rock albedo and monitoring of thermal conditions in respect of weathering some expected and some unexpected results broadly speaking there is at least within geomorphic circles a general acceptance that rocks with low albedos will warm both faster and to higher temperatures than rocks with high albedos reflectivity influencing radiative warming upon this foundation are built notions of weathering in respect of the resulting thermal differences both at the grain scale and at the scale of rock masses here a series of paving bricks painted in 20 per cent reflectivity intervals from black through to white were used to monitor albedo influenced temperatures at a site in northern canada in an attempt to test this premise temperatures were collected for five months for the rock surface and the base of the rock the blocks being set within a mass of local sediment resulting thermal data did indeed show that the dark bricks were warmer than the white but only when their temperatures were equal to or cooler than the air temperature as brick temperature exceeded that of the air so the dark and light bricks moved to parity indeed the white bricks frequently became warmer than the dark it is argued that this negating of the albedo influence on heating is a result of the necessity of the bricks both white and black to convect heat away to the surrounding cooler air the darker brick being hotter initially convects faster than the white as a product of the temperature difference between the two media thus where the bricks become significantly hotter than the air they lose energy to that air and so their respective temperatures become closer the albedo influence being superceded by the requirement to equilibrate with the surrounding air it is argued that this finding will have importance to our understanding of weathering in general and to our perceptions of weathering differences between different lithologies copyright 2005 john wiley sons ltd

metallogenic evolution of convergent margins selected ore deposit models abstract metallogenic patterns in convergent margin arcs are related to thickness of the arc crust and its petrologic evolution which are themselves linked by a positive correlation between average silica content of arc rocks and average thickness of arc crust in general tin mercury antimony and fluorine are most abundant in areas of thickest crust although the composition of ore deposits is strongly controlled by deep crustal and mantle features the actual form and type of many ore deposits is controlled by upper crustal features particularly the relative abundance of carbonate and silicate country rock for instance epithermal precious metal deposits are commonly associated with subaerial silicic volcanism which generally forms in the later stages of arc evolution deposits of this type will be absent if arc volcanism is terminated prematurely or removed if subduction of thickened or hot oceanic crust causes extreme uplift and consequent erosion of the upper parts of the arc similarly chimney manto limestone replacement lead zinc silver deposits are common only in terranes with extensive thick limestone units which are commonly formed in shallow shelf environments several important types of convergent margin deposits remain poorly understood acid sulfate deposits in primitive oceanic volcanic arcs are associated with bimodal volcanic suites that appear to have formed at an early stage in the evolution of the arc alkaline porphyry copper deposits are closely associated with calc alkaline porphyry copper deposits commonly in the same volcanic arc although they appear to have formed farther back from the trench or during periods of oblique subduction or arc reversal massive iron oxide deposits and related base and precious metal mineralization are closely associated with silicic magmas that form during later stages of arc evolution in addition to tectonic and petrologic factors metallogenic patterns probably reflect global forcing mechanisms the most important of which are global seawater anoxia and plate reorganizations global anoxia produces deep water environments that favor sedex mineralization and can promote subsurface ore deposition where anoxic bottom waters recharge underlying aquifers plate reorganizations can lead to ore deposition by providing extensional environments in the upper crust and possibly by facilitating partial melting of oceanic crust that has been modified by earlier subducting slabs

effect of moisture and temperature conditions on the decay rate of a purple mudstone in southwestern china soil formation and geomorphology are primarily influenced by the rock decay which in turn is strongly determined by moisture and temperature conditions however it remains unclear whether rock decay is dominated by thermal stresses or by hydration disintegration and there is little information on mudstone decay rate in southwestern china this study hypothesized that rock decay is dominated by hydration mechanism and focused on the physical decay characteristics of typical purple mudstones using a combination of field and laboratory based experiments the bedrock of a penglaizhen group j 3 p in yanting county sichuan province southwestern china was exposed and covered with nylon fabric in situ soil depths of 10 20 40 and 60 cm were laid on this nylon fabric in 2003 and the decay rate the quantity of clastic particles 2 mm that were decayed from the bedrock in t km 2 yr 1 under the nylon fabric was measured both in 2005 and 2009 in addition fresh mudstones sampled from the matoushan group k 2 m the tuodian group j 3 t and the lufeng group j 1 l in yuanmou county shuangbai county and lufeng county of yunnan province southwestern china respectively were subjected to alternating applications of moisture temperature and their interaction seven treatments in the laboratory and their decay ratios the mass of decayed rock of 2 mm clastic particles to sampled rock mass in percent were measured in 2010 in the field the decay rate of the bedrock showed a significant p 0 05 positive relationship with both the daily moisture and temperature variation at the interface between the soil and bedrock in the laboratory results showed that the effect of moisture variation but not temperature alternation on rock decay was apparent suggesting that purple rock decay is dominated by hydration mechanism freezing thawing in particular affects the sampled rocks because it causes more spalling and fracturing the j 3 t rock had the highest decay ratio because it had the highest clay mineral content and porosity of the three rock types hierarchical clustering analysis suggested that the variation of moisture content and h2o phase solid or liquid within rock plays a key role in rock decay processes both field and laboratory studies consistently showed that the alteration of wetting drying and freezing thawing as well as moisture content substantially influenced rock decay c 2012 elsevier b v all rights reserved

the sir c x sar synthetic aperture radar system the spaceborne imaging radar c x band synthetic aperture radar sir c x sar was a joint united states german italian space agency imaging radar system successfully flown aboard the shuttle endeavor in april 1994 and again in september october 1994 the multifaceted sir c x sar represents a major technological step forward in radar remote sensing and is the first spaceborne multifrequency polarimetric sar the united states developed sir c operated at l and c band each with quad polarization the sir c antenna was an active phased array with the capability for electronic beam steering and multiple swath width illumination the german italian x sar operated at x band with a single polarization using a slotted waveguide antenna mechanically steerable in elevation sir c and x sar were designed to operate synchronously collecting data over common sites synchronously a total of 143 hours 93 terabits of sar data were recorded on tape

