mechanism of arrested charnockite formation at nemmara palghat region southern india abstract the formation of arrested charnockite is an excellent example of structurally controlled channellised fluid flow along specific sites accompanied by selective elemental mobility and mineralogical changes the present paper recognises and focuses study on three types of arrested charnockite formation from palghat region namely shear controlled foliation parallel and boudin neck types and address their spatio temporal relations to regional scale charnoenderbite the shear controlled and foliation parallel types post date deformation and migmatisation the boudin neck type on the contrary is coeval with partial melting and followed the path of cooling and decreasing water activity in the gneiss k feldspar veining around plagioclase and quartz symplectitic intergrowth of biotite quartz after orthopyroxene and k feldspar and fluid inclusion data suggests the presence of alkalic supercritical brine and low density co2 rich fluid during charnockite formation charnockite domains developed following the breakdown of hornblende biotite and quartz are characterised by a more or less pronounced depletion of fe ca mg and ti and trace elements y and zr compared to their counterpart gneiss ree spectra indicate a subtle depletion in the hree near the centre of the charnockite domain although close pair samples of gneiss charnockite are isochemical on a scale of a few millimetres bi directional element movement related to the formation of new mineral was noted it is postulated that arrested charnockite formation developed in situ on local scale within the granitic domains of the hornblende biotite gneiss in the presence of co2 rich fluids and alkalic supercritical saline brine this process post dated the time of regional granulite charnoenderbite and large regional scale retrogression and migmatisation

halogen bearing minerals in syenites and high grade marbles of dronning maud land antarctica monitors of fluid compositional changes during late magmatic fluid rock interaction processes meta sedimentary rocks including marbles and calcsilicates in central dronning maud land cdml in east antarctica experienced a pan african granulite facies metamorphism with peak metamorphic conditions around 830 20 c at 6 8 0 5 kbar which was accompanied by the post kinematic intrusion of huge amounts of syenitic charnockitic magmas at 4 5 0 7 kbar the marbles and calcsilicates may represent meta evaporites as indicated by the occurrence of metamorphic gypsum anhydrite and cl rich scapolite that formed in the presence of saline fluids with x nacl in the range 0 15 0 27 the marbles and calcsilicates bear biotite tremolite and or hornblende and humite group minerals clinohumite chondrodite and humite which are inferred to have crystallized at about 650 c and 4 5 kbar the syenitic intrusives contain late magmatic biotite and amphibole formed between 750 and 800 c as well as relictic magmatic fayalite orthopyroxene and clinopyroxene two syenite and two calcsilicate samples contain fluorite corona textures in the marbles and calcsilicates suggest very low fluid rock ratios during the formation of the retrograde 650 c assemblages biotite in all but two syenite samples crystallized at log f h 2 o f hf ratios of 2 9 0 4 while in the calcsilicates both biotite and humite group minerals indicate generally higher log f h 2 o f hf values of up to 5 2 a few samples though overlap with the syenite values log f h 2 o f hcl derived from biotite covers the range 0 5 2 6 in all rock types within a single sample the calculated values for both parameters vary typically by 0 1 to 0 8 log units water and halogen acid fugacities calculated from biotite olivine orthopyroxene feldspar quartz equilibria and the above fugacity ratios are 1510 2790 bars for h2o 1 3 5 3 bars for hf and 7 600 bars for hcl the results are interpreted to reflect the reaction of relatively homogeneous magmatic fluids in terms of log f h 2 o f hf derived from the late magmatic stages of the syenites with both earlier crystallized still hotter parts of the syenites and with adjacent country rocks during down temperature fluid flow fluorine is successively removed from the fluid and incorporated into f bearing minerals close to the syenite into metamorphic fluorite in the course of this process log f h 2 o f hf increases significantly chlorine preferably partitions into the fluid and hence log f h 2 o f hcl does not change markedly during fluid rock interaction

carbonate silicate inclusions in garnet as evidence for a carbonate bearing source for fluids in leucocratic granitoids associated with granulites of the southern marginal zone limpopo complex south africa abstract we present a study of carbonate bearing polyphase inclusions in garnets from leucocratic granitoids intruding metapelitic granulites of the southern marginal zone smz of the neoarchean limpopo high grade complex south africa during the post peak stage 2710 2650 ma u pb ages for zircons and monazites ternary feldspar thermometry suggests that the granitoid magma cooled from temperatures 800 900 c at a pressure of ca 6 5 kbar abundant co2 fluid inclusions in quartz and t xco2 phase equilibria modeling via perple x imply action of an essentially carbonic fluid in the granitoids cores of almandine rich garnet grains from the granitoids contain polyphase carbonate bearing inclusions with a distinct negative crystal shape the major carbonate in the inclusions is a strongly zoned magnesite siderite variety whereas pyrophyllite is the predominant silicate phase raman spectra of unexposed inclusions revealed a presence of co2 as well as ch4 and h2o the carbonate bearing inclusions coexist with larger polyphase inclusions composed of biotite quartz k feldspar plagioclase sillimanite which are interpreted as relics of granitic melts modeling the mineral assemblage preserved within the carbonate bearing inclusions shows that their present mineral and chemical compositions are a product of interaction of the trapped aqueous carbonic fluid with host garnet during cooling below 400 c despite strong modifications the inclusions bear evidence for initial saturation of the fluid with mg carbonate this is taken as an evidence for an origin of the fluids by devolatilization of the mg rich carbonate bearing ultrabasic greenstone rocks of the kaapvaal craton that were buried under the smz being generated at temperatures between 650 and 700 c the fluid subsequently participated in anatexis and coexisted with the granite magma during exhumation and interaction of the smz granulites with cratonic rocks

pedogenic carbonate proxies for amount and seasonality of precipitation in paleosols the depth to carbonate nodular bk horizon in soils d in cm is correlated with mean annual precipitation p in mm so that bk horizons are deep in subhumid regions but shallow in semiarid regions previous quantifications of this relationship are unchanged by this new compilation of 807 soils p 137 24 6 45 d 0 013 d 2 where r 2 0 52 and standard error s e 147 mm in most north american postglacial soils the bk horizon is thin and well defined whereas in monsoonal tropical soils of pakistan and kenya the bk horizon is thick and diffuse data from 675 modern soils define the relationship between the thickness of soil with nodules t in cm and mean annual range of precipitation m in mm difference between monthly means of wettest and driest months m 0 79 t 13 71 where r 2 0 58 and s e 22 mm the relationship between carbonate nodule size s in cm and soil age a in ka is quantified by 9 radiocarbon dated soils from las cruces new mexico a 3 92 s 0 34 where r 2 0 57 and s e 1 8 k y these transfer functions are applied to reconstructing paleoclimatic change from paleocene eocene paleosols of the north horn formation and flagstaff limestone of axhandle canyon utah the terminal paleocene spike of warmth recorded by fossil plants in nearby wyoming was coincident with a brief peak in both mean annual precipitation and mean annual range of precipitation in utah

decompressed eclogites in the sveconorwegian grenvillian orogen of sw sweden petrology and tectonic implications relict eclogites and associated high pressure rocks are present in the eastern segment of the sw swedish gneiss region the tectonic counterpart of the parautochthonous belt of the canadian grenville these rocks give evidence of sveconorwegian eclogite facies metamorphism and subsequent pervasive reworking and deformation at granulite and amphibolite facies conditions the best preserved eclogite relics suggest a clockwise p t t history beginning in the amphibolite facies progressing through the eclogite facies decompressing and partially reequilibrating through the high and medium pressure granulite facies before cooling through the amphibolite facies textures demonstrate the former coexistence of the plagioclase free assemblages garnet clinopyroxene quartz rutile ilmenite garnet clinopyroxene kyanite rutile and garnet kyanite quartz rutile the former existence of omphacite is evidenced by up to 45 vol plagioclase expelled as small grains within large clinopyroxene matrix plagioclase is secondary and occurs expelled from clinopyroxene or in fine grained granulite facies reaction domains formed during resorption of garnet and kyanite garnet shows preserved prograde growth zoning with rimward increasing pyrope content decreasing spessartine content and decreasing fe fe mg ratio but is partly resorbed and reequilibrated at the rims p t estimates from microdomains with clinopyroxene plagioclase quartz garnet indicate pressures of 9 5 12 kbar and temperatures of 705 795 c for a stage of the granulite facies decompression the preservation of the prograde zoning suggests that the rocks did not reside at these high temperatures for more than a few million years and chemical disequilibrium and frozen reaction textures indicate heterogeneous reaction progress and overstepping of reactions during the decompression through the granulite facies together these features suggest a rapid tectonic exhumation the eclogite relics occur within a high grade deformation zone with wnw ese stretching and associated oblique normal sense top to the east sensu lato displacement suggesting that extension was a main cause for the decompression and exhumation probable tectonic scenarios for this deformation are sveconorwegian late orogenic gravitational collapse or overall wnw ese extension

early mesozoic triassic landscapes in australia evidence argument and implications abstract australia has strong claims to be known as the old continent in addition to landscapes of later cretaceous early tertiary derivation remnants of early mesozoic triassic jurassic surfaces which are part of the contemporary landscape are also recognized being of etch type they have two ages one referring to the period of preparation by subsurface weathering and the other to their date of exposure in many instances exposure can be dated and the period of preparatory weathering closely inferred such old paleosurfaces are demonstrated on kangaroo island and are strongly implied in for example the flinders gawler and macdonnell ranges in arnhem land and the arcoona plateaus in many parts of the eastern uplands and on several bornhardts in the yilgarn and gawler cratons they reinforce the suggestion that once in positive relief and shedding water surfaces persist with little change for long periods such ancient features are incompatible with several well known models of landscape e

charnockite and granite formation and influx of co 2 at kabbaldurga the discovery at kabbaldurga quarry karnataka south india1 3 of patches of charnockite apparently in an arrested state of development has refocused attention on the mechanism of charnockite formation in particular the relative roles of co2 and h2o during high grade metamorphism and charnockite development can be studied in such an area during an influx of a co2 rich volatile phase h2o may be liberated as a result of the reduction in the state of hydration by the breakdown of hydrous minerals4 the p t conditions in which this occurs are important because with an increase in xh2o conditions which may allow anatexis could be initiated in advance of such a co2 rich phase indeed weaver5 has suggested that the k rich acid charnockites found at pallavaram madras6 developed due to changes in volatile composition before the onset of charnockite conditions the exposure at kabbaldurga quarry is interpreted here as displaying evidence that such a process has taken place

