nitrogen and carbon isotopic composition in the diamonds of mbuji mayi zaire the concentration and isotopic composition of nitrogen measured in large diamonds gram size from the mbuji mayi kimberlite district zaire show a large range of variation 100 n 2100 ppm 11 2 15n 6 0 the15n depleted nitrogen is associated with the higher nitrogen concentrations the large diamonds are individually rather homogeneous in13c range of 13c 0 9 while variations occur within small octahedral diamonds from the same district range up to 5 8 the total range of 13c variation is about the same for the large diamonds 10 5 13c 5 5 the small octahedral diamonds 10 13c 4 6 and the carbonates from local kimberlites 11 8 13c 5 5 the diamond carbon isotopic data could indicate a complex story of crystallization within a deep seated system fractionating its carbon isotopes the nitrogen results indicate that nitrogen in diamonds is on the average markedly depleted in15n weighted average 5 15 relative to atmosphere sediments and upper mantle

most diamonds were created equal abstract diamonds crystallize deep in the mantle 150 km leaving their carbon sources and the mechanism of their crystallization debatable they can form from elemental carbon by oxidation of reduced species e g methane or reduction of oxidized ones e g carbonate bearing minerals or melts in response to decreasing carbon solubility in melts or fluids or due to changes in ph the mechanism of formation is clear for fibrous diamonds that grew from the carbonate bearing fluids trapped in their microinclusions however these diamonds look different and based on their lower level of nitrogen aggregation are much younger than most monocrystalline mc diamonds in the first systematic search for microinclusions in mc diamonds we examined twinned crystals macles assuming that during their growth microinclusions were trapped along the twinning plane visible mineral inclusions 10 m and nitrogen aggregation levels in these clear macles are similar to other mc diamonds we found 32 microinclusions along the twinning planes in eight out of 30 diamonds eight inclusions are orthopyroxene four contain 50 k2o probably as k2 mg ca co3 2 but the major element compositions of the remaining 20 are similar to those of carbonate bearing high density fluids hdfs found in fibrous diamonds we conclude that the source of carbon for these macles and for most diamonds is carbonate bearing hdfs similar to those found here and in fibrous diamonds combined with the old ages of mc diamonds up to 3 5 ga our new findings suggest that carbonates have been introduced into the reduced lithospheric mantle since the archaean and that the mechanism of diamond formation is the same for most diamonds

investigations of soil cracking and preferential flow in a weighing lysimeter filled with cracking clay soil an improved understanding of deep drainage processes in irrigated cracking soils is needed for sustainable irrigation management to investigate the effect of crack dynamics and macropore flow on drainage in cracking soils a series of irrigation experiments was carried out in a weighing lysimeter subsurface soil cracks of the initially very dry soil were investigated with a videoscope and changes in the surface expression of cracks in response to irrigation events were monitored by time lapse photography a bromide tracer was applied to one irrigation event variations in the combined soil and moisture mass and the volume of drainage out of the soil column was logged and the drainage ec and bromide content were determined no drainage occurred out of the soil column during the first 3 out of 6 irrigation events even though substantial surface runoff into the cracks occurred and at least initially soil cracks provided an uninterrupted flow path through the profile the breakthrough of the bromide tracer as well as an initially low ec of the drainage water indicate that preferential flow accounted for a substantial part of the first of the two drainage events even though the soil cracks were sealed on the surface at the onset of the irrigation causing the drainage the results show that lateral infiltration of macropore flow into the soil matrix can be substantial and should not be neglected while simulating macropore flow and deep drainage in cracking soils the results also indicate that soil cracks can remain pathways for preferential flow even after they are closed at the soil surface the type of water application appears to have an impact on the location of crack formation with flood irrigation favouring reappearance of cracks at previous crack locations and simulated rainfall resulting in shifting crack locations

a method for measuring the development of surface cracks in soils application to crack development after lowland rice abstract surface cracks develop in many clay soils as they dry since they are difficult to adequately sample in most volumetric samples it is useful to measure them so that volumetric measurements of water content for example can be corrected a method for measuring cracks in soils is described a transect consisting of six linked semi circles each of 1 m diameter is used to count intercepts with the cracks which allows estimation of the length of cracks per unit area la the semi circular shape avoids any bias due to preferred orientation of the cracks to minimise the effort required to achieve the greatest accuracy which depends on the number of cracks counted and not the transect length 50 intercepts are counted per replicate transect after which any remaining intercepts with the current semi circle are counted in addition crack depth and surface width are measured at a total of 60 intercepts over all replicate transects this allows calculation of means for depth and width mean vertical cross sectional area and the volume of crack per unit area can be calculated by assuming a rectangular triangular or square root shape model for the crack cross section the depth functions of la and vv crack volume per unit volume can also be calculated although the latter requires assumptions about crack shape the method is illustrated by application to two soils puddled for rice during the first four week drying after field drainage

ci chondrite like clasts in the nilpena polymict ureilite implications for aqueous alteration processes in ci chondrites abstract we have carried out a detailed petrographic and mineralogical study of carbonaceous chondrite matrix clasts in the nilpena polymict ureilite the bulk compositions of a number of clasts determined by electron microprobe show that they have close affinities to ci chondrite matrix and differ substantially from cm matrix material transmission electron microscopy studies show that the mineralogy of the clasts is also consistent with ci chondrite matrix indicated by the presence of saponitic smectite clays serpentine magnetite pentlandite pyrrhotite and ferrihydrite phases such as tochilinite and cronstedtite diagnostic of cm matrix are absent based on the oxygen isotopic composition of the matrix the phase chemistry and the bulk clast chemistry we suggest that the matrix clasts in nilpena represent material which is less altered than orgueil the difference in oxygen isotopic composition of the nilpena matrix clasts from ci chondrites may be because the clasts underwent alteration at a lower water rock ratio increased alteration of nilpena type material should result in the oxidation of fe bearing saponite and sulfides to produce ferrihydrite and more mg rich saponite such as that in orgueil matrix although the presence of ci like matrix clasts in the polymict ureilites suggests that ci matrix may have been a precursor to the ureilites in detail this seems highly unlikely the trace element and carbon isotopic compositions of ureilites are incompatible with a significant ci chondrite precursor we suggest that the ci like matrix clasts in nilpena represent a component of a late accreting veneer on the ureilite parent body

hillslope run off thresholds with shrink swell clay soils irrigation experiments on 12 instrumented field plots were used to assess the impact of dynamic soil crack networks on infiltration and run off during applications of intensity similar to a heavy rainstorm water was seen being preferentially delivered within the soil profile however run off was not observed until soil water content of the profile reached field capacity and the apertures of surface connected cracks had closed 60 electrical resistivity measurements suggested that subsurface cracks persisted and enhanced lateral transport even in wet conditions likewise single ring infiltration measurements taken before and after irrigation indicated that infiltration remained an important component of the water budget at high soil water content values despite apparent surface sealing overall although the wetting and sealing of the soil profile showed considerable complexity an emergent property at the hillslope scale was observed all of the plots demonstrated a strikingly similar threshold run off response to the cumulative precipitation amount copyright 2014 john wiley sons ltd

