crustal scale block tilting during andean trench parallel extension structural and geo thermochronological insights despite a long history of plate convergence at the western margin of the south american plate that has been ongoing since at least the early paleozoic the southern peruvian fore arc displays little to no evidence of shortening in the light of this observation we assess the deformation history of the southern peruvian fore arc and its geodynamic implications to accomplish this we present a new structural and geo thermochronological data set zircon u pb mica 40ar 39ar apatite and zircon fission track and zircon u th he analyses for samples collected along a 400 km long transect parallel to the trench our results show that the mesoproterozoic gneissic basement was mainly at temperatures 350 c since the neoproterozoic and was later intruded by jurassic volcanic arc plutons along the coast a peculiar apatite fission track age pattern coupled with field observations and a synthesis of available geological maps allows us to identify crustal scale tilted blocks that span the coastal peruvian fore arc these blocks bounded by normal faults that are orthogonal to the trench suggest post 60 ma trench parallel extension that potentially accommodated oroclinal bending in this region block tilting is consistent with the observed and previously described switch in the location of sedimentary sources in the fore arc basin our data set allows us to estimate the cumulative slip on these faults to be less than 2 km and questions the large amount of trench parallel extension suggested to have accommodated this bending

inversion of topographic evolution using low t thermal history a case study from coastal mountain system in southeastern china abstract the topographic evolution of a mountain system provides key information for understanding surface processes we present a new and relatively simple method to reconstruct two dimensional paleotopography composed of two steps 1 construction of thermal history using low temperature thermochronological data and 2 conversion of the thermal history into topographic evolution a new computer program low t topo was developed to perform the suggested conversion of thermal history to paleotopography this approach when applied to the coastal mountain system cms in southeastern china suggests an uneven topographic evolution along the changting zhangzhou section since the late cretaceous according to our modeling the se segment of the section was higher maximum peak elevation 3 8 km than the nw segment 3 4 km during 80 50 ma the modeling also suggests that both the se and nw segments experienced an initially higher exhumation rate of 0 14 km myr at 80 70 ma which steadily decreased to about 0 03 km myr at 40 ma since then exhumation rates stayed relatively low 0 05 km myr the elevation reduction in the cms since the late cretaceous played an important role introducing the warm and humid pacific air to the inland

u th he dating of apatite a potential thermochronometer abstract we found a gem quality crystal of durango fluorapatite to have a 4he content consistent with complete retention of radiogenic helium since its formation at about 31 ma isothermal heating and step heating analysis reveal 4he loss to occur systematically by volume diffusion at low temperatures the linear low temperature portion of the diffusion data yields an activation energy of 38 5 8 1 kcal mol and a frequency factor of in d 0 a 2 16 4 2 8 sec 1 corresponding to a closure temperature of 105 c 30 c cooling rate 10 c m y it appears that u th he dating of apatite might represent a useful new thermochronometer with a range similar to that of fission track dating of apatite from these results we infer that a number of the too young u th he dates reported in the literature on minerals such as zircon and magnetite may in fact represent valuable records of the low temperature thermal history of their host rocks

recent rapid uplift in the bolivian andes evidence from fission track dating apatite and zircon fission track cooling ages constrain the tertiary cooling and uplift history of the eastern cordillera and altiplano of bolivia fission track data are from two triassic plutons and surrounding paleozoic metasedimentary rocks in the eastern andes north of la paz zircon cooling ages indicate that the roof of the huayna potosi pluton was emplaced in the zircon partial annealing zone and that the zongo pluton was emplaced entirely in the zircon total annealing zone apatite cooling ages for both plutons record uplift in the past 5 15 m y and zircon cooling ages from the zongo pluton reflect uplift in the past 25 45 m y uplift rates calculated by these apatite and zircon cooling ages suggest that uplift rates were 0 1 0 2 mm yr between 20 and 40 ma and increased significantly between 10 and 15 ma by 3 ma uplift rates may have been as high as 0 7 mm yr