cool kaolins in finland we use d h and 18o 16o ratios to explore the age of kaolins on the fennoscandian shield sub cretaceous kaolins in southern scandinavia have isotopic compositions indicative of weathering under warm mean annual temperatures mats of 15 c deep kaolins on the shield surface in finland previously also have been regarded as products of humid tropical weathering of mesoproterozoic to eocene age new oxygen and hydrogen isotope ratios indicate however weathering by cool groundwater under mats of 13 15 c isotope ratios are also not consistent with deep 1 km burial by cover rocks indicating that a very old age for the weathering is unlikely palaeotemperatures are below cretaceous mats yet substantially above plio pleistocene mats comparisons with palaeotemperatures in n europe and around the arctic ocean indicate that the finnish kaolins developed on the shield surface in the palaeogene or alternatively miocene deep weathering was selectively developed in highly fractured shield rocks and took place in response to latest cretaceous and palaeogene uplift and after stripping of palaeozoic cover rocks the cool kaolins in finland indicate that previous routine attributions of kaolinitic weathering products in the geological record to humid tropical environments should be closely scrutinised

low temperature aqueous alteration of basalt mineral assemblages of deccan basalts and implications for mars spectra of basalt samples were dominated by fe 2 crystal field transitions with weak alteration bands near 1 4 and or 1 9 mm reststrahlen bands in mid infrared showed the convolution of plagioclase and pyroxene features typical of basalts saprolite samples were incompletely leached and their spectra were dominated by complex al and fe mg bearing smectite clays and retained no original mafic signatures xrd and mossbauer detected pyroxene and plagioclase not visible by reflectance spectroscopy in some saprolite samples zeolites were present throughout the saprolite the laterite was the most leached horizon and all analyses showed kaolinite and iron oxide assemblages this kaolinite and hematite association would be expected if kaolinite on mars formed through leaching under conditions similar to those on earth and has implications for abundant freshwater on the martian surface

chemical weathering of basalts southwest iceland effect of rock crystallinity and secondary minerals on chemical fluxes to the ocean river ground and peat water from a basaltic catchment area laxa in kjos southwest iceland were sampled and analyzed for major element concentrations to define the effect of glassy versus crystalline basalt the formation of secondary minerals and runoff on fluxes of dissolved elements to the ocean the proportions of the dissolved solids in the water samples derived from precipitation air and rock weathering were estimated the amounts of na mg ca k and s originating from precipitation were calculated from the respective solute cl marine ratios and the estimated aqueous cl originated from precipitation which was calculated using measured b content of the waters and b cl molal marine and rock ratios the rock contribution from weathering ranged from 22 to 46 percent of the total dissolved solids of the waters iron and al showed low mobility compared to na this was primarily due to consumption of these elements by ferrihydroxides allophane imogolite and clay minerals also si and to a lesser degree ca show apparent slightly lower mobility than na these results are in good agreement with these phases being dominant in the soils of the study area wada and others 1992 and the main secondary minerals of basaltic glass in iceland crovisier and others 1992 reaction progress calculations support these findings according to a model interaction of basaltic glass and meteoric water al fe and si are consumed by amorphous fe and al hydroxides and imogolite and allophane at low reaction progress with increasing reaction progress ca fe mg smectite became the primary secondary minerals limiting the mobility of ca fe mg si and al these findings suggest that the weathering in the laxa in the kjos catchment area has evolved into the beginning of the smectite weathering stage and that it is dominated by a relatively low reaction progress and a high water to rock ratio in the present study the effect of runoff and rock crystallinity was quantified for dissolved elemental fluxes temperature lithology other than rock crystallinity and rock age were similar in all of the catchment areas in this study silica ca f s al k mg and b had a very similar dependence on runoff on the other hand na fluxes were found to be less dependent on runoff and fe fluxes were found to be independent of runoff basaltic glass dissolves faster than fully crystallized basaltic rocks gislason and eugster 1987a therefore increased glass content of the primary rocks is thought to increase the leaching and elemental fluxes at constant runoff however because some of the solutes particularly al and fe were highly influenced or even controlled by the formation of secondary minerals this increasing dissolution with increasing glass content was hidden on the other hand basaltic glass was observed to enhance the fluxes of more mobile elements like na si ca f and s by a factor of 2 to 5 at a constant runoff of 200 cm yr constant vegetative cover and 0 to 100 percent glass content of the rocks the k and mg fluxes were found to be independent of rock crystallinity however runoff alone cannot explain the fluxes of these elements and it seems that vegetative cover and seasonal variations in biomass activities influence the k and mg fluxes

garnet biotite geothermometry revised new margules parameters and a natural specimen data set from maine the garnet biotite geothermometer has been recalibrated using recently obtained margules parameters for iron magnesium calcium garnet mn interactions in garnet and al interactions in biotite as well as the fe oxidation state of both minerals fe mg and dwal margules parameters for biotite have been retrieved by combining experimental results on 6 al free and 6 al bearing biotite using statistical methods margules parameters per mole of biotite are bt w 5 40 719 2 30t j mole mgfe

carbon isotope compositions of fluid inclusions in charnockites from southern india models for the formation of crustal granulites which include the metamorphism of anhydrous lithologies1 2 the extraction of hygroscopic granite melts3 4 and fluxing by co25 7 constrain the thermal and geochemical evolution of the lower crust and its interaction with mantle derived volatiles here we present abundances and carbon isotope compositions of co2 in fluid inclusions in quartz and garnet from gneiss granulite pairs from the incipient char nockite quarries of southern india determined by a stepped combustion thermal decrepitation carbon extraction technique which quantifies problematic sample contamination and allows precise lithological control the results show that the co2 in incipient charnockite is more abundant and isotopically heavier than the co2 in associated gneiss providing evidence for the influx of co2 rich fluids during their formation the inferred carbon isotope compositions of these fluids are consistent with a mantle source and at ponmudi the isotopic composition of coexisting graphite and co2 implies fluid rock volume ratios in excess of 0 15

the transformation of amphibolite facies gneiss to charnockite in southern karnataka and northern tamil nadu india amphibolite facies metamorphic grade gives way southward to the granulite grade in southern karnataka as acid gneisses develop charnockite patches and streaks and basic enclaves develop pyroxenes petrologic investigations in the transitional zone south of mysore have established the following points 1 the transition is prograde amphibole bearing gneisses intimately associated with charnockite at kabbal and several similar localities are not retrogressive after charnockite as proved by patchy obliteration of their foliation by transgressive very coarse grained charnockite high fluorine content of biotite and amphibole in gneisses and high large ion lithophile element contents in gneisses and charnockites these features are in contrast to very low fluorine in retrogressive amphiboles and biotites very low large ion lithophile element contents and zonal bleaching of charnockite in clearly retrogressive areas as at bhavani sagar tamil nadu 2 metamorphic temperatures in the transitional areas were 700 800 c pressures were 5 7 kbar and h2o pressures were 0 1 0 3 times total pressures based on thermodynamic calculations using mineral analyses dense co2 rich fluid inclusions in the kabbal rocks confirm the low h2o pressures at the first appearance of orthopyroxene farther to the south in the nilgiri hills and adjacent granulite massif areas peak metamorphic temperatures were 800 900 c pressures were 7 9 kbar and water pressures were very low so that primary biotites and amphiboles those with high f contents are rare 3 the incipient granulite grade metamorphism of the transitional areas was introduced by a wave of anatexis and k metasomatism this process was arrested by drying out under heavy co2 influx charnockites so formed are hybrids of anatectic granite and metabasite of metabasite and immediately adjacent gneiss or are virtually isochemical with pre existing gneiss despite gross recrystallization to granulite mineralogy these features show that partial melting and metasomatism are attendant rather than causative in charnockite development copious co2 from a deep crustal or mantle source pushed ahead of it a wave of more aqueous solutions which promoted anatexis granulite metamorphism of both neosome and paleosome followed the process is very similar to that deduced for the madras granulites by weaver 1980 the massif charnockites for the most part extremely depleted in lithophile minor elements show many evidences of having gone through the same process

hydraulics of interrill overland flow on stone covered desert surfaces the hydraulics of interrill overland flow on stone covered desert surfaces depend on the resistance to flow which may be partitioned into grain resistance form resistance wave resistance and rain resistance efforts to model large scale roughness in open channels suggest that resistance to overland flow on such surfaces is a function of grain reynolds number froude number flow depth and the size shape spacing and pattern of the roughness elements the effect of flow depth on flow resistance f is often hidden in the flow reynolds number re in laboratory and field studies alike f re relations have been found to be convex upward and negatively sloping and these shapes have been explained in terms of the progressive inundation of the roughness elements where laboratory or field based models have been developed for predicting f they invariably contain percent stone cover the prominence of this variable reflects the strong influence of stone size and spacing on flow resistance a laboratory study shows that where the froude number f 0 50 wave resistance increases with stone cover and dominates resistance to flow on all surfaces with stone covers greater than 10 a field study indicates that where f 0 50 and wave resistance is inconsequential grain and form resistance typically account for about 5 and 95 of f respectively these findings have important implications for sediment transport modeling because percent grain resistance is equal to percent grain shear stress and it has recently been suggested that in overland flow as in river flow sediment transport capacity is determined by grain shear stress rather than total shear stress a laboratory study however demonstrates that this is not the case sediment transport capacity is in fact greater than predicted by grain shear stress because energy dissipated in the wakes of roughness elements in overland flow is transformed into turbulence sufficiently close to the bed to affect sediment transport

high grade localized metasomatic alteration of the granitic gneiss surrounding a clinopyroxene rich pegmatoid dyke sondrum stenhuggeriet halmstad sw sweden the sondrum stone quarry halmstad sw sweden exposes a transition from migmatized granitic gneissic country rock into a foliated clinopyroxene free granitic gneiss and then a central pegmatoid dyke dominated by clinopyroxene megacrysts this transition zone represents a fracture controlled fluid alteration zone that developed under conditions of 650 700 degrees c and 790mpa mineral chemical trends in f cl fe ti mn and y are interpreted as documenting a fluid infiltration event associated with the formation of the pegmatoid dyke fluid inclusions from the pegmatoid dyke are co2 dominant whereas in the surrounding country rock they are dominated by h2o nacl cacl2 fluid inclusions from the intermediate foliated clinopyroxene free granitic gneiss are a mixture of the two types the pegmatoid dyke appears to have originated from a high ca activity fe mg enriched fluid rich granitic melt with a co2 component which was emplaced along a tectonic fracture in a regionally migmatized granitic gneiss in the lower crust this was accompanied by limited partial melting of the surrounding granitic gneiss the ca activity of the melt was high enough to allow for the formation of clinopyroxene megacrysts as opposed to orthopyroxene h2o enriched fluids expelled from the crystallizing pegmatoid dyke which retained the majority of the co2 helping to stabilize the clinopyroxene the expelled fluids coarsened and chemically affected the surrounding country rock resulting in trends in the mineral and fluid inclusion chemistry seen today in the foliated and regional granitic gneiss less

