lunar global shape and polar topography derived from kaguya lalt laser altimetry a global lunar topographic map with a spatial resolution of finer than 0 5 degree has been derived using data from the laser altimeter lalt on board the japanese lunar explorer selenological and engineering explorer selene or kaguya in comparison with the previous unified lunar control network ulcn 2005 model the new map reveals unbiased lunar topography for scales finer than a few hundred kilometers spherical harmonic analysis of global topographic data for the moon earth mars and venus suggests that isostatic compensation is the prevailing lithospheric support mechanism at large scales however simple rigid support is suggested to dominate for the moon venus and mars for smaller scales which may indicate a drier lithosphere than on earth especially for the moon and venus

the shape and internal structure of the moon from the clementine mission global topographic and gravitational field models derived from data collected by the clementine spacecraft reveal a new picture of the shape and internal structure of the moon the moon exhibits a 16 kilometer range of elevation with the greatest topographic excursions occurring on the far side lunar highlands are in a state of near isostatic compensation whereas impact basins display a wide range of compensation states that do not correlate simply with basin size or age a global crustal thickness map reveals crustal thinning under all resolvable lunar basins the results indicate that the structure and thermal history of the moon are more complex than was previously believed

planetary surface dating from crater size frequency distribution measurements partial resurfacing events and statistical age uncertainty abstract we describe the procedure to fit a cumulative production function polynomial to a partial crater size frequency distribution the technique is of particular use in deriving ages for surfaces which have undergone partial resurfacing events namely erosional or depositional events which have affected a limited diameter range of the crater population we demonstrate its use in obtaining times for both the surface formation and the resurfacing event we give a practical outline of the method for making age measurements from crater counts and how to identify resurfacing effects in the results we discuss the conversion of production function polynomials between common presentations and the statistical uncertainty of the determined ages with respect to the non linear chronology function and a minor refinement of data binning

the importance of secondary cratering to age constraints on planetary surfaces small craters less than one kilometer diameter can be primary craters produced by impact of interplanetary debris or they can be secondary craters produced by fallback of high velocity ejecta blocks from much larger but infrequent primary impacts the prevalent assumption over recent decades has been that primaries are most abundant so most small craters are independent random events and can be used for dating however recent results from europa and mars support the early theory that distant secondaries globally dominate the number of small lunar craters this would invalidate part of production functions that have been widely used for age dating crater excavation results in higher mean ejection velocities for smaller fragments resulting in a steeper size frequency distribution for secondary craters than is produced by the same size frequency distribution of interplanetary debris this review also discusses how small craters can sometimes be used to derive meaningful age constraints

the genesis of gold mineralisation hosted by orogenic belts a lead isotope investigation of irish gold deposits abstract lead isotope analyses have been performed on 109 gold and 23 sulphide samples from 34 irish gold occurrences including 27 placers and used to shed light on the sources of mineralising fluids and metals associated with gold mineralisation hosted by orogenic belts the pb isotope ratios of lode and placer gold range from 206pb 204pb 17 287 18 679 207pb 204pb 15 382 15 661 and 208pb 204pb 37 517 38 635 consistent with the pb isotopic data on previously reported irish sulphide mineralisation there is no evidence that gold mineralisation is associated with distinctive source regions and it appears to have been derived from similar sources to those responsible for the widespread sulphide mineralisation in ireland it is inferred that the principal controls on the au mineralisation are structural and not related to the distribution of au in their source rocks the range of pb isotope ratios favours the interaction of multiple source reservoirs predominantly during the caledonian orogeny c 475 380 ma underlying basement was the primary control on two key sources of pb gold occurrences located to the south east of the iapetus suture are characterised by pb compositions that derive predominantly from the late proterozoic crustal basement or overlying lower palaeozoic sediments whilst those located north west of the iapetus suture are characterised by less radiogenic pb signatures derived predominantly from late proterozoic or older crustal basement a third source relatively enriched in radiogenic pb also played a role in the formation of a number of irish gold occurrences and may have been associated with syn to post orogenic intrusives magmatic processes may therefore have played an important role in the formation of some orogenic gold occurrences

weathering model for the quantification of atmospheric oxygen evolution during the paleoproterozoic abstract a weathering model has been developed to quantify atmospheric oxygen evolution during the paleoproterozoic the weathering model calculates the concentrations of fe2 dissolved from fe2 bearing primary minerals and oxidized fe3 out of the dissolved fe2 at a given partial pressure of atmospheric oxygen p o 2 during weathering and establishes the relationships between p o 2 and where is the ratio of oxidized and then precipitated fe3 out of the fe2 dissolved from primary minerals to the dissolved fe2 in a whole weathering profile the weathering model considers controlling factors of the redistribution of fe during weathering that is the dissolution rate of fe2 bearing primary minerals the oxidation rate of fe2 and the groundwater flow rate the validity of the model was confirmed by applying the model to the experimental data of olivine dissolution carried out under low o2 conditions the sensitivity analysis of the model has revealed that the formation time of weathering the mineral dissolution rate and the diffusion of o2 into a weathering profile have no or slight influence on resulting in 0 0 and 0 3 changes in log p o 2 caused by four orders of magnitude change of the formation time more than 10 orders change of the mineral dissolution rate and assumed change of the o2 diffusion respectively on the other hand the temperature the ph and the groundwater flow rate have moderate to large effects on 0 6 1 4 and 1 5 changes in log p o 2 for changes of 5 c in temperature 0 5 in ph and one order of magnitude in groundwater flow rate respectively using possible surface temperature ph and groundwater flow rate estimated from the literature we calculated the p o 2 relationships which were then applied to the values of paleosols fossil weathering profiles formed between 2 5 and 1 8 ga taking account of the constraints given by the records of mass independent fractionation in sulfur isotopes and other geological proxies i e 10 6 atm at 2 32 ga and 10 3 atm at 2 0 ga our model implies that the p o 2 levels were 10 9 atm at 2 46 ga 10 4 5 10 2 atm at 2 25 2 0 ga and 10 2 atm at 1 85 ga the present weathering model can constrain p o 2 levels during the possible paleoproterozoic hot periods but not those during the glacial periods when temperature was

sulfide oxidation in brown coal overburden and chemical modeling of reactions in aquifers influenced by sulfide oxidation surface mining of brown coal in the rhineland brown coal mining area germany causes acidification of pyritic sandy overburden sediments convective transport of air indicated by an enrichment of nitrogen gas in oxidized overburden is in addition to diffusion of oxygen the driving mechanism for sulfide oxidation products of sulfide oxidation 2so42 2h fe2 stored in acidic material in the overburden dump are leached by groundwater filling the dump and react with the carbonate phases of nonacidic material the resulting hydrochemical composition up to 6000 mg l 1 so42 3000 mg l 1 fe2 ph 4 5 in groundwaters is controlled by simultaneous solubility equilibria with caso4 2h2o s fe oh 3 s fe0 9ca0 1co3 s and co2 g calculated equilibrium concentrations of major components and ph in groundwater partial pressure of co2 g in soil gas and coupled mass transfer match observed conditions

theoretical analysis of secondary cratering on mars and an image based study on the cerberus plains the issue of crater retention age estimates on planetary surfaces is discussed with an attempt to quantify the effect of overlapping primary and secondary impact crater populations in restricted crater diameter ranges the approach to this problem is illustrated with a simple model production function where the secondary crater input is artificially enhanced extrapolation of such a secondary crater model distribution to a global record results in extraordinarily high crater frequencies that do not exist on mars and implies the need of detailed studies of the size frequency distribution for remote secondary craters to date poorly known a key case the martian crater zunil and its secondary crater field illustrate that reasonable predictions for the secondary crater size frequency distribution at small 100 m crater diameters affected the standard model crater retention age for the cerberus plains less than the statistical uncertainty these observations show that age determination based on appropriate crater counting statistics is valid in a wide primary crater diameter range