martian gases in an antarctic meteorite significant abundances of trapped argon krypton and xenon have been measured in shock altered phases of the achondritic meteorite elephant moraine 79001 from antarctica the relative elemental abundances the high ratios of argon 40 to argon 36 2000 and the high ratios of xenon 129 to xenon 132 2 0 of the trapped gas more closely resemble viking data for the martian atmosphere than data for noble gas components typically found in meteorites these findings support earlier suggestions made on the basis of geochemical evidence that shergottites and related rare meteorites may have originated from the planet mars

stable isotope genealogy of meteorites one of the oldest problems in meteoritics is that of taxonomically grouping samples in recent years the use of isotopes particularly oxygen isotopes has proved very successful in this respect other light element systematics potentially can perform the same function for example nitrogen in iron meteorites and nitrogen and carbon in ureilites and snc meteorites these measurements will serve to extend and augment existing classification schemes and provide clues to the nature of meteorite parent bodies they can also aid in the recognition of the isotopic signatures relating to inaccessible regions of the earth

ureilites trace element clues to their origin carbonaceous vein separates from kenna and havero as well as bulk kenna were analyzed by rnaa for ag au bi br cd cs ge in ir ni pd os rb re sb se te tl u and zn the data are reviewed together with four earlier chicago analyses of bulk ureilites linear regressions confirm the presence of two metal components with the following cl normalized ratios ir ni 14 6 1 ge ni 5 4 2 4 au ni 2 3 0 9 the high ir component is enriched in vein separates and hence belongs to veins the lowir component belongs to the ultramafic rock vein material is enriched in all elements analyzed by us except zn and accounts for most of the c noble gases and presumably siderophiles in the meteorite most of the properties of ureilites apparently can be explained by the cumulate model of berkley et al 1980 with certain modifications comparison of ureilites with three other ultramafic rocks from different planets earth s mantle lunar dunite and chassigny suggests that the ureilite parent body had a primitive chondritic composition similar to c3v chondrites but richer in metal and carbon it melted causing depletion of incompatibles to a mean abundance of 0 02 cl and incomplete segregation of metal fes and c fractional crystallization or melting of metal in the presence of s and c apparently can explain the fractionations of ir re ni au and perhaps ge obviating the need for extraneous sources of vein metal or unusual parent body compositions noble gases from the parent material may have been retrapped in carbon during magmatism provided the system was closed

the role of fluid pressure and diagenetic cements for porosity preservation in triassic fluvial reservoirs of the central graben north sea anomalously high porosities and permeabilities are commonly found in the fluvial channel sandstone facies of the triassic skagerrak formation in the central north sea at burial depths greater than 3200 m 10 499 ft from which hydrocarbons are currently being produced the aim of our study was to improve understanding of sandstone diagenesis in the skagerrak formation to help predict whether the facies with high porosity may be found at even greater depths the skagerrak sandstones comprise fine to medium grained arkosic to lithic arkosic arenites we have used scanning electron microscopy petrographic analysis pressure history modeling and core analysis to assess the timing of growth and origin of mineral cements with generation and the impact of high fluid pressure on reservoir quality our interpretation is that the anomalously high porosities in the skagerrak sandstones were maintained by a history of overpressure generation and maintenance from the late triassic onward in combination with early microquartz cementation and subsequent precipitation of robust chlorite grain coats increasing salinity of pore fluids during burial diagenesis led to pore filling halite cements in sustained phreatic conditions the halite pore filling cements removed most of the remaining porosity and limited the precipitation of other diagenetic phases fluid flow associated with the migration of hydrocarbons during the neogene is inferred to have dissolved the halite locally dissolution of halite cements in the channel sands has given rise to megapores and porosities of as much as 35 at current production depths

criteria for the recognition of salt pan evaporites layered evaporites can accumulate in 1 ephemeral saline pans 2 shallow perennial lagoons or lakes and 3 deep perennial basins criteria for recognizing evaporites deposited in these settings have yet to be explicitly formulated the characteristics of the ephemeral saline pan setting have been determined by examining eight holocene halite dominated pans salt pans and their deposits marine and non marine from the u s mexico egypt and bolivia these salt pans are typified by alternating periods of flooding resulting in a temporary brackish lake evaporative concentration when the lake becomes saline and desiccation which produces a dry pan fed only by groundwater the resulting deposits consist of alternating layers millimetres to decimetres of halite and mud the layers of halite are characterized by 1 vertical and horizontal cavities rounded crystal edges and horizontal truncation surfaces due to dissolution during flooding 2 vertical chevrons and cornets grown syntaxially on the bottom during the saline lake stage 3 halite cements overgrowths and euhedral cavity linings and disruption of layering into metre scale polygons produced during the desiccation stage the muddy interbeds are characterized by displacive growth of halite during the desiccation stage immediately below the surface of the pan the halite layers are matured by repeated episodes of dissolution and diagenetic crystal growth this results in porous crusts with patches of chevron and cornet crystals truncated by dissolution clear diagenetic halite cement and internal sediment these layers of mature halite closely resemble the patchy cloudy and clear textures of ancient halite deposits holocene salt pans are known to cover thousands of square kilometres and cap halite deposits hundreds of metres thick so they are realistic models for ancient evaporites in scale e g permian salado formation of new mexico texas which preserves many primary salt pan features

metamorphic origin of ore forming fluids for orogenic gold bearingquartz vein systems in the north american cordillera constraints froma reconnaissance study of δ15n δd and δ18o the western north american cordillera hosts a large number of gold bearing quartz vein systems from the mother lode of southern california through counterparts in british columbia and southeastern alaska to the klondike district in central yukon these vein systems are structurally controlled by major fault zones which are often reactivated terrane bounding sutures that formed in orogens built during accretion and subduction of terranes along the continental margin of north america mineralization ages span mid jurassic to early tertiary and encompass much of the evolution of the cordilleran orogen nitrogen contents and 15n values of hydrothermal micas from veins are between 130 and 3 500 ppm and 1 7 to 5 5 per mil respectively these values are consistent with fluids derived from metamorphic dehydration reactions within the phanerozoic accretion subduction complexes which have 15n values of 1 to 6 per mil the 18o values of gold bearing vein quartz from different locations in the cordillera are between 14 6 and 22 2 per mil but are uniform for individual vein systems the d values of hydrothermal micas are between 110 and 60 per mil ore fluids have calculated 18o values of 8 to 16 per mil and d values of 65 to 10 per mil at an estimated temperature of 300 c d values of ore fluids do not show any latitudinal control these results indicate a deep crustal source for the ore forming fluids most likely of metamorphic origin low dh2o values of 120 to 130 per mil for a hydrous muscovite from the sheba vein in the klondike district reflect secondary exchange between recrystallizing mica and meteoric waters collectively the n h and o isotope compositions of ore related hydrothermal minerals indicate that the formation of these gold bearing veins involved dilute aqueous carbonic and nitrogen bearing fluids that were generated from metamorphic dehydration reactions at deep crustal levels these data are not consistent with either mantle derived fluids or granitoid related magmatic fluids nor do they support a model involving deeply circulated meteoric water