linking deformation migmatite formation and zircon u pb geochronology in polymetamorphic orthogneisses sveconorwegian province sweden absolute ages of migmatization in the polymetamorphic parautochthonous basement of the sveconorwegian province sweden have been determined using u pb ion probe analysis of zircon domains that formed in leucosome of migmatitic orthogneisses migmatite zircon was formed by recrystallization whereas dissolution reprecipitation and neocrystallization were subordinate the recrystallized migmatite zircon was identified by comparison of zircon in mesosomes and leucosomes it is backscatter electron bright u rich 800 4400 ppm with low th u ratios generally 0 01 0 1 unzoned or oscillatory ghost zoned and occurs as up to 100 m thick rims with transitional contacts to cores of protolith zircon protolith ages of 1686 12 and 1668 11 ma were obtained from moderately resorbed igneous zircon crystals generally th u 0 5 1 5 u 300 ppm in mesosomes protolith zircon is also present as resorbed cores in the leucosomes linkage of folding synchronous migmatization and formation of recrystallized zircon rims allowed direct dating of south vergent folding at 976 7 ma at a second locality similar recrystallized zircon rims in leucosome date pre sveconorwegian migmatization at 1425 7 ma an upper age bracket of 1394 12 ma for two overprinting phases of deformation upright folding along gently ssw plunging axes and stretching in ese was set by zircon in a folded metagranitic dyke lower age brackets for these events were set at 952 7 and 946 8 ma by zircon in two crosscutting and undeformed granite pegmatite dykes together with previously published data the present results demonstrate i tectonometamorphic reworking during the hallandian orogenesis at 1 44 1 42 ga resulting in migmatization and formation of a coarse gneissic layering ii sveconorwegian continent continent collision at 0 98 0 96 ga involving a emplacement of an eclogite unit b regional high pressure granulite facies metamorphism c southvergent folding subhorizontal east west stretching and migmatization all of which caused overprint or transposition of older mesoproterozoic and sveconorwegian structures the sveconorwegian migmatization and folding took place during or shortly after the emplacement of sveconorwegian eclogite and is interpreted as a result of north south shortening synchronous with east west extension and unroofing during late stages of the continent continent collision

canons revisited and reviewed lester king s views of landscape evolution considered 50 years later fifty years after its publication lester king9s canons of landscape evolution is reviewed and is considered in light of subsequent trends and actual developments some of his ideas such as the role of scarp recession and the antiquity of some surfaces remain current his broad view of the world and his interest in major relief anticipated trends that are now fashionable some of his interpretations however and in particular his downgrading of the importance of structural factors and his linking of scarp retreat and pedimentation have not stood the test of time other concepts such as the etch or two stage origin of forms which were mooted but not fully appreciated in king9s day have come to the forefront and technological advances in dating and survey particularly of the ocean floors have signaled new perspectives in landscape interpretation nevertheless king9s was a courageous attempt to provide guidelines for landscape study

comparing results from two continental geochemical surveys to world soil composition and deriving predicted empirical global soil pegs2 reference values analytical data for 10 major oxides al2o3 cao fe2o3 k2o mgo mno na2o p2o5 sio2 and tio2 16 total trace elements as ba ce co cr ga nb ni pb rb sr th v y zn and zr 14 aqua regia extracted elements ag as bi cd ce co cs cu fe la li mn mo and pb loss on ignition loi and ph from 3526 soil samples from two continets australia and europe are presented and compared to 1 the composition of the upper continetal crust 2 published word soil awerage values and 3 data from other continetal scale soil surveys it cab be demonstrated that average upper continetal crust values do not provide reliable estimates for natural concentrations of elements in soil for many elements there exist substantial differences between published world aoil averages and the median concentrations observed on two continets direct comparison with other continetal datasets is hampered by the fact that often mean instead of the statistically more robust median is reported using a database of the worldwide disstribution of lithological units it can be demonstrated that lithology is a poor predictor of soil chemistry climate related processes such as glaciation and weathering are strong modifiers of the geochemical signature inherited from bedrock during pedogenesis to overcome existing shortcomings of predicted global or world soil geochemical reference values we propose preliminary empirical global soil reference values based on analytical results of a representative number of soil samples from two continets pegs2

planning of urban underground infrastructure using a broadband seismic landstreamer tomography results and uncertainty quantifications from a case study in southwestern sweden abstractwe have developed a multicomponent broadband seismic landstreamer system based on digital sensors and particularly suitable for noisy environments and areas in which high resolution images of the subsurface are desired we have evaluated results interpretations and approaches using the streamer in the planning of an approximately 3 km long underground tunnel in the city of varberg in the southwestern sweden prospective targets were imaging of the shallow 20 m bedrock surface and weak zones such as fracture and shear zones over the course of three weeks 25 profiles were acquired with a total length of approximately 7 5 km using a source and receiver spacing of 2 4 m a novel approach of the data acquisition was to integrate the landstreamer with wireless sensors in areas in which the accessibility was restricted by roads and also to increase the source receiver distances offsets although the area was highly noisy the seismic data in conjunction with available boreholes successfully l

40ar 39ar geochronology across the mylonite zone and the southwester granulite province in the sveconorwegian orogen of s sweden abstract the crustal segment between the mylonite zone mz and the protogine zone in southern sweden the southwestern granulite province sgp is characterized by numerous occurrences of granulite and upper amphibolite facies rocks including migmatitic gneisses mafic granulites garnet amphibolites and charnockites the southwest part of the mylonite zone north of varberg marks a tectonic upper boundary of the sgp a 40 ar 39 ar study was initiated across the mylonite zone and within the sgp in order to constrain and compare the ages obtained from within the sgp with those obtained north of and within the mylonite zone 23 homblendes and one muscovite have been analyzed the results of these analyses indicate the following 1 hornblendes from within and near the mz yield 40 ar 39 ar hornblende ages of 915 ma these ages are interpreted to date the dynamic crystallization or cooling below 500 c of the deformation associated with the mz 2 away from the mz there is a distribution of ages between those which yield younger sveconorwegian ages of 931 934 ma and those which yield older sveconorwegian ages generally between 960 and 1007 ma the younger age may be associated with orogenic uplift while the older one may be associated with an earlier sveconorwegian crustal thickening event 3 the one muscovite age of 904 ma would indicate a late cooling rate of at least 6 15 c ma cooling rates of this magnitude may suggest that the final uplift of the sveconorwegian orogen was related to large scale crustal extension

determining the mean depth of overland flow in field studies of flow hydraulics in field studies of interrill overland flow conducted on runoff plots the mean depth of flow is usually obtained by averaging measurements of flow depth at regularly spaced points across the plot including points where there is no flow although this procedure may be appropriate in studies aimed at runoff prediction it is not in studies concerned with flow hydraulics in the latter studies more realistic results can be obtained by excluding those points where the depth is zero and reducing the width of flow in proportion to the number of points excluded failure to do this results in the underestimation of the actual mean flow depth reynolds number and friction factor where discharges are small or microtopography is large this underestimation is likely to be significant

anomalously low temperature orthopyroxene spinel and sapphirine occurrences in metasediments from the bamble amphibolite to granulite facies transition zone south norway possible evidence for localized action of saline fluids a reply the question has been raised whether isolated granulite facies islands which occur throughout the amphibolite facies of the regional amphibolite to granulite facies transition zone in the central part of the bamble sector southern norway are the result of prograde or retrograde metamorphism we have studied one of these islands the sapphirine granulites at hauglandsvatn despite the preponderance of amphibolite facies assemblages in the surrounding rocks and the small scale of distribution of the granulite facies assemblages the current assemblage is considered to be prograde and has developed at the expense of biotite in the regional main foliation leaving relict biotite separated from quartz by a continuous corona of orthopyroxene and k feldspar other high temperature low ah2o reactions resulted in the formation of spinel corundum albite oligoclase symplectites at the expense of biotite and sillimanite the symplectites have partially been replaced by symplectites of tiny blue sapphirine

evolution of regoliths and landscapes in deeply weathered terrain implications for geochemical exploration abstract thick commonly lateritic regoliths are widespread in inter tropical regions of the world and present particular challenges in exploration these are best tackled through a sound understanding of the evolution of the landscapes in which they occur the regoliths formed under humid warm to tropical conditions and although they may have been modified by later climatic changes i e to more humid or more arid conditions many chemical and mineralogical characteristics are retained these include the geochemical expressions of concealed mineralization erosional and depositional processes control the preservation and occurrence of specific regolith units that may be used as sample media and in turn target size element associations and contrast thereby influencing sampling procedures analysis and data interpretation these parameters are best summarized in terms geochemical dispersion models based on the degree of preservation of the pre existing lateritic regolith regolith landform mapping permits an assessment of the terrain in terms of such models in relict regolith landform regimes in which the lateritic regolith is largely preserved broad multi element anomalies in the upper ferruginous horizons lateritic residuum can be detected using sample intervals of 1 km or more in contrast in erosional regimes where this material is absent anomalies in upper saprolite and the soil and lag derived from it are more restricted in area and closer sampling intervals 200 40 m or less may be necessary lag and soil are generally ineffective in depositional areas except where the sediments are very thin e g

site classification for earthquake hazard and risk assessment in australia while site response phenomena are well recognized globally the influence of regolith properties on ground motion has not previously been investigated for much of australia in an effort to characterize the regolith in terms of its ability to modify earthquake ground shaking this validation study assesses the national site classification map of australia which has been developed for application in first order earthquake hazard and risk assessment in the absence of regolith thickness and fundamental period data site classes are assigned based on a method developed in california that uses the relationship between geological material and the shear wave velocity of the upper 30 m v s 30 the classification scheme is then adjusted to suit the australian geological environment including a correction for the presence of weathered in situ regolith commonly encountered in this stable tectonic setting the results are validated using geophysical and geotechnical data from a variety of quaternary sedimentary environments in the newcastle sydney and perth urban areas and from bedrock dominated environments at a range of sites across australia the results of these analyses demonstrate the utility but also highlight the limitations of applying a depth limited shear wave velocity method in site classification for seismic hazard assessment