dating topography of the sierra nevada california using apatite u th he ages the upward motion of rock masses relative to the earth s surface has been documented for most of the main mountain belts using thermochronological and petrological techniques more fundamental to the physical processes of mountain building however is the motion of the earth s surface itself which remains elusive here we describe a technique for estimating the age of topographic relief by mapping the low temperature thermal structure imparted by river incision using the ages of apatites determined from their uranium thorium and helium contents the technique exploits horizontal variations in temperature in the shallow crust that result from range normal river drainages because cooling beneath ancient river valleys occurs earlier than beneath intervening ridges our results from the sierra nevada california indicate that two of the modern transverse drainages the kings and the san joaquin had developed deep canyons by the late cretaceous period suggesting that the high topography of the range is 50 60 million years older than generally thought

thermochronological analysis of the dynamics of the southern alps new zealand the isotopic ages of material exposed close to the alpine fault in the southern alps new zealand vary in a consistent fashion along the orogen for the k ar system muscovite and biotite ages display two distinct spatial trends that meet in the area of fox glacier where a strong relationship is observed between k ar age and altitude excess argon is present in samples between mount kinnaird and haast pass in the southwest of the southern alps giving unrealistically old inconsistent k ar ages across this region incorporation of excess argon appears to be highly variable however and minimization of its influence on dynamical interpretations of thermochronology is possible through considering only the youngest age from a given area such treatment indicates that excess argon contamination does not play an important role in the systematic k ar age variation identified along the southern alps the observed age distribution is consistent with estimates of the modern rapid uplift and exhumation of the southern alps beginning ca 5 ma k ar mica ages older than this south of the copland valley indicate that substantial late cenozoic exhumation occurred along the southern alps prior to the development of the modern tectonic regime but at rates lower than at present total exhumation during the current phase of tectonism in the southern alps decreases from the whataroa river southward north of fox glacier the southern alps have attained a dynamical steady state such that the observed distribution of exhumation will not change significantly with further deformation and denudation under current conditions

ree mineralogy and geochemistry of the western keivy peralkaline granite massif kola peninsula russia abstract the authors have studied the geology geochemistry petrology and mineralogy of the rare earth elements ree occurring in the western keivy peralkaline granite massif kola peninsula nw russia aged 2674 6 ma the massif hosts zr and ree rich areas with economic potential e g the yumperuaiv and large pedestal zr ree deposits where 25 of ree are represented by heavy ree hree the main ree minerals are chevkinite ce britholite y and products of their metamict decay bastnasite ce allanite ce fergusonite y monazite ce and others the areas contain also significant quantities of zircon reaching potentially economic levels we have discovered that behavior of ree and zr is controlled by alkalinity of melt solution which in turn is controlled by crystallization of alkaline pyroxenes predominantly aegirine and amphiboles predominantly arfvedsonite at a late magmatic stage crystallization of mafic minerals leads to a sharp increase of k 2 o content and decrease of sio 2 content that cause a decrease of melt viscosity and ree and zr solubility in the liquid therefore ree and zirconium immediately precipitate as zircon and ree minerals there are numerous pod and lens like granitic pegmatites within the massif pegmatites in the ree rich areas are also enriched in ree but hree prevails over light ree lree about 88 of ree sum

timing and mechanisms of central himalayan exhumation discriminating between tectonic and erosion processes the ability to deduce exhumation mechanisms from thermochronological data is hampered by the fact that assumptions on the thermal state of the lithosphere have to be made additional argumentation is generally required to discriminate between erosion controlled and tectonically induced exhumation this problem can be overcome by studying the spatial distribution of zircon and apatite u th he and fission track data in this work the variation of four different low temperature isotopic systems generating age trends along a sampling line is used to infer mechanisms of quaternary exhumation in the central high himalayan metamorphic belt observed zircon age trends with southwards increasing cooling ages from 0 5 to 1 7 ma are attributed to tectonically induced exhumation the uniform apatite cooling ages clustered c 0 5 ma are attributed to erosion