40ar39ar laser probe dating of individual clinopyroxene inclusions in premier eclogitic diamonds abstract the ages of seven individual clinopyroxene inclusions in premier diamonds of eclogitic association have been determined using the 40 ar 39 ar dating technique syngenetic inclusions weighing between 10 and 130 g were exposed on cleaved surfaces of the diamonds and analysed using a laser probe the inclusion ages were found to be in the range 1111 35 to 1254 38 ma with an average of 1185 94 ma the ages obtained are in good agreement with previous determinations made on aggregates of eclogitic inclusions from premier diamonds and demonstrate the applicability of the laser probe to dating individual diamond inclusions

clay fine fissuring monitoring using miniature geo electrical resistivity arrays this article describes a miniaturised electrical imaging resistivity tomography technique to map the cracking pattern of a clay model the clay used was taken from a scaled flood embankment built to study the fine fissuring due to desiccation and breaching process in flooding conditions the potential of using a miniature array of electrodes to follow the evolution of the vertical cracks and number them during the drying process was explored the imaging technique generated two dimensional contoured plots of the resistivity distribution within the model before and at different stages of the desiccation process the change in resistivity associated with the widening of the cracks were monitored as a function of time experiments were also carried out using a selected conductive gel to slow down the transport process into the cracks to improve the scanning capabilities of the equipment the main vertical clay fissuring network was obtained after inversion of the experimental resistivity measurements and validated by direct observations

metasomatic origin of diamonds in the world s largest diamondiferous eclogite article i nfo the world s largest diamondiferous eclogite 8 8 kg ud 111 02 from the udachnaya kimberlite siberia is the subject of this investigation high resolution x ray computed tomography hrxct chemistry of host minerals and diamond inclusions stratigraphy of the diamonds cathodoluminescence zoning and carbon isotopes have been obtained hrxct images 3 d models and subsequent detailed dissection of this group b eclogite revealed linear distributions of diamonds along alteration zones both unusual multiple diamond clusters with dodecahedral morphologies and distinctive internal zoning recorded by cathodoluminescence analyses are indicative of multiple stages of diamond growth and resorption in ud 111 02 carbon isotope ratios 13 c of 16 diamonds have a total range of 7 2 0 to 9 2 with the majority at 5 4

the case for a martian origin of the shergottites nitrogen and noble gases in eeta 79001 abstract nitrogen and noble gases were measured in samples of a glass inclusion and the surrounding basaltic matrix from the antarctic shergottite eeta 79001 a nitrogen component trapped in the glass but not present in the matrix has a 15n value at least as high as 190 ratios of40ar 14n and15n 14n in the glass are consistent with dilution of a martian atmospheric component 15n 620 160 40ar 14n 0 33 0 03 by either terrestrial atmosphere adsorbed on the samples or by indigenous nitrogen from the minerals of the rock trapped noble gases in the glass reproduce within error the elemental and isotopic compositions measured in mars atmosphere by viking and are in general agreement with previous measurements except for much lower abundances of neutron generated krypton and xenon isotopes the most reasonable explanation at the present time for the noble gas pattern and the isotopically heavy nitrogen is that a sample of martian atmosphere has been trapped in the eeta 79001 glass and that this meteorite and thus the shergottites and probably the nakhlites and chassignites as well originated on mars nitrogen in the non glassy matrix of eeta 79001 amounts to less than 0 5 ppm and has a spallation corrected 15n value in the range 0 to 20 it may reflect indigenous nitrogen in the basalt or a mixture of indigenous and adsorbed terrestrial nitrogen spallogenic noble gases yield single stage exposure ages between 400 000 and 900 000 years depending on irradiation geometry trapped argon may have an unusually low36ar 38ar ratio trapped krypton except for a small excess at80kr is smoothly mass fractionated with respect to either terrestrial or chondritic kr the trapped xenon composition is consistent with addition of neutron capture radiogenic and fissiogenic isotopes to a base composition resembling terrestrial atmospheric xe the elemental84kr 132xe ratio of 25 is close to the terrestrial value and very different from the chondritic ratio

carbon isotopes in xenoliths from the hualalai volcano hawaii and the generation of isotopic variability abstract the isotopic composition of carbon has been determined in a suite of xenoliths from lava of the 1800 1801 kaupulehu eruption of hualalai volcano hawaii several lithologies are represented in the suite including websterite dunite wehrlite pyroxenite and gabbro in addition there are composite xenoliths in which contacts between lithologies are preserved most of the xenoliths represent deformed cumulates the contact relations in the composite samples indicate that the lithologies originated from the same source region which based on pressures determined from fluid inclusions is estimated to be at a depth of 20 km or near the crust mantle boundary samples were heated in steps from 200 to 1475 c to obtain separation of the different carbonaceous phases and the isotopic composition of carbon released at each step was determined grossular glass was found to be a suitable flux to fuse refractory samples upon heating carbon exhibits the typical bimodal evolution behavior observed in other studies of xenoliths and basalts carbon extracted from all samples at temperatures below 900 c is characterized by a 13 c of about 25 vs pdb and is thought to be composed dominantly of graphitic and organic material which is known to be present on virtually all cracks the 13 c of the carbon fraction extracted at 1200 c and above from wehrlite and dunite is in the range 1 5 to 5 2 whereas that extracted from websterite ranges from 22 to 26 similarly in one composite sample the compositions of dunite and websterite were found to be 2 4 and 7 0 respectively the large difference can be associated with specific petrographic features unique to each lithology in wehrlite and dunite carbon exists mostly as co 2 rich inclusions in arrays representing partially annealed microcracks the websterite xenoliths contain megascopic zones of large irregularly shaped inclusions the zones traverse entire thinsections and are interpreted to represent fractures annealed at depth most of the carbon is believed to exist in the inclusion rich zones and to consist of carbonaceous material precipitated from fluid the observations and isotopic results demonstrate that isotopic variability can be generated by multistage fractionation processes such as degassing of co 2 from magma and precipitation of co 2 rich fluids to form graphitic compounds such processes operated over regions the scales of which were determined by style and intensity of deformation and by lithology