what is underneath the juvenile ordovician macquarie arc eastern australia a question resolved using silurian intrusions to sample the lower crust abstract the ordovician intra oceanic macquarie arc of eastern australia collided with the eastern gondwanan margin at 440 ma however the deep crustal architecture resulting from this assembly is poorly known this is addressed here by a zircon u pb hf study of the post assembly silurian browns creek intrusive complex and davies creek granite dykes that intrude into the arc and not adjacent gondwanan sedimentary sequences zircon u pb dating integrated with cl imagery indicate two igneous phases at 430 437 ma and 420 426 ma and a zircon recrystallisation phase at 395 396 ma attributed to a late thermal event the magmatic zircon initial hf values vary from 5 1 to 4 7 this signature indicates the source of these granitic rocks is strongly influenced by typical pre silurian gondwanan material granitic rock and zircon compositions demonstrate that at the likely temperature of the silurian granitic magma especially the davies creek granite dykes inherited source zircons were mostly dissolved explaining the absence of pre ordovician xenocrysts within the zircon population the unradiogenic hf isotopic signatures preserved in the silurian magmatic zircons demonstrate the contribution of gondwanan crustal material to the magma source region these results support the interpretation of the macquarie arc as an intra panthalassa ocean allochthon emplaced and resting over the edge of gondwanan crystalline basement possibly including the continent derived sedimentary rocks of the adaminaby group

weakening of gneiss surfaces colonized by endolithic lichens in the temperate climate area of northwest italy a role of lithobionts in geomorphological processes is increasingly argued but the spatio temporal scale of their impact is largely unexplored in many ecosystems this study first characterizes in the temperate zone northwest italy the relationships between lithobiontic communities including endolithic lichens and the hardness of their siliceous rock substrate villarfocchiardo gneiss the communities are characterized on humid and xeric quarry surfaces exposed for decades and natural outcrops exposed for centuries in terms of lichen and microbial constituents using a combined morphological and molecular approach and with regard to their development on and within the gneiss a lichen species belonging to acarosporaceae polysporina sarcogyne acarospora group needing taxonomic revision chasmoendolithically colonizes both the humid and xeric quarry surfaces on which epilithic cyanobacterial biofilms and epilithic pioneer lichens respectively occur light and electron microscopic observations show the development of the endolithic thalli within rock microcracks and the hyphal penetration along crystal boundaries down to depths of 1 to 3 mm more pronounced within the humid surfaces such colonization patterns are likely related to biogeophysical deterioration while no chemical alteration characterizes minerals contacted by the endolithic lichen by contrast on natural outcrops where the endolithic colonization is negligible a reddish rind below epilithic lichens indicates chemical weathering processes schmidt hammer measurements highlight that the endolithic lichens deeply affect the hardness of the gneiss down to 60 with respect to fresh controls and surfaces only colonized by cyanobacteria exerting a significantly higher weakening effect with respect to the associated epilithic lithobionts the phenomenon is more remarkable on humid than on xeric quarry surfaces and natural outcrops where epilithic lichens are likely involved in long term hardening processes supporting surface stabilization endolithic lichens are thus active biogeomorphological agents at the upper millimetric layer of siliceous rocks in temperate areas exerting their weakening action during the early decade scaled stages of surface exposure copyright 2015 john wiley sons ltd

a crucial role for slab break off in the generation of major mineral deposits insights from central and eastern australia in the lachlan fold belt of southeastern australia major orogenic gold and porphyry gold copper deposits formed simultaneously within distinct tectonic settings during a very short time interval at ca 440 ma the driving mechanism that controlled the temporal coincidence of these deposits remains largely unexplained a review of contemporaneous metallogenic tectonic magmatic and sedimentological events in central and eastern australia reveals that a change in subduction dynamics along the australian sector of the early palaeozoic circum gondwana mega subduction system could have influenced lithospheric stress conditions far inboard of the subduction margin the magnitude of ore formation and the spatial extent of related events are proposed in this paper to have been controlled by the interplay of mantle processes and lithospheric changes that followed slab break off along a portion of the mega subduction system surrounding gondwana at that time slab break off after subduction lock up caused mantle upwelling that in turn provided an instantaneous heat supply for magmatic and hydrothermal events coincident reorganisation of lithospheric stress conditions far inboard of the proto pacific margin of australia controlled reactivation of deep lithospheric fault structures these fault systems provided a pathway for fluids and heat fuelled by mantle upwelling into the upper lithosphere and caused the deposition of 440 ma gold deposits in the lachlan fold belt as well as a range of metallogenic tectonic and sedimentary changes elsewhere in central and eastern australia

a note on the attenuation of surface gravity waves by rainfall rainfall has long been associated with damping of short surface gravity waves a theory is presented which uses a thin rain induced turbulent surface layer to explain the enhanced attenuation in the presence of a thin turbulent surface layer the e folding attenuation time for the 30 cm wavelength surface gravity waves needed for remote sensing of the ocean surface using synthetic aperture radar sar is reduced from several minutes to several seconds this explains the observation of low sar radar return from regions of high rainfall longer wavelengths are also affected depending on the strength of the mixing and the thickness of the turbulent layer

biosignatures and microbial fossils in endolithic microbial communities colonizing ca sulfate crusts in the atacama desert abstract since the description of microbial communities colonizing ca sulfate crusts in the atacama desert there has been much interest in the mechanisms that could lead to the formation and preservation of biosignatures or microbial fossils of these communities a key to understanding physico chemical processes of taphonomy and early diagenesis is to examine microfossils in their natural environment in this study we characterize organomineral traces and microbial fossils found around microbial communities present in these ca sulfate crusts through scanning electron microscopy microanalytical eds and raman spectroscopy techniques calcium carbonate precipitates were detected around remnants of cryptoendolithic algae beneath the crust surface as what seems to be the final step in the organomineralization of these cryptoendolithic communities we also observed alga cell remains permineralized by mg si rich minerals inside gypsum crystals additionally mg si bearing minerals formed a web like structure within the hypoendolithic cyanobacterial habitat via permineralization of extracellular polymeric substances our observations indicate that despite the extremely hyperarid environment microenvironmental conditions may be appropriate for the formation of biosignatures and microbial fossils of extinct endolithic microbial communities a model of the possible organomineralization processes involved is presented

origin of storm footprints on the sea seen by synthetic aperture radar spaceborne synthetic aperture radar can detect storm footprints on the sea coastal weather radar from cape hatteras provides evidence that the echo free hole at the footprint core is the result of wave damping by rain the increased radar cross section of the sea surrounding the echo free hole results from the divergence of the precipitation forced downdraft impacting the sea the footprint boundary is the gust front its oriention is aligned with the direction of the winds aloft which are transported down with the downdraft and its length implies downdraft impact 1 hour earlier at a quasi stationary impact spot the steady localized nature of the storm remains a mystery