evidence for basaltic volcanism on the moon within the past 100 million years the majority of basaltic volcanism on the moon occurred more than 3 billion years ago small mounded formations on the lunar nearside may be products of basaltic eruptions less than 100 million years ago suggesting a long decline of magmatic activity

the age of lunar mare basalts south of the aristarchus plateau and effects of secondary craters formed by the aristarchus event abstract using crater size frequency distributions csfds and careful discrimination of primary and secondary impact craters in the mare region south of aristarchus crater we reexamined the age of unit p60 determined previously by hiesinger et al 2003 to be one of the youngest basaltic surfaces on the moon owing to the apparently young age of these basalts this region is a potential site for future sample return missions we investigated this 55 000 km2 region with lunar reconnaissance orbiter camera lroc images to assess potential variations in csfds across the unit particularly in light of heavy contamination by secondary craters from aristarchus crater and to determine the age s of p60 over its full areal extent we are able to match within one standard error the previously determined age using approximately the same counting area in addition we defined twelve regions between the rays of secondaries to determine if and how the ages of p60 might vary across the unit for these inter ray regions we find a systematic progression of ages from west to east ranging from youngest 1 ga in the west to 1 8 ga southwest of aristarchus to 2 2 ga south of aristarchus and finally to 2 7 ga southeast of aristarchus this variation in ages is not solely attributable to secondary cratering indicating it must be at least partially due to volcanic resurfacing the northwestern most extension of p60 may belong to a different unit owing to topographic and crater distribution differences analysis of the summed csfd for p60 provides evidence for emplacement of the younger basalts

the clementine mission to the moon scientific overview in the course of 71 days in lunar orbit from 19 february to 3 may 1994 the clementine spacecraft acquired just under two million digital images of the moon at visible and infrared wavelengths these data are enabling the global mapping of the rock types of the lunar crust and the first detailed investigation of the geology of the lunar polar regions and the lunar far side in addition laser ranging measurements provided the first view of the global topographic figure of the moon the topography of many ancient impact basins has been measured and a global map of the thickness of the lunar crust has been derived from the topography and gravity

microchemical characterisation of natural gold and artefact gold as a tool for provenancing prehistoric gold artefacts a case study in ireland the importance of au to ancient societies has encouraged many archaeologists to search for the sources exploited in antiquity these projects generally involve detailed studies of artefacts and comparison of their chemical characteristics with those reported for natural au however descriptions of natural au are frequently inadequate for provenancing studies and the compositional variability of the material is not widely recognised the present study describes a new approach to gold provenancing using the technique of microchemical characterisation in which populations of gold grains are classified according to the alloy compositions and the assemblages of microinclusions of other minerals this technique originally developed to identify sources of alluvial gold during au exploration has proved applicable to provenancing studies in four main areas firstly microchemical characterisation of artefacts grouped according to archaeological criteria can indicate the number of sources exploited in relation to time and artefact taxonomy secondly knowledge of the total variation in chemical characteristics of natural au from a particular region provides an excellent database for provenancing and reduces the need for exhaustive sampling thirdly it is possible to predict how au alloys were modified during fabrication as a consequence of assimilation of mineral inclusions finally identification of inclusion phases in artefact au can provide information on metallurgical practices these principles have been applied to the search for the source of au used for the unique traditions of prehistoric irish metalworking studies of 180 irish au artefacts belonging to four major metalworking traditions dating from the early bronze age 2400 bc to the iron age 150 bc show that each group exhibits distinctive ag and cu contents parallel studies of 2267 natural au grains from 58 alluvial localities and four bedrock localities throughout ireland reveal a broad pattern of alloy compositions consistent with style of mineralisation and host geology the ranges of ag contents of early bronze age and middle bronze age artefacts suggests that the au source lies within lower palaeozoic sedimentary rocks of the southern uplands terrane and significantly that the same source or sources were used in both periods a different source of relatively ag rich au most probably at croagh patrick co mayo was exploited in the late bronze age iron age artefacts have ag contents higher than natural irish au evidence for evolution of metallurgical practice during the bronze age is provided by the increasing cu content of the gold alloys to levels far in excess of natural gold and the nature of inclusions in artefacts of different ages elevated sn in cu rich alloys suggests deliberate or accidental alloying with bronze this approach has provided the first clear indication that only a few individual indigenous irish sources of au were used during the bronze age and that their relative importance changed over time future archaeological investigations may adopt a geographical focus that was not previously possible

intra ordovician deformation in southeast ireland evidence from the geological setting geochemical affinities and u pb zircon age of the croghan kinshelagh granite the croghan kinshelagh alkali granite intrudes a cleaved volcano sedimentary sequenceon the border of counties wicklow and wexford in southeast ireland u pb dating of zircons fromthe granite indicate a mid caradoc emplacement age of 454 1 ma the duncannon group hostrocks form the southwestern end of the avoca volcanic belt a mid ordovician caradoc sequenceof acid and intermediate lavas and volcaniclastics dolerite dykes intrude the granite elsewhere in theregion dolerites are generally associated with volcanic rocks the main dl deformation within theduncannon group rocks is manifest as a steep dl cleavage generally regarded as a product of latecaledonian regional deformation in southeast ireland the croghan kinshelagh granite showsstrong geochemical coherence with subalkaline varieties of the caradoc volcanic rocks relativelyhigh th y nb and ree contents set it apart from any other known granite type in southeastireland together with the geochemical evidence the age determination of 454 ma indicates that thecroghan kinshelagh granite was generated and emplaced during ordovician volcanism in southeastireland volcanism was closely followed by penetrative deformation and emplacement of the granite the intra ordovician deformation may have been a consequence of closure of the iapetus ocean ormore localized events such as accretion on the hanging wall of the subduction zone the age of thecroghan kinshelagh granite provides an important datum for ordovician volcanism and subductionin southeast ireland

lunar polar topography derived from clementine stereoimages clementine stereoimagery has been used to produce digital elevation models of the moon at a scale of 1 km pixel these models cover regions poleward of 60 in both hemispheres and reveal topography beyond that covered by the clementine laser altimeter or earth based radar by combining these polar terrain models with the current clementine laser altimeter data we have produced a global topographic map of the lunar surface several topographic features in the new polar topographic data set are described including three previously unrecognized pre nectarian impact basins several known basins have also been mapped including the southern extent of the south pole aitken basin and other previously suspected basins have been verified

gld100 the near global lunar 100 m raster dtm from lroc wac stereo image data 1 we derived near global lunar topography from stereo image data acquired by the wide angle camera wac of the lunar reconnaissance orbiter camera lroc system from polar orbit tracks the lroc wac provides image data with a mean ground resolution at nadir of 75 m pixel with substantial cross track stereo overlap wac stereo images from the one year nominal mission and the first months of the science mission phase are combined to produce a near global digital terrain model dtm with a pixel spacing of 100 m the global lunar dtm 100 m or gld100 it covers 79 s to 79 n latitudes 98 2 of the entire lunar surface we compare the gld100 with results from previous stereo and altimetry based products particularly with the lunar orbiter laser altimeter lola altimetry which is the current topographic reference for the moon we describe typical characteristics of the gld100 and based upon the comparison to the lola data set assess its vertical and lateral resolution and accuracy we conclude that the introduced first version of the stereo based gld100 is a valuable topographic representation of the lunar surface complementary to the lola altimetry data set further improvements can be expected from continuative investigations

