented named lithological k1 and lithostratigraphical k2 in coal geochemistry seven figures were calculated for each trace element average content in hard coals and their ashes average content in brown coals and their ashes average content in all coals and their ashes and coal affinity index or coalphile index average content in all ashes clarke values of sedimentary rocks the black shale and coal clarkes presented here provide an important scientific base for many geochemical comparisons and issues

bottom current controlled sedimentation and mass wasting in the northwestern sea of okhotsk abstract quaternary sedimentation in the northwestern sea of okhotsk where tidal and thermohaline currents are active was studied using 8443 km of high resolution air gun profiles from four cruises it is characterized by 1 bottom current controlled processes which lead to widespread deposition of contourite drifts and sediment waves on the north okhotsk continental margin and the northernmost sakhalin slope as well as to erosion and sediment reworking on the northern sakhalin shelf 2 mass wasting triggered probably by shallow earthquakes by gas hydrate instability during sea level lowstands leading to slumps and debris flows in the western derugin basin 3 deposition of the fluvial load of the river amur which results in sediment drift bodies and prograding lowstand wedges during glacial periods and to contourite drifts and a fan during interglacial times and 4 ice rafted detritus and hemipelagic sedimentation interrupted by episodic turbidity current activity especially in the derugin basin and its northern eastern and southern flanks

a new type of nb ta zr hf ree ga polymetallic deposit in the late permian coal bearing strata eastern yunnan southwestern china possible economic significance and genetic implications abstract this paper describes a new type of nb ta zr hf ree ga polymetallic deposit of volcanic origin in the late permian coal bearing strata of eastern yunnan southwestern china well logging data especially natural gamma ray geochemical data high concentrations of nb ta zr hf ree and ga and mineralogical compositions nb ta zr hf or ree bearing minerals rarely observed together with the volcanic lithological characteristics indicate that there are thick 1 10 m mostly 2 5 m ore beds in the lower xuanwei formation late permian in eastern yunann of southwestern china the ore beds are highly enriched in nb ta 2 o 5 302 627 ppm zr hf o 2 3805 8468 ppm ree oxides of la lu y 1216 1358 ppm and ga 52 4 81 3 ppm the ore beds are mainly composed of quartz mixed layer illite smectite kaolinite berthierine and albite four types of ore beds in the study area were identified namely clay altered volcanic ash tuffaceous clay tuff and volcanic breccia preliminary studies suggest that the high concentrations of otherwise rare metals were mainly derived from the alkalic pyroclastic rocks the modes of occurrence spatial distribution and enrichment mechanism of the rare metals however require further study

small fast moving flow like landslides in volcanic deposits the 2001 las colinas landslide el salvador abstract fast moving landslides are one of the most significant dangers deriving from slope instabilities landslides involving large volumes can develop in rock or debris avalanches with extreme mobility and enormous destructiveness nevertheless a relevant number of casualties and damages derive from small fast moving landslides with flow like behaviour the las colinas landslide occurred at santa tecla el salvador central america during a strong earthquake it slid off the northern flank of the balsamo ridge and resulted in almost 500 casualties and can be considered one of the most destructive landslides ever known earthquake shaking was amplified by the rock mass and the steep ridge topography we collected original geological geomorphological and geophysical data in the cordillera del balsamo area the involved materials ranging from lapilli to tuff layers of different strength have been mapped and characterized slope stability analyses have been performed both under static and dynamic conditions through limit equilibrium and finite element methods hazard zonation for this type of landslides requires the forecast of the movement velocity and final deposition area we used a fully two dimensional fem model to simulate landslide spreading downslope the developed code allows the use of different constitutive models and yield rules with the possibility to model and study internal deformation of the landslide mass as well material entrainment and deposition