transpression and the build up of the cordillera the example of the bucaramanga fault eastern cordillera colombia widespread wrench tectonics have been described along the northern andes the bucaramanga fault described as sinistral strike slip bounds the high santander massif we combine structural and thermochronological data from the central southern portion of the fault to investigate the vertical displacement the structural survey data show old phases of activity preserved in the host rocks along the fault trace with the superimposition of different generations of slickenlines and both strike slip and dip slip kinematics indicators new and previous thermochronological data show that differential exhumation of the fault walls has been ongoing for the last 50 ma the hanging wall the santander massif records in the central portion decreasing exhumation rates from the early miocene to the mid to late miocene and in the southern portion constant rates from the late oligocene to the pliocene combining such observations the thermochronological offset resulting from the relative motion of the two fault walls is comparable with the observed drop in elevation across the fault suggesting that the present topography of the santander massif is related to vertical movement along the bucaramanga fault we infer that the fault has a significant neogene reverse component consistent with the present day horizontal global positioning system vector data long term exhumation rates and the structural assemblage supplementary material the supplementary materials contain methodological information on the thermochronological procedures a compilation of the previously published data used in this study and the structural geology dataset https doi org 10 6084 m9 figshare c 4620140

thermochronological evidence for a late pliocene climate induced erosion rate increase in the alps u th he and fission track analyses of apatite along deep seated tunnels crossing high relief mountain ranges offer the opportunity to investigate climate tectonic forcing on topographic evolution in this study the thermochronologic analysis along the simplon tunnel western central alps italy and switzerland constrains in detail the mechanisms controlling the topographic evolution of the simplon massif cooling rates vary from about 10 c ma at about 10 ma to about 35 c ma in the last 3 ma such increase in cooling rates corresponds to the inception of glacial cycles in the northern hemisphere age patterns show correlation with faults distribution until 2 ma suggesting that tectonics controlled rocks exhumed up to that age after 2 ma thermo chronometric data show that the simplon area has experienced primarily erosional exhumation all age patterns provided are not affected by topographic effects thus indicating that present day topography has been carved in the last 2 ma most likely controlled by glacial erosion

modeling of the temperature sensitivity of the apatite u th he thermochronometer apatite u th he apparent ages will generally reflect residence for extended periods at temperatures where helium is neither quantitatively retained nor lost by diffusion to characterize the response of apatite he ages to thermal histories involving partial he retention we explored solutions to the he production diffusion equation under thermally static conditions the analytical solution to this equation coupled with published diffusivity data demonstrates that the zone of partial he retention extends from about 40 c to 85 c this zone lies at temperatures 35 c cooler than the analogous fission track partial annealing zone he ages within the partial retention zone ultimately achieve a balance between he production and loss yielding a steady state age both the ultimate age and the time it takes to achieve this age are temperature dependent for example an apatite held at 75 c equilibrates to an age of 2 ma after 17 myr regardless of whether equilibrium is approached from a higher or a lower initial he age for representative dynamic thermal histories we evaluated apatite he ages using a numerical solution to the ingrowth diffusion equation the results illustrate the sensitivity of he ages to various geologic histories and are useful for understanding he age elevation relationships and for testing time temperature paths derived from apatite fission track length distributions in addition although he diffuses rapidly from apatite at shallow crustal temperatures modeling of ambient temperature fluctuations indicates that he ages are nearly unaffected by surficial processes

on the thermomechanical evolution of compressional orogens summary we present results from a newly developed fully coupled thermomechanical model of the continental crust in which crustal shortening at a convergent plate boundary is driven by a basal velocity discontinuity which represents delamination and subduction in the underlying mantle this new dynamical model incorporates complex rheologies elasticity thermally activated creep and brittle frictional behaviour allows for extremely large deformation and is coupled along its top boundary to a complex erosion sedimentation model the model is based on the dynamic lagrangian remeshing dlr method which uses lagrangian spatial discretization of the crust and therefore allows for an accurate tracking of rock particles as they travel through the deforming orogen this information is in turn used to produce synthetic ptt paths we have used this model to predict the distribution of apparent ages for a wide range of isotopic systems at the surface of an actively deforming orogen we have also predicted other geophysical and geological observables such as the metamorphic grade of exposed rocks regarded here as a first order approximation for total denudation topography surface heat flux and the thickness of sediment deposited in the adjacent foreland basins results clearly demonstrate that the highest exhumation rates and thus the youngest isotopic ages are found in regions of maximum topography near the centre of the orogen but that the most deeply exhumed rocks are found on the side of the orogen in the vicinity of the retro shear zone a crustal scale fault which accommodates most of the crustal shortening within the orogen it is also in this region that the isotopic systems characterized by the greatest closure temperatures display the youngest ages and the highest grade metamorphic rocks are found these conclusions are derived from the assumption of uniform erosion across the orogen in cases where rainfall and thus erosion is orographically controlled the tectonic style of the orogen is different from the uniform erosion case as is the distribution of isotopic ages and metamorphic grades across the orogen