the timescale and mechanism of granulite formation at kurunegala sri lanka incipient charnockite formation at kurunegala in sri lanka is characterized by the growth of orthopyroxene at the expense of amphibole and biotite in an originally homogeneous gneiss mineral equilibria in the charnockite assemblage record pressure temperature p t conditions of 738 60 c and 6 9 1 2 kbar at 17 0 1 2 log fo2 and ah2o 0 18 0 16 wholerock trace element and isotopic measurements show that charnockite formation was accompanied by a systematic depletion of sm rb pb u sr nd with a fractionation of rb sr sm nd and th u ratios and crystallization of the charnockite assemblage at 535 5 ma major element fe mg ca and sm nd equilibration between minerals occurred at 524 9 ma whereas pb and rb sr underwent continued exchange to 501 5 ma and 486 1 ma respectively trace element data for both amphibolite and charnockite minerals show that depletion on a whole rock scale can be accounted for either by changes in mineral modes or trace element abundances within the immediate area of dehydration the fractionation of sm nd on a whole rock scale is controlled by the breakdown of amphibole without the growth of a major new host phase for sm in the charnockite rubidium and sr are dependent on the relative behaviour of biotite plagioclase and alkali feldspar modelling of dehydration melting involving the breakdown of amphibole biotite and alkali feldspar reproduces the observed sm nd and rb sr fractionation and indicates the loss of small melt fractions on a cm scale from the charnockite these observations suggest that partial melting is the most plausible means of effecting both the dehydration and depletion that accompanies charnockite formation

determining friction coefficients for interrill flows the significance of flow filaments and backwater effects friction coefficients in overland flows are customarily estimated from mean flow properties depth velocity slope that subsume spatial variations in flow arising from two majo rc auses microtopography and obstacles this paper uses laboratory experiments in shallow flumes to examine the extent of non uniformity in flow conditions associated with each cause randomly placed emergent obstacles in a flume with a shallow axial channel generally yielded higher hydraulic roughness than the same pattern of obstacles on a planar flume as well as greater variation in roughness as the obstacle locations were altered in both flumes hydraulic roughness fell with increasing reynolds number for 10 obstacle cover showed a flattening trend at 20 cover and exhibited a convex downward trend at 30 obstacle cover these results indicate the progressive onset of flow controls at narrow gaps in the obstacle field in such flows the use of mean flow properties conceals the existence of two main subdivisions of flow flow filaments and backwater flows in the experiments flow filaments involved velocities more than twice the overall mean whereas backwater flows were much slower than the mean the existence of fast moving flow filaments may be significant in understanding soil transport in surface runoff and backwater depths may modify splash detachment similarly friction coefficients that fail to reflect these important non uniform flow components may not be optimal for hydraulic calculations or in erosion models it is concluded that new approaches to observing and processing flow data may be required in order to avoid the loss of important flow detail that is entailed in assuming uniform flow conditions copyright 2003 john wiley sons ltd

on the origin of arrested charnockitization in the chilka lake area eastern ghats belt india a reappraisal arrested type charnockite formation occurs in an assemblage of high grade gneisses at several localities of the chilka lake area that belongs to the proterozoic eastern ghats belt of india the isolated ellipsoidal domains are found exclusively in leucogranite leptynite bands that intruded lit par lit interbanded granulite grade supracrustal and intermediate igneous rocks khondalite enderbite macrostructures and microfabrics document a multiple deformation of the rock assemblage under high grade conditions the intrusion of the leucogranitic melts separates a first episode of deformation d 1 from a younger progressive deformation d 2 d 4 a transpressive regime and inhomogeneous deformation is indicated for d 2 d 4 by the associated structures and fabrics but quartz c axis patterns show that pure shear prevailed during the closing stages of deformation the spatial distribution and orientation of the ellipsoidal charnockite domains within the host leptynite and the orientation pattern of orthopyroxene c axes inside the domains provide evidence for a synkinematic in situ formation of the domains during d 3 through partial breakdown of the leptynite assemblage bt grt qtz fl 1 opx fsp ilm fl 2 l local fluid migration along steep foliation planes associated with large scale d 3 folds triggered the reaction orthopyroxene blastesis was confined to the centre of the domains and an envelope formed in which the residing fluid caused secondary intergranular formation of chlorite ore and carbonate imparting the domains typical greenish brown charnockite colour the shape of the envelope which varies from prolate in limbs to oblate in hinges of d 3 folds is responsive to the local stress field comparison of chemical rock compositions supports the in situ formation of charnockite in leptynite subtle compositional differences are controlled by the changing mineralogy compared to the host leptynite the charnockite domains are enriched in k 2 o ba rb and sr but depleted in feo mno y and zr the data obtained in this study provide conclusive evidence that the ellipsoidal charnockite domains do not represent remnants of stretched enderbite layers as proposed by bhattacharya sen acharyya but formed in situ in the leptynite as a result of localized synkinematic fluid migration late in the deformation history

u pb and sm nd dating of high pressure granulite and upper amphibolite facies rocks from sw sweden abstract geochronological data from different radiometric systems on high grade metamorphic rocks in the southwest swedish granulite region southwestern sweden are generally analytically precise but sometimes in conflict with each other age data from seven samples on which a variety of radiometric methods have been applied are presented the age of peak metamorphism is determined by metamorphic zircons from two garnet amphibolites at c 975 ma using the conventional u pb isotope and pb pb evaporation methods titanites from the same type of rocks give ages of c 923 3 ma and 945 2 ma the sm nd data on mafic granulites and garnet amphibolites yield surprisingly young ages between 945 and 900 ma similar to previous sm nd ages these ages are comparable to or even younger than the 40 ar 39 ar hornblende ages that range between 1030 and 930 ma assuming that the sm nd systematics are entirely controlled by volume diffusion the closure temperature of the sm nd system in minerals from these rocks would be comparable to or lower than that of ar diffusion in hornblende i e around 500 c

localized solid state dehydration associated with the varberg charnockite intrusion sw sweden the mineralogy petrology and fluid inclusion chemistry of two charnockite patches within a distance of 4 5 km of the varberg magmatic charnockite intrusion sw sweden are investigated and described utilizing sem empa and fluid inclusion microthermometry garnet clinopyroxene 890 930 degrees c garnet amphibole 600 800 degrees c and garnet biotite 670 860 degrees c fe mg exchange thermometry indicates high temperatures for charnockite patch i compared to relatively lower garnet orthopyroxene garnet amphibole and garnet biotite temperatures of 500 to 600 degrees c for charnockite patch ii plagioclase in the charnockitic patches tends to be more anorthitic and less albitic x an 0 20 x ab 0 76 than in the surrounding regional granitic gneiss x an 0 13 x ab 0 84 replacement antiperthite is commonly found in unrelated plagioclase grains from either patch compared to the regional granitic gneiss where it is relatively rare in either patch k feldspar is considerably less albitic x kfs 0 90 0 92 x ab 0 05 0 10 compared to k feldspar from the regional granitic gneiss it can also be found as micro veins along quartz grain rims both patches are dominated by clinopyroxene as opposed to orthopyroxene garnet biotite and amphibole and in both charnockite patches tend to have lower fe and correspondingly higher mg values compared with garnet biotite and amphibole from the surrounding regional granitic gneiss fluorapatite tends to be relatively enriched in cl and depleted in y ree compared with fluorapatite from the regional granitic gneiss fluid inclusions in charnockite patches i and ii are dominantly carbonic similar to what is seen for the varberg charnockite in addition to quartz relatively high density carbonic inclusions are also preserved in garnet and in fluorapatite it is presumed that pure carbonic fluids must have once coexisted with relic magmatic h2o co2 nacl fluids at peak metamorphic conditions the most likely scenario suggests that charnockite patches i and ii were formed during the later stages of crystallization of the varberg charnockite magmatic body during which copious amounts of co2 rich fluids with a brine cacl2 dominated component were expelled into the country rock via pegmatoid segregations both within and in the immediate surroundings of the charnockite body patch i appears to represent the extension of a pegmatoid segregation whereas patch ii appears to represent fluid induced lower temperature solid state dehydration transport was facilitated via a system of tectonic fissures and fractures generated in the regional migmatized granitic gneiss during its emplacement within the scope of what is known these two charnockite patches fall into the generally observed parameters for localized dehydration zones in general c 2014 elsevier b v all rights reserved less

incipient charnockite characterization at the type localities abstract fifty years after the discovery of incipient charnockite orthopyroxene bearing granitic rocks partially replacing amphibole biotite gneiss in southern india this phenomenon has been found in transitional amphibolite facies to granulite facies terrains on every continent and may be a characteristic feature of progressive deep crustal metamorphism the alteration is essentially a metasomatic transformation mass balance calculations for localities in southern india and sri lanka for which analytic data are most comprehensive show that the main reaction producing orthopyroxene in orthogneiss is breakdown of hornblende by reaction with biotite with loss of feo mgo tio 2 and cao as well as h 2 o from the host rock there is concomitant gain of sio 2 no significant change of alkalis can be demonstrated as essential to the transformation though advanced charnockitic alteration at the type locality of kabbal karnataka may also show large increase of k 2 o with removal of mafic constituents very similar orthopyroxene bearing veins in garnet biotite gneiss at the ponmudi type locality in kerala show definite but more subtle metasomatism with loss of feo and mgo and increase of sio 2 and alkalis both the kabbal and ponmudi alterations occurred at mid crustal levels 5 6 kbar and 700 750 c it is postulated that both types of charnockitic alteration may have been produced as open system processes by much the same kind of metasomatizing fluids nearly coeval co 2 rich and ultrasaline fluids based on fluid inclusion evidence the paragneiss alteration is mainly biotite breakdown with some involvement of garnet and leads to a distinct metamorphic facies type the presence of graphite in some of the garnet biotite gneisses at ponmudi would have resulted in lower oxygen fugacity and probably lower h 2 o activity than in the similar kabbal type metamorphism the fluid rock ratios for both types were small about 10 mass percent of the rocks and the fluids whatever their origin were largely rock governed the source of the metasomatizing fluids has not been definitely identified carbon isotopes of fluid inclusions seem to show an igneous or primitive mantle source at both type localities but ultrasaline fluids may be more plausibly explained by metasedimentary sources and calcareous metasediments have been identified as a source of co 2 in some occurrences much remains to be learned about incipient charnockite and its significance in processes of crustal evolution