trace elements in magnetite from porphyry cu mo au deposits in british columbia canada abstract this study examines trace elements in hydrothermal magnetite from five porphyry cu mo au deposits and two skarns in british columbia canada trace element concentrations vary several orders of magnitude both within and between magnetite from skarn and porphyry deposit settings the heterogeneous composition of hydrothermal magnetite may in part be due to the short duration low temperature and multiple fluid events that attend the formation of porphyry ore deposits principal component analysis shows two dominant patterns of trace element abundances in hydrothermal magnetite firstly positive correlations of ti al and v which account for nearly 40 of the total variation in magnetite are inferred to depend on temperature and oxygen fugacity secondly antithetic abundances of lower valence cations co mn with higher valence cations sn and mo may reflect variations in the redox potential acidity and metal speciation of hydrothermal fluids the cu fe and mn fe ratios calculated for fluids in equilibrium with the hydrothermal magnetite using experimental partitioning data are similar to those measured directly in brines trapped in quartz hosted fluid inclusions from porphyry cu mo au deposits

ages and stratigraphy of mare basalts in oceanus procellarum mare nubium mare cognitum and mare insularum accurate estimates of mare basalt ages are necessary to place constraints on the duration and the flux of lunar volcanism as well as on the petrogenesis of lunar mare basalts and their relationship to the thermal evolution of the moon we performed new crater size frequency distribution measurements in order to investigate the stratigraphy of mare basalts in oceanus procellarum and related regions such as mare nubium mare cognitum and mare insularum we used high resolution clementine color data to define 86 spectrally homogeneous units within these basins which were then dated with crater counts on lunar orbiter iv images our crater size frequency distribution measurements define mineralogical and spectral surface units and offer significant improvements in accuracy over previous analyses our data show that volcanism in the investigated region was active over a long period of time from 3 93 to 1 2 b y a total of 2 7 b y volumetrically most of the basalts erupted in the late imbrian period between 3 3 and 3 7 b y and we see evidence that numerous units have been resurfaced during the eratosthenian period significantly less basalt was erupted depending on the absolute model ages that one can assign to the lunar chronostratigraphic systems five units might be of copernican age younger basalts are generally exposed in the center of the investigated area that is closer to the volcanic centers of the aristarchus plateau and marius hills older basalts occur preferentially along the northwestern margin of oceanus procellarum and in the southeastern regions of the studied area i e in mare cognitum and mare nubium combining the new data with our previously measured ages for basalts in mare imbrium serenitatis tranquillitatis humorum australe and humboldtianum we find that the period of active volcanism on the moon lasted 2 8 b y from 4 b y to 1 2 b y on the basis of the basalts dated so far which do not yet include the potentially young basalts of mare smythii e g schultz and spudis 1983 we conclude that oceanus procellarum not only exhibits the widest range of ages of all investigated basins but probably also is the location of some of the youngest basalts on the lunar surface

characterization of gold mineralization in the northern cariboo gold district british columbia canada through integration of compositional studies of lode and detrital gold with historical placer production a template for evaluation of orogenic gold districts there is a strong association between regions containing orogenic gold mineralization and exploitation of placer gold although in many cases the nature of the source mineralization for these placer deposits remains unclear this study describes a novel approach to evaluating the economic potential of in situ orogenic gold mineralization through characterization of both lode and placer gold mineralogy followed by synthesis of this information with records of both mineral occurrences and historical placer mining the northern cariboo gold district in east central british columbia canada was chosen as a location for the study because of the gold endowment of the area 1 2 million ounces moz of lode gold and between 0 5 and 3 moz of placer gold and the information available from both placer and lode gold mining compositional analysis of 533 gold grains from 21 lode localities and 1 914 gold grains from 30 placer localities from throughout the cariboo gold district has identified four main compositional types in terms of their alloy compositions and associated suite of mineral inclusions revealed in polished section a distinctive low 4 7 ag gold that exhibits a strong bi association in the mineral inclusion suite is geographically limited to the wells area where it is recorded in both lode mineralization and its placer expression regionally pervasive mineralization yields gold of binary au ag alloy and a simple inclusion suite of sulfides and sulfarsenides gold in most large placers in trunk drainages was derived from multiple mostly small occurrences of this type the nature of compositional variation between gold grains liberated from hypogene ore has informed the history of episodic mineralization and suggests multiple stages of gold emplacement at some localities while others are dominated by gold deposited in a single stage the new information from gold grain analysis has been considered in the context of other information classification of a placer as either allocthonous or autocthonous both informs interpretation of compositional characteristics of the detrital gold grains and provides information on distance to the hypogene source mineral inclusion assemblages observed in sample populations of placer gold grains have been correlated with reports of hypogene vein mineralogy described in mineral occurrence records to clarify the geographical extent of specific mineralization types the compositional range of alloys of different gold types has been compared to historical records of gold production and gold fineness au ag ratio to reconstruct the size and distribution of hypogene sources prior to erosion synthesis of gold compositional studies with other publicly accessible data sets provides a new generic approach capable of evaluating the most attractive targets for future exploration and highlighting compositional signatures of placer gold which relate to undiscovered in situ sources

integration of detrital gold microchemistry heavy mineral distribution and sediment geochemistry to clarify regional metallogeny in glaciated terrains application in the caledonides of southeast ireland regional exploration for rare and precious metal enrichment traditionally uses multielement geochemical analysis of the fines 150 m fraction of stream sediments however these data can be misleading in glaciated regions with complex geology here we compare the spatial distributions of data from sediment fines with distributions of heavy mineral concentrates including detrital gold in the same region gold grains are characterized according to abundance and morphology plus a microchemical signature from the combination of alloy analysis and systematic identification of mineral inclusions revealed in polished sections these inclusions survive indefinitely and are indicative of hypogene mineralogy whereas the metal loadings of fines may be affected by weathering or anthropogenic activity all three approaches are mutually supportive sediment fines analyses provide a basis for more labor intensive targeted gold grain studies which in turn highlight specific gold element associations useful for interpretation of geochemical data sets spatial distributions of resistate heavy mineral suites constrain the directions and extents of glacial transport which facilitates more confident interpretations of placer lode relationships from gold grain studies characterization of 2 160 gold grains from 40 localities in the auriferous region of southeast ireland provided a clear indication of proximity of gold to source and identified gold derived from different episodes of mineralization a distinction is apparent between gold in the south of the region wexford likely derived from widespread stratabound au as fe s mineralization and that in the north wicklow where the historical placer mining district of the goldmines river yielded gold with inclusions exhibiting a distinctive pb bi as association the goldmines river placers formed by the efficient accumulation and preservation of detrital gold derived from several discrete intravalley sources we recommend that a combination of classic stream sediment geochemistry heavy mineral analysis and gold grain studies is used more widely to provide additional insights on the location and nature of gold mineralization and regional metallogeny in regions of poor exposure and complex geology

non mare silicic volcanism on the lunar farside at compton belkovich non basaltic volcanism is rare on the moon and has been found predominantly on the lunar nearside analysis of lunar reconnaissance orbiter camera images and spectral data reveal the presence of compositionally evolved non basaltic volcanism on the lunar farside

sulfide mineral oxidation and subsequent reactive transport of oxidation products in mine tailings impoundments a numerical model a versatile numerical model that couples oxygen diffusion and sulfide mineral oxidation pyrox has been developed to simulate the oxidation of pyrite in the vadose zone of mine tailings a shrinking core oxidation model and a finite element numerical scheme are used to simulate the transport of oxygen and oxidation of pyrite grains the rate of pyrite oxidation is assumed to be limited by the transport of oxygen to the reaction site the model determines the spatially variable bulk diffusion coefficient for oxygen on the basis of moisture content porosity and temperature all of which are variable input parameters the model pyrox has been coupled to an existing reactive transport model mintran which uses a finite element scheme for transport of contaminants and minteqa2 to solve for the equilibrium geochemistry the reactions described by mintran are subject to the local equilibrium assumption the resulting model mintox is capable of simulating tailings impoundments where the oxidation of pyrite or pyrrhotite is causing acidic drainage and where acid neutralization and attenuation of dissolved metals can be attributed to equilibrium reactions because mintox uses realistic boundary conditions and hydrogeological properties the potential benefits of various remediation schemes such as moisture retaining covers can be quantitatively evaluated