plio pleistocene increase of erosion rates in mountain belts in response to climate change here we review an ensemble of observations that point towards a global increase of erosion rates in regions of elevated mountain belts or otherwise high relief since the onset of northern hemisphere glaciation about 2 3 ma during that period of earth s history atmospheric co2 concentrations may have dropped and global climate cooled and evolved towards high amplitude oscillating conditions that are associated with the waxing and waning of continental ice sheets in the northern hemisphere we argue for a correlation between climate change and increased erosion rates and relief production which we attribute to some combination of the observed cooling onset of glaciation and climatic oscillation at orbital timescales in our view glacial erosion played a major role and is driven by the global cooling furthermore analyses of the sedimentary fluxes of many mountain belts show peaks of erosion during the transitions between glacial and inter glacial periods suggesting that the variable climatic conditions have also played a role

geology and age of the late archean keivy alkaline province northeastern baltic shield abstract the keivy alkaline province kola peninsula consists of six peralkaline granite bodies alkaline syenogranite dikes and two nepheline syenite intrusions emplaced between the tonalite trondhjemite granodiorite basement and the supracrustal keivy terrane u pb zircon ages for the keivy alkaline province range from 2613 to 2682 ma and for the spatially associated gabbro anorthosite complexes from 2659 to 2668 ma the keivy alkaline granitoids are geochemically different from other late archean alkaline rocks inferred to have been emplaced in subduction zone settings the keivy alkaline province may represent the earliest example of magmatism associated with continental rifting and the involvement of a mantle plume with oceanic island basalt like characteristics

rare earth deposits of the murmansk region russia a review this paper reviews the available information on the geology mineralogy and resources of the significant rare earth element ree deposits and occurrences in the murmansk region northwest russia the region has one of the largest endowments of ree in the world primarily the light ree lree however most of the deposits are of potential economic interest for the ree only as by products of other mining activity because of the relatively low ree grade the measured and indicated ree2o3 resources of all deposits in the region total 22 4 and 36 2 million tonnes respectively the most important resources occur in 1 the currently mined khibiny titanite apatite deposits and 2 the lovozero loparite eudialyte deposit the kovdor baddeleyite apatite magnetite deposit is a potentially important resource of scandium these deposits all have polymetallic ores i e ree would be a by product of p ti and al mining at khibiny fe zr ta and nb mining at lovozero and fe and ti mining at afrikanda the keivy block has potential for heavy ree exploitation in the peralkaline granite hosted yumperuaiv and large pedestal zr ree deposits and the nepheline syenite hosted sakharyok zr ree deposit with the exception of the afrikanda perovskite magnetite deposit lree in perovskite and the kovdor baddeleyite apatite magnetite deposit scandium in baddelyite carbonatite bearing complexes of the murmansk region appear to have limited potential for ree by products the sound transport energy and mining infrastructure of the region are important factors that will help ensure future production of the ree

cenozoic thermal evolution of the central sierra nevada california from uth he thermochronometry apatite u th he cooling ages are reported for igneous apatite samples from the central sierra nevada and compared to published apatite fission track ages and track length data from the same mineral separates helium ages are youngest at low elevations and increase systematically toward higher elevations ranging from 43 to 84 ma at yosemite valley 32 to 74 ma at kings river canyon and 23 to 75 ma at mt whitney helium ages from high elevation samples are generally concordant with corresponding fission track ages while lower elevation helium ages are substantially younger cooling histories inferred from present laboratory derived fission track annealing and helium diffusion models do not match well suggesting that either helium diffusion rates or fission track annealing rates are miscalibrated at temperatures below about 60 c for geologic exposure periods unlike the fission track results the helium data do not indicate a very low geothermal gradient in the sierra nevada during early to middle tertiary time

estimating exhumation rate and relief evolution by spectral analysis of age elevation datasets extracting independent information on mean exhumation rate and the rate of surface relief change from thermochronometric datasets is essential to improve our understanding of the complex coupling between tectonics and surface erosion i e the time scale over which landforms react to changes in uplift rate and or climate a new method based on spectral analysis of age elevation data collected along one dimensional profiles is presented that provides independent estimates of the mean exhumation rate and the relative change in surface relief the results are shown to be independent of the assumed geothermal gradient the method is applied to an existing age dataset from the sierra nevada california and provides constraints on the evolution of the present day relief the spectral analysis demonstrates how current sampling strategies should be modified to optimize the tectonic and geomorphic information that can be retrieved from a thermochronometric dataset