initiation of 2 45 2 1 ga intracratonic basin sedimentation of the hurwitz group keewatin hinterland northwest territories canada continental to shallow marine rocks of the hurwitz group exposed as outliers across the hearne province in northern canada were deposited between 2 45 and 2 11 ga on a 3 3 2 6 ga granite greenstone basement initiation of the hurwitz basin was characterized by low relief and rates of subsidence that never progressed beyond the intensity of regional sagging during stage 1 polymictic conglomerate lower noomut formation was deposited in palaeovalleys cut into archaean basement and subarkose to quartz arenite quartz pebble conglomerate upper noomut formation was deposited on a low relief sand plain abundant first cycle quartz rich sandstones are attributed to intense humid climate weathering in low relief source areas and at sites of temporary storage as well as to repeated fluvial and eolian reworking interbedding of pyritic palaeoplacers and continental redbeds denotes fluctuating levels of atmospheric oxygen disappearance of pyritic palaeoplacers upsection signifies ultimate changeover to an atmosphere with sustained free oxygen stage 2 padlei formation was marked by a climatic shift toward cold glacial conditions as indicated by dropstones greywacke till pellets and possible ikaite pseudomorphs in lacustrine rhythmites stage 3 kinga formation represents a return to wet warm conditions with fluvial eolian deposition of subarkose and quartz arenite on a low relief sand plain maguse member and deposition of supermature quartz arenite in a vast 100 000 km2 minimum shallow water lake or series of lakes whiterock member local chert beds at the top of the kinga formation hawk hill member formed by spring discharge due to regional gravity driven convective groundwater flow an intracratonic setting is implied by 1 a symmetric basin centred fill 2 absence of features indicating a shelf slope break 3 absence of rift rocks 4 a prolonged slow subsidence history 5 likely correlation with other continental to shallow marine deposits scattered across the keewatin hinterland and 6 positioning 1000 2000 km away from closest coeval passive margin sequences we speculate that hurwitz basin formed due to lithospheric stretching related to a large scale mantle upwelling during the protracted breakup of an earliest palaeoproterozoic supercontinent kenorland

the neoarchean gt 34 ni deposit carajas mineral province brazil an atypical iocg related ni sulfide mineralization abstract the gt 34 deposit located 12 km to the sw of the sossego copper gold mine in the carajas province northern brazil represents an unusual ni sulfide mineralization the deposit occurs along a ne sw trending sub vertical shear zone marked by progressive mg alkalic alteration zones predominantly hosted in granitic and locally in granodioritic to tonalitic orthogneisses initial alteration zones result in unique scapolite orthopyroxene assemblage which is partially preserved within pervasive hornblende chlorapatite plagioclase replacement zones nickel mineralization occurs mainly as matrix supported breccias characterized by a pentlandite pyrrhotite rich matrix and rounded fragments chiefly of hornblende and chlorapatite irregular stockworks and net textured veins containing chalcopyrite pentlandite are less common phlogopite talc actinolite alteration and late stage veinlets crosscut the previous alteration zones and the mineralization the phlogopite talc actinolite alteration occurs as irregular veins and chalcopyrite pyrrhotite magnetite are commonly observed where such alteration intersects the ni mineralization late stage veinlets are represented by k feldspar epidote chlorite calcite and quartz albite chlorite calcite epidote veins both containing minor amounts of millerite pyrite and f oh apatite high resolution sims u pb zircon geochronology obtained for the gt 34 deposit revealed an age of 2828 4 ma for zircon grains inherited from the host orthogneisses the timing of the mineralization altered zircon grains from the scapolite orthopyroxene and phlogopite talc actinolite alteration zones is attributed to an age interval between 2751 and 2720 ma although poorly constrained the geochronological data corroborate a neoarchean age for the gt 34 ni mineralization similar to that of other iocg deposits in the carajas province and coeval with the bimodal magmatism in the area the atypical orthopyroxene marialite mineral chemistry support a metasomatic crystallization at high temperatures 700 c low ah2o

volumetric displacement of flow depth by obstacles and the determination of friction factors in shallow overland flows large roughness elements such as stones or plant stems obstacles influence the depth of overland flows in two ways the first effect is a dynamic one involving frictional retardation of the flow and associated reduction in flow speeds the second influence is static and arises from the upward volumetric displacement of flow depth because of the submerged volume of the obstacles depending upon the distribution of submerged obstacle volume with height above the soil surface the proportion of the flow volume occupied and so the perturbation of flow depth arising from volumetric displacement can vary irregularly or systematically with flow stage furthermore the amount of volumetric displacement of flow depth would vary among surfaces carrying different cover fractions of identical obstacles consequently estimates of the change in friction factors arising from the drag on flow traversing varying obstacle cover fractions are confounded with the parallel shift volumetric displacement to understand the true frictional drag arising from obstacles a correction must be made for the volumetric displacement a method for making this correction is outlined new laboratory experiments provide precise observations of depths and friction coefficients in laminar flows passing fields of regular obstacles after making the proposed correction for volumetric displacement increases of 40 to 75 per cent in the derived value of the darcy weisbach friction factor f are found for an obstacle cover of 20 per cent many published studies of friction coefficients in shallow overland flows such as those on stone covered dryland soils involve larger obstacle cover fractions and evidently involve the significant confounding effect of volumetric displacement copyright 2002 john wiley sons ltd

macroscale surface roughness and frictional resistance in overland flow the hydraulics of overland flow on rough granular surfaces can be modelled and evaluated using the inundation ratio rather than the flow reynolds number as the primary dimensionless group determining the flow behaviour the inundation ratio describes the average degree of submergence of the surface roughness and is used to distinguish three flow regimes representing partially inundated marginally inundated and well inundated surfaces a heuristic physical model for the flow hydraulics in each regime demonstrates that the three states of flow are characterized by very different functional dependencies of frictional resistance on the scaled depth of flow at partial inundation flow resistance is associated with the drag force derived from individual roughness and therefore increases with depth and percentage cover at marginal inundation the size of the roughness elements relative to the depth of flow controls the degree of vertical mixing in the flow so that frictional resistance tends to decrease very rapidly with increasing depth of flow well inundated flows are described using rough turbulent flow hydraulics previously developed for open channel flows these flows exhibit a much more gradual decrease in frictional resistance with increasing depth than that observed during marginal inundation a data set compiled from previously published studies of overland flow hydraulics is used to assess the functional dependence of frictional resistance on inundation ratio over a wide range of flow conditions the data confirm the non monotonic dependence predicted by the model and support the differentiation of three flow regimes based on the inundation ratio although the percentage cover and the surface slope may be of importance in addition to the inundation ratio in the partially and marginally inundated regimes the reynolds number appears to be of significance only in describing well inundated flows at low to moderate reynolds numbers as these latter conditions are quite rare in natural environments the inundation ratio rather than the reynolds number should be used as the primary dimensionless group when evaluating the hydraulics of overland flow on rough surfaces 1997 by john wiley sons ltd

geochronology of eclogite facies metamorphism in the sveconorwegian province of sw sweden abstract decompressed eclogites in the sveconorwegian province sw sweden have been dated using u pb geochronology zircons are common as inclusions in garnet and kyanite and other minerals in the decompressed eclogites titanite inclusions are found exclusively in the core of garnets the mineral inclusions and the chemical zoning of the garnets suggest inital growth under prograde amphibolite facies conditions followed by eclogite facies metamorphism and subsequent decompression through the high pressure granulite and upper amphibolite facies the zircon and titanite thus formed prior to the eclogite stage of the p t path the age of the eclogite forming event was determined by ion probe dating of zircon inclusions in garnets the obtained age of 972 14 ma is the maximum age of the eclogitisation the age of the titanite inclusions in garnet is 945 4 ma this age is similar to other u pb ages of titanite in the region which suggest that the titanite has been isotopically reset and that the age reflects cooling the mode of occurrence textural relationships and the chemical homogeneity suggest that the zircons formed from zr released from magmatitic fe ti oxides and possibly amphiboles during breakdown of magmatic minerals at the onset of the sveconorwegian metamorphism spot analyses of complex zircons from a granitic dyke in the eclogite yielded an age of 1403 15 ma for magmatic cores and an age of 963 22 ma for metamorphic rims the older age is a minimum age of the eclogite protolith and correspond to the age of a generation of granites in the region the rim age is within error identical to the age of eclogite metamorphism the eclogite metamorphism in sw sweden is younger than its grenvillian counterparts in scotland canada and usa

variability of shallow overland flow velocity and soil aggregate transport observed with digital videography field experiments at tiramoana station 30 km north of christchurch new zealand using an erosion plot 16 5 m long 0 6 m wide and with a slope of 14 14 5 on rendzina soil aimed to measure the variability of flow velocity and of soil aggregates transport rate in shallow overland flow discharge cross section area ratio was used to estimate mean velocity and high speed digital video camera and image analysis provided information about flow and sediment transport variability six flow runs with 0 5 3 0 l s 1 discharges were supercritical with froude numbers close to or more than 1 mean flow velocity followed poiseuille law float numbers were more than 1 5 and hydraulic resistance was an inverse proportional function of the reynolds number which is typical for laminar flows hence actual velocity varied through time significantly and the power spectrum was of red noise which is typical for turbulent flow sediment transport rates had even higher variability and soil aggregates transport was a compound poisson process copyright 2008 john wiley sons ltd

cool climate lateritic and bauxitic weathering it is commonly held that laterites and bauxites form under tropical climates although some workers have suggested lateritic weathering was not representative of tropical climates the assertion is still almost universally made early tertiary 56 34 ma basalts are widespread in the monaro region of new south wales they overlie and enclose fluvial and lacustrine sediments hyaloclastites and tuffs and the upper parts of many flows are bauxitized the basalts are up to about 200 m thick and in one section comprise 22 flows eight tuffs and hyaloclastites two dolerites and nine interflow bauxitic profiles this region in the eastern australian highlands was tectonically stable and had probably been at its present elevation for some 50 100 ma immediately before the beginning of volcanism and during the extrusion and bauxitization of the earlier flows the region was at 57 5 s latitude climates were wet cool to cold and thermally seasonal and the region was well forested paleomagnetic studies sh

resistance to overland flow on desert hillslopes abstract this study examines the relation between the darcy weisbach friction factor f and the reynolds number re for overland flow on six runoff plots in semiarid southern arizona the surfaces of these plots are irregular and covered with stones as overland flow increases the stones and microtopographic protuberances which constitute the major roughness elements are progressively inundated thereby altering the flow resistance analyses of 14 cross sections reveal that the resulting f re relations have two basic shapes convex upward and negatively sloping these shapes bear little resemblance to the conventional f re relation for shallow flow over a plane bed whose shape is a function of the state of flow rather they are explained in terms of the simultaneous operation of two processes the first is the progressive inundation of roughness elements and increase in their wetted upstream projected area as discharge increases this process causes f to increase the second is the progressive increase in the depth of flow over already inundated parts of the bed as discharge increases this process causes f to decline whether the f re relation has a positive or a negative slope depends on whether the first or second process dominates and this depends on the configuration of the bed and level of discharge these findings have profound implications for the mathematical modeling of overland flow on desert hillslopes whether a model is based on the saint venant equations or makes use of the kinematic wave approximation it requires the specification of a relation between f and re or surrogates thereof and the computed hydrograph is very sensitive to the form of this relation hitherto the most widely used relation has been the conventional one for shallow flow over a plane bed however the present study suggests that this relation does not apply to desert hillslopes additional field and laboratory studies are needed to learn more of the behavior and controls of f re relations on such hillslopes so that models of overland flow can employ more realistic relations and better simulate runoff hydrographs