porphyry gold copper mineralisation in the cadia district eastern lachlan fold belt new south wales and its relationship to shoshonitic magmatism the cadia porphyry gold copper district is the largest hydrothermal intrusion related gold deposit in eastern australia discovered in 1992 by newcrest mining limited pre mine resources in the district were in excess of 585 t au and 2 35 mt cu the cadia district lies within shoshonitic subaqueous volcanic rocks of the late ordovician molong volcanic belt in the eastern lachlan fold belt lfb of new south wales an island arc tectonic setting is envisaged for the formation of these volcanic rocks but the nature of the arc basement and geometry of the subduction zone s is debated mineralisation occurs in four principal porphyry deposits cadia hill cadia ridgeway cadia east cadia far east and cadia quarry as sheeted and stockwork quartz sulfide veins and locally as broadly stratabound disseminated mineralisation cadia east and skarn big cadia and little cadia all of the porphyry deposits show a close spatial association with shoshonitic monzodiorite to quartz monzonite dykes and stocks of the cadia intrusive complex cic gold copper mineralisation is hosted by these intrusions and also by the enclosing forest reefs volcanics frv wall rocks hydrothermal alteration associated with mineralisation is potassic which is overprinted by selectively pervasive propylitic and silica albite assemblages petrological studies and major and trace element analysis of rocks of the cic and frv as well as of other intrusions in the cadia district that appear unrelated to mineralisation have been conducted unaltered samples from the cic are characterised by high k2o contents up to 6 5 wt and molecular k na ratios consistently 1 confirming the alkalic and shoshonitic nature of the complex the cic samples also fall just within the shoshonite field on ce yb ta yb and th yb ta yb plots although immediately adjacent to the calc alkaline field the frv are geochemically similar to the cic although lower in p2o5 and ce lree dacitic and hornblende porphyry intrusions from within the district but spatially unrelated to mineralisation have a distinctive geochemical signature and are not shoshonitic in composition the close spatial association between gold copper mineralisation and the shoshonitic monzonitic cic argues strongly for a genetic link between the two a similar association occurs at the economic goonumbla porphyry gold copper deposits in the eastern lfb while sub economic gold copper mineralisation at cargo and copper hill is associated with calc alkaline quartz diorite and dacitic intrusions the cadia district is considered to be an excellent example of the association of alkaline potassic magmas and gold copper porphyry style mineralisation

the wyoming gold deposits volcanic hosted lode type gold mineralisation in the eastern lachlan orogen australia the eastern lachlan orogen in southeastern australia is noted for its major porphyry epithermal skarn copper gold deposits of late ordovician age whilst many small quartz vein hosted or orogenic lode type gold deposits are known in the region the discovery of the wyoming gold deposits has demonstrated the potential for significant lode type mineralisation hosted within the same ordovician volcanic stratigraphy outcrop in the wyoming area is limited with the ordovician sequence largely obscured by clay rich cover of probable quaternary to cretaceous age with depths up to 50 m regional aeromagnetic data define a north south trending linear belt interpreted to represent the ordovician andesitic volcanic rock sequence within probable ordo silurian pelitic metasedimentary rocks drilling through the cover sequence in 2001 to follow up the trend of historically reported mineralisation discovered extensive alteration and gold mineralisation within an andesitic feldspar porphyry intrusion and adjacent volcaniclastic sandstones and siltstones subsequent detailed resource definition drilling has identified a substantial mineralised body associated with sericite carbonate albite quartz chlorite pyrite arsenopyrite alteration the wyoming deposits appear to have formed as the result of a rheological contrast between the porphyry host and the surrounding volcaniclastic rocks with the porphyry showing brittle fracture and the metasedimentary rocks ductile deformation the mineralisation at wyoming bears many petrological and structural similarities to orogenic lode style gold deposits although the timing of alteration and mineralisation in the wyoming deposits remain problematic a relationship with possible early to middle devonian deformation is considered likely

evidence for freeze thaw events and their implications for rock weathering in northern canada discussions regarding weathering in cold environments generally centre on mechanical processes and on the freeze thaw mechanism in particular despite the almost ubiquitous assumption of freeze thaw weathering unequivocal proof of interstitial rock water actually freezing and thawing is singularly lacking equally many studies have used the crossing of 0 c or values close to that as the basis for determining the number of freeze thaw events in order to assess the weathering regime at a site in northern canada temperatures were collected at the surface 1 cm and 3 cm depth for sets of paving bricks with exposures both vertical and at 45 orientated to the four cardinal directions temperature data were collected at 1 min intervals for 1 year these data provide unequivocal proof for the occurrence of the freezing and thawing of water on and within the rock freeze thaw events the freeze event is evidenced by the exotherm associated with the release of latent heat as the water actually freezes this is thought to be the rst record of such events from a eld situation more signi cantly it was found that the temperature at which freezing occurred varied signi cantly through the year and that on occasion the 1 cm depth froze prior to the rock surface the change in freeze temperature is thought to be due to the chemical weathering of the material coupled with on going salt inputs via the melting of snowfall which it is shown could occur throughout the winter despite air temperatures down to 30 c this nding regarding chemical weathering is also considered to be highly signi cant a number of thermal stress events were also recorded suggesting that rock weathering in cold regions is a synergistic combination of various chemical and mechanical weathering mechanisms copyright 2003 john wiley sons ltd

inception and early evolution of the ordovician macquarie arc of eastern gondwana margin zircon u pb hf evidence from the molong volcanic belt lachlan orogen abstract the ordovician macquarie arc is faulted against and surrounded by coeval gondwana derived quartz turbidites in the lachlan orogen of southeastern australia how these juvenile island arc rocks were emplaced and structurally interleaved with continental margin sequences of eastern gondwana is an ongoing debate understanding the inception of this arc is critical in building an accurate early paleozoic reconstruction for eastern gondwana however the arc s inception and early evolution are poorly constrained due to the lack of reliable geochronological data integrated field observations zircon u pb hf mineral and whole rock geochemistry are presented here for the oldest units of the molong volcanic belt which is a central strand of the dissected macquarie arc geochemistry indicates that these are calc alkaline rocks with high k locally shoshonitic to medium k affinities the stratigraphically lowest mafic volcanic and volcano sedimentary rocks of the mitchell formation have a unimodal earliest ordovician zircon u pb age of 479 8 3 8 ma with uniform depleted mantle like initial zircon ehf values of 12 to 13 the lack of pre ordovician zircons and the uniform positive initial ehf value indicate that the macquarie arc was initiated in an intra oceanic setting far from the influence of eastern gondwana the stratigraphically overlying fairbridge volcanics includes some more evolved volcano sedimentary components and has a polymodal but mostly ordovician zircon u pb age population with a youngest component at 444 3 2 4 ma overall its ordovician grains show a greater spread in initial ehf values from 14 down to 8 than the mitchell formation which suggests some continental influence at least 35 million years after the arc was initiated the lack of any significant gondwanan inheritance in early ordovician volcaniclastic rocks of the macquarie arc along with geochemical comparisons with modern island arcs suggest that the arc evolved outboard of gondwana probably as a result of steep easterly directed subduction as the macquarie arc approached eastern gondwana there would have been increasing quantities of continent derived sediment subducted beneath the arc which may account for the decreasing and more variable zircon initial ehf values and the appearance of sparse precambrian continental detritus at the arc s moribund stage the collision of the macquarie island arc with gondwana initiated the benambran orogeny and reflects an important mechanism of episodic continental growth involving the addition of juvenile oceanic crust to a continental margin which contrasts and alternates with periods of purely accretionary growth

