magnetic fabric in the malanjkhand granite central india implications for regional tectonics and proterozoic suturing of the indian shield abstract in this paper field microstructural and anisotropy of magnetic susceptibility ams data are presented from the 2 48 ga malanjkhand granite and adjacent gneiss with an aim to evaluate the time relationship between fabric development in the granite and regional tectonics the central indian suture cis that demarcates the southern margin of the ne sw to ene wsw trending central indian tectonic zone citz and is a consequence of the accretion between the northern and southern indian shields lies to the north of the granite the northern margin of the granite that has proximity to the cis is mylonitized and shows a dextral top to the ne sense of shear field and magnetic foliation in the gneiss are parallel to each other as well as to the field foliation in the western and northwestern margin of the granite also the field fabrics in the granite and gneiss curve clockwise into the cis the magnetic foliation trajectories curve from a ns orientation in areas remote from the cis to a ne sw orientation in parts that are proximal to the cis in the north the granite shows synmagmatic deformation fabrics such as preferentially oriented zoned feldspar phenocrysts as well as evidence of high t solid state deformation fabric such as chessboard pattern in quartz magnetic anisotropy increases towards the cis which is inferred to support synmagmatic deformation it is concluded that the tectonic evolution of the citz and emplacement fabric development in the malanjkhand granite were synchronous phenomena wnw ese directed convergence led to transpression which is inferred to be responsible for the emplacement of the granite it is concluded that in the malanjkhand granite the development of syndeformational emplacement fabrics to syntectonic cooling was a continuum and the suturing of the northern and southern indian shields along the cis took place during the palaeoproterozoic period thus the study provides an insight into the amalgamation and stabilization of the indian shield during the late archaean palaeoproterozoic time

objective landslide detection and surface morphology mapping using high resolution airborne laser altimetry a map of extant slope failures is the most basic element of any landslide assessment without an accurate inventory of slope instability it is not possible to analyze the controls on the spatial and temporal patterns of mass movement or the environmental human or geomorphic consequences of slides landslide inventory maps are tedious to compile difficult to make in vegetated terrain using conventional techniques and tend to be subjective in addition most landslide inventories simply outline landslide boundaries and do not offer information about landslide mechanics as manifested by internal deformation features in an alternative approach we constructed accurate high resolution dems from airborne laser altimetry lidar data to characterize a large landslide complex and surrounding terrain near christchurch new zealand one dimensional circular 2 d and spherical 3 d statistics are used to map the local topographic roughness in the dems over a spatial scale of 1 5 to 10 m the bedrock landslide is rougher than adjacent unfailed terrain and any of the statistics can be employed to automatically detect and map the overall slide complex furthermore statistics that include a measure of the local variability of aspect successfully delineate four kinematic units within the gently sloping lower half of the slide features with a minimum size of surface folds that have a wavelength of about 11 to 12 m and amplitude of about 1 m are readily mapped two adjacent earthflows within the landslide complex are distinguished by a contrast in median roughness and texture and continuity of roughness elements the less active of the earthflows has a surface morphology that presumably has been smoothed by surface processes the laplacian operator also accurately maps the kinematic units and the folds and longitudinal levees within and at the margins of the units finally two dimensional power spectra analyses are used to quantify how roughness varies with length scale these results indicate that no dominant length scale of roughness exists for smooth unfailed terrain in contrast zones with different styles of landslide deformation exhibit distinctive spectral peaks that correspond to the scale of deformation features such as the compression folds the topographic based analyses described here may be used to objectively delineate landslide features generate mechanical inferences about landslide behavior and evaluate relatively the recent activity of slides published by elsevier science b v

ar ar ages in phlogopites from marble hosted ruby deposits in northern vietnam evidence for cenozoic ruby formation abstract ruby growth in phlogopite bearing marbles has been indirectly dated using the 40 ar 39 ar laser stepwise heating technique on purified syngenetic phlogopite and other micas from ruby deposits in yen bai luc yen and quy chau mining districts in northern vietnam the principal results indicate the following 1 across the red river shear zone the phlogopites from the yen bai deposits yielded miocene cooling ages between 23 2 and 24 4 ma identical to those previously published using the same dating method on magmatic and metamorphic rocks from the day nui con voi range 2 luc yen ruby deposits in the lo gam zone on the eastern flank of the red river shear zone yielded oligocene cooling 40 ar 39 ar mica ages between 30 8 and 34 0 ma regarding the age of ruby crystallisation itself the most plausible hypothesis is that all rubies in both zones formed during the period 40 to 35 ma diachronism of cooling in adjacent zones leads to the conclusion that around 35 ma the ductile deformation in the lo gam zone ended and the ruby bearing marbles cooled rapidly while the high temperature deformation remained in the red river shear zone resulting in cooling through blocking temperature some 15 ma later 3 the quy chau ruby deposit is restricted to the quy chau shear zone that bounds the eastern part of the oligocene miocene bu khang dome phlogopite and biotite samples reveal miocene cooling ages between 21 and 22 5 ma which are minimum ages for ruby formation these ages could be linked with the end of the extension of the bu khang dome vietnamese ruby formation is linked to cenozoic tectonics resulting from continental collision between the asian and eurasian plates as for other marble hosted ruby deposits in central and southeast asia