3d mineralogical mapping of the kovdor phoscorite carbonatite complex russia the kovdor baddeleyite apatite magnetite deposit in the kovdor phoscorite carbonatite pipe is situated in the western part of the zoned alkali ultrabasic kovdor intrusion nw part of the fennoscandinavian shield murmansk region russia we describe major intrusive and metasomatic rocks of the pipe and its surroundings using a new classification of phoscorite carbonatite series rocks consistent with the iugs recommendation the gradual zonation of the pipe corresponds to the sequence of mineral crystallization forsterite hydroxylapatite magnetite calcite crystal morphology grain size characteristic inclusions and composition of the rock forming and accessory minerals display the same spatial zonation pattern as do the three minerals of economic interest i e magnetite hydroxylapatite and baddeleyite the content of sr rare earth elements rees and ba in hydroxylapatite tends to increase gradually at the expense of si fe and mg from early apatite forsterite phoscorite margins of the pipe through carbonate free magnetite rich phoscorite to carbonate rich phoscorite and phoscorite related carbonatite inner part magnetite displays a trend of increasing v and ca and decreasing ti mn si cr sc and zn from the margins to the central part of the pipe its grain size initially increases from the wall rocks to the inner part and then decreases towards the central part characteristic inclusions in magnetite are geikielite within the marginal zone of the phoscorite carbonatite pipe spinel within the intermediate zone and ilmenite within the inner zone the zoning pattern seems to have formed due to both cooling and rapid degassing pressure drop of a fluid rich magmatic column and subsequent pneumatolytic and hydrothermal processes

palaeoshoreline records of glacial isostatic adjustment in the dry valleys region antarctica we present a new record of crustal deformation for the dry valleys and surrounding region of antarctica values of crustal tilt resulting from the differential uplift of lacustrine strandlines are derived and linked with age data to provide a history of solid earth deformation since deglaciation we present tilt directions and gradients for 13 strandlines formed c 18 100 2100 cal yr bp derived gradient magnitudes increase exponentially with age and indicate an ongoing response to deglaciation since the last glacial maximum azimuths of crustal tilting are consistently down to the se towards west antarctica this tilt pattern is opposite to that predicted by models of glacial isostatic adjustment for antarctica tilt magnitudes are significantly larger than tilted strandlines documented elsewhere in the world suggesting an influence from thin crust and weak mantle underlying the region this study presents the first use of lacustrine strandline tilts to document crustal deformation due to glacial unloading in antarctica and provides an important new datum for constraining glacial isostatic adjustment models for more than a century observations of uplifted and tilted marine and lacustrine strandlines have been used to understand glacial isostatic adjustment gia from retreating ice sheets e g spencer 1891 goldthwait 1908 as the earth s crust rebounds in response to ice mass loss ice proximal shorelines are raised and tilted away from ice load centres these geological shoreline records can be used in different ways depending on whether original elevation and or age of the features are known when both the original elevation and age are known uplift through time can be reconstructed the most common application of this case is analysis of marine raised beaches and shorelines where past elevation is determined through comparison to present day sea level radiocarbon dates from organic material extracted from shoreline deposits are correlated with raised beach elevations to produce a relative sea level curve e g hall denton 1999 lambeck et al 2002b baroni hall 2004 when corrected for eustatic sea level change relative sea level curves reflect the influence of solid earth and geoid variations resulting from deglaciation providing essential constraints for models of glacial isostatic adjustment that solve the sea level equation farrell clark 1976 peltier et al 1978 lambeck chappell 2001 mitrovica milne 2003 peltier 2004 for lake palaeoshorelines the original shoreline elevation is unknown but differential uplift since the time of deposition results in shoreline tilt analysis of strandline tilt through time provides a record of solid earth deformation since deglaciation for the case of glacial isostatic adjustment the total amount of uplift is a function of shoreline position relative to former ice mass centres greatest uplift occurs closer to the centre of ice mass loss and decreases away from the load subsidence occurs in the forebulge region e g clark et al 1978 shorelines located between the ice load and forebulge tilt away from the centre of ice loss whereas shorelines outboard of the forebulge tilt towards the load centre in addition to tilt direction both temporal and spatial variances in tilt magnitude manifest ice history and geometry older deglacial shorelines have a greater magnitude of tilt than younger shorelines from the same location and shorelines closer to the centre of ice mass loss have a greater magnitude of tilt than shorelines of the same age located farther away from the load given these relationships analysis of the direction magnitude and rate of tilting provides valuable information regarding ice history intersections of projected strandline tilt directions have been used to interpret the location of past ice mass centres improving reconstructions of former ice geometry barnett peterson 1964 andrews barnett 1972 tilted palaeoshorelines linked with age data provide a relaxation curve for the earth s crust since deglaciation enabling studies of mantle rheology and lithospheric thickness parameters crucial for understanding the geodynamic processes involved in from hambrey m j barker p f barrett p j bowman v davies b smellie j l tranter m eds antarctic palaeoenvironments and earth surface processes geological society london special publications 381 http dx doi org 10 1144 sp381 26 the geological society of london 2013 publishing disclaimer www geolsoc org uk pub ethics by guest on september 16 2013 http sp lyellcollection org downloaded from