ice volcano interaction of the 1996 gjalp subglacial eruption vatnajokull iceland volcanic eruptions under glaciers can cause dangerous floods and lahars1 2 3 and create hyaloclastite fragmented glassy rock mountains4 5 6 7 8 but processes such as the rate of heat transfer between ice and magma edifice formation and the response of the surrounding glacier are poorly understood because of the lack of data here we present observations from the fissure eruption at vatnajokull ice cap iceland in october 1996 in the 13 days of the eruption 3 km3 of ice were melted and the erupted magma fragmented into glass forming a hyaloclastite ridge 6 7 km long and 200 300 m high under 500 750 m of ice meltwater of temperatures of 15 20 c flowed along a narrow channel at the glacier bed into the grimsvotn subglacial lake for five weeks before draining in a sudden flood or jokulhlaup subsidence and crevassing of the ice cap occurred over the eruptive fissure and the meltwater path whereas elsewhere the glacier surface remained intact suggesting that subglacial eruptions do not trigger widespread basal sliding in warm based glaciers

thermal weathering of granite spheroidal boulders in a dry temperate climate northern dobrogea romania weathering microforms associated with exfoliation were investigated on 40 granitic spheroidal boulders identified on pricopan ridge m cin mountains in order to establish a spatial distribution pattern continuous thermal monitoring allowed the frequency and intensity distribution assessment of short term temperature changes triggered by summer storms of intense day night amplitudes and frost cycles across a uniform rounded boulder rock strength estimated by schmidt hammer tests differentiates a significantly weaker resistance on the southern face of the boulders rebound values of 27 to 33 in comparison with the northern face 43 50 the lowest resistance of the north south cross boulder profile corresponds to the southern gentle slopes 0 45 thus defining the most susceptible area to exfoliation and other weathering processes it is argued that this low resistant sector fits well with the maximum frequency and intensity of thermal processes recorded on the low and mid slopes 0 45 of the boulders south side with small differences from one process to another whilst the sector of 20 to 30 south corresponds to the peak activity of all in accordance the overlay map of exfoliated surfaces places the high frequency area on a spherical cap developed similarly between 5 north and 45 south the smallest exfoliated surfaces normally appear around 30 south and are inferred to extend in time both to the boulder top and downslope the correlations between the frequency intensity maps of thermal processes and the frequency map of exfoliated surfaces point to a complementary action in the exfoliated surfaces development of the short term temperature changes and diurnal cooling and heating due to the directional insolation effect as similarly inferred in the development of meridional cracks copyright 2016 john wiley sons ltd

on the discrimination of radar signatures of atmospheric gravity waves and oceanic internal waves on synthetic aperture radar images of the sea surface synthetic aperture radar sar images acquired over the ocean frequently show sea wave like patterns that have wavelengths well above those of ocean surface waves and that are sea surface signatures of oceanic internal waves oiws or of atmospheric gravity waves agws however it is often difficult to decide whether they result from the first or the second kind of waves which has led many investigators to misinterpret sar images of the sea surface based on solitary wave and radar imaging theories of agws and oiws we present criteria that help distinguish between them however there are cases where these criteria which are based solely on the shape and structure of the features visible on the sar images yield ambiguous results in these cases one must resort to additional information on the generation of agws and oiws which are listed in this paper

metallogenic relationships to tectonic evolution the lachlan orogen australia abstract placing ore formation within the overall tectonic framework of an evolving orogenic system provides important constraints for the development of plate tectonic models distinct metallogenic associations across the palaeozoic lachlan orogen in se australia are interpreted to be the manifestation of interactions between several microplates and three accretionary complexes in an oceanic back arc setting in the ordovician significant orogenic gold deposits formed within a developing accretionary wedge along the pacific margin of gondwana at the same time major porphyry cu au systems formed in an oceanic island arc outboard of an evolved magmatic arc that in turn gave rise to granite related sn w deposits in the early silurian during the ongoing evolution of the orogen in the late silurian to early devonian sediment hosted cu au and pb zn deposits formed in short lived intra arc basins whereas a developing fore arc system provided the conditions for the formation of several volcanogenic massive sulphide deposits inversion of these basins and accretion to the australian continental margin triggered another pulse of orogenic gold mineralisation during the final consolidation of the orogenic belt in the middle to late devonian

new insights into rock weathering from high frequency rock temperature data an antarctic study of weathering by thermal stress a major limitation of many weathering studies has been the acquisition of rock temperature data at insufficiently frequent intervals for the meaningful determination of the rate of change of temperature t t equipment and or logistical constraints frequently facilitate temperature measurement at only hourly intervals or at best every 10 min such data are not adequate for the determination of t t required for the evaluation of the freeze thaw mechanism or thermal stress fatigue recent undertakings at different sites in antarctica and at other cold region locations provide rock temperature measurements at 1 min intervals which indicate that the perception of the weathering regime would be very different from that generally assumed from longer interval geomorphological data these data clearly show that thermal stress fatigue and thermal shock may be more active components of the antarctic weathering regime than have generally been recognised the aridity of the study area limits the role of freeze thaw weathering values of t t of 2 c min 1 that suggest thermal stress fatigue shock is operative were recorded observations of rock flaking are thought to reflect the impact of thermal stress further the data show that contrary to general perceptions the southern aspect can in summer experience higher rock surface temperatures than the north facing exposure an examination of rock fracture patterns found in the field shows great similarity to fracture patterns developed in the laboratory as a direct result of thermal shock the argument is made that greater cognizance should be given to thermal effects

