the physical properties of quartz micaschist and their application to freeze thaw weathering studies in the maritime antarctic as part of a study on freeze thaw weathering in the maritime antarctic an investigation was made of the physical properties of the local rock tests were made of point load compressive strength schmidt hammer in situ rock strength moisture content indentor resistance and the size range of weathering products the resulting data were used to consider the form of freeze thaw weathering operative in the field and its relationship to laboratory simulations a distinct difference between massive rock and intact rock is observed in the field it is suggested that future studies should generate a greater database pertaining to rock properties as it is an invaluable aid in the study of mechanical weathering

the role of the subcutaneous zone in karst hydrology abstract the subcutaneous zone is the upper weathered layer of rock beneath the soil but above the permanently saturated phreatic zone it is of particular hydrological importance in karst because of its high secondary permeability arising from the considerable chemical solution in this zone however corrosional enlargement of fissures diminishes with depth thus permeability decreases in the same direction with the result that percolation is inhibited except down widened master joints and faults storage of water consequently occurs in this zone particularly after storms the upper surface of this suspended saturated layer in the subcutaneous zone is defined by a perched water table which slopes towards points of rapid vertical percolation the potential induces lateral water movement converging on the most permeable areas such as beneath dolines leakage from the subcutaneous store sustains slow percolation in the vadose zone cross correlation of rainfall with percolation rates in caves in new mexico u s a and new zealand reveal response lags of 2 14 weeks with no apparent relationship to depth below the surface other percolation sites show no correlation with rainfall interpreted as being a consequence of considerable friction in tight fissure networks the recognition of storage and rapid as well as very slow percolation from the subcutaneous zone requires re interpretation of the components of hydrographs from karst springs and of some conceptual models of karst aquifers the importance of subcutaneous storage in sustaining baseflow discharge at some sites must be recognised as must the contribution of subcutaneous water to flood hydrographs methods of estimating the volumes of subcutaneous and phreatic components of karst spring flood hydrographs are presented the paper concludes with a discussion of the significance of subcutaneous hydrologic processes for an understanding of karst geomorphology the desirability of explaining karst landform evolution in terms of hydrologic processes is stressed

silicate perovskite and majorite signature komatiites from the archean abitibi greenstone belt implications for early mantle differentiation and stratification three komatiite tholeiite sequences from the archean abitibi southern volcanic zone svz which are separated by major terrane boundaries show systematic differences in composition rare earth element ree patterns and high field strength element hfse ree fractionation komatiites from tisdale township are al undepleted with mgo 12 24 al2o3 tio2 13 17 cao al2o3 1 1 3 and high ni 722 1275 ppm and cr 1875 2820 ppm contents mg tholeiites and fe tholeiites are spatially associated with komatiites both komatiites and mg tholeiites have flat ree patterns la yb n 0 6 1 2 and nb nb zr zr and hf hf 1 calculated using primitive mantle normalized values and adjacent rees in the incompatibility sequence of elements in mid ocean ridge basalt morb suggesting that they may have formed by high degree partial melting of primitive mantle materials with olivine as the main liquidus phase at shallow depths 1 consistent with having been derived from mg perovskite enriched sources at depths 700 km below the transition zone whereas spatially associated tholeiites have la yb n 1 2 and nb nb zr zr and hf hf 1 suggesting a shallow undepleted mantle source distinct from the komatiites komatiites and tholeiites from boston township are characterized by mgo 11 29 al2o3 tio2 4 5 5 4 cao al2o3 l 4 2 5 high ni 203 3420 ppm and cr 194 1965 ppm contents al sc y and heavy rare earth element hree depletion and pronounced negative normalized zr and hf anomalies zr zr and hf hf 1 in accord with either partial melting of a majorite depleted mantle source or majorite fractionation during magma formation in the depth range of 300 600 km the fractionated hfses and rees of munro and boston area komatiites indicate that these archean komatiites may have preserved some signatures of early mantle differentiation which so far has only been inferred based on high pressure experimental studies and theoretical predictions further geochemical studies of archean komatiites especially precise multiple trace element analysis combined with improved measurements of partition coefficients over a wide pressure range will provide better understanding on early mantle differentiation stratification and the transition zone

petrological constraints on the density of the martian crust new insights into the chemistry of the martian crust have been made available since the derivation of crustal thickness maps from mars global surveyor gravity and topography data that used a conservative range of density values 2700 3100 kg m3 a new range of crustal density values is calculated from the major element chemistry of martian meteorites 3100 3700 kg m3 igneous rocks at gusev crater 3100 3600 kg m3 and from the surface concentration of fe al ca si and k measured by the gamma ray spectrometer on board mars odyssey 3250 3450 kg m3 in addition the density of mineral assemblages resulting from low pressure crystallization of primary melts of the primitive mantle are estimated for plausible conditions of partial melting corresponding to the noachian to amazonian periods 3100 3300 kg m3 despite the differences between these approaches the results are all consistent with an average density above 3100 kg m3 for those materials that are close to the surface the density may be compatible with the measured mass of mars and the moment of inertia factor but only if the average crustal thickness is thicker than previously thought approaching 100 km a thicker crust implies that crustal delamination and recycling could be possible and may even control its thickness globally or locally alternatively and considering that geoid to topography ratios argue against such a thick crust for the highlands our results suggest the existence of a buried felsic or anorthositic component in the southern hemisphere of mars

constraints on the u pb isotopic systematics of mars inferred from a combined u pb rb sr and sm nd isotopic study of the martian meteorite zagami uranium lead rb sr and sm nd isotopic analyses have been performed on the same whole rock mineral and leachate fractions of the basaltic martian meteorite zagami to better constrain the u pb isotopic systematics of martian materials although the rb sr and sm nd systems define concordant crystallization ages of 166 6 ma and 166 12 ma respectively the u pb isotopic system is disturbed nevertheless an age of 156 6 ma is derived from the 238u 206pb isotopic system from the purest mineral fractions maskelynite and pyroxene the concordance of these three ages suggest that the 238u 206pb systematics of the purest zagami mineral fractions have been minimally disturbed by alteration and impact processes and can therefore be used to constrain the behavior of u and pb in the zagami source region the value of the zagami source region can be estimated with some confidence from the 238u 206pb isochron to be 3 96 0 02 disturbance of the u pb isotopic systems means that this represents a minimum value the value of the zagami source is significantly lower than the values estimated for most basaltic magma sources from earth and the moon this is surprising given the high initial 87sr 86sr ratio 0 721566 82 and low initial end value 7 23 0 17 determined for zagami that indicate that this sample is derived from one of the most highly fractionated reservoirs from any known planetary body this suggests that mars is characterized by a low bulk planet u pb ratio a feature that is consistent with its relatively volatile rich nature the leachates contain terrestrial common pb that was probably added to the meteorite during handling curation or sawing the mineral fractions particularly those with significant amounts of impact melt glass contain a second contaminant the presence of this contaminant results in pb pb ages that are older than the crystallization age of zagami indicating that the contaminant is characterized by a high 207pb 206pb ratio such a contaminant could be produced by removal of single stage pb from a relatively high martian reservoir before 1 8 ga and therefore could be an ancient manifestation of hydrous alteration of martian surface material