diagenetic evolution of aptian evaporites in the namibe basin south west angola the widespread and dissected nature of the angolan gypsiferous salt residuals offers a uniquely detailed view of the lateral and vertical relations inherent to secondary evaporite textures which typify exhumed salt masses worldwide such secondary textures are sometimes misinterpreted as primary evaporite textures thin metre scale and patchy dome like gypsum accumulations are well exposed within strongly incised present day river valleys along the eastern margin of the namibe and benguela basins south west angola these sections are time equivalent to the main basinward subsurface evaporites aptian loeme formation which mostly consist of halite the gypsum here called the bambata formation is interpreted to represent the final residual product of fractional dissolution and recrystallization of the halite mass that occurred during late cretaceous margin uplift and continues today this halite underwent multiple episodes of diagenetic alteration between its deposition and its final exhumation leading to the formation of various secondary gypsum fabrics and solution related karst and breccia textures that typify the current evaporite outcrop four different diagenetic gypsum fabrics are defined thinly bedded alabastrine nodular alabastrine displacive selenite rosettes and fibrous satin spar gypsum current arid conditions are responsible for a thin weathered crust developed at the top of the outcropping gypsum but the fabrics in the main core of the current at surface evaporite unit mostly formed during the telogenetic stage of uplift prior to complete subaerial exposure alteration occurred as various dissolving and rehydrating saline minerals encountered shallow aquifers in the active phreatic and vadose zones geomorphological and petrographic analyses mostly based on the cross cutting relations and crystallographic patterns in the outcrop are used to propose a sequence of formation of these different fabrics

synsedimentary dissolution pipes and the isolation of ancient bacteria and cellulose coarse clear halite from synsedimentary dissolution pipes in the permian salado formation in southeastern new mexico usa yielded viable halotolerant bacteria and well preserved cellulose believed to be permian in age here we show that geologic and hydrologic conditions have isolated these rocks since permian time pipes were dissolved most likely along cracks created by thermal contraction or desiccation and the boundaries of salt polygons saucers on exposed salado formation salt pan surfaces down to the level of the water brine table macropores developed at the brine level in some horizons as the water level rose coarse halite cemented the open space fluid inclusions millimeter scale trapped bacteria which were probably in a spore state as well as cellulose inclusion water from pipes in some cycles may have isotopic values reflecting permian meteoric water while other cycles may show evaporated permian seawater exposure surfaces are more prominent in the upper part of salado formation depositional cycles due to basin desiccation as indicated by cracks and dish shaped laminae clays were concentrated on many exposure surfaces by floods wind and dissolution dissolution pipes formed from these surfaces and a synsedimentary age is confirmed by undisturbed overlying halite beds salado formation halite has very low permeability 10 22 m 2 effectively preventing significant fluid flow and passage of fluids through the formation either to recrystallize salt or to introduce modern bacteria stratigraphic relationships halite textures fluid inclusion chemistry and hydraulic properties are all consistent with a synsedimentary origin of the dissolution pipes their crystals and the bacteria and cellulose recovered from the salado formation

latter day origin of diamonds of eclogitic paragenesis syngenetic mineral inclusions in diamonds provide the best means of determining their origin among such inclusions the peridotitic paragenesis of olivine orthopyroxene and chrome pyrope garnet is on average far more abundant than the eclogitic paragenesis of pyrope almandine garnet and omphacitic clinopyroxene1 3 diamonds of peridotitic paragenesis from the 100 myr old kimberley and finsch kimberlites in southern africa were previously shown to have originated in 150 200 km thick lithosphere beneath the kaapvaal craton 3 300 myr ago4 5 at a few localities such as the premier kimberlite in southern africa and the argyle lamproite in northwestern australia diamonds of eclogitic paragenesis predominate6 8 allowing recovery of sufficient material for complementary analysis the results of which are reported here eclogitic garnet and clinopyroxene inclusions in premier and argyle diamonds yield sm nd isochron ages of 1 150 and 1 580 myr respectively compared with host diatreme emplacement ages9 10 of 1 100 1 200 myr eclogitic inclusion ages and precursor isotopic signatures indicate a second genetically distinct origin of diamonds apparently related in time and space to kimberlite or lamproite magmatism

stable isotope o h s c and n systematics of quartz vein systems in the turbidite hosted central and north deborah gold deposits of the bendigo gold field central victoria australia constraints on the origin of ore forming fluids the central and north deborah gold deposits are located in one of 15 mining centers of the bendigo gold field central victoria australia a major world class gold province developed in a turbidite terrane gold mineralization occurs primarily within domes and reverse fault systems in multiply deformed lower ordovician metaturbidites deformation and thrusting occurred between 450 and 420 ma coevally with regional metamorphism at zeolite to greenschist facies in the central and north deborah deposits six stages of quartz veining each with characteristic geometry and mineral paragenesis developed sequentially stages 1 2 and 4 are gold bearing whereas stages 3 5 and 6 are barren gold related quartz veins were deposited at temperatures of 350 25 c based on oxygen isotope geothermometry of silicate phases quartz muscovite and sulfur isotope compositions of coexisting sulfide mineral pairs sphalerite galena this result is consistent with temperatures inferred from fluid inclusions the 18o values of gold bearing vein quartz and coexisting hydrothermal muscovite are uniform within and between the six vein stages ranging from 15 9 to 17 2 per mil and 11 6 to 12 8 per mil respectively the d values of hydrothermal muscovites are also uniform at 68 to 55 per mil ore fluids have calculated 18o values of 8 to 11 per mil and d values of 37 to 17 per mil pyrite of synsedimentary diagenetic origin in slate and sandstone displays sulfur isotope compositions of 23 5 to 8 0 per mil and 0 1 to 11 9 per mil respectively sulfides from gold bearing quartz veins have a range of 7 4 to 8 1 per mil median ca 2 5 the relatively uniform vein pyrites indicate a large uniform sulfur source most likely from desulfidation reactions of sulfide minerals interaction of the ore forming fluid with depleted sulfides at the site of deposition may have shifted the sulfur isotope signatures of source sulfides to more negative values carbon isotope compositions of carbonates range from 5 1 to 9 0 per mil median ca 6 5 nitrogen concentrations and nitrogen isotope compositions of hydrothermal muscovite from quartz veins are 652 to 895 ppm and 2 84 to 4 49 per mil respectively collectively the data define a band in n content vegh rsus 15n coordinate space from higher n and lower 15n in the phanerozoic metasedimenary hosted central and north deborah gold deposits to lower n and higher 15n in predominantly meta igneous hosted neoarchean gold provinces collectively the h o s c and n isotope compositions of ore related hydrothermal minerals indicate that the dilute aqueous carbonic and n bearing ore forming fluids were generated from metamorphic dehydration reactions at deeper crustal levels and were variably influenced by exchange with wall rocks during transport to the site of deposition this genetic model for the central and north deborah gold deposits is consistent with other turbidite hosted lode gold deposits and counterparts in volcanic plutonic terranes in contrast these data are not consistent with either mantle derived fluids or magmatic fluids nor do they support a deeply circulated meteoric surface water model for vein formation