rb sr and sm nd geochronology of the eppawala metamorphic rocks and carbonatite wanni complex sri lanka abstract petrological studies on the surrounding metamorphic rocks of the eppawala carbonatite body wanni complex sri lanka revealed that these rocks had been metamorphosed under amphibolite to granulite facies conditions garnet sillimanite biotite gneiss shows lower range of metamorphic temperature 730 770 c than the migmatite gneiss 750 780 c and the pressure varies from 6 6 7 8 kbar to 5 6 6 4 kbar respectively the metamorphic age of the garnet sillimanite biotite gneiss and migmatite gneiss dated 607 23 ma and 626 16 ma respectively for mineral whole rock isochron in sm nd system these ages are compatible with the ages of regional high grade metamorphism occurred 610 550 ma in the three crustal units in sri lanka rb sr system for biotite apatite and whole rock fractions suggests 493 5 ma for the eppawala carbonatite body this age indicates the cooling age of the biotite the presence of non crystalline carbonatite matrix and large hexagonal apatite crystals suggests a slow cooling history further low closure temperature of biotite in rb sr system suggests that the intrusion age of carbonatite body should be more than 493 ma but non metamorphosed nature provides evidence that the intrusion age of the carbonatite body should be less than the period of regional metamorphism 610 550 ma therefore eppawala carbonatite body has a strong possibility to be a late to post magmatic intrusion the other late to post magmatic intrusions in the wanni complex and highland complex are dated between 580 550 ma therefore the most probable intrusion age of the eppawala carbonatite body is suggested to be around 550 ma

a digital simulation model for the unsteady state radial flow to a dug well abstract a digital simulation model has been presented for the solution of the unsteady state radial flow to a large diameter dug well perforating the full saturated thickness of an unconfined aquifer the numerical solution is based on the finite difference approach the computational algorithm is an iterative version of the alternating direction implicit method the time variant discharge from the aquifer and the reduction in saturated thickness due to water withdrawal during both the abstraction and recovery phases have been suitably incorporated in the simulation model a sensitivity analysis has been carried out on the model parameters of the aquifer namely lateral permeability anisotropy specific storage and specific yield the results indicate that the model response of hydraulic heads in the aquifer is mainly sensitive to variations in lateral permeability and specific yield alone the simulation model has also been applied to analyse data from well pumping tests the particular combination of parameters characterizing the aquifer at the test site have been identified by a parameter adjustment procedure

transient flow to a large diameter well in an aquifer with storative semiconfining layers the hantush theory of leaky aquifers with storge in the semiconfining layers is combined with large diameter well theory to produce equations that can be used in the analysis of pumped well and observation well data for stratified formations included in the equations are storage in the pumped well and a linear resistance to flow at the sand face or well bore skin three cases proposed by hantush are considered these depend upon whether the upper boundary of the overlying semiconfining layer or the lower boundary of the underlying semiconfining layer are constant head or no flow boundaries laplace transform solutions valid for the complete time domain are given for each of the three cases for the hydraulic head in the pumped well the aquifer and each of the semiconfining layers type cures obtained by numerical inversion are selected to illustrate the effects of well bore storage well bore skin and leakage although several dimensionless parameters are involved these parameters tend to influence the character of different portions of the type curves suggesting that unique matches are possible the type curves show that well bore storage in a large diameter well may completely obliterate effects of leakage derived from compressible storage in semiconfining layers for the purposes of aquifer testing it may be possible to reduce the magnitude of well bore storage in a large diameter well and thus reveal the presence of leaky semiconfining layers this may help to prevent erroneous interpretation of the well test data and incorrect evaluation of the aquifer parameters

dunite glimmerite and spinellite in achankovil shear zone south india implications for highly potassic co2 rich melt influx along an intra continental shear zone in the kakkaponnu area within the achankovil shear zone acsz southern india an undeformed ultramafic body occurs within intensely deformed granulite facies metamorphic rocks of pan african age the kakkaponnu ultramafic body is composed of spinel dunite phlogopite dunite glimmerite graphite spinel glimmerite and phlogopite graphite spinellite the spinel dunite is a fine to medium grained rock composed mainly of olivine and aluminous spinel and is characterized by relatively high mgo 50 39 50 90 wt mg mg fe 0 95 al2o3 7 8 8 98 wt and low ni 10 14 ppm the phlogopite dunite comprises serpentinized olivine phlogopite and subordinate amounts of dolomite and is high in mgo 36 5 wt mg mg mg fe 0 97 and k2o 5 5 wt olivine in the spinel dunite is marked by unusually high mgo mg 0 96 and extremely low nio 0 14 wt spinels in all rock variants are highly aluminous with low cr cr al cr ratio 0 01 magnesian ilmenite mg 59 rutile zirconolite and baddeleyite are main accessory phases no significant compositional variation is noted between large grains and small inclusions for all minerals abundant graphite magnesite melt and ubiquitous co2 fluid inclusions are identified in the olivine and spinel grains the data imply that the kakkaponnu ultramafic body was formed by progressive crystallization of highly potassic co2 rich melts injected into lower crustal levels k ar ages of 470 5 9 3 and 464 5 9 2 ma are obtained for phlogopite separates from glimmerite and phlogopite dunite respectively these ages are comparable to the phlogopite k ar ages reported from lithospheric shear zones in southern madagascar which was once conjugated to the southern peninsular india prior to the gondwana breakup this implies widespread highly potassic co2 rich fluid melt influx along shear zones in this part of east gondwana continent

zirconolite and baddeleyite in an ultramafic suite from southern india early ordovician carbonatite type melts associated with extensional collapse of the gondwana crust abstract we report here the occurrence of rare zirconium bearing minerals zirconolite cazrti2o7 and baddeleyite zro2 from an unusual ultramafic suite within the achankovil shear zone acsz in southern india zirconolite occurs as inclusions within spinel in phlogopite graphite spinellite and shows characteristic development of radial cracks baddeleyite is commonly observed as an included phase within phlogopite from phlogopite dunite and graphite spinel glimmerite the mineral also occurs less commonly within spinel and graphite from graphite spinel glimmerite the composition of zirconolite is characterized by an enrichment of u and th over rare earth elements baddeleyite shows abundance of zr with minor hf ti and u the mode of occurrence along with the chemical composition of these minerals implies their formation as early stage crystallization products from a silica undersaturated melt that was enriched in carbonatite phile elements such as ca zr ti and volatiles co2 and h2o we report