ground water behaviour in karst example of the ombla spring croatia abstract the hydro electric power plant hepp which will exclusively use water from a karst underground storage basin will be built in the vicinity of the abundant karst spring ombla in croatia this paper presents the results obtained by hydrogeologic hydrologic and hydraulic investigations related to the principles of ground water circulation in the karst the analyses included the determination of the effective porosity ne of the karst aquifer and the definition of the volume of large conduits and small fractures in the karst which form the aquifer volume the position and dimensions of large karst conduits have also been defined it was established that in three small springs zaton zavrelje and slavljan water overflows from the ombla spring in periods of high ground water levels it was also discovered that at certain periods the dupuit expression for steady state flow in an unconfined aquifer can be used in accordance with this it was possible to determine the values of hydraulic conductivity k in m s 1 for the ombla aquifer they range from 2 10 3 to 5 10 3 m s 1 and are inversely proportional to the ombla spring discharge continuous measurements of the ground water level by several piezometers located in the karst hinterland of the ombla spring and simultaneous measurement of the discharge made it possible to define discharge curves of the ombla spring dependent upon the ground water levels at various locations characteristic features of the discharge curves made the identification of the position and dimensions of the main karst conduits possible

modeling the influence of epikarst evolution on karst aquifer genesis a time variant recharge boundary condition for joint karst epikarst development 1 the epikarst a zone of increased weathering near the land surface determines the distribution of recharge to a karst aquifer in both space and time it links climatic and near surface geological conditions with the karstification of a limestone aquifer defining both the hydraulic and the chemical boundary conditions for the development of the karst system realistic modeling of the epikarst is therefore a prerequisite for the simulation of karst aquifer genesis a conceptual model of the joint karst epikarst evolution is presented in this paper an epikarst module is developed and implemented in a numerical continuum discrete conduit flow model for karst genesis which accounts for the joint evolution of the epikarst and the main karstic conduit network under unconfined conditions the influence of epikarst genesis on the evolution of the underlying karst aquifer is investigated in four scenarios it is found that only the interaction of epikarst and initial heterogeneity in the underlying carbonate rock leads to the development of a dendritic cave system if no heterogeneity in the initial conduit network or in the recharge distribution is included maze type caves develop

phase relations of peridotites under h2o saturated conditions and ability of subducting plates for transportation of h2o phase relations of peridotites under h2o saturated conditions up to 28 gpa and 2600 c have been clarified based on the high pressure experimental results in the mgo feo sio2 h2o mgo sio2 al2o3 h2o cao mgo al2o3 sio2 h2o and natural systems based on the phase assemblages deduced and the chemical compositions of the phases the maximum h2o contents for two bulk rock compositions lherzolite and harzburgite have been calculated using mass balance then the potential ability of subducting plates for transportation of h2o is discussed by simple models combining the phase relations and the thermal structures of subduction zones as a function of the age of subducting plate a 15 130 ma the subduction velocity u0 2 25 18 cm year and angle 30 and 60 and the mantle potential temperature tp 1300 and 1350 c the results confirm the importance of choke point a cusp around 6 2 gpa and 550 c at which the stability field of major hydrous phases is minimized in terms of temperature although the choke point is exceeded by the mg sursassite bearing assemblage that has the maximum h2o content of 0 4 0 7 wt around 5 7 gpa and 550 700 c if the geotherm of the coldest part across the subducting plate passes below the choke point maximum 4 6 wt h2o can subduct whereas h2o less than 0 4 0 7 wt can subduct above the choke point the critical conditions are clarified as follows if 30 and tp 1300 c a 15 ma with u0 9 cm year or a 30 ma with u0 2 25 cm year is the critical condition if 60 and tp 1300 c or 30 and tp 1350 c the critical conditions slightly shift to an older age or a greater velocity e g a 30 ma with u0 3 5 cm year the slab thermal parameter au0sin is useful to predict roughly the critical condition however within the younger plate the spatial extent of a cold region with major hydrous phases is thinner hence less h2o is subducted even with the same slab thermal parameter this indicates that the age of the plate and the subduction velocity act differently on the h2o transportation ability of subducting plates

a 164 ka record of environmental change in the american southwest from a carlsbad cavern speleothem abstract a horizontal core 2 8 m in length drilled from the georgia giant column in carlsbad cavern provides climate information for the last 164 ka forty six alpha spectrometric u series ages determined at intervals of 7 6 cm along the core indicate five periods of deposition and five hiatuses the longest from 136 to 110 ka variations in growth rate 0 to 70 mm ka in the abundance of aragonite chalcedony and fe bearing phases and in 13c indicate that glacial intervals of the last 164 ka ois 6 4 and 2 were much wetter than today as were the colder substages 5d and 5b of ois 5 by contrast during the two warmest periods of the past 164 ka namely ois 5e and 1 there was no deposition on either side of the speleothem suggesting conditions as dry or drier than today the record from carlsbad parallels data from many other sites in the southwestern usa and northern mexico and data from marine sediments and ice cores demonstrating the extent to which ice sheet fluctuations influenced conditions in southern new mexico detailed correlation of 13c values in the georgia giant which range from 6 6 to 0 9 relative to pdb with distant speleothem records and with data from ice cores further documents the linkage of southwestern climate with global scale extent of glaciation values of 18o in the georgia giant core range from 9 7 to 4 7 relative to pdb and average 6 6 18o depleted carbonate in the georgia giant during ois 6 at a time when the world s oceans were enriched in 18o suggests that precipitation during cold intervals was brought largely by pacific air masses in fall winter and spring as a result of the southward displacement of the polar jet stream by the growth of the laurentide ice sheet termination ii marking the end of the penultimate glaciation is well defined in the core s 18o data analytical uncertainties in the radiometric ages do not preclude a start of termination ii as late as 128 ka as suggested by specmap data however data from the georgia giant core are more compatible with an earlier start like that obtained from devils hole and vostok data raising the possibility that early warming was widespread in the u s southwest region by 145 ka