metamorphic charnockite in contact aureoles around intrusive enderbite from natal south africa in the port edward area of southern kwa zulu natal south africa charnockitic aureoles up to 10 m in width in the normally garnetiferous nicholson s point granite are developed adjacent to intrusive contacts with the port edward enderbite and anhydrous pegmatitic veins mineralogical differences between the country rock and charnockitic aureole suggest that the dehydration reaction bt qtz opx kfs h2o and the reaction of grt qtz opx pl were responsible for the charnockitization the compositions of fluid inclusions show systematic variation with 1 the port edward enderbite being dominated by co2 and n2 fluid inclusions 2 the non charnockitized granite by saline aqueous inclusions with 18 23 eqwt nacl 3 the charnockitic aureoles by low salinity and pure water inclusions 7 eqwt nacl 4 the pegmatites by aqueous inclusions of various salinity with minor co2 as a result of the thermal event the homogenization temperatures of the inclusions in charnockite show a much larger range up to 390 c compared to the fluid inclusions in granite mostly 250 c contrary to fluid controlled charnockitization brines co2 which may have taken place along shear zones away from the intrusive body the present proximal charnockitized granite formed directly at the contact with enderbite the inclusions indicate contact metamorphism induced by the intrusion of dry enderbitic magma into wet granite resulting in local dehydration this was confirmed by cathodoluminescence microscopy showing textures indicative for the local reduction of structural water in the charnockite quartz two pyroxene thermometry on the port edward enderbite suggests intrusion at temperatures of 1000 1050 c into country rock with temperature of 700 c the temperature of aureole formation must have been between 700 c breakdown of pyrite to form pyrrhotite and 1000 c charnockitization was probably controlled largely by heat related to anhydrous intrusions causing dehydration reactions and resulting in the release and subsequent trapping of dehydration fluids the salinity of the metamorphic fluid in the contact zones is supposed to have been higher at an early stage of contact metamorphism but it has lost its salt content by k metasomatic reactions and or the preferential migration of the saline fluids out of the contact zones towards the enderbite the low water activity inhibited the localized melting of the granite mineral thermobarometry suggests that after charnockite aureole genesis an isobaric cooling path was followed during which reequilibration of most of the aqueous inclusions occurred

the relationship between metamorphic charnockite and marble near speculator central adirondack mountains new york granites and charaockites with similar bulk compositions are exposed in a series of roadcuts along rt 8 3 east of the central adirondack town of speculator the mineralogy of these rocks is correlated with their associated rock types with the orthopyroxene bearing varieties occurring in the marble rich portion of the sequence mineral assemblages in a charnockite boudin enclosed in marble appear to be consistent with equilibration with a co 2 rich fluid under high grade t 700 c p 7 kb conditions while high density co 2 rich fluid inclusions occur in a quartz vein enclosed within the boudin it is suggested that small amounts of charnockite may have been produced in this area by the influx of co 2 produced by devolatilization reactions in the marble however carbonic metamorphism in the adirondacks appears to have been at most a minor local process and did not operate on the regional scale that has been suggested for some other granulite terranes thus the presence of abund

arrested charnockite formation in southern india and sri lanka arrested prograde charnockite formation in quartzofeldspathic gneisses is widespread in the high grade terrains of southern india and sri lanka two major kinds of orthopyroxene producing reactions are recognized breakdown of calcic amphibole by reaction with biotite and quartz in tonalitic granitic gray gneiss produced the regional orthopyroxene isograd manifest in charnockitic mottling and veining of mixed facies exposures as at kabbal karnataka and in the kurunegala district of the sri lanka central highlands chemical and modal analyses of carefully chosen immediately adjacent amphibole gneiss and charnockite pairs show that the orthopyroxene is produced by an open system reaction involving slight losses of cao mgo and feo and gains of sio2 and na2o rb and y are depleted in the charnockite another kind of charnockitization is found in paragneisses throughout the southern high grade area and involves the reaction of biotite and quartz garnet to produce orthopyroxene and k feldspar although charnockite formation along shears and other deformation zones at such localities as ponmudi kerala is highly reminiscent of kabbal close pair analyses are not as suggestive of open system behavior this type of charnockite formation is found in granulite facies areas where no prograde amphibole bearing gneisses exist and connotes a higher grade reaction than that of the orthopyroxene isograd metamorphic conditions of both kabbaltype and ponmudi type localities were 700 800 c and 5 6 kbar lower p h2o in the ponmudi type metamorphism was probably the definitive factor

lateritic bauxite in central germany and implications for miocene palaeoclimate intense chemical weathering during middle miocene times led to the formation of deep ferralitic weathering profiles on the vogelsberg basaltic massif saprolite more than 50 m thick was formed and in its higher parts bauxite concretions developed by absolute accumulation of aluminium the tops of the profiles consist mostly of allochthonous lateritic bauxite which has been mined intensively in the past similar high latitude bauxites occur on the paleogene basalts of ireland these formed during a phase of recognized greenhouse conditions with a climatic optimum near the paleocene eocene boundary while during the miocene the climate was already changing toward quaternary icehouse conditions however the occurrence of deep weathering profiles with lateritic bauxite at the high palaeolatitude of 45 n may be interpreted as pointing to extreme climatic conditions also during the middle miocene the associated laterites and bauxites on middle miocene basalts 17 15 ma provide evidence for a global climatic optimum around 17 14 5 ma reduced uplift rates of the himalayan tibetan plateau and associated reduced co2 consumption coupled with additional volcanogenic co2 production could have induced high atmospheric co2 and an intensification of the global greenhouse effect this may be reflected in accelerated chemical weathering and bauxite formation basalt volcanism has thus provided both a source eruption and a sink via weathering of co2

flow resistance in concentrated overland flow on rough slope surfaces field experiments have been done on simulated flows over different rough pre rill and rill bed surfaces the purpose of the experiments was to evaluate the hydraulic roughness properties of these bed surfaces conventional equations describing the relation of the resistance coefficient to the reynolds number for flow in closed conduits or open channels can also be applied to shallow flows provided the boundary values of the reynolds number which discriminate between the various flow regimes are adapted when the reynolds number is less than 100 the flow regime is laminar above this figure the flow is either transitional or turbulent depending on the roughness of the bed surface the degree of turbulence can be deduced from a morphological description of the pre rill and rill bed surface roughness

the use of duricrusts and topographic relationships in geomorphological correlation conclusions based in australian experience though there are many possible pitfalls duricrusted surfaces provide morphostratigraphic markers which are useful in preliminary extrapolation and correlation at the local and regional scales especially if other factors such as landscape evolution and topographic relationships are also considered particular reference is made to ferruginous and siliceous cappings close stratigraphic dating of the duricrusts allows regional differentiation but correlations are preferably intra rather than inter regional and are at best general and involve age ranges rather than narrow time frames problems broached include type of landscape development the relation of surface and duricrusts and the temporal equivalence of duricrust facies i e duricrusts of similar chemical tendencies but contrasted morphology the roles of duricrusts in relief inversion surface preservation and climatic interpretation are also mentioned

hydraulics of interrill overland flow on rough bare soil surfaces a set of laboratory experiments on bare rough soil surfaces was carried out to study the relationship between soil surface roughness and its hydraulic resistance existing models relating roughness coefficients to a measure of surface roughness didnotpredictthehydraulicresistancewellforthesesurfaces therefore anewmodelisdevelopedtopredictthehydraulic resistanceofthesurface basedondetailedsurfaceroughnessdata roughnessprofilesperpendiculartotheflowareusedto calculatethewetcross sectionalareaandhydraulicradiusgivenacertainwaterlevel thealgorithmofsavatisthenapplied tocalculatethehydraulicresistance thevaluefortheequivalentroughness whichisusedinthealgorithmofsavat couldbe predictedfromtheroughnessprofiles here thetortuosityofthesubmergedpartofthesurfacewasused whichmeansthat thecalculatedroughnessdependsonflowdepth theroughnessincreasedwithdischarge duetothefactthatrougherpartsof the surface became submerged at higher discharges therefore a single measure of surface roughness e g random roughness isnotsufficienttopredictthehydraulicresistance theproposedmodelallowstheextensionoftheflowoverthe surfacewithincreasingdischargetobetakenintoaccount aswellastheroughnesswithinthesubmergedpartofthesurface therefore themodelisabletopredictflowvelocitiesreasonablywellfromdischargeandroughnessdataonly copyright 2000 john wiley sons ltd

a critique of the schellmann definition and classification of laterite abstract schellman s definition and classification of laterite are based on the sio2 al2o3 and fe2o3 contents of weathered formations in comparison to the chemical composition of the underlying rocks from which the weathered materials are assumed to be derived this approach is open to misinterpretation because many regolith materials have formed by lateral transport both physical and chemical it ignores the role of absolute accumulation it pays little attention to the morphological characteristics of laterites that give clues to their origins it ignores the detailed mineralogical compositions of weathered materials and laterite and it does not permit field identification understanding of geology stratigraphy geomorphic evolution mineralogy and micromorphology are essential ingredients of regolith investigations chemical analysis alone is insufficient schellmann s chemical classification seems appropriate only to a small subset of potential laterites in which the whole profile is of bedrock and saprolite and where there has been no lateral movement of solids or solutions schellmann s definition demands formation by tropical weathering which eliminates ferruginous duricrusts formed outside the tropics his approach produces confusion by grouping disparate ferruginous aluminous materials together as laterite the range of applications of the term laterite is so broad that it has become meaningless and the schellmann approach has not resolved this issue

diffusion controlled growth of pyroxene bearing margins on amphibolite bands in the granulite facies of rogaland southwestern norway implications for granulite formation in the rogaland granulites of southern norway thin anhydrous pyroxene bearing margins 5 10 mm are observed mainly in migmatitic banded gneisses at the contact between hornblende rich metabasites and charnockites according to field data the development of these margins post dates any deformation petrographic data show that they are zoned three different types have been recognized 1 metabasite plagioclase orthopyroxene plagioclase clinopyroxene gneiss 2 metabasite plagioclase orthopyroxene clinopyroxene plagioclase clinopyroxene gneiss 3 metabasite plagioclase orthopyroxene gneiss