40ar 39ar age constraints on deformation and mineralization rosebery zn pb cu and mount lyell cu deposits tasmania australia the 40ar 39ar dating of alteration muscovite from the rosebery zn pb cu and mount lyell cu deposits tasmania australia has determined a succession of deformation events which occurred from 400 378 ma and comprises the devonian tabberabberan orogeny the dates from rosebery range from 400 390 ma are a minimum age for mineralization indicate the time of deformation and provide a maximum age limit for granitoid emplacement in the vicinity of the deposit the ages from the mount lyell field range from 400 378 ma are a minimum for mineralization and date cleavage development the north lyell cu mineralization which was probably broadly coeval with deformation may have formed at 400 ma all pre devonian alteration micas in the rosebery and mount lyell areas have been recrystallized or reset the tabberabberan deformation in western tasmania was broadly contemporaneous with widespread crustal shortening in southeastern australia as established from the dating of alteration minerals associated with deformation related precious and base metal deposits

coeval biochemical and biophysical weathering processes on quaternary sandstone terraces south of rabat temara northwest morocco despite numerous investigations on substrate inhabiting microflora especially lichens very little is known about the colonization of coastal escarpments by lithobiontic micro organisms inland of a retreating coastline in africa reported herein are the results of a combined field observation and microscopy study focusing on the connection between microrelief of the substrate colonies of lithobiontic micro organisms in particular the lichen xanthoria parietina and microstructures of putative bacterial origin the occurrence of weathering pits in which the early stages of the biotic development occurs and the subsequent disintegration of the rock indicate that lichens mosses and fungi act synergistically by alternating chemical and mechanical weathering penetration of grains by expansion and contraction of the hyphae depletes the rock matrix and contributes to the mechanical breakdown of the rock calcite rhombs on the weathered surfaces of the calcite cemented sandstones are severely etched with well developed rhomb shaped etch pits spiky calcite holes or has one or more of the faces removed and their cores exposed and leached nanofilaments c 100 700 nm and nanomicrobial fruiting bodies c 250 nm emanating from micropores appear to be common on affected crystalline structures weddellite present immediately below the thallus is a strong indicator of biomineralization quartz responds differently to chemical weathering by producing peeling structures and microbrecciation features the dissolution of these crystals appears to be a surface reaction controlled process mediated by microbial microfilaments and nanofilaments a model is proposed firstly indicating early stage biochemical weathering followed by biophysical weathering disintegration of the rock outcrops in due to a complex interplay of several events probably beginning at the nanoscale with penetration of sites on crystal faces copyright 2006 john wiley sons ltd

microscale biopitting by the endolithic lichen verrucaria baldensis and its proposed role in mesoscale solution basin development on limestone data are reported demonstrating the potential role of microscale morphologies induced by endolithic lichen communities specifically verrucaria baldensis in the initiation and development of mesoscale solution basin formation on limestone in the burren county clare a biophysical model is proposed outlining the different microscale stages leading to solution basin initiation with a progression from initial lichen colonization and growth associated perithecial biopitting followed by biopit coalescence to form biotroughs their subsequent enlargement and eventual incipient solution basin formation this model provides one explanation for solution basin development as this end state may also be achieved through simple solutional means without biological input the complexity of interactions at the lichen rock interface are identified with emphasis on the spatial and temporal variability of these underlining the point that as with macrotopographies at the landscape scale rock surface microtopographies also reflect historical weathering legacies copyright 2011 john wiley sons ltd

natural building stone composed of light transmissive minerals impacts on thermal gradients weathering and microbial colonization a preliminary study tentative interpretations and future directions a number of modern buildings employing claddings of granites or marbles have experienced bowing of the rock panels together with weathering of the material theoretical and field based data analysis and laboratory experimentation have assumed that heat exchange resulting from incoming solar radiation is at the material surface however a number of recent experiments have clearly shown that some lithologies including both marble and granite comprise a number of light transmissive minerals that significantly change the thermal responses in the outer few millimetres of the rock further this translucence will create mineral to mineral stresses where light transmissive minerals are in contact with opaque ones the whole is further exacerbated by differences in thermal coefficients of expansion and conductivity which themselves may depend on the mineral axis surface modifiers such as paints further complicate the situation the degree of light penetration based on field measurements can be significant and can facilitate rapid changes in temperature t t 2 c min 1 at depth within the rock thereby increasing the sub surface stresses the amount of light penetration for any given mineral will be dependent upon material slope the latitude season and albedo albedo is identified as a complex variable changing as a function of the angle of the sun to the particular surface polished surfaces as often with cladding will further influence this data analysis suggests that in the northern hemisphere south of the polar circle the summer may not be the time of the largest heat loading on the southern aspect and that larger loadings coupled with lower air temperatures occur early and late in the year this seasonal impact has great potential for thermal stresses on the southern aspect the presence of light transmissive minerals also allows sub surface biotic colonization and results in weathering overall where light transmissive minerals lithologies occur the thermal responses are highly complex and in need of more rigorous consideration

40ar 39ar dating of alunite from the pueblo viejo gold silver district dominican republic new 40 ar 39 ar ages for alunite from the moore and monte negro deposits in the pueblo viejo district as well as from a newly discovered alunite bearing zone on loma la cuaba west of the known deposits are reported here the ages range from about 80 to 40 ma with closely adjacent samples exhibiting very different ages interpretation of these results in the context of estimated closure temperatures for alunite and the geologic and tectonic evolution of hispaniola does not lead to a simple conclusion about the age of mineralization the simplest interpretation that mineralization was caused by a buried late cretaceous 80 ma intrusion is complicated by lack of intrusions of this age in the area and absence of alteration in overlying limestone the alternative interpretation that mineralization was formed during early cretaceous 110 ma magmatism and that the 40 ar 39 ar ages were completely reset by late cretaceous thrusting is complicated by a lack of information on the timing and thermal effects of thrusting in central hispaniola alunite studies have yielded similar unclear results in other pre cenozoic ore systems notably those of the lachlan fold belt in australia

sir c x sar observations of rain storms abstract the spaceborne imaging radar c x band synthetic aperture radar observations of rain storms are the first multipolarization and multifrequency observations of precipitation from space in addition to numerous often dramatic images of severe weather systems obtained by forming a synthetic aperture in the usual side looking attitude several data takes were performed while the radar antennas were parallel to the ground and the radar beams were pointing at nadir these opportunities coincided with the passage of the shuttle over tropical cyclone odille in the southern indian ocean during the first flight and over typhoon seth in the western pacific during the second flight the resulting observations or more appropriately the resulting measurements demonstrate for the first time the capability of a spaceborne multifrequency multipolarization microwave radar system to quantify precipitation rates to detect hydrometeor phase and to classify rain type