shock induced deformation of shergottites shock pressures and perturbations of magmatic ages on mars shergottites and chassignites practiced major deformation effects whose nature magnitude and relevance were controversially evaluated and disputatively debated our studies of many shocked shergottites present contrary to numerous previous reports ample evidence for pervasive shock induced melting amounting of at least 23 vol of the shergottite consisting of maskelynite and pyrrhotite partial melting of pyroxene titanomagnetite ilmenite and finding of several high pressure polymorphs and pressure induced dissociation reactions our results cast considerable doubt on using the refractive index ri or cathodoluminescence cl spectra of maskelynite in estimating the magnitudes of peak shock pressure in both shergottites and ordinary chondrites ri of maskelynite was set after quenching of the feldspar liquid before decompression to maskelynite glass followed by glass relaxation after decompression at the closure temperature of relaxation the ri procedure widely practiced in the past 38 years revealed unrealistic very high pressure estimates discrepant with the high pressure mineral inventory in shocked shergottites and ordinary chondrites and with results obtained by robust laboratory static experiments shergottites contain the silica high pressure polymorphs the scrutinyite structured polymorph seifertite a monoclinic ultra dense polymorph of silica with zro2 structure stishovite a dense liquidus assemblage consisting of stishovite na hexa aluminosilicate na cas and both k lingunite and ca lingunite applying individual high pressure silica polymorphs alone like stishovite to estimate the equilibrium shock pressure is inadequate due to the considerable shift of their nominal upper pressure bounds intrinsically induced by spatially variable absorptions of minor oxides like al2o3 na2o feo mgo and tio2 this practice revealed variable pressure estimates even within the same shergottite subjected to the same peak shock pressure occurrence of na cas stishovite lack of the naalsio4 ca ferrite structured polymorph or jadeite indicates that the peak shock pressures barely exceeded 22 gpa we present convincing and ample evidence refuting the claim that the shock induced high pressure inventory in shergottites and ordinary chondrites are disequilibrium assemblages resulted from local pressure spikes in excess of 80 gpa and during the decompression stage such scenario calls for a series of incomplete and quenched retrograde reactions starting with the crystallization of mg silicate perovskite magnesiowustite if the claimed peak shock pressure was in excess of 80 gpa this would be followed by replacement of this pair by majorite pyrope ss magnesiowustite or akimotoite magnesiowustite below 23 gpa and 2000 degrees c polycrystalline ringwoodite above 16 gpa respectively and finally replacement by polycrystalline olivine below 16 gpa such incomplete retrograde reactions were never encountered in any shergottite chassignite or shocked ordinary chondrite so far olivine ringwoodite phase transformation in the l6 y 791384 commences with the coherent mechanism producing ringwoodite lamellae with their 111 planes parallel to the 100 of olivine followed by the incoherent mechanism due to build up of strain in the parental olivine this is in accord with the olivine ringwoodite settings produced in static laboratory experiments in a multi anvil device olivine ringwoodite phase transitions were also encountered in comparable settings in the shergottite nwa 1068 application of experimentally obtained kinetic parameters of the olivine ringwoodite phase transitions reveals possible duration of the natural dynamic events up to few seconds thus unambiguously refuting the claimed disequilibrium decompression mechanism the shock induced pervasive melting of labradorite pyrrhotite titanomagnetite ilmenite and partial melting of clinopyroxene strongly suggests shock induced partial to complete resetting of the ar ar rb sr sm nd re os u pb and lu hf radiometric systems this also casts considerable doubt on the radiometric ages shorter than 575 ma reported in the past 38 years to allegedly be the igneous crystallization ages these short ages probably resulted from partial or total shock induced age resetting c 2012 elsevier ltd all rights reserved

melting relations of hydrous pyrolite in cao mgo al2o3 sio2 h2o system at the transition zone pressures phase relations and melt compositions in cao mgo al2o3 sio2 pyrolite under hydrous 2 of h2o and anhydrous conditions have been determined at 13 20 gpa and 1600 2220 c liquidus and solidus temperatures for the hydrous system are about 50 100 c and 180 240 c lower than those for the dry system respectively majorite is a liquidus phase of the hydrous pyrolite from 13 to 20 gpa olivine is a liquidus phase at 13 gpa and both periclase and majorite are the liquidus phases at 20 gpa in the dry pyrolite we observed expansion of the stability field of anhydrous phase b in hydrous experiments compositions of partial melts at 13 20 gpa are generally similar in dry and hydrous systems but hydrous melts contain more sio2 at 13 17 gpa the melts formed by low degree of melting have al2o3 depleted and cao rich compositions trends of hydrous melt compositions are generally consistent with those of aluminum depleted komatiite magmas

developments in a non destructive method of determining rock strength material strength is an important variable for any study of the relationships between rock mass geomechanical characteristics and landform development standard field and laboratory tests for measuring strength present a variety of problems to the geomorphologist recent studies allison 1988 have described a laboratory based non destructive method for indirectly determining material strength by measuring dynamic young s modulus data presented here suggest that the same apparatus can be used as a field technique tests have been conducted on the devonian limestone of the napier range western australia laboratory results obtained using the non destructive ultrasonic apparatus have a high correlation with triaxial hoek cell tests results from on site tests have much greater accuracy than data collected using the schmidt hammer which is currently the most widely used geomorphological field technique for determining rock strength

soil and karst aquifer hydrological controls on the geochemical evolution of speleothem forming drip waters crag cave southwest ireland abstract in recent years there has been increased interest in cave speleothems as archives of palaeoclimate monitoring of rainfall and soil and karst water chemistries was performed at crag cave castleisland co kerry southwest ireland in august 1997 and january 1998 in order to understand temporal and spatial variations in karst water hydrology and chemistry and their implications for interpreting the potential palaeohydrological signal preserved by speleothems at this site temporal variations in karst water drip rates and geochemistry allow drips to be classified by hydrological response to rainfall and the associated processes of dilution piston flow source change and prior calcite precipitation during aquifer throughflow evolution from soil matrix and preferential flow solutions has also been determined to exert an important control on karst water chemistries as a result of these findings we present hydrogeochemical models and plumbing diagrams that delineate the controls on karst water evolution at a number of sampling locations within the cave at this site we propose that a palaeohydrological signal may be recorded by crag cave speleothems that may be interpreted via the study of mg ca ratios in speleothems linked to monitoring of modern drip water chemistry