fluid immiscibility in metamorphic rocks evidence of fluid immiscibility in metamorphic rocks comes in the best of all worlds from fluid inclusion observations in fact fluid immiscibility should be anticipated over the full range of metamorphic conditions provided that appropriate bulk fluid compositions are present in a review paper entitled metamorphic fluids the evidence from fluid inclusions crawford and hollister 1986 summarized the role of fluid immiscibility in metamorphism was only recognized after serious study of fluid inclusions in metamorphic rocks was underway in the late 1970s and has yet to attract the attention of more than a handful of petrologists studying metamorphic rocks since then tremendous progress has been made a huge amount of fluid inclusion studies have convincingly shown that immiscible fluids can be present in rocks of all bulk compositions and at all p t conditions thermodynamic databases of minerals solid solutions and fluid mixtures along with the development of gibbs free energy minimization programs now allow for detailed prediction of the evolution of phase assemblages and mineral compositions in p t space significant progress has also been made in understanding reaction kinetics diffusional and convective mass transport and the interpretation of fluid rock interaction during metamorphism given the vast fluid inclusion evidence of immiscibility it would appear however that phase petrology and mass transport in any specific rock where fluids are involved are not correctly interpreted if possible or proven immiscibility is not considered relatively few studies directly link mineral reactions with immiscible fluids therefore this review aims at working out the effects of fluid immiscibility on the progress of metamorphic reactions and fluid transport over a wide range of conditions questions arise directly from the fluid inclusion record in metamorphic rocks this chapter however is organized the other way round at first it summarizes phase relations of fluid systems pertinent to

surface tension and friction coefficients in shallow laminar overland flows through organic litter this study investigates the contribution of surface tension forces to friction coefficients in shallow laminar interrill flows friction coefficients in these flows are known to be increased greatly by organic litter and by stems fine litter provides extensive edges along which surface tension menisci can be drawn up and evaluating the significance of this in the frictional retardation of flow was the primary objective of the experiments reported here using both standardized litter particles small wooden blocks of fixed dimensions and natural plant litter meniscus behaviour and the darcy weisbach friction coefficient were evaluated in shallow flows on a laboratory sand board for some tests the surface tension of ordinary water was reduced by 40 per cent by the addition of a surfactant and the friction coefficient redetermined results show that the presence of surface tension menisci flanking litter particles provides areas of deeper flow that are up to 7 mm in width and which can increase flow depths by 100 300 per cent these zones support significantly higher flow speeds increased water depths within menisci are additionally associated with reduced depths beyond the menisci so that an increase in the spatial variability of flow depths is a second consequence of meniscus formation these modifications of flow depth by surface tension menisci are shown to reduce rather than increase the overall friction coefficient applicable to the flow consequently additional frictional retardation does not arise within the menisci flanking litter particles and so cannot account for the greater drag arising from litter than from other surface features different factors possibly the direct obstruction of flow paths must therefore underlie the frictional drag copyright 2002 john wiley sons ltd

solubility of cepo4 monazite and ypo4 xenotime in h2o and h2o nacl at 800 c and 1 gpa implications for ree and y transport during high grade metamorphism abstract monazite and xenotime are important accessory minerals in metasediments because they host ree and are useful for geochronology and geothermometry it is therefore essential to understand their behavior during metasomatic processes that attend metamorphism and subduction in order to constrain the solubility of monazite and ypo 4 xenotime at high pressure and temperature we carried out weight loss experiments on synthetic single crystals of cepo 4 monazite and ypo 4 xenotime using hydrothermal piston cylinder methods at 800 c and 1 gpa in h 2 o and h 2 o nacl fluids results indicate that cepo 4 and ypo 4 dissolved congruently and that their solubilities in pure h 2 o are very low 0 04 0 04 and 0 25 millimolal respectively the solubility of cepo 4 rises to an increasing extent with added nacl to 7 94 0 07 millimolal at 50 mol nacl in contrast the solubility of ypo 4 rises to a decreasing degree with increasing nacl to 4 36 0 08 millimolal at 50 mol nacl best fit equations for the solubilities of the two phases are m cepo 4 3 56 10 5 5 82 10 3 x nacl 1 97 10 2 x 2 nacl and m ypo 4 2 48 10 4 1 26 10 2 x nacl 8 89 10 3 x 2 nacl the solubility of ypo 4 is greater than that of cepo 4 at nacl mole fractions x nacl of 0 00 0 27 the solubility enhancement behavior implies that ce dissolves as anhydrous chloride complexes whereas y forms mixed cl oh solutes the results provide a simple mechanism for redistributing ree and y in deep crustal and upper mantle environments the h 2 o ce ratio inferred for subduction zone melts and silicate rich fluids can also be produced by a cepo 4 saturated fluid with x nacl 0 1 in addition neutral ph h 2 o nacl fluids can transport substantial ree and y obviating the need to invoke highly acid solutions in environments where they are unlikely

dehydration reaction and isotope front transport induced by co2infiltration at nuliyam south india the field relations from a quarry at nuliyam south india illustrate dehydration of an amphibolite facies gneiss to granulite facies charnockite by co2 influx over a scale of 30 m both the calc silicate source of the fluids and the full extent of their penetration into the gneiss are preserved in a continuous section fluid flow is by a hydraulic fracture mechanism but is thought to be pervasive the sharp reaction front predicted by the continuum mechanical theory for advective fluid transport is not observed the front spreading is on too large a scale for either diffusive or dispersive control and is due to local kinetic disequilibrium between the fluid and rock although the divariant nature of the reaction may also have a limited effect the time integrated fluid flux varies from the instantaneous porosity at the fluid front to 20 vol adjacent to the calc silicate carbon isotope budgets suggest that decarbonation of the calc silicate by a rayleigh fractionation process provides a sufficient source for the co2 influxing into the gneiss graphite abundances vary from 0 01 to 0 1 by weight it is principally derived by precipitation from the fluid and may be modelled from phase equilibria carbon isotope fronts coincide with the reaction front on the scale of sampling although isotopic disequilibrium between graphite and inclusion co2 also implies local fluid rock disequilibrium

protolith ages and timing of deformation in the eastern marginal part of the sveconorwegian orogen southwestern sweden abstract u pb zircon and titanite ages from variably metamorphosed igneous rocks in the eastern marginal part of the sveconorwegian orogen eastern segment north of lake vanern sweden suggest that these rocks belong to the younger c 1 71 1 65 ga igneous suite of the c 1 85 1 65 ga transscandinavian igneous belt tib two porphyritic meta granites and one isotropic monzonite yield u pb zircon ages of 1661 27 1674 7 and 1674 7 ma respectively these ages support earlier interpretations that the eastern segment north of lake vanern contains tectonically reworked tib rocks and that there is no major lithological discontinuity either across the sveconorwegian frontal deformation zone or within the eastern segment igneous brown coloured titanites from five samples yield similar u pb ages as the zircons in contrast colourless and oblate shaped titanites from the western penetratively deformed parts of the eastern segment give concordant ages of 976 4 and 956 6 ma further to the east similar titanite from both a penetratively deformed meta granite and a ductile shear zone within a porphyritic quartz monzonite are strongly discordant close to late sveconorwegian lower intercept ages this type of titanite is interpreted to be syntectonic and formed during the upper greenschist east to amphibolite west facies fabric forming event in the eastern segment since the brown igneous titanites and the zircons share a common igneous origin and the single type of metamorphic titanites are either concordant or strongly discordant towards late sveconorwegian intercept ages it is inferred that no major tectonothermal event occurred between the time of tib emplacement and the late sveconorwegian tectonothermal reworking pre sveconorwegian palaeo to mesoproterozoic deformational and metamorphic events gothian which have been inferred west of and further south within the eastern segment appear to be absent in the northern part of this crustal unit

cool climate or warm spike lateritic bauxites at high latitudes abstractlaterites and bauxites and their associated ultisols and oxisols are widespread in warm wet climates today and their spread to high latitudes has been attributed to episodes of past global warming bauxitic paleosols from the early eocene monaro volcanics of southeastern australia have been claimed as exceptions formed in a cool wet climate reexamination and chemical analysis of a sequence of intrabasaltic paleosols in the bega no 7 core of radiometrically dated monaro volcanics now show highly variable paleotemperature and precipitation the core includes 53 successive paleosols mostly nonbauxitic but bauxitic paleosols reveal local spikes in warmth and precipitation coincident with early eocene 55 52 51 and 48 ma global spikes of warmth precipitation and high atmospheric co2 these bauxitic paleosols thus formed in warm wet not cool dry climates and their poleward spread coincided with global greenhouse spikes

late sveconorwegian metamorphism and deformation in southwestern sweden abstract the precambrian of southwestern sweden is divided into eastern and western crustal segments separated by a major tectonic boundary the mylonite zone the southern part of the eastern segment is characterized by numerous occurrences of mafic granulites and charnockites the western segment comprising greenschist to amphibolite facies gneisses of supracrustal and plutonic origin sm nd mineral ages of the granulite facies metamorphism in the eastern segment range from 920 to 880 ma garnet pyroxene feldspar whole rock sm nd isochrons of the varberg charnockite and the traslovslage mafic granulite yield ages of 893 5 ma and 881 4 ma respectively this late sveconorwegian late grenvillian granulite facies metamorphism in southern sweden appears to be confined to the eastern segment while the last high grade metamorphic event in the western segment is contemporaneous with the 1100 ma old granulite facies metamorphism in the bamble area of se norway at least three phases of regionally important deformation postdate the late sveconorwegian metamorphism in southwestern sweden deformation related to movements within the mylonite zone was contemporaneous with or later than the granulite facies metamorphism in the varberg area and took place mainly under retrograde metamorphic conditions leading to almost complete replacement of garnet and pyroxene by amphibole biotite and plagioclase extensional tectonics were presumably important during the uplift of the granulite terrain east of the mylonite zone peak p t conditions during the late sveconorwegian metamorphic event were considerably higher than those required for the melting of granitoid rocks the sm nd ages of granulite facies parageneses within the eastern segment are approximately the same as those of numerous late sveconorwegian granite intrusions in southwestern scandinavia suggesting a genetic relationship between high grade metamorphism at depth and the emplacement of granites at higher crustal levels the nd model ages of the varberg charnockite agree reasonably well with the nd model ages of 1700 1600 ma old granites within the same crustal domain while the model age of the mafic granulite originally a mafic dyke corresponds roughly to the model ages of 930 ma old mafic dykes in se sweden