hydrology and hydraulic properties of a bedded evaporite formation the permian salado formation in the delaware basin of new mexico is an extensively studied evaporite deposit because it is the host formation for the waste isolation pilot plant a repository for transuranic wastes geologic and hydrologic studies of the salado conducted since the mid 1970 s have led to the development of a conceptual model of the hydrogeology of the formation that involves far field permeability in anhydrite layers and at least some impure halite layers pure halite layers and some impure halite layers may not possess an interconnected pore network adequate to provide permeability pore pressures are probably very close to lithostatic pressure in the near field around an excavation dilation creep and shear have created and or enhanced permeability and decreased pore pressure whether flow occurs in the far field under natural gradients or only after some threshold gradient is reached is unknown if far field flow does occur mean pore velocities are probably on the order of a meter per hundreds of thousands to tens of millions of years flow dimensions inferred from most hydraulic test responses are subradial which is believed to reflect channeling of flow through fracture networks or portions of fractures that occupy a diminishing proportion of the radially available space or through percolation networks that are not saturated fully interconnected this is probably related to the directional nature of the permeability created or enhanced by excavation effects inferred values of permeability cannot be separated from their associated flow dimensions therefore numerical models of flow and transport should include heterogeneity that is structured to provide the same flow dimensions as are observed in hydraulic tests modeling of the salado formation around the wipp repository should also include coupling between hydraulic properties and the evolving stress field because hydraulic properties change as the stress field changes

water movement and soil swelling in a dry cracked vertisol abstract vertisols are widely used for irrigated rice in the senegal river basin where farmers are increasingly reporting problems with soil salinization water movement at the onset of the growing season when soils are dry and cracked may have a large impact on soil salinity and water economy water movement and soil swelling processes were studied in a dry cracked vertisol in the senegal river valley surface irrigation and simulated rainfall intensity 88 mm h 1 on cracked 2 25 m 2 plots crack width 0 01 0 02 m crack depth 0 3 m resulted in crack closure within 4 5 h starting at the soil surface soil swelling was separated into two components 1 swelling of the 0 01 0 02 m border zone of a soil island soil mass distinctively separated by cracks and 2 swelling of the rest of the soil island as a whole soil swelling was heterogeneous with a very rapid expansion of the border zone at the moment of crack closure the relative contributions of these two components to crack closure were respectively 80 90 and 10 20 24 h later these percentages changed slightly only maximum bulk linear shrinkage determined at the field level was only 7 results indicate the importance of rapid local heterogeneous swelling processes to water flow into cracked vertisol resulting in limited bypass flow use of bulk shrinkage curves and assumptions on isotropy of shrinkage and swelling processes when modelling water and solute flow in cracked vertisols should therefore be done with great care

first evidence of hydrous silicic fluid films around solid inclusions in gem quality diamonds abstract diamonds form from fluids or melts circulating at depth in the earth s mantle analysis of these fluids is possible if they remain entrapped in the diamond during its growth but this is rarely observed in gem quality stones we provide the first evidence that typical mineral inclusions in gem quality diamonds from the siberian and kaapvaal cratons are surrounded by a thin film of hydrous silicic fluid of maximum thickness 1 5 m the fluid contains si 2 o oh 6 si oh 4 and molecular h 2 o and was identified using confocal micro raman spectroscopy and synchrotron based x ray tomographic microscopy as the solid mineral inclusions have both peridotitic and eclogitic affinities and occur in two cratonic regions our results demonstrate the strong connection between water rich fluids and the growth of gem quality lithospheric diamonds the presence of the fluid films should be taken into account for a proper evaluation of h 2 o contents in the mantle based on h 2 o contents in solid inclusions and for a robust assessment of diamond formation pressures based on the residual pressures of the inclusions

associated chemical and carbon isotopic composition variations in diamonds from finsch and premier kimberlite south africa abstract the carbon isotopic composition of 66 inclusion containing diamonds from the premier kimberlite south africa 93 inclusion containing diamonds and four diamonds of two diamond bearing peridotite xenoliths from the finsch kimberlite south africa was measured the data suggest a relationship between the carbon isotopic composition of the diamonds and the chemical composition of the associated silicates for both kimberlites similar trends are noted for diamonds containing peridotite suite inclusions p type and for diamonds containing eclogite suite inclusions e type higher 13c p type diamonds tend to have inclusions lower in sio2 ol al2o3 opx gt cr2o3 mgo mg mg fe ol opx gt and higher in feo ol opx gt and cao gt higher 13c e type diamonds tend to have inclusions lower in sio2 al2o3 gt cpx mgo mg mg fe gt na2o k2o tio2 cpx and higher in cao ca ca mg gt cpx consideration of a number of different models that have been proposed for the genesis of kimberlites their xenoliths and diamonds shows that they are all consistent with the conclusion that in the mantle regions exist that are characterized by different mean carbon isotopic compositions

variations in the hydrology of an underdrained clay hillslope abstract this paper presents evidence for the existence of the hydrological routes by which rainfall moves to the drainage system through clay soil at wytham in oxfordshire uk focusing particularly on the hydrology of the a horizon tile drain discharge was continuously monitored at the site and piezometer and tensiometer arrays were installed over the hillslope in order to study the spatial variations in hydrological response to rainfall a combination of dye tracing ring and tension infiltrometry was used to determine the variations in infiltration capacity over the hillslope and to characterise macropore flow the study established that both lateral and vertical macropore flow through inter pedal cracks are an important component of the hydrology of an underdrained site two regions of macropore discontinuity were identified in the soil profile at the base of the rotovated layer and at the base of the a horizon saturated layers developed at both these locations during rainfall over the winter a surface seal developed at the base of the hillslope tension infiltrometer measurements suggested that once the soil surface was sealed earthworm burrows of 6 mm diameter were responsible for up to 86 of the vertical infiltration into the a horizon temporal variations in hydrological characteristics were noted due to the swelling of the clay soil as it wetted up during the autumn and winter period lateral flow took place by a combination of macropore and preferential routes in saturated regions within the a horizon during periods of winter drainflow lateral macropore flow in the top 10 cm of the soil was the most important lateral route for water and was initiated by a critical pore water pressure of 0 3 kpa deeper lateral flow was limited and occurred predominantly through the soil matrix during autumn drainflow however inter pedal cracks were well developed through the a horizon and lateral flow at the base of the a horizon was dominant