infiltration processes and flow rates in developed karst vadose zone using tracers in cave drips the purpose of this research was to identify groundwater recharge mechanisms and measure flow velocities through the epikarst and the vadose zone in a typical site of mediterranean carbonate karst in natural rain conditions by avoiding artificial flushing more realistic travel times could be measured and the effective resultant vadose flow velocity could be inferred additionally detailed monitoring enabled better description and quantification of infiltration and percolation processes nine different cave drips were monitored and sampled for three hydrological years in fractured karst lithology on mount carmel israel at three drips discharge was measured continuously by tipping buckets rainfall and soil water content were recorded above the cave an artificial tracer experiment was conducted using uranine placed in a joint and at the soil rock interface at soil pockets both 27 m above the cave four hydrological types of drips post storm seasonal perennial and overflow were identified each demonstrating different characteristics in terms of discharge and chemistry the maximum effective flow velocities uranine dye arrival times were 41 76 cm h tracer mass flux was computed from the uranine breakthrough curves and drip hydrographs the dominant flow velocities derived from the peak of tracer mass flux were 0 35 0 41 cm h from post storm drips and 22 24 cm h from the other drips pulse through intra event piston flow was indicated by the time lags between the increase in drip rate and the time of drop in salinity and appearance of the tracer in most of the measured drips chloride concentrations were used to distinguish between old matrix water and preferential flow water in the perennial drips demonstrating a two component mixing model in 2005 2006 preferential flow water reached up to 20 25 from annual discharge of these drips this study promoted a method to compute dominant effective flow rates in the vadose zone in natural rain conditions copyright 2010 john wiley sons ltd

hydrous solidus of cmas pyrolite and melting of mantle plumes at the bottom of the upper mantle 1 we showed in previous experiments that the melting temperature of hydrous pyrolite at the transition boundary between wadsleyite and olivine is abruptly reduced by the presence of 2 wt h2o in this paper we determine the apparent solidus for cao mgo al2o3 sio2 pyrolite with lower and geologically more reasonable h2o contents 0 5 wt phase relations and melt compositions have been determined at pressures of 13 5 17 0 gpa and temperatures of 1600 to 2100 c there was no abrupt decrease of solidus temperature along the phase boundary between olivine and wadsleyite in pyrolite with 0 5 wt h2o however significant gradual decrease of the solidus temperature at pressures below 15 16 gpa still supports previous models for a hydrous origin of some ancient komatiites by dehydration melting of rising wet plumes at pressures of 4 10 gpa

hydrochemical variations during flood pulses in the south west china peak cluster karst impacts of caco3 h2o co2 interactions high resolution measurements of rainfall water level ph conductivity temperature and carbonate chemistry parameters of groundwater at two adjacent locations within the peak cluster karst of the guilin karst experimental site in guangxi province china were made with different types of multiparameter sonde the data were stored using data loggers recording with 2 min or 15 min resolution waters from a large perennial spring represent the exit for the aquifer s conduit flow and a nearby well measures water in the conduit adjacent fractured media during flood pulses the ph of the conduit flow water rises as the conductivity falls in contrast and at the same time the ph of groundwater in the fractures drops as conductivity rises as ca 2c and hco3 were the dominant 90 ions we developed linear relationships both r 2 0 91 between conductivity and those ions respectively and in turn

the case for old basaltic shergottites abstract the crystallization age of shergottites is currently not agreed upon although mineral 87 rb 87 sr 147 sm 143 nd 176 lu 176 hf and u pb isochrons all give very young ages typically in the range of 160 180 ma 207 pb 206 pb data support a much older crystallization age at 4 1 ga which is consistent with published whole rock 87 rb 87 sr data on basaltic shergottites different isotopic systems present different complexities but crater counting chronology which shows that a substantial fraction of the martian surface was resurfaced during the late heavy bombardment is in favor of an old martian lithosphere with ages in accordance with pb pb and rb sr isotopic data a 4 1 ga pb pb age of shergottites also agrees with the 142 nd and 182 w anomalies found in these rocks and concur with the presence of an actively convecting mantle during the first 500 myr of the planet s history we here present new sm nd lu hf and pb pb mineral isochrons for the basaltic shergottites shergotty and los angeles complementing our previous results on zagami bouvier a blichert toft j vervoort j d and albarede f 2005 the age of snc meteorites and the antiquity of the martian surface earth planet sci lett 240 221 233 the internal 147 sm 143 nd and 176 lu 176 hf isochrons give young ages of respectively 172 40 mswd 2 0 and 188 91 mswd 3 1 for shergotty and 181 13 mswd 0 14 and 159 42 mswd 0 01 for los angeles in contrast the pb isotope compositions of the leached whole rock fragments and maskelynite separates of shergotty and los angeles fall on the whole rock isochron previously established for zagami and other shergottite samples and collectively yield a pb pb age of 4050 70 ma for the crystallization of the basaltic shergottite suite the contrast between the 170 ma ages of internal isochrons and the 4 1 ga age supported by pb pb and 87 rb 87 sr on whole rocks simply reflects that the younger age dates the perturbation of a suite of rocks of noachian age the internal rb sr sm nd lu hf and u pb errorchrons are heavily biased by the presence of disseminated phosphate minerals and inclusions for which d h ratios d 4600 indicate strong interaction with martian subsurface waters in contrast baddeleyite occasionally present in sncs and also having extremely young u pb ages reflect resetting under the shock conditions that prevailed either during shergottite extraction from the planet or from impacts associated with a major break up event of planetesimals in the main asteroid belt we finally also re examine 39 ar 40 ar data on snc meteorites and suggest that they as well support old crystallization ages

flow and solute transport monitoring in the karst aquifer in sw slovenia the role of the unsaturated zone in the karst aquifer hydraulic behaviour was brought into focus in these studies of the catchment of the hubelj spring sw slovenia the variations of natural tracers in precipitation and in groundwater during a summer storm event made it possible to trace local flow and solute transport in the observed aquifer the results produced data on the aquifer recharge storage and discharge processes as well as on mechanisms that affected them which reflects a karst groundwater dynamics also at a regional scale they point out the significance of effects of the fast preferential flow epiflow that is the main factor controlling solute contaminant transport towards the aquifer saturated zone numerous arguments indicate that the karst aquifer flow and solute transport mechanisms depend on the hydraulic behaviour of the epikarst zone

martian meteorite chronology and the evolution of the interior of mars abstract the earth moon and mars are the only three planets for which satellite and ground observations can be confronted with extensive chronological and geochemical observations of rock samples here we use new pb isotope data on shergottites nakhlites chassigny and the alh 84001 orthopyroxenite to reassess chronological evidence and discuss its bearing on the evolution of the interior of mars we find that the depleted shergottites formed at 4 3 ga i e 170 ma after the last equilibration of pyroxene rich cumulates with the magma ocean while the younger enriched and intermediate shergottites as well as alh 84001 formed 200 ma later at 4 1 ga after the residual part of the mantle had been largely mixed back into these cumulates we also demonstrate that the th u ratios inferred from pb isotopes require shergottite ages older than 4 0 ga we finally reexamine the implications of this new chronological framework for the interpretation of 142 nd and 182 w anomalies in martian meteorites we conclude that shergottites represent samples that derived from a volcanic basement subsequently shattered by the 3 9 ga late heavy bombardment lhb although the magmatic activity of mars had strongly declined by the time of the lhb the new chronology of martian meteorites proposed here allows the martian mantle to be convective until today the 1 3 ga old emplacement of nakhlites and chassignites corresponds to decompression melting of ilmenite rich mantle domains and not to renewed global magmatic activity of the planet with the exception of this event the history of the interior of mars therefore somewhat resembles that of the moon