quantifying subglacial bed roughness in antarctica implications for ice sheet dynamics and history abstract glaciated landscapes consist of complex assemblages of landforms resulting from ice flow dynamic regimes and ice sheet history superimposed over and in turn modifying preglacial topography lithology and geological structure insights into the formation of glaciated landscapes can in principle be obtained by analysing modern ice sheet beds but terrain analyses beneath modern ice sheets are restricted by the inaccessibility of the bed it is however possible to quantify roughness the vertical variation of the subglacial interface with horizontal distance along two dimensional images of the bed obtained from radio echo sounding res here we collate several case studies from antarctica where roughness calculations have been used as a glaciological tool to infer basal processes and ice sheet history over large 500 km 2 areas we present two examples from west antarctica which demonstrate the utility of bed roughness in determining the presence and extent of subglacial sediments glacial dynamics and former ice sheet size we also present two examples from east antarctica which illustrate how roughness provides knowledge of ice sheet dynamics in the interior and pre quaternary ice sheet histories in modern ice sheet settings characterising bed roughness along res tracks has the twin advantages of being relatively simple to calculate while producing informative subsurface data and is especially powerful at furthering understanding when coupled with knowledge of ice flow from field satellite and modelling investigations the technique also offers significant potential for the comparison of modern and former ice sheet terrains contributing to an improved understanding of the formation and evolution of glaciated landscapes

tectonically assisted exhumation and cooling of variscan granites in an anatectic complex of the central iberian zone portugal constraints from la icp ms zircon and apatite u pb ages understanding the exhumation of middle to lower crustal rocks is of utmost importance to unravel intracrustal mass transfer processes during orogenic build up the figueira de castelo rodrigo lumbrales anatectic complex fcr lac is located within the autochthonous terrane of the variscan central iberian zone and is an example of the association between s type granites and migmatites the anatectic complex contacts to the north and south with low grade metamorphic units through the huebra and juzbado penalva do castelo shear zones respectively integration of new u pb zircon and apatite age data allowed us to obtain variscan crystallization ages inherited zircon ages and unprecedented cooling rates for different facies of the fcr lac granites the zircon crystallization ages mostly cluster around 313 317 ma for the syn tectonic granites whereas the dated late tectonic granite provided an age of 300 ma the cooling rates range from 13 to 35 c ma 1 which implies fast exhumation 0 3 0 84 mm a 1 and shallow emplacement ca 8 km deep compatible with exhumation facilitated by large crustal scale shear zones inherited zircon in the granites reveals melting of cadomian metasediments 650 550 ma upper cambrian lower ordovician 495 470 ma metaigneous rocks ollo de sapo formation and of minor older components suggesting protolith affinity with the northern domain of the central iberian zone

cooling of a late syn orogenic pluton evidence from laser k feldspar modelling of the carion granite madagascar since the late 1980s it has been hypothesized that the wide range of apparent argon ages seen within single k feldspar samples might be due to a distribution of diffusion domain sizes within the mineral to test and apply this idea an analytical technique that combines conventional laboratory degassing experiments resistance heating with numerical inversion procedures has been developed to extract cooling history information from feldspars a key part of the method involves careful control of temperature in the laboratory to constrain the diffusion parameters of the feldspar samples in our study we have k feldspar data from single crystals that mimic the types of data seen in classic resistance heater fusion experiments our step heating data are based on using a continuous argon ion laser with no direct control on temperature however with only a single added free parameter in the model we show that it is possible to analyze this data in the multi domain style and make some simple inferences on the nature of the cooling history of the carion pluton in central madagascar the carion granitic pluton in central madagascar was intruded into warm continental crust following orogenic events related to the final amalgamation of gondwana u pb shrimp dating of the pluton yields an emplacement age of 532 1 5 2 ma followed by relatively slow cooling as constrained by 40ar 39ar ages on hornblende biotite and k feldspar four hornblende samples yielded a mean 40ar 39ar age of 512 7 2 6 ma a biotite sample yielded an age of 478 9 1 0 ma and modeled k feldspar ages show cooling from 350 c at 466 ma to 100 c by 410 ma collectively the data suggest that the pluton cooled from 850 c at 532 1 5 2 u pb zircon ma to 500 c at 512 7 2 6 ma 40ar 39ar hornblende or approximately 18 c ma slowing to 4 c ma between 512 ma and 478 ma and finally to about 3 c ma between 478 and 410 ma

multistage metamorphic evolution of the trivandrum granulite block southern india abstract the trivandrum granulite block tgb southern india records evidence for three distinct stages of evolution m1 m3 during the pan african high grade metamorphism with possible temperature gradient from north to south of the terrain as detected from mineral phase equilibria thermobarometry in three classic localities namely nuliyam kunnanpara and nellikkala the charnockites both incipient and massive were formed during the first stage m1 at temperatures higher than their host rocks and at appreciably lower pressures charnockite formation was dominantly controlled by an increase in partial pressure of co 2 along structural locales during subisothermal decompression although an increase of potash activity could have also been an important factor in this process the charnockites at nellikkala in the northern margin of tgb were formed under appreciably more h 2 o rich conditions x h 2 o 0 53 0 03 than those at nuliyam x h 2 o 0 25 0 02 in the southern margin it is inferred that during the period between the metamorphic stages m1 and m2 the terrain experienced subisobaric cooling comparison of results from thermobarometry with data on absolute age determinations from geochronology of the metamorphic rocks in tgb allows the interpretation that the m1 metamorphic event took place during 540 600 ma m2 at about 530 ma and m3 in the interval of 440 470 ma mineralogic and thermobarometric evidence for earlier high grade metamorphic processes if any have been erased from these rocks the processes of charnockite formation and post peak retrograde metamorphism in the tgb took place under high geothermal gradients 40 150 km this probably testifies to the existence of a local heat source either magmas at depth or mantle plume beneath the region the general metamorphic cycle in the tgb is estimated to be ca 100 160 ma which is much shorter in time span than that in the other regions of southern peninsular india such as the karnataka craton and the eastern ghats mobile belt during this period the terrain experienced rapid exhumation of approximately 6 7 cm year with the total amplitude of vertical movements estimated to be about 16 17 km

the roughness of natural terrain a planetary and remote sensing perspective we examine the various methods and parameters in common use for quantifying and reporting surface topographic roughness it is shown that scale dependent roughness parameters are almost always required though not widely used we suggest a method of standardizing the parameters that are computed and reported so that topographic data gathered by different workers using different field techniques can be directly and easily intercompared we illustrate the proposed method by analyzing topographic data from 60 different surfaces gathered by five different groups and examine the information for common features we briefly discuss the implications of our analysis for studies of planetary surface roughness lander safety and radar remote sensing modeling and analysis