the origin of tonsteins an overview and links with seatearths fireclays and fragmental clay rocks abstract tonsteins are volcanic ash falls in coal bearing sequences that have altered to kaolinite only in the last twenty years or so has the volcanic origin become firmly established the evidence for the volcanic origin encompasses bed form including lateral extent structures textures volcanogenic mineralogy and geochemistry the lines of evidence are reviewed from a historical perspective tonsteins came to prominence over a hundred years ago because of their stratigraphic value tonsteins continue to be of value in coalfield exploration but their stratigraphic value has been enhanced in recent years with the ability to determine radiometric ages with a high level of accuracy the geochemistry not only provides good evidence for the volcanic origin but also enables tectomagmatic deductions to be made for areas external to the coal basin in addition some tonsteins are the indicators for the discovering of rare metal ore deposits nb rees and ga there is also the potential to use the geochemistry to identify specific tonsteins essentially a chemostratigraphic approach tonsteins are seen as one class of bentonites others include k bentonites metatonsteins and possibly illitic bentonites tonsteins have been linked to seatearths fireclays and fragmental clay rocks although all such rocks contain kaolinite the origins differ the seatearths contain rootlets and were subjected to pedogenic activity alteration of the silicate minerals is limited under conditions of a high water table and in the presence of organic matter reducing conditions prevailed leading to gleization on the other hand the fireclays show extensive alteration to kaolinite there is a link with the major marine bands and this has implications in terms of sequence stratigraphy the fragmental clayrocks have also been linked to soil forming processes but in this case possibly the reworked soil was the product of an open system containing free alumina minerals that reacted with silica in solution during diagenesis

the limon costa rica earthquake of april 22 1991 back arc thrusting and collisional tectonics in a subduction environment on april 22 1991 a large earthquake mw 7 7 occurred along the caribbean coast of costa rica and western panama the rupture area of the fault mapped from the aftershocks is 45 85 km2 the distribution of aftershocks and the local geological record suggest that faulting occurred on a blind thrust sheet that shallows toward the northeast uplift of the caribbean coast ranging from 1 5 m near puerto limon and decreasing gradually toward the southeast was observed along the caribbean northwest of puerto limon no significant coastal uplift was observed this observation agrees with the aftershock data suggesting the rupture did not extend to the northwest of this location the limon earthquake also triggered aftershocks on secondary faults in the crust these events are apparently associated with a family of imbricate thrust and strike slip faults that lie in the eastern piedmont of the talamanca cordillera the historical seismicity indicates that the caribbean coast has been the site of several historical earthquakes with magnitudes greater than 7 0 on april 26 1916 another earthquake ms 6 9 took place in the same region summing the scalar seismic moment release along the caribbean coast the average rate of slip is approximately 0 8 cm yr compared with a value of 0 4 to 0 8 cm yr along the pacific subduction zone depending on the estimated width of the seismogenic zone therefore a large fraction of the relative plate motion between the cocos and caribbean plates 9 8 cm yr appears to be taken up by crustal deformation in the back arc the tectonic regime in the area appears to be dominated by the collision of the buoyant cocos ridge with the subduction zone the absence of a wadati benioff zone where the cocos ridge collides with the trench suggests the slab does not subduct beneath the osa peninsula this is supported by the pliocene gap of volcanism present in costa rica thus the predicted relative motion between the cocos and caribbean plates appears to be absorbed by a low rate of seismic moment release in the forearc and by a broad zone of active crustal shortening and underthrusting in the back arc this type of tectonic deformation resembles more a collisional regime than a typical subduction zone environment

new insights into the lowest xuanwei formation in eastern yunnan province sw china implications for emeishan large igneous province felsic tuff deposition and the cause of the end guadalupian mass extinction abstract a previous study suggested that the lowest xuanwei formation is derived from weathered clastic materials of silicic composition from the emeishan large igneous province elip based on chemostratigraphic correlations al 2 o 3 tio 2 ratios between the two in this study we have adopted the model that the emeishan mantle plume commenced and terminated within a short duration and have investigated the detailed mineralogy and geochemistry of carefully sampled rocks from the lower sections of the xuanwei formation eastern yunnan province southwest china these samples are intensely argillized and characterized by high proportions of clay minerals and quartz the samples with al 2 o 3 tio 2 7 from the lowest xuanwei formation have an anomalous natural gamma response and high concentrations of nb ta zr hf th u ga and rey rare earth elements and yttrium our results suggest that the samples with al 2 o 3 tio 2 7 from the lowest xuanwei formation represent felsic volcanic tuff instead of acidic clasts as originally proposed the lowest xuanwei formation and the wangpo bed are the felsic tuffaceous layers interbedded with clastic rocks derived from the emeishan high ti basalts such volcanic layers most likely represent elip felsic tuff originated from the extrusive equivalent of nb zr enriched alkaline syenitic magmatism at the waning stage of emeishan mantle plume activity this study has verified the existence of extensive alkaline felsic volcanism of early late permian age such alkaline volcanism may have been catastrophic and have contributed to the end guadalupian mass extinction