climate influence on geochemistry parameters of waters from santana perolas cave system brazil abstract a four year study of water geochemistry and hydrology was performed in a relatively deep cave system overlying bedrock thickness varies from 100 to 300 m as part of two monitoring programs from june 1990 to february 1992 and from march 2000 to march 2002 the ph saturation index for calcite ca and so 4 concentrations and elemental ratios of mg ca and sr ca were measured in surface well and drip waters throughout the system despite local hydrological and geological differences among sampling sites the monitoring revealed significant synchronous intersite variations in these parameters that are related to seasonal changes in rainfall recharge suggesting that element ratios of speleothems formed in deep caves are capable of recording short term climate variations groundwater residence time appears to be the main factor affecting the water composition in the epikarst epikarstic waters are always undersaturated with respect to calcite but both saturation index s i and dissolved solids content increase substantially during drier periods because of longer residence times and longer interaction between meteoric water and limestone by contrast results from cave drips and rimstone pools indicate constant supersaturation for calcite and demonstrate that a major control on trace element ratios of waters in the deep vadose zone is the degree of prior calcite precipitation this mechanism is more effective during drier periods when higher mg ca and sr ca values are observed in all drip and pool sites however variations do occur independently of the general trend of drip discharge which suggest non linear features in cave seepage water geochemistry in addition synchronous variations in so 4 and cl concentration indicate high connectivity between different water flow pathways characterized by similar response to interseasonal changes in vadose water level fluctuations in trace element ratios of cave streams appear to reflect increased contribution of waters flushed from the vadose fissure aquifer during very wet periods by a piston flow mechanism flushing episodes are also responsible for maintaining more positive saturation indices in streams even during periods of high river discharge our results suggest that trace elements are a potential proxy for past rainfall changes but they also reveal different scenarios for interpreting trace elements ratios of speleothems and freshwater tufa deposited in a deep cave systems located in tropical humid areas

rock hardness and landform development in the gunong mulu national park sarawak e malaysia rock hardness measured by the schmidt test hammer is an important factor in explaining some of the sharp contrasts in relief and wide variety of landforms in the gunong mulu national park it is also useful in consideration of contemporary geomorphological processes such as landsliding

the age of snc meteorites and the antiquity of the martian surface we report new sm nd lu hf and pb pb mineral and whole rock isotope data for the basaltic shergottite zagami as well as pb pb whole rock isotope data for the basaltic shergottite los angeles the lherzolitic shergottite dar al gani 476 dag 476 and the clinopyroxenite nakhla in agreement with previous findings our new sm nd and lu hf mineral ages on the martian meteorite zagami are young 155 and 185 ma respectively the 207pb 206pb 204pb 206pb compositions of the insoluble fractions of shergottites zagami los angeles and literature data for shergotty and eeta79001 form an excellent alignment indicative of a 4 0 ga crystallization age the range of pb isotope compositions observed in the leachates of these samples attests to negligible contamination of the shergottites by terrestrial pb and argues against mixing relationships the age of 4 048 0 017 ga mswd 1 5 provided by the pb isotope compositions of the zagami whole rock and residues is therefore taken to date the crystallization of this rock which so far was believed to be only not vert similar 180 ma old based on this result we argue that the lithosphere of mars is extremely old and that most mineral ages were reset recently by acidic aqueous solutions percolating through the martian surface this interpretation is consistent with photographic interpretations of erosional features on mars it also relieves the constraint imposed by the presence of anomalies of 142nd and 182w both products of extinct radioactive nuclides that the martian mantle should have preserved primordial isotopic heterogeneities thus allowing for the planet interior to be actively convecting

a new technique for non destructive field measurement of rock surface strength an application of the equotip hardness tester to weathering studies tafone like depressions have developed on the aoshima sandstone blocks used for a masonry bridge pier in the coastal spray zone a thin layer of partial granular disintegration was found on the surface in depressions to evaluate quantitatively the strength of the thin weathered layer the hardness was measured at the surface of the sandstone blocks using both an equotip hardness tester and an l type schmidt hammer comparison of the two testing results indicates that the equotip hardness value is more sensitive in evaluating the strength of a thin layer of weathered surface rock than the schmidt hardness value by applying two methods i e both the repeated impact method and the single impact method the equotip tester can evaluate the strengths of fresh internal and weathered surficial portions of rocks having a thin weathering layer comparison of the two strengths enables evaluation of strength reduction due to weathering copyright 2007 john wiley sons ltd

stemflow influences on the formation of solution pipes in bermuda eolianite abstract soil filled pipes consisting of calcite casings were found in all of the eolianite formations of bermuda except the rocky bay formation the pipes are cylindrical in shape taper vertically downwards and occur in aggregated clusters they are most commonly exposed in areas of shoreline erosion in the form of soil filled cylindrical rims of calcite projecting up from the surrounding host eolianite in the early literature on the geology of bermuda it was suggested that these features were fossilized stumps of the bermuda palmetto tree sabal bermudiana in the study presented here this hypothesis is rejected on the basis of the morphology and stratigraphic position of these geomorphic features and their basal area and areal density compared with existing natural stands of s bermudiana the soil filled pipes of bermuda however cannot be simply explained as random solutional features that correspond to points where percolating soil water happened to converge and cause localized subsurface dissolution in situ measurements of stemflow from indigenous tree species suggest that the soil filled solution pipes of bermuda may be the product of stemflow drainage from particular tree species stemflow from s bermudiana was the most acidic with ph values as low as 4 29 compared to the gross rainfall in the open which had a ph of 5 58 the crowns of the bermuda cedar juniperus bermudiana and the subtropical tree species eugenia axillaris had the most significant funnelling effect stemflow volumes from individual trees representing these two species were 20 times greater than the volume of water that would have been collected in rain gauges with orifice areas equivalent to the trees trunk basal areas tree species capable of acidifying intercepted rainwater and funnelling large quantities down their trunks as stemflow may be the cause of subsurface dissolution loci extending vertically downward through bermuda s soluble eolianite formations stemflow from long lived trees representing these species could account for the diameters the cyclindrical shape the vertical orientation and the soil filled interiors of the pipes successive generations of these trees in preferred habitats could explain their clustered distribution and high areal densities 103 pipes ha