microchemical studies of placer and lode gold in the klondike district yukon canada 2 constraints on the nature and location of regional lode sources alloy compositions and associated suites of opaque mineral inclusions have been used to define the micro chemical signature of 3 050 placer gold grains from 34 localities and 561 gold grains from six lode localities from the northeastern central and southern klondike gold district yukon canada these data augment those from a detailed parallel study of placer lode gold relationships in the western part of the klondike goldfield see chapman et al 2010 gold compositions have been considered in association with chemical controls on alloy compositions to establish whether variation between signatures represents zonation within a single mineralizing event or discrete episodes of mineralization three main gold types have been identified each of which exhibits subtypes type 1 gold is generally a simple au ag alloy with low ag 12 25 and an inclusion suite dominated by pyrite and simple base metal sulfides type 2 gold is generally ag rich 18 55 and contains hg 9 type 3 gold 10 40 ag hg 4 is prevalent in the south of the region analysis of large sample sets has allowed us to delineate the geographic extent of each gold type and their relative importance within the placer populations type 1 gold is the major component of placer deposits in bonanza hunker dominion and upper sulphur creeks type 2 gold is relatively trivial but contributes to placer gold in bear creek and some of the paleoplacers in white channel gravel in the north of the study area type 3 gold is actively augmenting the placer inventory in the south of the region this study builds upon a detailed parallel study in the western klondike which concluded that types 1 and 2 gold were emplaced by a single hydrothermal system of limited geographic extent centered on the lone star ridge here we propose that small rich hydrothermal systems were also present in the upper reaches of bear and last chance creeks and hunker dome if correct this model shows that economically important orogenic gold mineralization can be formed in smaller hydrothermal systems than previously recognized in addition type 3 gold is widespread in the south of the study area where it appears to be present at the surface consideration of the abundance of the various gold types contributing to the placers has established type 1 gold to be the most important and originally present in geographically constrained vertically persistent mineralization we propose that this type offers the best target for exploration in the northern and central klondike in the southern klondike the large placers containing only type 3b gold suggest a potentially important undiscovered source in the catchment of gold run creek

lunar mare basalt flow units thicknesses determined from crater size frequency distributions accurate lava flow unit thicknesses estimates are necessary to place constraints on volcanic flux estimates we refine the technique of using the shape of crater size frequency distribution csfd curves to estimate the thickness of individual lunar mare flow units we find that a characteristic knee often observed in csfd curves is reasonably interpreted to represent the presence of two lava flow units separated in time and that the diameter at which this knee occurs is related to the thickness of the overlying flow unit examination of 58 curves with this characteristic knee in several lunar nearside basins oceanus procellarum imbrium tranquillitatis humorum cognitum nubium and insularum allowed us to identify flow units that have not been detected in low sun images we found that the range of flow unit thickness is 20 220 m and the average is 30 60 m this technique expands considerably the ability to assess lava flow unit thicknesses and volumes on the moon and planets

origin of discrepancies between crater size frequency distributions of coeval lunar geologic units via target property contrasts abstract recent work on dating copernican aged craters using lunar reconnaissance orbiter lro camera data re encountered a curious discrepancy in crater size frequency distribution csfd measurements that was observed but not understood during the apollo era for example at tycho copernicus and aristarchus craters csfds of impact melt deposits give significantly younger relative and absolute model ages amas than impact ejecta blankets although these two units formed during one impact event and would ideally yield coeval ages at the resolution of the csfd technique we investigated the effects of contrasting target properties on csfds and their resultant relative and absolute model ages for coeval lunar impact melt and ejecta units we counted craters with diameters through the transition from strength to gravity scaling on two large impact melt deposits at tycho and king craters and we used pi group scaling calculations to model the effects of differing target properties on final crater diameters for five different theoretical lunar targets the new csfd for the large king crater melt pond bridges the gap between the discrepant csfds within a single geologic unit thus the observed trends in the impact melt csfds support the occurrence of target property effects rather than self secondary and or field secondary contamination the csfds generated from the pi group scaling calculations show that targets with higher density and effective strength yield smaller crater diameters than weaker targets such that the relative ages of the former are lower relative to the latter consequently coeval impact melt and ejecta units will have discrepant apparent ages target property differences also affect the resulting slope of the csfd with stronger targets exhibiting shallower slopes so that the final crater diameters may differ more greatly at smaller diameters besides their application to age dating the csfds may provide additional information about the characteristics of the target for example the transition diameter from strength to gravity scaling could provide a tool for investigating the relative strengths of different geologic units the magnitude of the offset between the impact melt and ejecta isochrons may also provide information about the relative target properties and or exposure degradation ages of the two units robotic or human sampling of coeval units on the moon could provide a direct test of the importance and magnitude of target property effects on csfds

mineral chemistry and in situ upb geochronology of the mare basalt northwest africa 10597 implications for low ti mare volcanism around 3 0 ga abstract unbrecciated mare basalts are rare in the lunar meteorite collection found in 2015 northwest africa nwa 10597 is a medium grained low ti mare basalt with a subophitic texture the meteorite consists mostly of mm sized pyroxene and plagioclase with minor olivine spinel ilmenite phosphates silica and trace zr rich minerals such as baddeleyite zirconolite and tranquillityite a portion of plagioclase and silica has been transformed to their high pressure polymorphs due to shock metamorphism nwa 10597 has a low tio2 content 2 9 wt but is relatively enriched in rare earth elements ree laaverage 65 ci with an overall unfractionated pattern except for a negative eu anomaly calculated ree concentrations of parent melts in equilibrium with mg rich pyroxene and ca rich plagioclase suggest no significant assimilation of ree rich melts after the onset of pyroxene crystallization in situ u pb analyses of baddeleyite and apatite reveal a mutually consistent age of 3 0 ga which is also in excellent agreement with that of low ti mare basalts nwa 4734 and lapaz icefield lap 02205 dated with other independent techniques the concordance suggests no significant thermal disturbance in the u pb isotopic system of nwa 10597 although it was heavily shocked nwa 10597 closely resembles nwa 4734 in terms of petrographic texture mineral chemistry and geochronology indicating a pairing relationship

grail identified gravity anomalies in oceanus procellarum insight into subsurface impact and magmatic structures on the moon abstract four quasi circular positive bouguer gravity anomalies pbgas that are similar in diameter 90 190 km and gravitational amplitude 140 mgal contrast are identified within the central oceanus procellarum region of the moon these spatially associated pbgas are located south of aristarchus plateau north of flamsteed crater and two are within the marius hills volcanic complex north and south each is characterized by distinct surface geologic features suggestive of ancient impact craters and or volcanic plutonic activity here we combine geologic analyses with forward modeling of high resolution gravity data from the gravity recovery and interior laboratory grail mission in order to constrain the subsurface structures that contribute to these four pbgas the grail data presented here at spherical harmonic degrees 6 660 permit higher resolution analyses of these anomalies than previously reported and reveal new information about subsurface structures specifically we find that the amplitudes of the four pbgas cannot be explained solely by mare flooded craters as suggested in previous work an additional density contrast is required to explain the high amplitude of the pbgas for northern flamsteed 190 km diameter the additional density contrast may be provided by impact related mantle uplift if the local crust has a density 2800 kg m3 then 7 km of uplift is required for this anomaly although less uplift is required if the local crust has a lower mean density of 2500 kg m3 for the northern and southern marius hills anomalies the additional density contrast is consistent with the presence of a crustal complex of vertical dikes that occupies up to 50 of the regionally thin crust the structure of southern aristarchus plateau 90 km diameter an anomaly with crater related topographic structures remains ambiguous based on the relatively small size of the anomaly we do not favor mantle uplift however understanding mantle response in a region of especially thin crust needs to be better resolved it is more likely that this anomaly is due to subsurface magmatic material given the abundance of volcanic material in the surrounding region overall the four pbgas analyzed here are important in understanding the impact and volcanic plutonic history of the moon specifically in a region of thin crust and elevated temperatures characteristic of the procellarum kreep terrane