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

macro scale bed roughness of the siple coast ice streams in west antarctica subglacial bed conditions are key to understanding ice stream behaviour and evolution with bed roughness re ecting substrate composition and ow resistance here we present an analysis of bed roughness in the siple coast region of west antarctica from airborne radio echo sounding data the ice streams are associated generally with low bed roughness values which decrease downstream the bed of the slow owing ice stream c 10 000 km2 is also characterized by being smooth at all scales wavelengths ranging from 5 km to in excess of 40 km furthermore the bed is smooth either side of ice stream c this suggests the location of the ice stream is controlled by internal ice sheet dynamics rather than by bed morphology if the ice stream were encouraged to migrate laterally when active there would be little resistance offered by the subglacial morphology other inter ice stream regions are rough however indicating a subglacial topographic in uence on ice stream position bed roughness increases up ow of ice streams which unless the bed is modi ed may limit the inland migration of these systems copyright 2004 john wiley sons ltd

meter scale slopes of candidate mer landing sites from point photoclinometry photoclinometry was used to analyze the small scale roughness of areas within the proposed mars science laboratory msl landing ellipses the landing ellipses presented in this study are those in eberswalde crater gale crater and holden crater the mawrth vallis site could not be measured due to its albedo variations we were able to constrain surface slopes on length scales comparable to the hirise image resolution 0 25 meters pixel the msl mission has various engineering constraints that each candidate landing ellipse must satisfy these constraints indicate that the statistical value of the slopes at one two and five meter baselines are an important criterion we used our technique to estimate surface slopes across large swaths of each image and built up slope statistics for the images in each landing ellipse we are confident that all three final msl landing site ellipses that could be measured in this study are within the small scale roughness constraints our results have provided input into the landing hazard assessment process

quantitative methods for analyzing the roughness of the seafloor the bathymetry of the world ocean has been mapped using a variety of acoustic sounding instruments and traditional contouring methods prior to this study relatively few quantitative studies have been focused on the detailed morphology of the seafloor the work of most investigators has generally dealt with the analysis of seafloor relief without regard to spatial frequency or concern for obvious morphologic anisotropies a brief review of previous work is presented and is accompanied by an identification of the specific applications and limitations of those approaches the availability of more precise digital sounding data coupled with the development of higher resolution sonar mapping instruments e g deeptow seamarc now make it possible to investigate quantitatively many important aspects of seafloor relief and the geological processes responsible for its formation typical bathymetric contour maps represent a low frequency deterministic model of the seafloor to describe the higher frequency variability or roughness of the seafloor requires the development of an appropriate statistical method for generating a valid stochastic model new methods are developed herein which allow valid statistical models of the variability of oceanic depths to be derived from existing digital bathymetric soundings the smooth contoured surface often preserved as a geographic grid of depths when supplemented by such a roughness model can provide an essentially complete statistical description of the relief statistical models of seafloor roughness are also valuable tools for predicting acoustic scattering and bottom loss and in addition contain a wealth of information for more comprehensive interpretations of deep sea relief forming geological processes to allow the variability of depths to be described as a function of scale spatial frequency the amplitude spectrum is employed as the fundamental statistic underlying the model since the validity of the amplitude spectrum depends upon the assumption of a statistically stationary sample space a computer algorithm operating in the spatial domain was developed which delineates geographic provinces of limited statistical heterogeneity within each of these provinces a spectral model is derived by fitting the amplitude estimates with one or two two parameter power law functions using specialized regression techniques the distribution of resultant model parameters is examined for a large test area adjacent to the coast of oregon 42 45 n 130 124 w which includes several contrasting geologic environments the distribution of roughness corresponds generally with the various physiographic provinces observed in the region within some provinces additional complexities are apparent in the roughness model which cannot be inferred by simply studying the bathymetry these patterns are related to a variety of geological processes operating in the region such as the convergence of the continental margin and the presence of a propagating rift on the northern gorda rise in contrast a very large area of the continental margin off the east coast of the united states was found to have in common a single distinct amplitude spectrum this amplitude spectrum is almost identical to that found from the tufts abyssal plain region off the west coast of the united states spectra from both of these areas can be clearly separated into two straight line segments of different slope the two segments of these spectra are interpreted as reflecting two dominant relief forming processes the higher frequency band representing a sedimentary regime and the lower frequency band representing an underlying tectonic volcanogenic regime in many cases the calculated roughness statistics are not constant for data collected along different ship track directions this is due to the anisotropic nature of the seafloor relief a simple model is developed which describes the roughness statistics as a function of azimuth the parameters of this model quantify the anistropy of the seafloor allowing insight into the directionality of the corresponding relief forming processes and the physical meaning of the derived model statistical parameters finally the model is used to successfully predict the roughness of a surface at scales much smaller than those resolvable by surface sonar systems the model regression line derived from a hull mounted sonar is compared to data from deep towed sonars and bottom photographs the amplitude of roughness is predicted to within half an order of magnitude over five decades of spatial frequency and this prediction capability can probably be improved even further the stochastic models presented also demonstrate the potential for closely approximating the full two dimensional nature of some areas of the seafloor with only four statistical parameters these parameters can be estimated from random ship track data given a sufficient number of tracks and range of headings