biophysical effects on soil crack morphology in a faunally active dryland vertisol abstract faunal behavior in dryland ecosystems may physically influence swelling soil hydrologic and pedologic processes due to its contributions to soil crack formation in order to provide a physical link between this faunal activity and pedological processes we use a resin visualization technique and x ray imaging to characterize the biomechanical influences of biocompaction mega meso herbivores and bioturbation termites on 3d crack morphology and topology in a faunally active dryland vertisol system results show increased soil cracking intensity due to faunal influence however this increased cracking diverged by faunal influence bioturbation creates surficial shallow extensive crack networks while biocompaction creates systematic deep narrow crack networks compared to a reference soil biocompacted soils also exhibit a memory of past wetting and drying events via vertically layered crack morphologies despite differences in these crack magnitudes between the faunal influences crack structures show morphological and topological similarity as a topological network these persistent differences in field crack systems may potentially create convectively driven hotspots of enhanced water and carbon gas transport in dryland ecosystems as a result of crack formation highlighting the importance of considering fracture behavior in both an ecological atmospheric and pedologic context

origin of depositional cycles in a permian saline giant the salado mcnutt zone evaporites of new mexico and texas two types of metre scale depositional cycles have been recognized within the mcnutt potash zone of the permian salado evaporites the cycles record progressive drawdown and concentration of brine in a shallow marginal marine basin type i cycles made of basal carbonate siliciclastic mudstone then anhydrite polyhalite pseudomorphous after primary gypsum overlain by halite and capped by muddy halite are interpreted as marine sea water dominated they formed by massive spillover of sea water through a connection with the permian ocean at high relative sea level stands lagoonal mudstone and anhydrite polyhalite after subaqueous gypsum followed by relative lowering of sea level and gradual basin restriction shallow saline lake and salt pan halite and ending with a desiccated basin isolated from the permian ocean salt pan halite and saline mudflat muddy halite cycle cap type ii cycles occur between the type i cycles and contain halite overlain transitionally by muddy halite they record a temporal evolution of environments from a shallow saline lake to an ephemeral salt pan saline mudflat complex and are interpreted as continental dominated sequences sourced by meteoric inflow from surrounding land areas that mixed with variable amounts of sea water either residual or introduced into the salado basin by seepage the vertical stacking of type i cycles is best explained by periodic invasions of sea water into the salado basin coincident with eustatic sea level rises the continental dominated type ii cycles formed during intervening periods of eustatic sea level fall and low stands the maximum time interval between major marine incursions is an average of 10 5 yr

modeling multidomain hydraulic properties of shrink swell soils shrink swell soils crack and become compacted as they dry changing properties such as bulk density and hydraulic conductivity multidomain models divide soil into independent realms that allow soil cracks to be incorporated into classical flow and transport models incongruously most applications of multidomain models assume that the porosity distributions bulk density and effective saturated hydraulic conductivity of the soil are constant this study builds on a recently derived soil shrinkage model to develop a new multidomain dual permeability model that can accurately predict variations in soil hydraulic properties due to dynamic changes in crack size and connectivity the model only requires estimates of soil gravimetric water content and a minimal set of parameters all of which can be determined using laboratory and or field measurements we apply the model to eight clayey soils and demonstrate its ability to quantify variations in volumetric water content as can be determined during measurement of a soil water characteristic curve and transient saturated hydraulic conductivity ks as can be measured using infiltration tests the proposed model is able to capture observed variations in ks of one to more than two orders of magnitude in contrast other dual permeability models assume that ks is constant resulting in the potential for large error when predicting water movement through shrink swell soils overall the multidomain model presented here successfully quantifies fluctuations in the hydraulic properties of shrink swell soil matrices and are suitable for use in physical flow and transport models based on darcy s law the richards equation and the advection dispersion equation

multiple growth events during diamond genesis an integrated study of carbon and nitrogen isotopes and nitrogen aggregation state in coated stones the internal structure and growth history of diamonds have been investigated by the study of carbon isotopes and the abundance isotope composition and aggregation state of nitrogen polished plates of zoned diamonds coated stones were laser sectioned for infrared mapping and isotope profiling nine small cubic and three small octahedral diamonds from zaire and two coated stones and five small cubic diamonds specifically from the mbuji mayi area of that country were also investigated the isotope composition and infrared characteristics of the diamonds of cubic habit including coats were found to be indistinguishable with 13c in the range 5 9 to 7 5 and all the nitrogen being present as the paired structure iaa with a 15n of between 3 1 and 8 0 the diamonds of octahedral habit including the cores of the coated stones were more variable 13c varied from 4 9 to 9 8 infrared spectra of the octahedral diamond exhibited either strong iaa characteristics or a combination of iaa and iab platelets were present in most cases 15n values from octahedral diamonds varied from 5 8 to 13 4 the data suggest that the octahedral diamonds represent a variety of growth events separated in time and or space and that the diamonds resided in the lithosphere for a period sufficient for thermal maturation in the case of the coated stones the octahedral diamonds were later involved in an event which added a component from a single relatively homogeneous reservoir cubic habit diamonds were formed at the same time this latter event is believed to be related to the kimberlite eruption comparison of the data with carbon isotope analyses of cubic diamond from other sources suggests that this reservoir could be widespread

origin and diagenetic evolution of gypsum and microbialitic carbonates in the late sag of the namibe basin sw angola abstract ephemeral evaporitic conditions developed within the uppermost part of the transgressive late sag sequence in the namibe basin sw angola leading to the formation of extensive centimetre to metre thick sulphate bearing deposits and correlative microbialitic carbonates rich in pseudomorphs after evaporite crystals the onshore pre salt beds examined in this study are located up to 25 m underneath the major mid aptian evaporitic succession which is typified at the outcrop by gypsiferous bambata formation and in the subsurface by the halite dominated loeme formation carbonate evaporite cycles mostly occur at the top of metre thick regressive parasequences which progressively onlap and overstep landward the former faulted rift topography or fill major pre salt palaeo valleys the sulphate beds are made up of alabastrine gypsum associated with embedded botryoidal nodules dissolution related gypsum breccia and are cross cut by thin satin spar gypsum veins nodular and fine grained fabrics are interpreted as being diagenetic gypsum deposits resulting from the dissolution and recrystallisation of former depositional subaqueous sulphates whereas gypsum veins and breccia result from telogenetic processes the carbonates display a broader diversity of facies characterised by rapid lateral variations along strike thin dolomitic and calcitic bacterial mediated filamentous microbialitic boundstones enclose a broad variety of evaporite pseudomorphs and can pass laterally over a few metres into sulphate beds dissolution related depositional breccias are also common and indicate early dissolution of former evaporite layers embedded within the microbialites sulphate and carbonate units are interpreted as being concomitantly deposited along a tide dominated coastal supra to intertidal sabkha and constitute high frequency hypersaline precursor events prior to the accumulation of the giant saline mid aptian bambata and loeme formations petrographic and geochemical analyses reveal successive dissolution recrystallisation and cementation phases that occurred during burial uplift and exhumation implying a complex diagenetic evolution of both gypsum and carbonates influenced by pore fluids of diverse composition which distinctly varied from meso to telogenetic domains