the application of microchemical analysis of alluvial gold grains to the understanding of complex local and regional gold mineralization a case study in the irish and scottish caledonides terranes of the appalachian caledonian orogen north of the iapetus suture host gold mineralization in north america scotland and ireland to date commercial exploitation has been confined to the appalachian terrane of canada in scotland and ireland regional analysis of the types of gold mineralization has been handicapped by the relatively small number of bedrock gold occurrences available for study however there are a large number of alluvial gold localities a technique of microchemical characterization of gold grains has been applied to facilitate the classification of alluvial gold localities in terms of the style or styles of source mineralization thereby permitting a more complete interpretation of regional gold mineralization the technique of microchemical characterization used in this study classifies populations of gold grains from each locality in terms of the assemblage of opaque mineral inclusions enclosed within the gold grains and the concentration of minor alloying elements in the gold a total of 2 400 gold grains collected from 44 sites in ireland and scotland have been studied the microchemical signatures of populations of gold grains extracted from bedrock samples correlate closely with those from adjacent alluvial populations and furthermore our data are compatible with the descriptions of the vein mineralogy of bedrock mineralization reported by other workers this result has facilitated informed speculation on the type of source mineralization of other alluvial occurrences where the bedrock source remains undiscovered populations of alluvial gold from individual localities have been grouped into larger regional data sets on the basis of similarities in microchemical signature the signatures of these data sets were analyzed using the same criteria and 10 classes of gold were identified regional analysis of the distribution of the gold classes showed that the occurrence of the four major classes correlates strongly with host terrane irrespective of geographical location gold from the southern uplands terrane is characterized by inclusions of base metal sulfides and sulfarsenides with the silver content of the gold being less than 15 percent in contrast populations of alluvial gold from the grampian and highland terranes commonly exhibit median silver contents of over 20 percent and frequently contain silver telluride and bismuth telluride inclusions which are extremely rare in gold from the southern uplands terrane however in other cases the style of mineralization is controlled by specific host or source rocks and is independent of the terrane two examples are gold mineralization within porphyry systems and gold associated with red bed sediments the study has confirmed the value of the technique of gold grain characterization using information from both concentrations of alloying elements and inclusion assemblages as a powerful tool in interpreting complex local and regional gold mineralization

assessment of heavy metals pollution in groundwater of golgohar iron ore mine area iran the golgohar iron ore mine in southern iran is a large open pit that operates below the groundwater table dewatering operations and mining activities could be responsible for generating metal contamination in the groundwater of the area in order to assess this groundwater soil solid waste and rock samples were collected and analyzed for heavy metals evaluation was done by comparing the results with the heavy metal pollution index the heavy metal evaluation index and the degree of contamination c d the only mean concentrations of elements in water samples above the who maximum admissible concentration values for drinking water are al 97 of water samples as 46 and mn 34 despite exceeding the concentration of these elements above the permissible levels the indices show that most of the water samples are low and moderately contaminated and overall contamination levels are not dangerous the low concentration of the heavy metals in the groundwater of the area is mainly due to the limited presence of sulfide minerals in the ore combined with the presence of calcite caco3 in the area which neutralizes any acid generated from sulfide oxidation

evidence for self secondary cratering of copernican age continuous ejecta deposits on the moon crater size frequency distributions on the ejecta blankets of aristarchus and tycho craters are highly variable resulting in apparent absolute model age differences despite ejecta being emplaced in a geologic instant crater populations on impact melt ponds are a factor of 4 less than on the ejecta and crater density increases with distance from the parent crater rim although target material properties may affect crater diameters and in turn crater size frequency distribution csfd results they cannot completely reconcile crater density and population differences observed within the ejecta blanket we infer from the data that self secondary cratering the formation of impact craters immediately following the emplacement of the continuous ejecta blanket by ejecta from the parent crater contributed to the population of small craters 300 m diameter on ejecta blankets and must be taken into account if small craters and small count areas are to be used for relative and absolute model age determinations on the moon our results indicate that the cumulative number of craters larger than 1 km in diameter per unit area n 1 on the continuous ejecta blanket at tycho crater ranges between 2 17 10 5 and 1 0 10 4 with impact melt ponds most accurately reflecting the primary crater flux n 1 3 4 10 5 using the cratering flux recorded on tycho impact melt deposits calibrated to accepted exposure age 109 1 5 ma as ground truth and using similar crater distribution analyses on impact melt at aristarchus crater we infer the age of aristarchus crater to be 280 ma the broader implications of this work suggest that the measured cratering rate on ejecta blankets throughout the solar system may be overestimated and caution should be exercised when using small crater diameters i e 300 m on the moon for absolute model age determination

a distinctive pd hg signature in detrital gold derived from alkalic cu au porphyry systems abstract this study comprises the first systematic classification of native gold geochemistry within alkalic porphyry cu au systems and the placer expression of such systems the geochemistry and mineral associations of gold from four alkalic porphyry deposits in british columbia canada afton mount milligan mount polley and copper mountain have been compared to comment on the likely detrital gold expression of similar systems globally populations of gold grains collected from in situ hypogene mineralization as well as fluvial deposits downstream of these deposits have been characterized in terms of their alloy composition au ag cu hg and pd and associated mineral inclusions these data are combined to generate a microchemical signature gold compositions vary according to the alteration zone within a porphyry system previous compositional studies of gold in porphyry systems have focused on the most economically important ore associated with potassic alteration wherein native gold hosted either by bornite or chalcopyrite comprises tiny blebs typically 5 20 m containing detectable cu in the gold alloy to a maximum of around 5 but quite variable 2 30 wt ag the presence of such grains have been confirmed in hypogene ore from the four systems studied but they have been shown to be compositionally distinct from detrital gold collected from nearby fluvial placers which exhibit a strong pd and hg signature both in the alloy and as mineral inclusions several workers have described late stage veins associated with alkalic porphyries which contain distinctive pd hg bearing minerals in association with other sulphides and sulphosalts this unusual mineralogy has been observed in the mineral inclusion suites of populations of detrital gold grains collected in the environs of the porphyry systems we conclude that whilst the micron scale cu rich gold grains formed in potassically altered rocks are in general too small to be recovered during routine sediment sampling those formed in later stage hydrothermal systems are larger and exhibit a distinctive microchemical signature which may be differentiated from those of gold formed in other mineralizing systems consequently compositional studies of detrital gold could underpin a mineral indicator methodology in the exploration for alkalic porphyry cu au deposits