phase relationships of i type granite with h2o to 35 kilobars the dinkey lakes biotite granite from the sierra nevada batholith the dinkey lakes biotite granite from the sierra nevada batholith was reacted with varying percentages of h 2o in sealed platinum capsules in a piston cylinder apparatus between 10 and 35 kbar the results were combined with the results from previously published experiments to provide comprehensive phase relationships for an i type granite a p t diagram with excess h 2o isobaric t x h 2o diagrams at 25 30 and 35 kbar showing h 2o undersaturated relations the h 2o undersaturated liquidus surface mapped with contours for constant h 2o contents and fields for near liquidus minerals and the solubility of h 2o in granite liquids to 35 kbar results and their implications show 1 the solidus temperature decreases from 680 c at 2 kbar to 620 c at 10 kbar then increases to 700 c at 35 kbar because of changes from less dense to more dense subsolidus mineral assemblages 2 the melting interval with excess h 2o which is only 35 c at 2 kbar increases to 105 c at 10 kbar and 150 c at 35 kbar because the liquidus minimum in the complex rock system departs from granite composition with increasing pressure 3 the solubility of h 2o in granite liquid is 27 2 5 weight percent at 35 kbar and 850 c indicating that a miscibility gap persists between h 2o saturated silicate magmas and aqueous vapor phase at least to pressures corresponding to 120 km depth in the mantle dissolution of alkali feldspar 20 of rock in the subsolidus aqueous vapor phase indicates that deep seated aqueous fluids are concentrated solutions 4 quartz and coesite are the liquidus minerals at mantle pressures for all h 2o contents indicating that granites and rhyolites cannot be primary magmas from mantle peridotite or subducted oceanic gabbroic crust 5 the liquidus surface at crustal pressures with plagioclase and quartz as primary minerals indicates that primary liquids of granite composition with moderate h 2o contents can be generated in the crust at reasonable temperatures these liquids could rise to near surface levels without vesiculation granite liquid together with residual crustal minerals could constitute plutonic magmas of intermediate composition

high radiogenic heat production in the kerala khondalite block southern granulite province india in situ radioelemental k u and th analysis and heat production estimates have been made at 59 sites in the kerala khondalite block kkb of the southern granulite province sgp of india together with the in situ analyses on granulites and gneisses previously reported from 28 sites and heat production estimated from the published geochemical analyses on granites and syenites of the kkb the new data set allows good characterization of heat production for the major granulite facies rocks and granitoids of the kkb garnet biotite gneisses are characterized by high levels of th and u with mean values of 60 and 3 ppm respectively khondalites leptynites and charnockites have slightly lower levels of th 23 20 and 22 ppm respectively and u 2 9 2 4 and 0 9 ppm respectively the mean k u th abundances for the granites leucogranites and granitic gneisses ranges from 3 9 to 4 3 2 6 to 4 3 ppm 22 to 50 ppm respectively and for the syenites 4 8 2 ppm and 5 7 ppm mean radiogenic heat production values for garnet biotite gneiss khondalite leptynite and charnockite are 5 5 2 7 2 4 and 2 2 w m 3 respectively for the granites leucogranites granitic gneisses and syenites it is 2 6 3 4 4 6 and 1 4 w m 3 respectively heat production of granulite facies rocks which are the most abundant rocks in kkb correlate well with th but less with u suggesting that variation is caused by th and u bearing accessory minerals such as monazite and zircon the high heat production of the kkb granulites are in contrast to the low heat production of the late archaean granulites of the northern block nb of the sgp which are highly depleted in radioelements and also the granulites of madurai block mb that have higher radioelemental abundances than in the granulites of the nb the high heat production of the kkb granulites could be due to the nature of protoliths and or metasomatism associated with neoproteroic to pan african alkaline magmatic activity represented by alkali granite and syenite carbonatite emplacements and emplacement of pegmatites

multiscale analysis of topographic surface roughness in the midland valley scotland surface roughness is an important geomorphological variable which has been used in the earth and planetary sciences to infer material properties current past processes and the time elapsed since formation no single definition exists however within the context of geomorphometry we use surface roughness as an expression of the variability of a topographic surface at a given scale where the scale of analysis is determined by the size of the landforms or geomorphic features of interest six techniques for the calculation of surface roughness were selected for an assessment of the parameter s behavior at different spatial scales and data set resolutions area ratio operated independently of scale providing consistent results across spatial resolutions vector dispersion produced results with increasing roughness and homogenization of terrain at coarser resolutions and larger window sizes standard deviation of residual topography highlighted local features and did not detect regional relief standard deviation of elevation correctly identified breaks of slope and was good at detecting regional relief standard deviation of slope sdslope also correctly identified smooth sloping areas and breaks of slope providing the best results for geomorphological analysis standard deviation of profile curvature identified the breaks of slope although not as strongly as sdslope and it is sensitive to noise and spurious data in general sdslope offered good performance at a variety of scales while the simplicity of calculation is perhaps its single greatest benefit