reconstruction of subduction and back arc spreading in the nw pacific and aleutian basin clues to causes of cretaceous and eocene plate reorganizations the eocene 50 45 ma major absolute plate motion change of the pacific plate forming the hawaii emperor bend is thought to result from inception of pacific plate subduction along one of its modern western trenches subduction is suggested to have started either spontaneously or result from subduction of the izanagi pacific mid ocean ridge or from subduction polarity reversal after collision of the olyutorsky arc that was built on the pacific plate with ne asia here we provide a detailed plate kinematic reconstruction of back arc basins and accreted terranes in the northwest pacific region from japan to the bering sea since the late cretaceous we present a new tectonic reconstruction of the intraoceanic olyutorsky and kronotsky arcs which formed above two adjacent oppositely dipping subduction zones at 85 ma within the north pacific region during another pacific wide plate reorganization we use our reconstruction to explain the formation of the submarine shirshov and bowers ridges and show that if marine magnetic anomalies reported from the aleutian basin represent magnetic polarity reversals its crust most likely formed in an 85 to 60 ma back arc basin behind the olyutorsky arc the olyutorsky arc was then separated from the pacific plate by a spreading ridge so that the 55 to 50 ma subduction polarity reversal that followed upon olyutorsky ne asia collision initiated subduction of a plate that was not the pacific hence this polarity reversal may not be a straightforward driver of the eocene pacific plate motion change whose causes remain enigmatic

opening of the kuril basin deduced from the magmatic history of central hokkaido north japan abstract the kuril basin is a fan shaped back arc basin in the northwestern pacific rim the basin is separated by the kuril arc from the pacific ocean to the southeast and is bounded by the subsided okhotomorsk block to the north and by the late eocene to early miocene hidaka magmatic arc to the west the clastic sediments constituting the late cretaceous to early eocene proto kuril arc which underlies the modern kuril arc were transported from the okhotomorsk block between them the kuril basin now intervenes this suggests that the kuril basin had not opened and that the proto kuril arc had been located in the southern margin of the okhotomorsk block at least until early eocene time it also indicates that the kuril basin was not entrapped by the proto or modern kuril arc the tertiary hidaka magmatic arc in central hokkaido was formed along a n s trending subduction zone where the pacific plate was subducting beneath the eurasian plate therefore the kuril basin was not yet present on the east of central hokkaido during the period when the hidaka magmatism was taking place based on the fact that the hidaka arc magmatism ceased at 17 16 ma and coevally along its n s trending extension it is suggested that the kuril basin opened just after 16 ma by the southward retreat of the proto kuril arc trench system in central hokkaido an extensional stress regime during the middle miocene is inferred from the occurrence of a type magmatism and graben like sedimentary basins this stress field can be attributed to subsidence of the pacific slab covered by the retreated proto kuril arc during the opening of the kuril basin the occurrence of an undeformed and horizontal sedimentary cover on the rugged basement of the kuril basin is consistent with rather rapid opening at 16 15 ma during the middle miocene the kuril basin and japan basin were formed by a similar process i e rotation and oceanward retreat of an arc trench system opening of the two back arc basins along different plate boundaries i e the pacific north american boundary for the kuril basin and the pacific eurasian boundary for the japan basin may have been caused by the migration of a hot region across the overriding plate boundary

earthquake induced landslides in central america central america is a region of high seismic activity and the impact of destructive earthquakes is often aggravated by the triggering of landslides data are presented for earthquake triggered landslides in the region and their characteristics are compared with global relationships between the area of landsliding and earthquake magnitude we find that the areas affected by landslides are similar to other parts of the world but in certain parts of central america the numbers of slides are disproportionate for the size of the earthquakes we also find that there are important differences between the characteristics of landslides in different parts of the central american isthmus soil falls and slides in steep slopes in volcanic soils predominate in guatemala and el salvador whereas extensive translational slides in lateritic soils on large slopes are the principal hazard in costa rica and panama methods for assessing landslide hazards considering both rainfall and earthquakes as triggering mechanisms developed in costa rica appear not to be suitable for direct application in the northern countries of the isthmus for which modified approaches are required