effect of water on melting phase relations and melt composition in the system mg2sio4mgsio3h2o up to 15 gpa melting experiments in the system mg2sio4 mgsio3 h2o up to pressures of 15 gpa show that the presence of h2o drastically changes melting temperature liquidus phases and the coexisting melt composition the system mg2sio4 h2o shows incongruent melting characterized by a high mgsi ratio of the eutectic composition exceeding 2 0 above 12 gpa whereas it exhibits congruent melting up to at least 7 7 gpa in the mgsio3 h2o system incongruent melting is observed up to 3 gpa which switches to congruent melting above 5 5 gpa and persists to at least 12 gpa the variation of the eutectic composition in the system mg2sio4 mgsio3 h2o is consistent with the variations of the melting temperatures in the systems mg2sio4 h2o and mgsio3 h2o the melting temperature solidus in the system mg2sio4 h2o decreases from 1800 c at atmospheric pressure to less than 1200 c at 10 gpa while in the system mgsio3 h2o it is reduced to a minimum value of 1250 c at approximately 5 5 gpa and then increases with pressure the composition of the initial melt in this system drastically changes at around 5 5 gpa the mgsi ratio being about 3 at 15 gpa variations of the ternary phase diagrams mgo sio2 h2o with pressure are compiled and compared with previous work on the relevant systems a modified spinel like hydrous phase is synthesized at 15 5 gpa the maximum amount of h2o accommodated in this phase is estimated to be 3 3 wt from observed chemical composition and crystal chemical considerations implying that a significant amount of h2o can be accommodated in the mantle transition zone the overall effect of h2o on ultrabasic magma genesis in the mantle is discussed a possibility is presented for the formation of komatiite magma involving the effect of h2o in the mantle of the early earth mg rich komatiite magma was possibly generated at a depth of only 200 km at temperatures much lower than that having been assumed previously

majorite fractionation and genesis of komatiites in the deep mantle abstract melting experiments of the primitive mantle indicate that majorite fractionation is the key process to determine the geochemical nature of magmas generated in the deep upper mantle and the transition zone a model of petrogenesis of komatiite magma is presented by using the melting relations of the primitive mantle and the partitioning data of lithophile elements between majorite and the liquid alumina depleted komatiite generally observed in the early archean can be generated by any degree of partial melting at depths from 450 to 650 km this type of komatiite is also generated by a relatively low degree of partial melting at depths from 180 to 450 km alumina enriched komatiite can be generated by remelting of the residual mantle after separation of alumina depleted komatiite alumina undepleted komatiite generally observed in the late archean can not be formed by a low degree of partial melting of the primitive mantle at any depths this type of komatiite can be generated only by a high degree of partial melting of the mantle at the depths shallower than 450 km as an alternative model the alumina depleted komatiite can be formed by a high degree of partial melting of the archean upper mantle depleted in majorite such heterogeneity in the archean upper mantle was generated by a global melting event succeeding the accretion of the earth and erased by convection by the later archean hf isotope data seem to favour the former model of the petrogenesis of komatiite i e single stage melting of the primitive mantle at various depths

garnet fractionation in a hydrous magma ocean and the origin of al depleted komatiites melting experiments of hydrous pyrolite with rees at high pressure abstract melting experiments of a representative mantle composition doped with some key trace elements were conducted under hydrous conditions at pressures to 20 gpa the results demonstrate that only 5 25 of garnet fractionation and relatively low pressures 3 5 ga in the solidifying hydrous magma ocean this suggests that the archean mantle was much cooler than so far believed from the origin of the komatiites based on anhydrous experiments

field survey and analysis of hillslopes on tower karst in guilin southern china limestone dissolution in tropical and subtropical humid southern china created residual hills with steep slopes a landform that is referred to as tower karst two types of tower karst landform feature fenglin or peak forest isolated towers and fengcong or peak cluster linked base towers were identified in guilin previous studies proposed two hypotheses regarding their origin and evolution one is the sequential evolution model from peak cluster to peak forest the other is a parallel development model which postulates that both peak cluster and peak forest have developed simultaneously through detailed field survey and analysis of slope forms on tower karst in guilin it was found that the mean slope angle of the towers is very high 62 4 and ranges from 60 to 75 there is no significant difference in mean slope angle and slope angle distribution between towers in the peak cluster basin and peak forest floodplain areas mean slope angle increases with intensified fluvial dissection three levels of caves in the towers of the peak forest in guilin were identified in previous research the isolated towers of the peak forest as well as scattered residuals of peak cluster are generally distributed in the centre of the guilin syncline favourable circumstances of allogenic water concentration indicate that development of the peak forest resulted from the combined effects of subcutaneous and subterranean dissolution as well as subsequent collapse and recession by fluvial erosion after uplifting by contrast peak clusters generally occur on the limbs of the syncline or at the periphery of the guilin basin with relatively higher elevations the thick vadose zone and predominantly vertical flow suggests that peak clusters are mainly formed by the combination of intensive uplifting and the enhancement of original dolines the evidence of slope survey and slope analysis suggests that both isolated towers and linked base towers developed simultaneously but by different mechanisms of formation and different combinations of development processes copyright 2000 john wiley sons ltd

developments in a non destructive method of determining rock strength a reply in a previous publication allison 1989 a non destructive method for indirectly determining rock strength by measuring dynamic young s modulus was described data were presented to assess the grindosonic apparatus in relation to standard laboratory techniques a further short communication allison 1990 evaluated the non destructive test as a field technique in part achieved by comparing the grindosonic results with data collected using the schmidt hammer the schmidt hammer is a widely used field technique in geomorphology for determining rock strength see for example day and goudie 1977 day 1981 allison 1989 1990 also suggested that the elastic properties of materials are becoming increasingly important in geomorphological studies the opportunity to provide additional information and comments here is appreciated

geochronology of the martian meteorite zagami revealed by u pb ion probe dating of accessory minerals abstract the precise chronology of geological events on mars is hampered by the lack of absolute ages for the martian timescale and the significant uncertainties that result from the extrapolation of the lunar timescale to mars hartmann and neukum 2001 martian meteorites represent the only samples of mars currently available attempts to identify source craters for the meteorites have thus far proven inconclusive hamilton et al 2003 lang et al 2009 mouginis mark and boyce 2012 precluding their use in constraining the absolute martian timescale the majority of the known martian meteorites are basalts shergottites all dated shergottites have mineral separate rb sr or sm nd ages of borg et al 2005 here we report a 238u 206pb age of 182 7 6 9 ma by ion microprobe analysis of baddeleyite zro2 grains in the zagami shergottite there is no correlation between discordancy and baddeleyite grain location relative to shock metamorphism mineral petrography demonstrates that baddeleyite is the result of late stage igneous crystallization and raman spectroscopy shows that baddeleyite has not been transformed by shock into preservable high pressure polymorphs supported by an age of 153 81 ma for phosphate grains obtained using the same method we conclude that zagami crystallized at 180 ma in agreement with previous results from mineral separate geochronology therefore the shergottites represent igneous rocks preferentially ejected from young terrains on mars in a small number of ejection events