multiple tectonothermal events in the granulite blocks of southern india revealed from epma dating implications on the history of supercontinents abstract we report age data on zircon monazite uraninite and huttonite from a suite of 29 samples covering four major granulite blocks in southern india using an electron microprobe technique the rocks analysed in this study cover all of the major lithounits in these terrains and include garnet bearing and garnet free charnockites garnet biotite gneisses khondalites calc silicate rocks and a suite of orthogneisses biotite gneiss biotite hornblende gneiss two pink metagranites representing the magmatic phase were also analysed zircons from the madras block yield well defined isochrons at 2 5 2 6 ga core to rim analyses of single zircon grains show age zoning with 2 6 2 9 ga igneous cores mantled by 2 4 2 5 ga rims detrital zircons show age up to ca 3 2 ga monazites in this block have cores and rims with 2 5 2 3 ga a suite of 19 samples from the madurai block brings out the multiple tectonothermal events in this terrain zircons from an orthogneiss yield well defined isochrons at 1 7 0 1 ga 0 82 0 05 ga and 0 58 0 04 ga from core inner rim and rim portions respectively zircon grains in other rocks preserve either core or secondary growth ages at 0 8 1 0 ga zircons in a pink metagranite from this block show sharply defined isochrons of 0 68 0 03 ga for the core and 0 57 0 01 ga for the secondary portion a late pan african overprint is observed throughout this block with zircon rims monazite uraninite and huttonite yielding age values in the range of 0 45 0 60 ga zircons from both the trivandrum and nagercoil blocks show a major tectonothermal event at 0 55 ga with faint indications of previous tectonothermal events during 0 8 1 0 and 1 7 2 0 ga monazite data from both the trivandrum and nagercoil blocks are essentially similar to those from the madurai block except for presence of relic monazite in the former our study confirms the notion that the palghat cauvery shear zone marks the major terrain boundary between an archean craton in the north and proterozoic terrains in the south it also strengthens the view of paleoproterozoic accretion and pan african reworking of blocks south of this shear zone the ages of production accretion and reworking in the terrains of southern india yield important information for the histories of columbia 1 8 1 5 ga rodinia 1 1 1 0 ga and gondwana 0 6 0 5 ga supercontinents the southern indian terrains formed part of a worldwide network of orogenic belts that is centered around 1 8 ga and outlines the configuration of columbia accretion of terrains in the madurai block to archean rocks north of the palghat cauvery shear zone at this time is consistent with the ages suggested to be the oldest metamorphic event in the eastern ghats orogen of eastern india and the rayner belt of coastal east antarctica our data confirm earlier evidence that all of southernmost india underwent resetting of isotopic systems during the final accretion of gondwana at the time of the pan african orogeny 0 5 ga the possibility that the trivandrum and nagercoil terrains accreted to the madurai block after 0 7 ga suggests that this pan african zone may also have involved accretion and closure of ocean basins if that happened then this zone may be the long sought suture between east and west gondwana

surface roughness on the greenland ice sheet from airborne laser altimetry high resolution airborne laser altimetry is used to determine the small scale surface relief in central greenland and estimate the contribution from spatial noise to stratigraphic records the standard deviation of the surface roughness is 1 6 cm water equivalent corresponding to a standard deviation of annual layer thickness of 2 3 cm we this estimate agrees with an independent assessment of the spatial variability 2 5 cm we based on nine shallow ice cores the agreement suggests that the statistical nature of the surface in central greenland remains unchanged throughout the year by conducting airborne altimetry around proposed drilling sites the expected noise level in the core can be evaluated and sites selected where this level is lowest

analysis of flow near a dug well in an unconfined aquifer a numerical analysis of flow to a dug well in an unconfined aquifer is made taking into account well storage elastic storage release gravity drainage anisotropy partial penetration vertical flow and seepage surface at the well face and treating the water table in the aquifer and water level in the well as unknown boundaries the pumped discharge is maintained constant the solution is obtained by a two level iterative scheme the effects of governing parameters on the drawdown development of seepage surface and contribution from aquifer flow to the total discharge are discussed the degree of anisotropy and partial penetration are found to be the parameters which affect the flow characteristics most significantly the effect of anisotropy on the development of seepage surface is very pronounced

surface roughness and geological mapping at subhectometer scale from the high resolution stereo camera onboard mars express the quantitative measurement of surface roughness of planetary surfaces at all scales provides insights into geological processes a characterization of roughness variations at the scale of a few tens of meters is proposed that complements the analysis of local topographic data of the martian surface at kilometer scale as achieved from the mars orbiter laser altimeter mola data and at the subcentimeter scale using photometric properties derived from multi angular observations relying on a gabor filtering process an algorithm developed in the context of image classification for the purpose of texture analysis has been adapted to handle data from the high resolution stereo camera hrsc the derivation of roughness within a wavelength range of tens of meters combined with analyses at even longer wavelengths gives an original view of the martian surface the potential of this approach is evaluated for different examples for which the geological processes are identified and the geological units are mapped and characterized in terms of roughness

characterizing arid region alluvial fan surface roughness with airborne laser swath mapping digital topographic data 1 range front alluvial fan deposition in arid environments is episodic and results in multiple fan surfaces and ages these distinct landforms are often defined by descriptions of their surface morphology desert varnish accumulation clast rubification desert pavement formation soil development and stratigraphy although quantifying surface roughness differences between alluvial fan units has proven to be difficult in the past high resolution airborne laser swath mapping alsm digital topographic data are now providing researchers with an opportunity to study topography in unprecedented detail here we use alsm data to calculate surface roughness on two alluvial fans in northern death valley california we define surface roughness as the standard deviation of slope in a 5 m by 5 m moving window comparison of surface roughness values between mapped fan surfaces shows that each unit is statistically unique at the 99 confidence level furthermore there is an obvious smoothing trend from the presently active channel to a deposit with cosmogenic 10be and 36cl surface exposure ages of 70 ka beyond 70 ka alluvial landforms become progressively rougher with age these data suggest that alluvial fans in arid regions smooth out with time until a threshold is crossed where roughness increases at greater wavelength with age as a result of surface runoff and headward tributary incision into the oldest surfaces

floodplain friction parameterization in two dimensional river flood models using vegetation heights derived from airborne scanning laser altimetry two dimensional 2 d hydraulic models are currently at the forefront of research into river flood inundation prediction airborne scanning laser altimetry is an important new data source that can provide such models with spatially distributed floodplain topography together with vegetation heights for parameterization of model friction the paper investigates how vegetation height data can be used to realize the currently unexploited potential of 2 d flood models to specify a friction factor at each node of the finite element model mesh the only vegetation attribute required in the estimation of floodplain node friction factors is vegetation height different sets of flow resistance equations are used to model channel sediment short vegetation and tall and intermediate vegetation the scheme was tested in a modelling study of a flood event that occurred on the river severn uk in october 1998 a synthetic aperture radar image acquired during the flood provided an observed flood extent against which to validate the predicted extent the modelled flood extent using variable friction was found to agree with the observed extent almost everywhere within the model domain the variable friction model has the considerable advantage that it makes unnecessary the unphysical fitting of floodplain and channel friction factors required in the traditional approach to model calibration copyright 2003 john wiley sons ltd