surface temperature differences between minerals in crystalline rocks implications for granular disaggregation of granites through thermal fatigue thermal expansion differences between minerals within rocks under insolation have previously been assumed to drive breakdown by means of granular disaggregation however there have been no definitive demonstrations of the efficacy of this weathering mechanism different surface temperatures between minerals should magnify thermal expansion differences and thus subject adjacent minerals to repeated stresses that might cause breakdown through fatigue failure this work confirms the existence of surface temperature differences between minerals in granitic rocks under simulated short term temperature fluctuations so as to discriminate their potential for initiating granular disaggregation the influence of colour as a surrogate for albedo and crystal size as a function of thermal mass are specifically identified because of their ease of quantification four rock types with a range of these properties were examined and subjected to repeated short term temperature cycles by radiative heating and cooling under laboratory conditions results show that while albedo is the main control for overall and individual maximum temperatures crystal size is the main factor controlling higher temperature differences between minerals thus stones with large differences of mineral sizes can undergo magnified stresses due to thermal expansion differences

simultaneous observations of rain cells over the ocean by the synthetic aperture radar aboard the ers satellites and by surface based weather radars radar images acquired over the ocean by the c band synthetic aperture radar sar aboard the european remote sensing satellites ers 1 and ers 2 often show sea surface manifestations of rain cells we have searched the archives of several weather stations for weather radar data acquired concurrently with ers sar data and have found four concurrent data pairs one in the south china sea two in the baltic sea and one in the north sea the comparison of ers 1 2 sar images showing radar signatures of rain cells with weather radar images reveals that the radar signatures of rain cells on ers sar images vary considerably which makes it often difficult to distinguish them from radar signatures of other mesoscale or submesoscale atmospheric and oceanic phenomena the present analysis together with results obtained from previous analyses of spaceborne multifrequency sar data and laboratory data as well as results obtained from theoretical models on radar backscattering at the sea surface suggest the following c band radar signatures of rain cells with rain rates below 50 mm h are mainly caused by a modification of the sea surface roughness induced by 1 the raindrops impinging on the sea surface and thus modifying the sea surface roughness and by 2 local wind field variations associated with rain cells spreading downdrafts raindrops impinging on the sea surface generate ring waves as well as turbulence in the upper water layer depending on rain rate drop size distribution wind speed and temporal evolution of the rain event the net effect can be an increase or a reduction of the amplitude of the c band bragg waves and thus of the backscattered radar power thus ocean areas struck by rain can show up on ers sar images as areas with higher or lower image brightness than the surroundings

a review of the metallogeny and tectonics of the lachlan orogen future mineral exploration within eastern australia will be enhanced by resolving the tectonic evolution of the lachlan orogen to establish the spatial and temporal terrane distribution of the various mineral deposits the lachlan orogen from north eastern tasmania through to central and eastern new south wales is host to a number of major mineral deposit styles including orogenic gold e g stawell ballarat bendigo volcanic hosted massive sulphide e g woodlawn currawong sediment hosted cu au e g cobar basin deposits porphyry au cu e g cadia parkes cowal and granite related sn e g ardlethan beechworth each of these mineral deposit styles is a sensitive and diagnostic indicator of the prevalent tectonic environment during their formation in this review we briefly summarise the deposit to large scale factors that define the diverse metallogenic evolution of the lachlan orogen this overview is intended to set the scene for subsequent specialist papers published in this thematic issue on the metallogeny and tectonics of the lachlan orogen in south east australia

a quantitative determination of the effect of moisture on purple mudstone decay in southwestern china aims the moisture condition is well known to be a key factor that apparently influences rock decay but little is known about the quantitative correlations between a rock s decay rate and its moisture content which makes it difficult to quantitatively predict the rate of rock decay under varied moisture conditions thus in this paper our aim is to observe the decay rates of various purple mudstones with different moisture contents and to develop an equation to calculate the decay rate

geological characteristics and genesis of the jurassic no i porphyry cu au deposit in the xiongcun district gangdese porphyry copper belt tibet abstract the xiongcun district located in the western segment of the gangdese porphyry copper belt gpcb hosts the only known jurassic mineralization in the gpcb tibet prc the no i deposit in the xiongcun district is related to the middle jurassic quartz diorite porphyry 167 161 ma and the mineralization was formed at ca 161 5 2 7 ma ore bearing middle jurassic quartz diorite porphyry emplaced into the early jurassic volcano sedimentary rock sequences of the xiongcun formation veinlets and disseminated mineralization developed within the middle jurassic quartz diorite porphyry and the surrounding metamorphosed tuff hosting a measured and indicated resource of 1 04 mt copper 143 31 t gold and 900 43 t silver with an average grade of 0 48 copper 0 66 g t gold and 4 19 g t silver the mineralization can be assigned to four stages including three main stages of hypogene mineralization and one epigenetic stage the main alteration associated with mineralization is potassic seven mineralization related hydrothermal veins have been recognized including quartz sulfide biotite sulfide magnetite sulfide quartz molybdenite sulfide chalcopyrite pyrite pyrrhotite pyrite and polymetallic veins the s and pb isotopic compositions of the ore sulfides and the re contents of the molybdenite suggest a mantle source for the ore forming materials with minor contamination from the subducted sediments hydrogen and oxygen isotope compositions of quartz in the ores suggest that both magmatic and meteoric waters were involved in the ore forming process the ore bearing porphyry 167 161 ma and ore forming 161 5 2 7 ma ages of the no i deposit correspond to the time of northward subduction of neo tethys oceanic slab the geochemical data of the ore bearing porphyry indicate that the no i deposit formed in an intra oceanic island arc setting and the ore bearing porphyry originated from the partial melting of mantle with limited contribution of subducted sediments the genesis of the ore bearing porphyry and no i deposit is interpreted as being related to northward intra oceanic subduction of neo tethys oceanic slab in the middle jurassic time 167 161 ma