surface sediment characteristics and tower karst dissolution guilin southern china abstract dissolution of extensive outcrops of limestone and dolostone in humid tropical and subtropical southern china produced numerous caves and residual hills that are referred as tower karst this study identifies and relates the physical and chemical characteristics of the surface sediment with the limestone bedrock in guilin to assess the influence of the limestone dissolution process on sediment composition the results of this study indicated that i both limestone and dolostone of the region are very pure 99 5 and 98 5 of caco 3 and mgco 3 respectively ii the material composition of limestone and dolostone is different from that of soil and sediment of the region constituents of surface sediments are highly related with the clastic sedimentary rocks such as the mudstone but show negative correlation with limestone and dolostone iii the limestone formations are highly resistant to physical weathering and disintegration their durability versus physical weathering and their high susceptibility to chemical dissolution account for why residual towers can form and persist iv a dual zone environmental structure exists vertically downward from the surface in guilin the zone of unconsolidated clastic sediments that is predominantly acidic and the zone of karstified limestone that is predominantly basic the evidence suggests that the environment and processes differ in these two zones the chemical dissolution of limestone that formed tower karst of the region is not mainly responsible for the accumulation of clastic sediment on the surface

quantification of rock control in geomorphology abstract rock control the influence of rock properties on landform development has for long been a relatively under researched topic but numerous techniques have been developed especially by geotechnical engineers and stone conservationists that are now being applied to geomorphological issues by geomorphologists these techniques range in scale from the quantification of major discontinuities through to analysis of micro pores rock control studies that have taken place over the last few decades have contributed important insights into our understanding of such diverse phenomena as 1 river terraces bedrock channel forms and gradients pot hole development drainage density and gully badland development 2 slope forms and failures especially with respect to rock mass strength 3 the form of glacial troughs and of subglacial erosional landforms 4 weathering controls on rock durability and the association of weathering with porosity 5 classic karst features including various types of karren 6 sandstone landforms 7 inselbergs and tors and 8 cliffs and shore platforms

solution doline development on glaciokarst in alpine and dinaric areas abstract in this study the evolution the development and the development environment of solution dolines of glaciokarst the alps and the dinarides are studied based on morphological observations partly with the help of literary data the dolines of sample sites were put into doline types giant solution doline small sized solution doline and schachtdoline the various features of the dolines belonging to different doline types were analysed and compared their size shape elongated nature and the slope angle of their side slope giant solution dolines are much more similar to the dolines of the temperate belt rather than to small sized solution dolines or schachtdolines at temperate climate giant solution dolines developed under the tree line similarly to dolines of the temperate belt and not above the tree line below the tree line the dolines grew horizontally to the effect of horizontal dissolution later in the glacials they developed laterally mainly along their longer axis by glacial erosion they got into their periglacial environment during the uplifting of the bearing area in mountains where they are absent the circumstances of their environment were not present either because the uplifting of the mountain was fast or it was covered by non karstic rock the shapes of small sized solution dolines and schachtdolines prove that their increase happened by deepening their deepening was caused by the meltwater of the snow patches of snow drifts which water does not move laterally because of the rock debris of the floor and thus solution works downwards in the features deepening and snow accumulation strengthen each other these karstic depressions are connected to the periglacial zone because treeless environment favours snow drifts if the depression is completely filled with snow in most part of the year the snow patch is wide thus dissolution affects the total width of the doline a doline schachtdoline with vertical sides and plain floor develops if snow fill is only partial in most part of the year the snow patch and thus dissolution will have a smaller area and a small sized solution doline with funnel shape develops

phase relations and melt compositions in cmas pyrolite h2o system up to 25 gpa abstract phase relations and melt compositions in the cao mgo al 2 o 3 sio 2 pyrolite under hydrous 2 of h 2 o and anhydrous conditions have been determined at 10 25 gpa and temperatures from 1400 to 2400 c at the pressure of 16 and 25 gpa the apparent solidus temperatures for the hydrous system are about 200 and 100 c lower than the solidus temperatures for the dry system respectively the apparent solidus temperature changes drastically from 1600 c at 13 5 gpa to about 1850 c at 16 gpa majorite is a liquidus phase in the hydrous pyrolite from 10 to 25 gpa the liquidus phases in the dry pyrolite are olivine at 10 14 gpa majorite at 14 20 gpa and periclase at pressures above 20 gpa we observed expansion of the stability field of anhydrous phase b and its complex relations with the other phases in the cmas pyrolite system we suppose it is formed not only by incongruent melting of wadsleyite but also by the subsolidus reaction of wadsleyite and majorite in the dry condition compositions of partial melts formed by low degree of melting 10 20 have al 2 o 3 depleted and cao rich compositions up to 22 gpa and enriched in al 2 o 3 5 7 wt and cao at 25 gpa at 10 gpa dry and hydrous melts formed by low degree of melting have high sio 2 48 51 wt and relatively high al 2 o 3 3 5 5 2 wt their compositions are generally consistent with those of aluminum depleted komatiite at 13 22 gpa dry and hydrous melts have low sio 2 44 49 wt and al 2 o 3 1 7 3 0 wt and high cao contents 9 15 wt an essential depression of the apparent solidus temperature in the hydrous deep upper mantle compared to that in the transition zone provides the dehydration melting of the hydrous plume the present results support a model of komatiite genesis by dehydration melting of rising wet plumes at the base of the upper mantle

melting and phase relations in the system mg2sio4 mgsio3 at 20 gpa under hydrous conditions an experimental study was performed on the melting and subsolidus phase relations in a synthetic magnesium silicate system at a pressure of about 20 gpa and over the temperature range of 1700 2500 c under hydrous conditions the modified spinel mg2sio4 is stable up to 2250 c above which it melts incongruently into phase b mg23si8o42h6 and liquid at higher temperatures phase b melts again incongruently into periclase and liquid the liquid coexisting with periclase has an atomic ratio mg si 1 5 at 2360 c and 1 7 at 2500 c for mgsio3 composition the ilmenite is stable at lower temperatures and it transforms to a garnet with increasing temperatures to 2000 c at above 2200 c clinopyroxene replaces the garnet and then melts congruently at 2250 c the triple point of clinopyroxene garnet and liquid is closely located at 20 gpa and 2250 c the binary system of mg2sio4 mgsio3 shows a eutectic melting between modified spinel and garnet with a eutectic point located at 2150 c and mg si 1 3

a non destructive method of determining rock strength rock material strength is an important component of many geomorphological studies current methods for determining this parameter result in sample destruction preventing further analysis a new non destructive technique is described for indirectly determining material strength by measuring dynamic young s modulus tests have been conducted on jurassic portland limestone and upper cretaceous chalk to assess the apparatus young s modulus is becoming an increasingly important rock material property