lunar mare volcanism stratigraphy eruption conditions and the evolution of secondary crusts abstract lunar mare basalt deposits cover 17 of the lunar surface occur preferentially in topographic lows on the nearside and have a total volume estimated at 1 107 km3 analysis of returned samples and photogeologic and remote sensing studies shows that mare volcanism began prior to the end of heavy bombardment the period of cryptomare formation in pre nectarian times and continued until the copernican period a total duration approaching 3 5 4 ga stratigraphic analyses show that the flux was not constant but peaked in early lunar history during the imbrian period which spans the period 3 85 3 2 ga average volcanic output rate during this peak period was about 10 2 km 3 a very low relative to the present global terrestrial volcanic output rate and comparable to the present local output rates for individual volcanoes such as vesuvius and kilauea hawaii volcanic landforms indicate that many eruptions were of high volume and long duration some eruptions associated with sinuous rules may have lasted of the order of a year and emplaced 103 km3 of lava representing the equivalent in one year of about 70 000 years at the average flux shallow magma chambers were uncommon the nearsidefarside mare deposit asymmetry can be readily explained by differences in crustal thickness magma ascending from the mantle or from a buoyancy trap at the base of the crust should preferentially extrude to the surface on the nearside but should generally stall and cool in dikes in the farside crust extruding only in the deepest basins the occurrence of farside maria within craters whose diameter is generally near to or less than the thickness of the crust may be accounted for by the difference between local and regional compensation dikes that establish pathways to the surface on the nearside should have very high volumes comparable to the volumes associated with many observed flows and sinuous rilles an abundance of dikes should exist in the lower crust of the moon many more than those feeding surface eruptions the upper limit is 37 50 of the crust by volume the presence and abundance of such dike swarms have important implications for the interpretation of the average composition of the lunar crust and the composition of basin and crater ejecta the interplay between thermal contraction and differentiation leads to net cooling and ultimate contraction of the outer portions of the moon resulting in a regional horizontal compressive stress acting on the lunar crust in addition overall cooling and deepening of sources require the production of ever larger volumes of magma in order to reach the surface with time stresses became high enough so that few dikes could open to the surface causing eruptive activity to be severely diminished in the eratosthenian and perhaps to cease in the copernican period lower stress levels are required to terminate eruptive activity on the lunar farside consistent with the imbrian age of the farside maria and the nearside location of the youngest maria lunar mare deposits provide an example of the transition from primary crusts to secondary crusts and illustrate the significance of several factors in the evolution of secondary crusts such as crustal density variations in crustal thickness presence of impact basins state and magnitude of stress in the lithosphere and general thermal evolution these factors are also responsible for the extremely low volcanic flux even during periods of peak extrusion

ages of mare basalts on the lunar nearside the chronology of lunar volcanism is based on radiometric ages determined from apollo and luna landing site samples regional stratigraphic relationships and crater degradation and size frequency distribution data for units largely defined prior to the end of the apollo program here we report on new crater size frequency distribution data for 139 spectrally and morphologically defined basalt units which are exposed in six nearside impact basins australe tranquillitatis humboldtianum humorum serenitatis and imbrium crater size frequency distribution measurements are a statistically robust and accurate method to derive absolute model ages of unsampled regions of the moon compared to crater degradation ages crater size frequency ages performed on spectrally defined units offer significant improvements in accuracy our investigation showed that 1 in the investigated basins lunar volcanism was active for at least 1 5 2 0 b y starting at about 3 9 4 0 b y and ceasing at 2 0 b y 2 most basalts erupted during the late imbrian period at about 3 6 3 8 b y 3 significantly fewer basalts were emplaced during the eratosthenian period 4 basalts of copernican age were not found in any of the investigated basins 5 lunar basin filling volcanism probably started within 100 m y after the formation of the individual basins we also assessed the relationship between impact basin age and the history of mare basalt emplacement in these basins we found that 1 in all pre nectarian basins australe and tranquillitatis as well as in the humboldtianum basin which is of nectarian age the distribution of surface ages is clearly dominated by only a single peak in the number of erupted units at 3 6 3 8 b y 2 in the younger basins humorum serenitatis and imbrium a second peak at 3 3 3 5 b y is observed 3 basalt eruptions younger than 2 6 b y occur only intermittently and 4 in the youngest basins serenitatis and imbrium we see an extended period of active basin filling volcanism 1 5 1 6 b y which is 500 m y longer than in the australe and humorum and even 1 0 b y longer than in tranquillitatis and humboldtianum

atmospheric oxidation of the pyritic waste rock in maardu estonia 2 an assessment of aluminosilicate buffering potential the assessment of the aluminosilicate buffering potential during acid weathering of the estonian alum shale is provided it is found that the stoichiometric interaction between dissolved pyrite oxidation products and illite of the shale best describe the buffering process and are consistent with earlier field studies the scheme includes incongruent dissolution of illite with smectite and k jarosite precipitating this complex mechanism involves buffering of 8 of the acidity by k and temporary precipitation of 25 of the acidity as k jarosite dissolution proceeds at a low ph 1 5 3 until all pyrite in the shale particle is oxidised hence if the total amount of illite present is larger than needed for stoichiometric interactions only part of it is involved in a buffering process neutralising a certain percentage of acidity the next stage in shale weathering is the incongruent dissolution of k jarosite with the release of the precipitated acidity and the formation of ferric oxyhydroxide

initial observations from the lunar orbiter laser altimeter lola as of june 19 2010 the lunar orbiter laser altimeter an instrument on the lunar reconnaissance orbiter has collected over 2 0 10 9 measurements of elevation that collectively represent the highest resolution global model of lunar topography yet produced these altimetric observations have been used to improve the lunar geodetic grid to 10 m radial and 100 m spatial accuracy with respect to the moon s center of mass lola has also provided the highest resolution global maps yet produced of slopes roughness and the 1064 nm reflectance of the lunar surface regional topography of the lunar polar regions allows precise characterization of present and past illumination conditions lola s initial global data sets as well as the first high resolution digital elevation models dems of polar topography are described herein

improved chandrayaan 1 m3 data a northwest portion of the aristarchus plateau and contiguous maria abstract we provide and test a method to obtain significant improvement of available chandrayaan 1 m3 data the advance is achieved using the gaussian convolution of spectra and fourier filtration of images the main result is imagery of the reflectance across different wavelengths as well as parameters of 1 m and 2 m absorption bands with unprecedented quality this approach can be particularly useful for further investigations using m3 data since it produces improved imagery of various lunar surface characteristics we studied a region comprising a portion of the aristarchus plateau montes agricola and a small part of the mare surface in ocean procellarum to the north of montes agricola we found that the lava flows in the area between the aristarchus plateau and montes agricola have a chemical mineral composition different in comparison with mare areas to the northwest of the ridge montes agricola we also identified distinct spectral properties of morphologically young craters located on the plateau and mare surface a correlation diagram for positions of the minima of the 1 m and 2 m bands allows a cluster analysis of the region and we map areas associated with a cluster corresponding to pyroclastic glasses relationships between geologic and spectral parameter maps were established

tourmalinite as a potential host rock for gold in the caledonides of southeast ireland initial investigations designed to test the potential for gold in a series of lithologies associated with tourmalinites and coticules in the neighbourhood of the caledonian leinster granite of southeast ireland are reported the results of geological mapping geochemical analyses and panning of stream sediments indicate that significant levels of gold are associated with some tourmalinite zones the possible exploration implication of this work is that tourmalinites have potential as target indicators although secondary controls on mineralization are also important