mobility of components in metasomatic transformation and partial melting of gneisses an example from sri lanka reaction textures fluid inclusions and metasomatic zoning coupled with thermodynamic calculations have allowed us to estimate the conditions under which a biotite hornblende gneiss from the kurunegala district sri lanka hornblende nmg 38 42 biotite nmg 42 44 plagioclase quartz k feldspar ilmenite magnetite was transformed into patches of charnockite along shear zones and foliation planes primary fluid inclusion data suggest that two immiscible fluids an alkalic supercritical brine and almost pure co2 coexisted during the charnockitisation event and subsequent post peak metamorphic evolution of the charnockite these metasomatic fluids migrated through the amphibolite gneiss along shear zones and into the wallrock under peak metamorphic conditions of 700 750 c 5 6 kbar and aflh2o 0 52 0 59 this resulted in the formation of charnockite patches containing the assemblage orthopyroxene nmg 45 48 k feldspar or70 80 quartz plagioclase an28 in addition to k feldspar microveins along quartz and plagioclase grain boundaries remnants of the co2 rich fluid were trapped as separate fluid inclusions the charnockite patches show the following metasomatic zonation patterns

the geochemistry of proterozoic lower crustal depletion in southwest sweden abstract examination of the geochemistry of a proterozoic composite intrusion of charnockite and granite in southwest sweden and its surrounding country rocks allows evaluation of mechanisms of crustal depletion affecting rocks already strongly dehydrated by regional metamorphism in situ charnockitisation of amphibolite facies granite gneisses is marked by removal of si k rb and th the u and ree compositions remain unchanged in the process which was controlled by dehydration reactions instigated by contemporaneous basic magma intrusion in limited partial melting of the charnockitised granite gneisses during a new influx of basic magma rb th u ree h 2 o and co 2 were concentrated in the melt phase in zones where intergrain cohesion was lost in the anatexis crystal melt amalgams rose and fractionated by melt segregation and restite crystal accumulation this led to the formation of a fugitive melt dominated fraction which crystallised to form lile rich alkaline granite chemically similar to rapakivi granite leaving massive charnockitic depleted residues at varberg the separation was incomplete so that products and residues remain in association the revealed mechanisms provide a model for the widespread proterozoic development of rapakivi like granites at upper crustal levels associated with charnockitic depleted lower crust

surface roughness for shallow overland flow on crushed stone surfaces results of laboratory experiments carried out to determine the effective surface roughness for shallow overland flow as a function of the runoff rate roughness element height and underlying soil condition are presented this work was conducted to extend the understanding of the mechanics of shallow overland flows based on the relationships between the reynolds number froude number and surface resistance over a wide range of conditions results exhibit a strong dependence of the effective roughness on the ratio between the depth of flow and the height of the roughness element and a strong inverse relationship was found between manning s n and the darcy weisbach friction factor f and the froude number three distinct subcritical flow regimes were identified 1 submerged flow r 1 200 and 3 transitional partially submerged flow 300 r 1 200 analysis and synthesis of laboratory data allowed relationships between the reynolds and froude numbers and manning s n

geologic and palaeomagnetic constraints on the formation of weathered profiles near inverell eastern australia abstract we use geologic and palaeomagnetic observations to constrain the timing and duration of weathering of the oakwood bauxite which outcrops in the new england region of new south wales australia the bauxite is developed on and overlain by mafic volcanic flows prior geochronologic results from surrounding regions indicate that age of these flows and thus the age of the bauxite is most likely between 18 and 26 ma though volcanics elsewhere in the central volcanic province have a much greater range of between 6 and 56 ma similarly comparison of a new palaeomagnetic pole computed from the bauxite pole latitude 75 4 n longitude 311 3 e n 58 a95 4 4 with the australian apparent polar wander path gives estimated ages of 21 27 ma individual samples of the bauxite have both normal and reversed polarity components of magnetization which beside providing a positive palaeomagnetic reversal test suggests that the duration of weathering exceeded 10 000 years and more likely lasted several million years our results suggest that the oakwood region had a palaeoclimate and palaeoenvironment that was conducive for deep weathering over a significant period in a the time interval from the mid oligocene to the early miocene

grus weathering mantles problems of interpretation abstract grus is an ill defined product of deep weathering of coarse grained rocks whose relationships to other weathering changes remain unclear this paper attempts to address this issue by reviewing a number of examples of coarse saprolites from a variety of climatic and topographic settings grus is the category of weathering mantle that possesses the following characteristics sand gravel 75 100 silt clay

paleoatmospheric consequences of co2 released during early cenozoic regional metamorphism in the tethyan orogen the eocene was the warmest epoch of the cenozoic with published estimates of eocene atmospheric co2 content ranging from two to six times the current value calculations of co2 consumption by silicate weathering show that co2 fluxes to the atmosphere of ca 1018 myr could account for inferred paleocene eocene atmospheric co2 contents and the resulting greenhouse effect would have contributed to eocene warmth extensive portions of the tethyan orogen underwent regional metamorphism culminating in the eocene prograde metamorphism may have been contemporaneous with the late paleocene global warming we calculated the amount of metamorphic co2 produced at depth in the himalayan orogen with data on the timing of the india asia collison duration of prograde regional metamorphism and proportions and bulk compositions of metamorphic co2 source rocks if co2 was generated at a constant rate over a 10 myr period of prograde metamorphism in the himalayan orogen we estimate that ca 1018 1019 moles myr of metamorphic co2 were produced at depth significant expulsion of metamorphic co2 to the atmosphere may have occurred by focused fluid flow along shear zones such as the extensive main central thrust in the himalayan orogen an additional ca 1018 myr could have been contributed by eocene regional metamorphism in the mediterranean tethys i e from the alps to turkey the extensive metamorphism associated with the india asia collision and the closing of tethys may have contributed to co2 greenhouse warming in the early to mid cenozoic

arrested charnockite formation at kottavattam southern india at kottavattam southern kerala india late proterozoic homogeneous leptynitic garnet biotite gneisses of granitic composition have been transformed on a decimetric scale into coarse grained massive charnockite sensu stricto along a set of conjugate fractures transecting the gneissic foliation charnockitization post dates the polyphase deformation regional high grade metamorphism and anatexis and evidently occurred at a late stage of the pan african tectonothermal history geothermobarometric and fluid inclusion data document textural and chemical equilibration of the gneiss and charnockite assemblages at similar p lith t conditions 650 700 degrees c 5 6kbar in the presence of carbonic fluids internally buffered by reaction with graphite and opaque mineral phases x co2 0 7 0 6 x h2o 0 2 0 3 x n2 0 1 logf o2 l7 5 mineralogical zonation indicates that charnockitization of the leptynitic gneiss involved first the breakdown of biotite and oxidation of graphite in narrow outward migrating transition zones adjacent to the gneiss followed by the breakdown of garnet and the neoblastesis of hypersthene in the central charnockite zone compared to the host gneiss the charnockite shows higher concentrations of k na sr ba and zn and lower concentrations of mg fe ti v y zr and the hree with a complementary pattern in the narrow transition zones of biotite breakdown the p lith t x h2o data and chemical zonation patterns indicate charnockitization through subsolidus dehydration reaction in an open system subsequent residence of the carbonic fluids in the charnockite resulted in low grade alteration causing modification of the syn charnockitic elemental distribution patterns and the properties of entrapped fluids we favour an internally controlled process of arrested charnockitization in which during near isothermal uplift the release of carbonic fluids from decrepitating inclusions in the host gneiss into simultaneously developing fracture zones led to a change in the fluid regime from fluid absent in the gneiss to fluid present in the fracture zones and to the development of an initial fluid pressure gradient triggering the dehydration reaction

fluid induced nucleation of y ree phosphate minerals within apatite nature and experiment part i chlorapatite this study investigates chlorapatite ideally ca10 po4 6cl2 from two spatially separated locations in the odegardens verk apatite mine bamble sector se norway which was partially metasomatized under amphibolite facies conditions relative to the original chlorapatite metasomatized areas in sample dl136 are enriched in oh and f depleted in na si and y ree and contain numerous inclusions 1 15 m of monazite and xenotime in contrast metasomatized areas in sample tn174 are enriched in f and si depleted in na show y ree abundances similar to the original chlorapatite and host only a few monazite and xenotime grains in order to define the role of fluids in the formation of y ree phosphate minerals associated with apatite a series of experiments covering wide ranges of temperature 900 300 c and pressure 1000 500 mpa for a series of fluid compositions pure h2o a 50 50 molar mix of h2o and caf2 and co2 with 1 2 wt h2o were conducted on unaltered chlorapatite from the odegardens verk in the h2o experiments features due to metasomatic alteration depletion in na si and y ree as well as numerous monazite and xenotime inclusions as observed in the natural sample dl136 were fully reproduced monazite and xenotime grains were also observed growing on the surface of the apatite in dissolution embayments in metasomatized areas in the 50 50 caf2 h2o experiments metasomatized regions are strongly enriched in f and si depleted in na show unchanged y ree abundances and contain only a very few small monazite and xenotime grains similar to what was observed in sample tn174 natural and experimental observation imply the presence of two coupled substitutions na y ree 3 2 ca2 and si4 y ree 3 p5 ca2 in the case of dl136 and h2o fluid experiments na and si4 went into solution whereas the released y ree contributed to the growth of monazite and xenotime within the metasomatized apatite structure for sample tn174 and the 50 50 caf2 h2o fluid experiments na in apatite became depleted but si was enriched thereby stabilizing the y ree in the now recrystallized fluor hydroxylapatite structure which retarded the growth of monazite or xenotime inclusions the basic conclusion of this study is that nucleation of monazite and xenotime in the metasomatized chlorapatite is principally a function of the composition of the infiltrating fluid and to a much lesser extent temperature and pressure

carbonic fluid inclusions in south indian granulites evidence for entrapment during charnockite formation field evidence and fluid inclusion studies on south indian incipient charnockites suggest that charnockite formation occurred during a decompressional brittle regime following the peak of metamorphism and regional deformation the most abundant type of inclusions in quartz and garnet grains in these charnockites contain high density carbonic fluids although lower density fluids occur in younger arrays of inclusions discrete fluid inclusion generations optically are observed to decrepitate over well defined temperature intervals and quantitative measurements of co2 abundance released from these inclusions by stepped thermal decrepitation show up to a four fold increase by volume in the incipient charnockites relative to the adjacent gneisses from which they are derived studies based on optical thermometry visual decrepitation and stepped heating inclusion release together indicate that entrapment of carbonic fluids coincided with charnockite formation we confirm that an influx of carbon dioxide rich fluids is associated with the amphibolite granulite transition as recorded by the incipient charnockites the remnants of which are commonly preserved as the earliest generation of high density fluid inclusions