role of lichens in weathering of granodiorite in the sila uplands calabria southern italy this paper explores the role of five recurrent epilithic lichen species aspicilia intermutans nyl arnold xanthoparmelia pulla ach o blanco a crespo elix d hawksw lumbsch rhizocarpon lecanorinum anders tephromela atra huds hafellner and lecanora bolcana pollini poelt which encrust granodiorite spheroidal boulders exposed in the sila uplands calabria southern italy in weathering of plutonic rocks in a typical mountainous mediterranean environment a detailed investigation was carried out on the lichen rock interface of each species by comparing them mutually and with lichen free granodiorite samples for this purpose the lichen species were sampled together with the encrusted rock surface for detailed mineral petrographic analyses performed in thin and ultra thin sections optical and scanning electron microscopy of these sections and of bulk samples permitted us to highlight the peculiar modes of physical and chemical attacks of lichen thalli and hyphae on and into the substratum for each species crack systems often parallel to the outer rock surface appear often intruded by hyphae which cause rupture of primary minerals with detachment and progressive incorporation of their fragments into the thallus in particular the species l bolcana and t atra revealed an unexpected partly endolithic behavior presumably enhanced by the presence of rock fractures earlier generated by other physical breakage processes already affecting the spheroidal boulders in the sila mountains dissolution features often affect primary minerals even quartz that may show very peculiar patterns which are suggestive of a biologically induced control various phyllosilicate clay minerals were identified using sem eds microprobe analyses and ft ir spectroscopy which also enabled the identification of possible amorphous silica or quartz micrograins rhizocarpic acid and carotenoid at the encrusted granodiorite interface in contrast neither oxalic acids nor oxalates were detected

crack propagation by differential insolation on desert surface clasts abstract in the southwest u s cracks in alluvial fan surface clasts have a preferred orientation independent of rock fabric and shape in this paper we show that differential insolation of incipient cracks of random orientations predicts a distribution of crack orientations consistent with field observations in this model crack growth by hydration and or thermal weathering is primarily a function of local water content at the crack tip crack tips that experience minimal solar insolation maintain a greater average moisture and hence weather more rapidly than cracks that experience greater solar insolation to show this we used a numerical radiative transfer code to quantify the solar insolation of rectangular cracks at 35 n latitude with a range of depths and orientations the amount of solar energy reaching the bottom of each crack was calculated at 5 min intervals over the day for several days of the year to determine hourly daily seasonal and annual energy deposition as a function of crack depth and orientation by assuming that only crack orientations that effectively shield their interiors and minimize their water loss are able to grow the pattern of cracks produced by the model is consistent with field observations the annual average insolation which controls water retention is associated with the two primary modes of crack orientation the effect of daily recharge by summer rains of the north american monsoon system is consistent with the observed deviations from these primary modes model results suggest that both the annual average insolation and the daily pattern of rainfall is recorded in the preferred crack orientations of surface clasts in the southwest u s

component separation of oceanic helium a new procedure to quantify the components of oceanic helium terrigenic 3he and 4he released from the ocean floor and tritiugenic 3he from tritium decay is described terrigenic he and nonatmospheric 3he i e terrigenic and tritiugenic combined are obtained in terms of measured concentrations of the he isotopes and also of neon ne which improves the separation considerably assuming terrigenic he to vanish in the mixed layer for the subsequent separation of terrigenic and tritiugenic 3he additional information is required and 3he due to natural tritium represents a complication the procedure is applied to data from a hydrographic section in the south atlantic 19 s 1991 and one in the eastern mediterranean 1987 the 1 data precisions and a systematic error accounting for uncertainties in mixed layer he are approximately 0 3 sections of the new representations of oceanic he and 3he and comparisons to the nearest classical quantities i e 3he he are presented in the south atlantic the 3he distribution reflects the hydrographic structure east of 20 w the average 3he 4he ratio of terrigenic he below 800 m is 4 5 0 8 times the atmospheric ratio which implies a substantial contribution of crustal he in the upper waters tritiugenic 3he 0 5 tritium units 20 is separated from terrigenic 3he in the eastern mediterranean tritiugenic 3he is quantified throughout the water column in the presence of substantial levels of terrigenic he the release rate of terrigenic he from the sea floor is found to be 3 1 1 2 1010 atoms m 2 s 1 similar to the rate for continental crust with a mantle he contribution of 5 1 2 only recommendations for future work are to reduce the mentioned systematic error and the uncertainty margins of the he and ne solubilities and of 3he due to natural tritium

chronology and tectonic framework of turbidite hosted gold deposits in the western lachlan fold belt victoria results abstract 40 ar 39 ar data constrain the history of metamorphism deformation and mineralization in the western subprovince of the lachlan fold belt rocks in the mount stavely volcanic complex and the bushy creek pluton give 40 ar 39 ar ages of about 500 ma for hornblende and biotite the dates from the mount stavely volcanic complex limit the age of mineralization in the metavolcanic rocks of the stavely belt whereas the date for the bushy creek pluton extends the area of cambrian ordovician plutons of the delamerian orogeny to east of the grampians mountains and helps define the surface expression of the western border of the paleozoic lachlan fold belt 40 ar 39 ar dating of metamorphic mica growth phengite in cleaved slates and phyllites within the landsborough fault avoca fault zone heathcote fault zone and mount wellington fault zone gives ages of 453 2 440 2 426 4 and 410 390 ma respectively these data indicate a progression of deformation from west to east starting in late ordovician early silurian time in the stawell and bendigo ballarat structural zones the major phase of deformation in the western subprovince of the lachlan fold belt is therefore silurian and not devonian sericites from major gold deposits in the stawell zone and bendigo ballarat zone give 40 ar 39 ar dates of about 440 ma that are coincident with folding and thrusting a second episode of mineralization and fault reactivation at about 420 to 410 ma is found in some deposits in these zones based on data from a previous study in the melbourne zone including the woods point dike swarm and locally in the bendigo ballarat zone some gold deposits give sericite dates of about 380 360 ma these ages are consistent with the close association of many melbourne zone gold deposits with devonian dikes and plutons the results indicate that gold mineralization in the stawell zone bendigo ballarat zone and melbourne zone was episodic and both temporally and spatially associated with crustal heating linked to regional metamorphism and plutonism initial stages of mineralization in the province comprising many of the large deposits in western and central victoria e g bendigo ballarat stawell wattle gully tarnagulla accompanied metamorphism folding and thrusting subsequent mineralization is widespread but produced mainly smaller deposits

applying spatial prospectivity mapping to exploration targeting fundamental practical issues and suggested solutions for the future abstract despite many decades of development spatial prospectivity modelling is not yet widely used or accepted throughout the global mineral exploration industry a common criticism of the method is that it is not practically useful because it has a bias to mature well known areas and generates excessively large areas of high prospectivity it is suggested that the reason for this is not primarily related to limitations in the prospectivity mapping algorithms but rather to issues relating to the use of input data sets specifically it is common that the input data such as geological interpretations do not uniformly and objectively represent the search space of interest omit critical targeting relevant geoscientific elements such as major deep seated ore controlling structures and have a large degree of unrecognised dependence it is considered that these problems are not in principle barriers to the eventual successful deployment of this technology however future approaches to spatial prospectivity modelling need to explicitly address these concerns it is suggested that the most effective method may be a hybrid of subjective human geological interpretation and objective machine based analysis that captures the best aspects of these alternative approaches i e an intelligence amplification ia rather than an artificial intelligence ai approach a roadmap is proposed for improving the effectiveness of spatial prospectivity modelling that has implications for the broader community interested in mineral exploration targeting