thermal and magmatic evolution of the moon as with all science our continually developing concepts of lunar evolution are firmly tied to both new types of observations and the integration of these observations to the known pool of data this process invigorates the intellectual foundation on which old models are tested and new concepts are built just as the application of new observational tools to lunar science in 1610 galileo s telescope and 1840 photography yielded breakthroughs concerning the true nature of the lunar surface the computational and technological advances highlighted by the apollo and post apollo missions and associated scientific investigations provided a new view of the thermal and magmatic evolution of the moon 1 1 pre apollo view of the thermal and magmatic evolution of the moon many of the early views of the moon manifested in mythology and art throughout the world were primarily tied to lunar and terrestrial cycles and the relationships between the sun and the moon prophetically myths involving the lunar deities mwuetsi from zimbabwe and coyolxauhqui from mexico told of rather violent or catastrophic events in which the moon was expunged from the earth numerous ancient scientific observations were made about the nature of the moon ranging from those uncovered in early neolithic sites that correctly identified mare crisium and mare humorum to the insights made by greek philosophers such as anaxagoras ca 500 428 b c and democritus ca 460 370 b c who attached terrestrial analogues to its character stone mountains with the advent of the telescope 1610 and photography 1840 as scientific tools for lunar exploration semiquantitative data could be collected that would provide an intellectual foundation for scientific interpretation initially modern terrestrial geological analogs were extended to the moon lunar highlands volcanic craters seas combined with the rigors of computational modeling these observational data were extended to predict the original thermal state of the moon and its thermal and magmatic history its proximity to the earth

a new indicator mineral methodology based on a generic bi pb te s mineral inclusion signature in detrital gold from porphyry and low intermediate sulfidation epithermal environments in yukon territory canada porphyry epithermal and orogenic gold are two of the most important styles of gold bearing mineralization within orogenic belts populations of detrital gold resulting from bulk erosion of such regions may exhibit a compositional continuum wherein ag cu and hg in the gold alloy may vary across the full range exhibited by natural gold this paper describes a new methodology whereby orogenic and porphyry epithermal gold may be distinguished according to the mineralogy of microscopic inclusions observed within detrital gold particles a total of 1459 gold grains from hypogene eluvial and placer environments around calc alkaline porphyry deposits in yukon nucleus revenue casino sonora gulch and cyprus klaza have been characterized in terms of their alloy compositions au ag cu and hg and their inclusion mineralogy despite differences in the evolution of the different magmatic hydrothermal systems the gold exhibits a clear bi pb te s mineralogy in the inclusion suite a signature which is either extremely weak or most commonly absent in both yukon orogenic gold and gold from orogenic settings worldwide generic systematic compositional changes in ore mineralogy previously identified across the porphyry epithermal transition have been identified in the corresponding inclusion suites observed in samples from yukon however the bi te association repeatedly observed in gold from the porphyry mineralization persists into the epithermal environment ranges of p t x conditions are replicated in the geological environments which define generic styles of mineralization these parameters influence both gold alloy composition and ore mineralogy of which inclusion suites are a manifestation consequently we propose that this methodology approach can underpin a widely applicable indicator methodology based on detrital gold

the formation and potential importance of cemented layers in inactive sulfide mine tailings abstract investigations of inactive sulfide rich tailings impoundments at the heath steele new brunswick and waite amulet quebec minesites have revealed two distinct types of cemented layers or hardpans that at heath steele is 10 15 cm thick occurs 20 30 cm below the depth of active oxidation is continuous throughout the tailings impoundment and is characterized by cementation of tailings by gypsum and fe ii solid phases principally melanterite hardpan at the waite amulet site is only 1 5 cm thick is laterally discontinuous 10 100 cm occurs at the depth of active oxidation and is characterized by cementation of tailings by fe iii minerals principally goethite lepidocrocite ferrihydrite and jarosite at heath steele an accumulation of gas phase co2 of up to 60 of the pore gas occurs below the hardpan the calculated diffusivity of the hardpan layer is only about 1 100 that of the overlying uncemented tailings the pore water chemistry at heath steele has changed little over a 10 year period suggesting that the cemented layer restricts the movement of dissolved metals through the tailings and also acts as a zone of metal accumulation generation of a cemented layer therefore has significant environmental and economic implications it is likely that in sulfide rich tailings impoundments the addition of carbonate rich buffering material during the late stages of tailings deposition would enhance the formation of hardpan layers

long term controls on continental scale bedrock river terrace deposition from integrated clast and heavy mineral assemblage analysis an example from the lower orange river namibia abstract establishing relationships between the long term landscape evolution of drainage basins and the fill of sedimentary basins benefits from analysis of bedrock river terrace deposits these fragmented detrital archives help to constrain changes in river system character and provenance during sediment transfer from continents source to oceans sink thick diamondiferous gravel terrace deposits along the lower orange river southern namibia provide a rare opportunity to investigate controls on the incision history of a continental scale bedrock river clast assemblage and heavy mineral data from seven localities permit detailed characterisation of the lower orange river gravel terrace deposits two distinct fining upward gravel terrace deposits are recognised primarily based on mapped stratigraphic relationships cross cutting relationships and strath and terrace top elevations and secondarily on the proportion of exotic clasts referred to as proto orange river deposits and meso orange river deposits the older early to middle miocene proto orange river gravels are thick up to 50 m and characterised by a dominance of karoo supergroup shale and sandstone clasts whereas the younger plio pleistocene meso orange river gravels 6 23 m thick are characterised by more banded iron formation clasts mapping of the downstepping terraces indicates that the proto gravels were deposited by a higher sinuosity river and are strongly discordant to the modern orange river course whereas the meso deposits were deposited by a lower sinuosity river the heavy minerals present in both units comprise magnetite garnet amphibole epidote and ilmenite with rare titanite and zircon grains the concentration of amphibole epidote in the heavy minerals fraction increases from the proto to the meso deposits the decrease in incision depths recorded by deposit thicknesses above strath terraces and the differences in clast character size and roundness and type between the two units are ascribed to a more powerful river system during proto orange river time rather than reworking of older deposits changes in provenance or climatic variations in addition from proto to meso orange river times there was an increase in the proportion of sediments supplied from local bedrock sources including amphibole epidote in the heavy mineral assemblages derived from the namaqua metamorphic complex this integrated study demonstrates that clast assemblages are not a proxy for the character of the matrix and vice versa because they are influenced by the interplay of different controls therefore an integrated approach is needed to improve prediction of placer mineral deposits in river gravels and their distribution in coeval deposits downstream

microchemical studies of placer and lode gold in the klondike district yukon canada 1 evidence for a small gold rich orogenic hydrothermal system in the bonanza and eldorado creek area orogenic gold camps are commonly associated with placer deposits although in many cases the relationship between placer and lode source may be unclear placer gold deposits in bonanza and eldorado creeks in the northern klondike district goldfield yukon canada probably yielded more than 2 million ounces moz from a small geographic area but known occurrences of gold bearing orogenic style veins from which the placers were derived accounted for only a few thousand ounces the alloy chemistry and mineralogy of opaque mineral microinclusions microchemical signatures within these gold grains were compared to that of samples collected during a detailed placer gold sampling program collection of placer samples from the headwaters of watercourses in this unglaciated area allowed identification of microchemical signatures within gold populations from proximal sources which augmented information from lode gold sources to facilitate characterization of local gold mineralization a total of 1 163 gold grains from 18 lode sources and 2 777 grains from 27 placer localities within the bonanza and eldorado creek drainages were characterized in terms of the ag and hg content of the alloy together with the associated inclusion suite and two main compositional ranges along with several subtypes were identified type 1 gold is a simple au ag alloy but various subtypes have been identified on the basis of different ranges of ag and or specific inclusion assemblages type 2 gold is an au ag hg alloy composition the spatial arrangement of the gold types shows a systematic change in microchemical signature the lowest ag gold occurs in the lone star ridge area and the ag content increases both in the northeast and southwest the appearance of te bearing mineral inclusions in populations coincides with increasing ag and argentite inclusions are present only in high ag gold toward the periphery of study area type 2 gold is absent at lone star ridge and all localities to the east but is progressively more abundant in sample localities to the west the geographic distribution of gold types correlates well with placer abundance inferred from the production from previous mining activity and the study area is bounded by creeks and gulches in which there was insufficient placer gold for economic extraction we conclude that the lone star ridge area represents the epicenter of a single hydrothermal system in which spatial and temporal fluid evolution has generated compositional zonation variation in ag is ascribed to decrease in au ag aq following preferential au deposition in the center of the system controls on hg contents within au alloy are unclear but may be a consequence of mineralization temperature the complex but consistent signatures of placer gold samples from the eldorado creek drainage represents liberation of types 1 and 2 gold grains which coexist in some lode occurrences the different proportions of types 1 and 2 gold observed in placer and lode samples from west of lone star ridge reflect both temporal and spatial evolution of the hydrothermal system the main eldorado creek placers exhibit a signature most similar to lode gold from the buckland and nugget zones on lone star ridge placer gold in upper bonanza creek is distinguished by a relatively narrow ag range and the small but consistent presence of hessite in the inclusion suite no corresponding lode occurrence for this gold type has been identified to date this is the first time that the compositional signatures of major placer gold deposits derived from orogenic gold vein systems has been studied in this detail and the application of basic chemical principles to fluid evolution and electrum precipitation has allowed demarcation of an area in which extremely rich gold mineralization was formerly present while simultaneously identifying the most promising areas for further exploration for undiscovered lode gold