kilometer scale roughness of mars results from mola data analysis the mars orbiter laser altimeter mola data are used to characterize the kilometer scale surface roughness of mars the median absolute value of the differential slope at a given baseline is proposed as a data derived measure of the surface roughness at this scale study of the scale dependence of roughness for the smoothest terrains gives an independent estimate of 20 cm for mola ranging accuracy the baseline lengths from 0 6 to 20 km are used and kilometer scale roughness is mapped for the entire surface the maps show that different geological units have distinctive roughness characteristics scale dependence of roughness for a number of geological units is presented and discussed the southern polar cap is rougher than the northern at kilometer and subkilometer scale which suggests differences in the sublimation condensation balance the vastitas borealis formation has a distinctive 3 km scale background surface topography which suggests a nonvolcanic origin for its upper layer young volcanic plains in amazonis planitia and the eastern part of elysium planitia are very similar to each other in their roughness characteristics and differ from other volcanic plains on mars which suggests a distinctive eruption style there are systematic latitudinal variations of roughness in both the southern highlands and the northern lowlands terrains at high latitude are smoother at short baselines the characteristic vertical scale related to this difference is several meters processes that could be responsible for formation of this trend include creep of ice rich near surface material at high latitudes treatment of the surface with repetitive deposition and sublimation of seasonal frost climate controlled deposition and or cementation of dust at high latitudes and repetitive sublimation and accumulation of subsurface ice at low latitudes with climate variations all mechanisms of origin could operate more effectively under different climate conditions relevant morphological observations favor mechanisms involving deposition of smooth blankets at high latitudes

geostatistical analysis of glacier roughness data in most glaciological and hydrological models surface roughness of snow and ice is an important parameter however roughness is generally used only as an estimated parameter for lack of available observations in this paper we present a method to collect and analyze ice surface roughness data using a specially designed instrument for survey and geostatistical methods for analysis the glacier roughness sensor grs built at the university of trier records variations in microtopography at 0 2 m 0 1 m resolution when pulled across an ice surface global positioning system data are used for location after several processing steps the data are analyzed using geostatistical methods the mathematical tool used to achieve a morphological characterization of ice surface types is the variogram grs data variograms and surface roughness analysis are ideal matches for morphological characterization because none of them requires or provides absolute elevation values morphology is described not by absolute elevation values but by the change of elevation in space which is the derivative of elevation surface roughness values the variogram is calculated from incremental values parameters extracted from variograms of grs data serve to distinguish lake surfaces wind structures ridge and vauey systems melting structures and blue ice areas examples are from jakobshavn isbrae drainage basin west greenland

spectral roughness of glaciated bedrock geomorphic surfaces implications for glacier sliding a microroughness meter mrm was used to measure the high frequency roughness of a number of geomorphic surfaces in the forefield of glacier de tsanfleuron switzerland resulting spectral power densities are added to low frequency spectra measured by electro optical distance meter edm to generate composite roughness spectra that include almost 5 orders of magnitude of roughness in the frequency domain these are used to define two roughness indices a general index of bed roughness is defined as the integral of the raw spectral power densities and a sliding related index of bed roughness is defined as the integral of the spectral power densities weighted to account for the optimum dependence of glacier sliding speed on hummock wavelength results indicate that mrm measured geomorphic components vary in roughness by 3 orders of magnitude principally depending on the surface microenvironment measured and profile orientation relative to the direction of former ice flow both mrm and edm measured roughnesses are lower parallel to the direction of former ice flow than perpendicular to it composite roughness spectra consequently indicate that the glacier bed is smoothed in the direction of former ice flow at all horizontal scales from 1 mm to 40 m typically resulting in an order of magnitude decrease in sliding related roughness relative to that measured perpendicular to ice flow comparison of data from two survey sites located adjacent to and 1 2 km from the current glacier margin indicates that postglacial subaerial weathering homogenizes bedrock roughness in particular reducing high frequency flow orthogonal roughness accounting for the effect of 28 ice bedrock separation over one of the profiles reduces net sliding dependent roughness by between 27 and 43 depending on the transition wave number used

residual relief separation digital elevation model enhancement for geomorphological mapping geomorphologically mapped data form a primary set of observations that can be used to infer former environmental conditions thus objective and consistent mapping of landforms from remotely sensed data e g satellite imagery digital elevation models dems is paramount for reconstructing palaeoenvironments this paper proposes a technique residual relief separation to enhance landforms in dems prior to visualization and digital mapping this is applied to a 600 km2 region surrounding lough gara ireland where drumlins 200 m wide overlie a regional relief of hills 10 km wide here residual relief separation uses this difference in width scale regional relief is approximated by a 1 km wide median filter then subtracted to leave the drumlins in a residual topography in a second step the residual relief is normalized to allow for amplitude variations in the drumlins across the area 5 40 m high finally visualization uses a simple black to white colour scale for height although not numerically outperforming other visualization techniques this method performs equally well and as the data are not illuminated there is no azimuthal bias additional benefits include the relatively simple calculation intuitive visual comprehension no emphasis of noise and the possibility of using any desired visualization technique after the landscape has been topographically manipulated