quantitative constraints on the rate of landform evolution derived from low temperature thermochronology in recent years the nature of the complex interactions between the solid earth and the overlying atmosphere has been the subject of much debate england and molnar 1990 whipple et al 1999 braun et al 1999 does erosion play an important role in the dynamics of mountain building is there a strong feedback into the balance of forces at the crustal scale from mass transport by erosional and depositional processes at the earth s surface or does erosion passively react to changes in the earth s surface topography to shape mountains with tectonic forces originating in the underlying convecting mantle dominating the dynamics of plate interactions and crustal deformation at convergent plate margins the answers to these fundamental questions lie in our ability to determine the rate at which surface processes can react to tectonic forcing whipple et al 1999 where erosion is efficient the coupling will be strong as the rate of change of surface loading by mass transport will be similar to the rate of creation of topography by crustal deformation this may lead to a concentration of deformation and thus exhumation in regions of intense erosion koons 1990 willett et al 1993 beaumont et al 2001 koons et al 2002 2003 braun and pauselli 2004 where erosion is relatively inefficient mountain building is the result of a balance between internal driving forces and those originating from the deflection of an upper free surface there is no feedback from erosional processes low temperature thermochronology such as u th he he or fission track ft dating in apatite and zircon provides information on the rate at which rocks cool as they are exhumed towards the cold earth surface duddy et al 1988 warnock et al 1997 farley 2000 reiners and farley 1999 because the

constraints on the rate of post orogenic erosional decay from low temperature thermochronological data application to the dabie shan china we have investigated whether low temperature thermochronological datasets can be used to constrain the rate of surface evolution during the post orogenic phase of a mountain belt we use a numerical method to solve the heat transport equation in the earth s crust including the effects of a changing finite amplitude topography and the resulting flexural isostatic rebound we demonstrate that accurate estimates of the amount of relief loss can be obtained by applying a recently developed spectral method that is based on estimates of the relationship between age and surface elevation as a function of topographic wavelength we also show that the rate at which topography decays with time following cessation of tectonic activity can be constrained from estimates of exhumation rate derived from the slope of age elevation profiles collected across short wavelength topography using the neighbourhood algorithm to perform a thorough search through parameter space we are able to find a tectonomorphic scenario that predicts age distributions compatible with a thermochronological dataset collected in the dabie shan of eastern china by reiners et al american journal of science 2003 vol 303 pp 489 518 we demonstrate that in the dabie shan the mean topographic relief has decreased by a factor of 2 5 to 4 5 during the last 60 80 ma while the mountain belt experienced a mean exhumation rate of 0 01 to 0 04 km ma 1 we confirm the