cratering history and lunar chronology the moon is exceptional and important because it is the only planetary body besides the earth for which we have both a detailed stratigraphic history and datable rock samples that can be related to specific geomorphologic units fig 5 1 the moon has preserved much of its magmatic and impact record of at least the last 4 billion years while its endogenic history is of great interest for the fundamentals of planetary interiors and surfaces the moon has become a calibration plate for the cratering record of the earth moon system and by extrapolation of the entire inner solar system if one assumes a heliocentric origin for impactor populations these populations range from asteroids through long and short period comets to interplanetary dust and cover a size range from hundreds of kilometers to micrometers figure 5 1 telescopic view of the nearside of the earth s moon with landing sites of the apollo and luna missions this chapter reviews the presently available data sets in support of this paradigmatic assumption as follows 1 the phenomenology of lunar impact craters 2 the terrestrial record of the impact cratering process and the interpretation of terrestrial impactites as far as this ground truth is relevant for the interpretation of lunar impact craters and datable lunar impact breccias and melt rocks 3 the theory and numerical simulation of the cratering process and the characteristics of the earth moon crossing population of impactors asteroids and comets 4 the principles of relative age dating of lunar surface units and the general lunar stratigraphy 5 the stratigraphic significance and ages of lunar samples impactites and basalts and based on this data set the absolute ages of lunar surface units 6 the cratering rate of the moon as a function of time and 7 the time calibration of this cratering rate based on the

the variability of crater identification among expert and community crater analysts abstract the identification of impact craters on planetary surfaces provides important information about their geological history most studies have relied on individual analysts who map and identify craters and interpret crater statistics however little work has been done to determine how the counts vary as a function of technique terrain or between researchers furthermore several novel internet based projects ask volunteers with little to no training to identify craters and it was unclear how their results compare against the typical professional researcher to better understand the variation among experts and to compare with volunteers eight professional researchers have identified impact features in two separate regions of the moon small craters diameters ranging from 10 m to 500 m were measured on a lunar mare region and larger craters 100s m to a few km in diameter were measured on both lunar highlands and maria volunteer data were collected for the small craters on the mare our comparison shows that the level of agreement among experts depends on crater diameter number of craters per diameter bin and terrain type with differences of up to 45 we also found artifacts near the minimum crater diameter that was studied these results indicate that caution must be used in most cases when interpreting small variations in crater size frequency distributions and for craters 10 pixels across because of the natural variability found projects that emphasize many people identifying craters on the same area and using a consensus result are likely to yield the most consistent and robust information

atmospheric oxidation of the pyritic waste rock in maardu estonia 1 field study and modelling a field survey and modelling of the oxidation and carbonate buffering reactions inside the alum shale containing waste rock dumps located in maardu estonia was accomplished in the slope areas the shale has been altered at high temperatures due to the spontaneous combustion and the pyritic acidity has been eliminated through migration of sox gases out from the dump in the central parts of the waste rock plateaus low temperature pyrite oxidation fronts develop towards the dump depth and towards the centres of individual shale lumps the main secondary phases precipitating in the weathering profile are gypsum ferric oxyhydroxide k jarosite and smectite the respective field data made it possible to calibrate the two stage oxygen diffusion model and the characteristic pyrite oxidation rate 0 06 0 08 mol of pyrite reacted per kg of available water pyrox h2o value was estimated to describe the first tens of years of dump performance the model is capable to compare different shale disposal strategies that are illustrated with two case scenarios the buffering of sulphuric acid by mg calcite appears to be an incongruent reaction with gypsum precipitating that leads to the build up of the high mg ca ratio in the leachate application of the mg ca method estimates the pyrox h2o value in the range of 0 05 0 14 mol kg

lunar coordinates in the regions of the apollo landers laser retroreflectors were placed on the moon by apollo 11 apollo 14 apollo 15 and lunakhod 2 since then lunar laser ranging retroreflector measurements of the true distances between retroreflectors and earth based laser telescopes have been made by recording transit times the accuracy of these measurements has evolved from 10 cm in the 1970s to 3 cm in the 1990s accurate lunar coordinates of the retroreflectors were determined from these measurements williams et al 1996 apollo lunar surface experiment packages alsep were delivered to the lunar surface on missions 12 14 15 16 and 17 coordinates of these stations were determined from very long baseline interferometry vlbi measurements of their transmissions the vlbi measurements were combined with the laser ranging coordinates available at that time king et al 1976 these solutions for the alsep locations have been modified to be compatible with the current retroreflector solutions coordinates of lunar module locations and nearby craters are given

environmental magnetism as a dating proxy for recent overbank sediments of peri industrial regions in the czech republic and uk abstract twenty five floodplain sediment profiles from seven rivers in eastern czech republic and three in north west england were collected to examine the hypothesis that magnetic enhancement in recent sediments is predominantly of anthropogenic origin and that magnetic parameters can be used as a dating proxy reflecting changes in intensity of industry sources over time natural sources of magnetic enhancement were excluded and anthropogenic enhancement was identified as exhibiting elevated values of lf arm sirm sirm and s ratios with low values of fd magnetic spherules typically formed through fossil fuel combustion processes were observed by scanning electron microscopy sem in these sediments to assess the potential of magnetic parameters as a chronometer the approach was compared with frequently used dating techniques concentrations of heavy metals and 137 cs the floodplain profiles were divided to three groups according to the characteristics of their trends with depth in magnetic parameters lf in particular and the suitability of magnetic properties as a dating proxy group 1 which included the majority of the profiles exhibited magnetic enhancement in the upper part of its profiles and a single maximum in lf this group exhibited a clear suitability for our proposed magnetic dating as the magnetic record reflected the industrial history of the region and was aligned with the chronologies of the other dating techniques profiles magnetically enhanced throughout their depth and lacking any clear trend comprised group 2 here a mineral magnetic approach to dating was limited as the magnetic signal was diluted by a high sedimentation rate or impacted by local anthropogenic factors all profiles from england were included in group 3 because their magnetic depth profiles were influenced by natural sources of magnetic particles or specific sedimentary conditions and a longer industrial history and thus needed an individual interpretation however they still reflected the regional deposition history of industrial sources of ferrimagnetic particles overall magnetic parameters proved to be an efficient dating proxy with potential for recently aggrading rivers