the application of c isotope measurements to the identification of the sources of c in diamonds a review abstract in the past decade the isotopic compositions of c in 600 inclusion bearing diamonds have been determined such analyses have revealed the following isotopic characteristics 1 peridotitic diamonds which typically contain garnet chromite olivine and or orthopyroxene inclusions with refractory compositions high mg cr have 13 c values predominantly between 10 and 1 with a sharp peak in the distribution near 5 2 eclogitic diamonds which commonly contain inclusions of omphacitic clinopyroxene cr poor pyrope and or eclogitic accessory minerals such as rutile kyanite coesite or sanidine have 13 c values between 34 and 3 with a smaller peak near 5 3 the isotopic compositions obtained for suites of diamonds from individual occurrences are in general unique and do not resemble the range and distribution obtained by amalgamating the diamond isotope data from a number of localities 4 isotopic zoning patterns and heterogeneities are found in some diamonds cores of coated diamonds tend to be depleted in 13 c relative to the rims and within single octahedral diamonds 13 c variations of nearly 6 have been reported because expected c isotope fractionations at mantle temperatures are small attempts to model the full range of diamond isotope values through fractionating a homogeneous mantle c source have been unsuccessful nevertheless fractionation is probably responsible for some of the observed variation in 13 c values two other models have also been proposed to account for the diamond characteristics outlined above the primordial model suggests that the range and distribution of c isotope compositions are inherited from primordial c in the mantle which has an inhomogeneous isotopic composition such as that found in meteorites the subduction model suggests that subducted crustal c is the source of c in diamonds as organic and inorganic c compounds in the crust exhibit a range of 13 c values similar to that observed in diamonds this paper reviews the c isotope characteristics of diamonds and compares the models which have been proposed to explain the origins of these characteristics

geomorphic development of the canadian river valley texas panhandle an example of regional salt dissolution and subsidence development of the canadian river valley in the texas panhandle resulted mostly from regional subsidence following dissolution of permian bedded salts salts of the clear fork glorieta san andres and seven rivers formations have undergone dissolution along the margins of the palo duro dalhart and anadarko basins the canadian river valley follows a zone of subsidence for

green ampt infiltration model for sloping surfaces 1 this work quantifies and explains the direct physical effects of slope angle on infiltration and runoff generation by extending the green ampt equation onto sloping surfaces a new extended solution using identical precipitation hydrographs was compared to the original formulation and then used to calculate the infiltration and runoff generation for different slope angles but for identical horizontal projection lengths homogeneous and isotropic soil is assumed and two different boundary conditions for vertical rainfall are studied ponded infiltration and infiltration under steady rainfall infiltration under unsteady rainfall was found to be similar to cases with steady rainfall both theoretical and numerical results show that infiltration increases with increasing slope angle for cases with ponded infiltration the slope effect was generally not significant for mild to moderate slopes but the slope effect became more important for low intensity and short duration rainfall events especially as it delayed the time for ponding it was also found that the cumulative vertical infiltration depth ihp at ponding or the initial loss increases with increasing slope angle the model was compared to richards equation on horizontal and sloping surfaces and found to perform well the model s applicability for nonuniform slopes was discussed and it was found that the model is generally applicable for isotropic and mildly anisotropic soils except for some small scale topographic elements finally the occurrence of nonvertical rainfall could increase runoff with increasing slope angle when rainfall deflects a large angle to upslope

noble gas state of the ancient mantle as deduced from noble gases in coated diamonds cores and coats of five coated diamonds one from botswana and four from zaire were separately analyzed for their noble gases noble gases in the diamonds are essentially of a trapped origin including radio and nucleogenic components such as4he 40ar 21neexcess and excesses in xe isotopes 129 131 136 the fairly precise elemental and isotopic abundances allow us to infer the noble gas state in the ancient mantle 20ne 22ne ratios are fairly constant 11 8 0 4 and very close to that of sep solar energetic particle ne but distinctly different from the atmospheric ratio 21ne 22ne ratios range from 0 028 to 0 06 which is attributed to nucleogenic 21ne from 18o n 21ne and 24mg n 21ne reactions the difference in 20ne 22ne between atmosphere and mantle can be attributed to the hydrodynamic escape of hydrogen from the primitive atmosphere during the very early stage in the earth s history 38ar 36ar and kr isotopic ratios are identical to the atmospheric values within 1 after correction for 238u or 244pu fission xe the 131 136xe abundance ratios are indistinguishable from atmospheric ratios lighter xe isotopes 124 128xe are also likely to be atmospheric but a final conclusion must wait until better data are obtained in a 136xe 130xe 129xe 130xe diagram diamond data lie on the same line as defined for morb the observed identical correlation for both diamonds and morb s appears to suggest that the progenitor of the excess131 136xe is 244pu but not238u though the direct xe isotopic measurements was not precies enough to decide unanimously the progenitor

n δ 13 c inclusion profiles of cloudy diamonds from koffiefontein evidence for formation by continuous rayleigh fractionation and multiple fluids abstract six diamonds with a fibrous core intermediate zone and monocrystalline outer zone cloudy diamonds from the koffiefontein mine south africa were investigated for n concentrations carbon isotope compositions and micro inclusion compositions along core to rim traverses this study evaluates the nature of the change from fibrous to gem diamond growth and the relation between major element composition of high density fluid inclusions and n 13c in fibrous growth zones three diamonds contain saline to carbonatitic fluid micro inclusions with constant or increasing carbon isotope values which are inferred to have formed by varying amounts of rayleigh fractionation in a closed system of a carbonate bearing fluid continuous n 13c fractionation trends from the fibrous to gem growth zone in two of the diamonds and equally low nitrogen aggregation states indicate formation of diamond shortly before kimberlite eruption from a single fluid without a time gap between fibrous and gem diamond growth high major element co32 ratios in the growth media resulted in a constant major element composition of the fluid inclusions found in the studied fibrous diamonds the transition from fibrous to gem diamond growth is likely caused by the precipitation of diamond reducing the degree of oversaturation of carbon in the fluid and hence decreasing the rate of diamond growth two other diamonds have inclusions that change from silicate minerals in the inner fibrous growth zones towards pure saline fluid compositions in the outer fibrous growth zones this decrease in si mg and ca and increase in k and cl in the inclusions is accompanied by a decrease in 13c values and n contents these trends are suggested to be the result from gradually mixing in more saline fluids with lower 13c values one diamond with silicic inclusions has significant n aggregation into b centres suggesting this fluid is different and that diamond formation occurred significantly e g 1250 c gives 10 ma before the kimberlite eruption