economic minerals of the kovdor baddeleyite apatite magnetite deposit russia mineralogy spatial distribution and ore processing optimization abstract the comprehensive petrographical petrochemical and mineralogical study of the kovdor magnetite apatite baddeleyite deposit in the phoscorite carbonatite complex murmansk region russia revealed a spatial distribution of grain size and chemical composition of three economically extractable minerals magnetite apatite and baddeleyite showing that zonal distribution of mineral properties mimics both concentric and vertical zonation of the carbonatite phoscorite pipe the marginal zone of the pipe consists of apatite forsterite phoscorite carrying fine grains of ti mn si rich magnetite with ilmenite exsolution lamellae fine grains of fe mg rich apatite and finest grains of baddeleyite enriched in mg fe si and mn the intermediate zone accommodates carbonate free magnetite rich phoscorites that carry medium to coarse grains of mg al rich magnetite with exsolution inclusions of spinel medium grained pure apatite and baddeleyite the axial zone hosts carbonate rich phoscorites and phoscorite related carbonatites bearing medium grained ti v ca rich magnetite with exsolution inclusions of geikielite ilmenite fine grains of ba sr ln rich apatite and comparatively large grains of baddeleyite enriched in hf ta nb and sc the collected data enable us to predict such important mineralogical characteristics of the multicomponent ore as chemical composition and grain size of economic and associated minerals presence of contaminating inclusions etc we have identified potential areas of maximum concentration of such by products as scandium niobium and hafnium in baddeleyite and rees in apatite

rare earth elements in phoscorites and carbonatites of the devonian kola alkaline province russia examples from kovdor khibina vuoriyarvi and turiy mys complexes abstract the devonian ca 385 360 ma kola alkaline province includes 22 plutonic ultrabasic alkaline complexes some of which also contain carbonatites and rarely phoscorites the latter are composite silicate oxide phosphate carbonate rocks occurring in close space time genetic relations with various carbonatites several carbonatites types are recognized at kola including abundant calcite carbonatites early and late stage with subordinate amounts of late stage dolomite carbonatites and rarely magnesite siderite and rhodochrosite carbonatites in phoscorites and early stage carbonatites the rare earth elements ree are distributed among the major minerals including calcite up to 490 ppm apatite up to 4400 ppm in kovdor and 3 5 wt ree2o3 in khibina and dolomite up to 77 ppm as well as accessory pyrochlore up to 9 1 wt ree2o3 and zirconolite up to 17 8 wt ree2o3 late stage carbonatites at some localities are strongly enriched in ree up to 5 2 wt ree2o3 in khibina and the ree are major components in diverse major and minor minerals such as burbankite carbocernaite ca and ba fluocarbonates ancylite and others the rare earth minerals form two distinct mineral assemblages primary crystallized from a melt or carbohydrothermal fluid and secondary formed during metasomatic replacement stable c o and radiogenic sr nd isotopes data indicate that the ree minerals and their host calcite and or dolomite have crystallized from a melt derived from the same mantle source and are co genetic

plio plistocene in sequence thrust propagation along the main central thrust zone kumaon garhwal himalaya india new thermochronological data abstract the kumaon and garhwal himalayas nw india have similar geologic tectonic topographic and precipitation pattern however low temperature thermochronological age pattern varies significantly along the strike as well as across the strike of major faults here we interpret the new set of thermochronological age data across the strike of major faults namely vaikrita thrust vt munsiari thrust mt berinag thrust bt and the baijnath nappe along pindari valley in the kumaon garhwal himalaya in the present work 18 new apatite fission track aft ages of samples collected along a north south transect have been reported ages in the hanging wall of vt which range from 2 1 0 2 to 4 2 0 7 ma have been found to be becoming younger linearly with distance from north to the vt this trend crosses the vt with significant jump in ages in the south of the vt ages are lying between 0 3 0 1 and 3 9 0 8 ma and show linear variation with distance from the vt to bt no significant jump in ages across the mt is observed and the linear trend of younging southward is continuing till the bt the break and displacement in age pattern with youngest ages close to thrusts possibly indicate progressive late thrust movement it reflects sequential uplift and cooling towards the south from the vt to bt which is consistent with an in sequence style of thrust propagation we compare our new data to the published thermochronological data from its adjacent traverses along the goriganga and dhauliganga valleys 25 km away from the present traverse towards east and west respectively in the kumaon garhwal himalaya in order to understand potential along strike variations in the kinematics our observations indicate a dynamic coupling between tectonic and surface processes in the garhwal kumaon himalaya and support that the geometry of crustal scale faults and their associated kinematics control exhumation pathways of rocks