elementary forms for land surface segmentation the theoretical basis of terrain analysis and geomorphological mapping abstract land surface morphology is fundamental to geomorphological mapping and many gis applications review and comparison of various approaches to segmentation of the land surface reveals common features and permits development of a broad theoretical basis for segmentation and for characterization of segments and their boundaries within the context of defining landform units that maximise internal homogeneity and external differences this paper introduces the concept of elementary forms segments units defined by constant values of fundamental morphometric properties and limited by discontinuities of the properties the basic system of form defining properties represents altitude and its derivatives constant values of which provide elementary forms with various types of homogeneity every geometric type of elementary form can be characterized by a defining function which is a specific case of the general polynomial fitted function various types of boundary discontinuity and their connections and transformations into other types of morphological unit boundaries are analysed the wealth of types of elementary forms and their boundaries is potentially unbounded and thus is sufficient to cover the real variety of landforms elementary forms in the basic set proposed here have clear potential for genetic and dynamic interpretation a brief worked example documents the possibility of analytical computation of various models of ideal elementary forms for particular segments of landform ideal elementary forms can be considered as attractors to which the affinity of surface segments can be measured by multivariate statistical methods the use of the concept of elementary forms in landscape segmentation is promising and it could be adapted for elementary segmentation of various other spatial fields

cooling history of the puttetti alkali syenite pluton southern india abstract the puttetti alkali syenite pluton in southern india belongs to the suite of felsic magmatic intrusives emplaced during the late neoprotrozoic cambrian time during the final phase of amalgamation of the gondwana supercontinent in this study we evaluate the cooling history of this pluton based on various isotopic systems we present whole rock pb pb data on the syenite which yields an isochron age of 508 25ma three phlogopite separates from the syenite pluton give k ar ages of 454 0 9 0 448 5 8 9 and 445 6 8 8 ma indicating cooling age at temperatures of 415 c u pb analyses of zircons from this syenite yielded an age of 572 2 ma in a previous study with u pb closure temperatures 800 o c this age probably indicates the timing of emplacement of the puttetti pluton collectively we estimate from the isotopic age data and respective closure temperatures that the syenite body cooled at about 3 2 o c ma from about 800 o c to about 415 o c the markedly low cooling rate of the syenite pluton absence of chilled margin effects and common occurrence of pyroxene feldspar phlogopite and zircons megacrysts in the rock indicate that the host granulites were at high temperatures during the emplacement of the syenite magma the cooling history of puttetti syenite estimated in this study is closely comparable with the 3 4 o c ma cooling rate estimated for a granite pluton in a previous study from madagascar our study suggests protracted cooling rates for the late pan african intrusives emplaced within the gondwana crust with a long residence history in a hot crust bore they were exhumed to shallower levels

analysis of lidar derived topographic information for characterizing and differentiating landslide morphology and activity abstract this study used airborne laser altimetry lidar to examine the surface morphology of two canyon rim landslides in southern idaho the high resolution topographic data were used to calculate surface roughness slope semivariance and fractal dimension these data were combined with historical movement data global positioning systems gps and laser theodolite and field observations for the currently active landslide and the results suggest that topographic elements are related to the material types and the type of local motion of the landslide weak unconsolidated materials comprising the toe of the slide which were heavily fractured and locally thrust upward had relatively high surface roughness high fractal dimension and high vertical and lateral movement the body of the slide which predominantly moved laterally and consists mainly of undisturbed older canyon floor materials had relatively lower surface roughness than the toe the upper block consisting of a down dropped section of the canyon rim that has remained largely intact had a low surface roughness on its upper surface and high surface roughness along fractures and on its west face unrelated to landslide motion the upper block also had a higher semivariance than the toe and body the topographic data for a neighboring older and larger landslide complex which failed in 1937 are similarly used to understand surface morphology as well as to compare to the morphology of the active landslide and to understand scale dependent processes the morphometric analyses demonstrate that the active landslide has a similar failure mechanism and is topographically more variable than the 1937 landslide especially at scales 20 m weathering and the larger scale processes of the 1937 slide are hypothesized to cause the lower semivariance values of the 1937 slide at smaller scales

flow to a well of finite diameter in a homogeneous anisotropic water table aquifer a laplace transform solution is presented for the problem of flow to a partially penetrating well of finite diameter in a slightly compressible water table aquifer the solution which allows for evaluation of both pumped well and observation piezometer data accounts for effects of well bore storage and skin and allows for the noninstantaneous release of water from the unsaturated zone for instantaneous release of water from the unsaturated zone the solution approaches the line source solution derived by neuman as the diameter of the pumped well approaches zero delayed piezometer response which is significant during times of rapidly changing hydraulic head is included in the theoretical treatment and shown to be an important factor in accurate evaluation of specific storage by means of a hypothetical field example it is demonstrated that evaluations of specific storage ss using classical line source solutions may yield values of ss that are overestimated by a factor of 100 or more depending upon the location of the observation piezometers and whether effects of delayed piezometer response are included in the analysis theoretical responses obtained with the proposed model are used to suggest methods for evaluating specific storage

geomorphological mapping of glacial landforms from remotely sensed data an evaluation of the principal data sources and an assessment of their quality abstract this paper presents the results of an experiment to compare glacial geomorphology mapped from remotely sensed imagery with 1 10 000 scale field mapping the field mapping was validated against high resolution lidar imagery of an area glacierized during the younger dryas and found to provide an essentially reliable if not complete representation of the glacial geomorphology the experiment consists of comparing the field mapping with digital elevation models shuttle radar topography mission c band landmap os panorama os profile nextmap and satellite imagery landsat thematic mapper of a 100 km2 region of central scotland north of glasgow that was last glaciated during the last glacial maximum and during the younger dryas respectively c 14 5 and 11 5 cal ka bp for the purposes of this exercise we concentrated on glacial lineaments flutes drumlins and crag and tail but attention was also given to moraine ridges and eskers qualitative and quantitative comparisons are performed and the results show that of the remotely sensed data sets only nextmap great britain provided results that showed any approximation to the field mapping os panorama and os profile provided very poor approximations and the other methods fail to provide any information of value attention is given to the issues of scale and the differences between a small scale detailed study such as this experiment in which a high resolution glacial geomorphological reconstruction is required and the small scale studies where the remote sensing techniques used here provide important evidence of regional significance when glaciers formed the largest elements of the landscape the paper concludes with a consideration of protocols for future geomorphological mapping exercises and outlines some of the requirements that must be adopted as these protocols are developed