co existing fluid and silicate inclusions in mantle diamond we document the compositions of co existing silicate macro inclusions and fluid micro inclusions in the fibrous coats of eight coated diamonds from the panda kimberlite canada the mineral inclusions in the diamond coats come from either the peridotite suite cr pyrope orthopyroxene olivine and cr diopside or the eclogite suite omphacite therefore fibrous diamonds grow in the same paragenetic environments as octahedral diamonds the inclusions document a more fertile source composition lower mg and higher cao than for equivalent phases in octahedral diamonds from panda and worldwide however moderate to high cr2o3 contents in garnet and clinopyroxene inclusions suggest that this apparent fertility is due to a secondary process geothermometry of the silicate inclusions yields low equilibration temperatures of 930 to 1010 c the co existing fluid micro inclusions are dominated by h2o carbonate and kcl fluid inclusions in both the peridotitic and eclogitic samples fall along linear arrays between fe ca mg carbonate and kcl inclusions in the one eclogitic sample also contain quartz we suggest that the diamonds have trapped both metasomatised minerals and the metasomatic fluid and so provide a snap shot of a metasomatic event in the mantle

monitoring the transition from preferential to matrix flow in cracking clay soil through changes in electrical anisotropy abstract transition from preferential flow to matrix flow in a vertisol was investigated by combined use of square array resistivity measurements and stable water isotopes two irrigation events with water of different water isotope composition were carried out on a 0 5 m deep initially dry and cracked soil profile in a weighing lysimeter throughout the irrigation events depth profiles of resistivity square array measurements were collected to calculate profiles of the anisotropy index ai and mean resistivity the stable isotope composition of the drainage water showed that water from the second irrigation bypassed the soil matrix with limited mixing to form the collected drainage this bypass showed that even though the soil cracks at the surface were visually closed at the onset of the second irrigation preferential flow paths must have remained open changes of the ai with applied irrigation volume were used to detect the dominant flow processes in the soil with a stable ai indicating matrix flow and an unstable ai indicating preferential flow the ai showed that over the course of the irrigation events the dominant flow process changed from preferential flow to matrix flow the use of the ai allowed for the first time to detect the exact timing of this transition matrix dominated flow didn t occur until ponding water at the soil surface was observed the onset of matrix flow started at the top of the profile and progressed downwards complete crack closure in terms of water flow occurred long after visual closure of soil cracks and could be detected by monitoring changes in the ai

40ar 39ar laser probe studies of clinopyroxene inclusions in eclogitic diamonds abstract 40 ar 39 ar laser probe ages are reported for individual clinopyroxene inclusions in thirty two eclogitic diamonds from four localities jwaneng and orapa both in botswana udachnaya siberia and argyle australia ages obtained from cleaved diamonds from jwaneng 244 ma orapa 102 ma and udachnaya 425 ma are similar to those of their host kimberlites however there is considerable variation in age between individual laser extractions obtained from the same inclusion which we suspect is mainly due to partial retention of radiogenic argon that diffused to the inclusion diamond interface while the diamond was in the mantle some of this argon was lost when the diamonds were cleaved as part of the experimental procedure the presence of an ambient mantle 40 ar component trapped in inclusions may be an additional cause of scatter in ages however this cannot be validated with the present data in support of the diffusive loss process the results from an udachnaya inclusion completely enclosed within host diamond with the argon being released by laser drilling yielded an age of 1149 37 ma which is considerably older than the host kimberlite about 340 400 ma likewise the scatter in 40 ar k ratios for eclogitic diamonds from jwaneng and orapa indicates that they too are probably xenocrysts therefore a combination of sample preparation technique and laser drilling can be used to offer a useful extension of the original method enabling both diamond formation from buried inclusions and host rock emplacement ages from cleaved inclusions to be determined argyle clinopyroxenes similarly cleaved to the diamond surface also show a considerable range of inclusion ages 1159 1540 ma only in this case there is a relationship between age and k ca ratio of the inclusions such a relationship is difficult to reconcile in terms of partial loss of 40 ar and instead indicates that there was a protracted period of diamond growth

the salt that wasn t there mudflat facies equivalents to halite of the permian rustler formation southeastern new mexico four halite beds of the permian rustler formation in southeastern new mexico thin dramatically over short lateral distances to correlative clastic mudstone beds the mudstones have long been considered residues after post burial dissolution subrosion of halite assumed to have been deposited continuously across the area hydraulic properties of the culebra dolomite member have often been related to rustler subrosion in cores and three shafts at the waste isolation pilot plant wipp however these mudstones display flat bedding graded bedding cross bedding erosional contacts and channels filled with intraformational conglomerates cutans indicate early stages of soil development during subaerial exposure smeared intraclasts developed locally as halite was removed syndepositionally during subaerial exposure we interpret these beds as facies formed in salt pan or hypersaline lagoon transitional and mudflat environments halite is distributed approximately as it was deposited breccia in limited areas along one halite margin indicates post burial dissolution and these breccias are key to identifying areas of subrosion a depositional model accounts for observed sedimentary features of rustler mudstones marked facies and thickness changes are consistent with influence by subsidence boundaries as found in some modern continental evaporites a subrosion model accounts for limited brecciated zones along depositional halite margins but bedding observed in the mudstones would not survive 90 reduction in rock volume depositional margins for these halite beds will be useful in reconstructing detailed subsidence history of the late permian in the northern delaware basin it also no longer is tenable to attribute large variations in culebra transmissivity to rustler subrosion

evaluation of halite dissolution at a radioactive waste disposal site andrews county texas waste control specialists wcs has been granted permits to dispose of radioactive waste at their surface facility in western andrews county texas u s a the facility is located over permian age halite bearing formations and the possibility of dissolution and its effects on the long term performance of the disposal site must be considered we compare data from the wcs site and vicinity to three conceptual hydrologic models of dissolution processes shallow deep and stratabound geophysical logs yield stratigraphic and lithofacies data from the underlying halite bearing units the permian rustler and salado formations the halite units are continuous and thickness and lithofacies vary by depositional process with no discernible postdepositional dissolution modest structural trends in these units differ from local changes in evaporite thickness therefore deformation is not related to thickness differences local thickness changes in the middle of the salado formation indicate depositional variations core obtained from upper evaporite bearing formations at the wcs site show normal depositional features and no brecciation that would be associated with postdepositional dissolution deeply buried bedded halite behaves as a ductile material and the effective stress is close to zero so that the pressure in pore fluids approaches lithostatic hydraulic gradients are outward from halite toward overlying and underlying rocks eliminating access for low salinity fluids formation fluids at depth are commonly saline and slow moving further limiting the dissolution process the hydrologic systems at the site limit the potential for future dissolution