scandium of the kovdor baddeleyite apatite magnetite deposit murmansk region russia mineralogy spatial distribution and potential resource abstract despite extensive industrial application global scandium resources are uncertain although sc is mainly supplied as a by product of mining of rare earth metals uranium or aluminum it is also concentrated by carbonatite process both magmatic and post magmatic in this paper we report data on sc distribution within the kovdor baddeleyite apatite magnetite deposit phoscorite carbonatite pipe in the murmansk region of russia which seems to be a significant reservoir of this strategic metal we show that baddeleyite is the main sc concentrating mineral and reveal the spatial distribution of sc bearing baddeleyite within the kovdor phoscorite carbonatite pipe the scandium content in baddeleyite differs according to the petrographic zonation of the pipe culminating in the inner axial zone of the pipe and in dolomite carbonatites cutting the pipe we have estimated the amount of sc2o3 in the kovdor deposit as amounting to 420 t at average content in baddeleyite of 0 078 wt and revealed the economic potential for sc recovery as a by product other sc bearing minerals pyrochlore and ilmenite groups zirconolite and juonniite have been described and opportunity of sc recovery was examined too

multiple episodes of fast exhumation since cretaceous in southeast tibet revealed by low temperature thermochronology abstract the southeast margin of the tibetan plateau is characterized by deeply incised river valleys separated by a perched low relief landscape that gently descends from the high tibetan plateau towards the southeast when and how this unique landscape formed is debated the onset of increased river incision is often interpreted as a proxy for the timing of surface uplift here apatite and zircon u th he and apatite fission track thermochronometries are employed to map the spatial and temporal pattern of exhumation in the region vertical profiles of granitic rocks were collected near deqin 28 5 n and weixi 27 5 n the two transects share a similar exhumation history with two episodes of relatively fast exhumation 100 300 m myr in the cenozoic during the paleocene to eocene 60 40 ma and miocene to present 20 0 ma separated by an intervening period of slow exhumation a pulse of moderate to high exhumation 70 300 m myr during the mid to late cretaceous 120 80 ma is also present in the data however the rate and total amount of exhumation near deqin is larger than at weixi and is especially pronounced in the interval between 20 ma to present we interpret this difference as possibly related to differences in erosion rates between the lancang deqin and the jinsha weixi rivers the paleocene to eocene episode of fast exhumation is likely in response to early cenozoic deformation along tectonic boundary structures related to the transpressional collision of the indian plate with this region pre miocene episodes of fast exhumation corroborate recent paleoaltimetric studies which show that the southeast margin of the tibetan plateau was elevated prior to the oligocene

paleo geomorphology of the sierra nevada california from u th he ages in apatite new apatite u th he ages from the central sierra nevada california place limits on the morphology and evolution of longitudinal profiles of major transverse river drainages developed in the late cretaceous helium ages from a new orogen parallel constant elevation sample transect are relatively uniform 60 ma and not correlated with topography unlike those from a similar lower elevation transect approx 15 km to the west we interpret the marked difference in the two orogen parallel profiles to reflect a headward decrease in long wavelength transverse relief at the time of cooling consistent with either a concave up stream gradient typical of those observed near the headwaters of modern sierran trunk streams or a convex gradient like those found along slope breaks of eroding plateau edges from the san joaquin drainage we obtained a new helium age versus elevation profile which has a comparable slope to those previously reported for the yosemite valley kings canyon and mt whitney areas this new profile yields slightly older ages at a given elevation as expected from its position adjacent to the largest major drainage the age versus elevation profiles imply that the mean denudation rate of the region in the cenozoic was about 0 04 to 0 05 mm yr we show that long wavelength 70 km relief inferred from longitudinal helium age variations is a strong function of erosion rate such that even relatively subdued relief is detectable with helium age profiling provided that denudation rates were low using the rate implied by sierran age versus elevation profiles we infer long wavelength relief of 1500 500 m in the late cretaceous by analogy with modern orogenic plateaus this value of long wavelength relief suggests a cretaceous interior cordilleran plateau lay at an elevation of at least 3000 m