enhanced bedrock weathering in association with late lying snowpatches evidence from livingston island antarctica an indication of the extent of weathering on different aspects of rock outcrops on livingston island antarctica was obtained by means of a schmidt hammer a cone indenter and measurement of weathering rind thickness results show that weathering particularly chemical weathering is enhanced on the lee side of outcrops where snow accumulates as a result of prolonged wetting by the melting snow rock moisture and temperature data indicate that the south facing snow accumulation side of obstacles have high rock moisture levels and maintain relatively high temperatures whilst chemical weathering is greater on the leeward side of outcrops mechanical processes are greater on the windward side the presence of late lying snow thus appears to exert a strong influence on weathering

speleogenesis in aeolian calcarenite a case study in western victoria most studies of karst landscapes and their processes have been concerned with consolidated often well jointed limestones there are particular problems involved in the study of karst procesess in softer less compact limestones such as chalk coral reefs and aeolian calcarenite previous studies in aeolian calcarenite indicated these problems and a scheme was developed of speleogenesis in aeolian calcarenite a study of karst processes in aeolian calcarenite at bats ridge in western victoria has developed this scheme further the karst features and processes at bats ridge are an integral part of the landscape of a mid pleistocene calcarenite dune system the resolution of problems of the rapid subaerial speleogenesis in the area is achieved by the synthesis of the known karst features of the ridge and the geology and geomorphology of the area karst development on this aeolianite ridge depends on lithological conditions as well as the availability of aggressive water capable of solution the diagenesis of the calcarenite is occurring now and must have been occurring by the mid pleistocene this simultaneous lithification of the carbonate dunes into aeolian calcarenite rock and the development of solutional karst features in the dunes is the characteristic feature of the speleogenesis in this area it is the formation of a hardened kankar layer cap rock in the dunes of sufficient compressive and tensile strength to support cavities which is the result of these interrelated factors that has strongly determined the formation of the karst features

the use of the schmidt hammer and equotip for rock hardness assessment in geomorphology and heritage science a comparative analysis rapid field based measurements of rock hardness are of use in investigating many geomorphological and heritage science problems several different methods are now available for taking such measurements but little work has been done to assess their comparability and strengths and weaknesses we review here the capabilities of two types of schmidt hammer classic n type and silver schmidt bl type alongside two types of equotip standard type d and piccolo for investigating rock hardness in relation to rock weathering on various types of sandstone and limestone as well as basalt and dolerite whilst the two schmidt hammers and the two equotips show comparable results when tested at 15 individual sites interesting differences are found between the equotip and schmidt hammer values which may reveal information about the nature of weathering on different surfaces operator variance is shown to be an issue in particular for the equotip devices which also exhibit higher variability in measurements and necessitate larger sample sizes carborundum pre treatment also has varying effects on the data collected depending on the nature of the surface studied the equotip devices are shown to be particularly useful on smaller blocks and in situations where edge effects may affect schmidt hammer readings we conclude that whilst each device contributes to geomorphological research they do not necessarily produce comparable information indeed using schmidt hammer and equotip in combination and looking at any differences in results may provide invaluable insights into the structure of the near surface zones and the nature of weathering processes copyright 2010 john wiley sons ltd

provenance versus weathering control on sediment composition in tropical monsoonal climate south china 1 geochemistry and clay mineralogy abstract this study presents an integrated mineralogical and geochemical database on mud and sand transported by the pearl river zhujiang and coastal rivers of se china clay mineralogy and bulk geochemistry of fluvial sediments are used to trace changes in weathering intensity across south china a vast tropical to subtropical region characterized by a strong longitudinal rainfall gradient the control of climate induced weathering is manifest in the mineralogy and geochemistry of pearl river mud although mud and to a greater extent sand composition are also largely affected by the lithology of parent rocks the depletion in mobile alkali and alkaline earth metals increases steadily from the drier western part of the pearl river catchment to the wetter eastern part and is most marked in easternmost tributaries of the pearl river and in southern coastal rivers na and ca are the most strongly depleted elements in pearl river sediments whereas the low concentration of ca and mg in river sand of coastal se china also reflects the felsic character of parent rocks in the cathaysia block eastward increasing weathering conditions are most clearly highlighted by the progressive eastward increase in kaolinite across the pearl river catchment whereas the weathering effect in sand is blurred by quartz addition owing to widespread recycling of quartz rich siliciclastic source rocks this actualistic case study from a region characterized by monsoonal climate underscores the care that should be taken while inferring climatic conditions from the geochemical composition of sediments and sedimentary rocks which is controlled by multiple geological factors including the felsic versus mafic character of parent rocks and the presence of extensive carbonate or siliciclastic covers in source areas most reliable indications are provided by the kaolinite illite chlorite ratio and by al indices for na ca mg and sr which consistently increase eastward across south china thus paralleling the marked eastward increase in monsoonal precipitation towards the coast

melting relations of peridotite and the density crossover in planetary mantles melting relations of primitive peridotite were studied up to 25 gpa the change of the liquidus phase from olivine to majorite occurs at 16 gpa we confirmed the density crossover of the feo rich peridotite melt and the equilibrium olivine fo90 at 7 gpa sinking of equilibrium olivine fo95 in the primitive peridotite melt was observed up to 10 gpa the compression curves of feo rich peridotitic and komatiite melts reported in this and earlier work suggest that the density crossover in the earth s mantle will be located at 11 12 gpa at 2000 c consistent with an previous estimation by c b agee and d walker the density crossover can play a key role in the moon and the terrestrial planets such as the earth venus and mars majorite and some fraction of melt could have separated from the ascending diapir and sunk downwards at the depths below the density crossover this process could have produced a garnet rich transition zone in the earth s mantle the density crossover may exist in the feo rich lunar mantle at around the center of the moon the density crossover which exists at the depth of 600 km in the martian mantle plays a key role in producing a fractionated mantle which is the source the parent magmas of the snc meteorites

slope form erosion and hydrology in some belizean karst depressions detailed slope surveys were made in seven karst depressions in central belize four major slope types were identified inclined bedrock slopes staircases broken cliffs and talus slopes depression bases are dominated by inclined bedrock and talus slopes midslopes largely by broken cliffs and near hill summits by staircases erosional weight loss tablets deployed in 1975 1981 and 1980 1985 show significant variations between the different slope types with a maximum near depression bases throughfall measurements in 1980 and 1985 show that midslope and near summit sites receive 10 20 per cent less water than do depression bases surface runoff monitored using coloured dyes is of limited distance and duration but still contributes to surface corrosion and morphology vadose seepage monitored by tracing water from the surface to a small shallow cave is rapid and subsurface corrosion exceeds that at the surface overall near surface form and process are consistent with hydrological models of depression development williams 1983 1985 and surface processes contribute significantly to overall depression form moreover surface activity complements that in the subcutaneous zone by directing recharge into the epikarstic aquifer