metallogenic episodes of the tasman fold belt system eastern australia precise dating of alteration minerals and host rocks to au and base metal deposits in the tasman fold belt system eastern australia has established a number of distinct metallogenic epochs which correspond to episodes of magmatism or to deformation events base and precious metal mineralization was emplaced in the mount read volcanics tasmania at about 500 ma and other hydrothermal or deformational events may have occurred in the hellyer deposit between approximately 480 and 440 ma copper and au mineralization was emplaced in the lachlan fold belt new south wales at about 440 ma and appears to be related to the end stages of ordovician magmatism that spans a period from approximately 480 through to 440 ma gold deposits or base metals which formed in new south wales and tasmania at about 420 to 380 ma are essentially coeval with deformation and or are broadly related to siluro devonian magmatism that largely occurred from about 420 to 390 ma gold mineralization in the anakie inlier northeast drummond basin north queensland was essentially coeval with the emplacement of the host drummond sequence at about 350 ma

synchronous compression and extension in east gondwana tectonic controls on world class gold deposits at 440 ma the collision of a seamount or microcontinental block with an arc may produce complex strain distributions and changes in the tectono magmatic setting slab rollback and associated upwelling of asthenosphere occurred ca 440 ma near the margin of east gondwana in response to subduction zone lock up following arc collision ca 455 ma world class porphyry copper gold deposits e g cadia formed in the backarc during extension and magmatism associated with slab rollback upwelling of the asthenosphere also provided the heat engine for generation of hydrothermal fluids the result was elevated fluid pressures and compressional brittle deformation associated with orogenic gold mineralization e g bendigo inboard of the east gondwana margin

investigation of multifrequency multipolarization radar signatures of rain cells over the ocean using sir c x sar data radar signatures of rain cells are investigated using multifrequency multipolarization synthetic aperture radar sar images acquired from the space shuttle endeavour during the spaceborne imaging radar c x band sar sir c x sar missions in april and october 1994 in sir c x sar images radar signatures of rain cells over the ocean usually consist of irregularly shaped bright and dark patches that strongly depend on radar frequency and polarization the radar signatures of rain cells observed in sir c x sar imagery of the ocean originate from 1 the scattering and attenuation of the microwaves by raindrops and ice particles in the atmosphere and 2 the modification of the sea surface roughness induced by the impact of raindrops and by wind gusts associated with rain cells raindrops impinging on the sea surface generate ring waves which enhance the sea surface roughness but they also generate turbulence in the upper water layer which reduces the sea surface roughness depending on the radar wavelength ocean areas struck by rain can have higher or lower normalized radar cross section nrcs than the surrounding rain free area in ocean areas where heavy rain is impinging on the sea surface the x and c band nrcs is usually enhanced and the l band nrcs is reduced from the phase difference between the horizontally and vertically copolarized signals estimates of the rain rate are obtained the present analysis shows further that the presently used wind speed retrieval algorithms for the scatterometers aboard the ers and adeos satellites may yield biased wind fields if several rain cells lie within a scatterometer resolution cell

zonation of alteration facies at western tharsis implications for the genesis of cu au deposits mount lyell field western tasmania the western tharsis deposit located in the mount read volcanic belt of western tasmania is one of 22 mainly cu au deposits in the mount lyell district although the orebody at western tharsis is characterized mainly by disseminated pyrite chalcopyrite like most other deposits in the mount lyell district it also contains bornite rich ores characteristic of a second less common type of deposit the deposit is stratiform and occurs within intermediate and felsic volcanic rocks of the 500 ma central volcanic complex alteration is developed broadly symmetrically around the ore zone with an ore bearing core characterized by a quartz chlorite sericite assemblage the core is enveloped by a quartz pyrophyllite topaz fluorite zunyite woodhouseite assemblage with local bornite bearing ore zones this zone in turn is enveloped by a pyritic quartz sericite assemblage the outermost quartz chlorite carbonate sericite albite assemblage is only developed in the stratigraphic footwall more than 200 m below the ore position the hypogene pyrophyllite bearing assemblage is more characteristic of high sulfidation than volcanic hosted massive sulfide vhms related alteration assemblages moreover the close relationship of this alteration assemblage with the more prevalent quartz chlorite sericite assemblage associated with disseminated pyrite chalcopyrite mineralization suggests that these two types of mineralization are two stages of one mineralizing event not the two separate events suggested by previous authors e g arnold and carswell 1990 geologic relationships and radiogenic isotope data are consistent with an ordovician 460 ma timing for mount lyell cu au mineral deposits this mineralization may be related to the geologic event that formed the local haulage unconformity these observations indicate a potential new exploration model for mineralization in the mount read volcanic belt and in surrounding ordovician rocks

evolution of the peak hill high sulfidation epithermal au cu deposit eastern australia the early palaeozoic macquarie arc southeastern australia hosts a variety of major late ordovician to earliest silurian subduction related deposits e g cadia east ridgeway cadia hill cowal and northparkes however there is uncertainty about whether coeval high sulfidation epithermal deposits which occur in intra oceanic metallogenic belts elsewhere in the west pacific e g lepanto and chinkuashih are also present in the macquarie arc this has led to suggestions that their absence may be due to the poor preservation potential of deposits that form at relatively shallow crustal levels in ancient rocks we present here an interpretation for evolution of the peak hill au cu deposit based on the distribution of alteration facies sulfur isotope data from several textural forms of pyrite and barite and an assessment of the regional volcanic and sedimentary facies architecture these data show that the peak hill deposit displays a distinct sub vertical zoning with a pyrophyllite and vuggy quartz core that today extends about 350 m east west and at least 550 m north south which grades out through paragonite muscovite kaolinite to a chlorite epidote alteration zone at the margin the alteration zoning reflects both lower temperatures and neutralisation of acid fluids with increasing distance from the core which represents the conduit along which hot acidic hydrothermal fluids were channelled several temporally overlapping events of silicification bladed quartz pyrite veining brecciation and pyrite veining occurred during the last stages of hydrothermal alteration although most appear to predate mineralisation au cu mineralisation was associated with late quartz pyrite barite veins and the highest gold grades occur mainly in microcrystalline quartz altered rocks in the paragonite muscovite alteration zone generally within 50 m outward from the boundary of the pyrophyllite and vuggy quartz core sulfur and lead isotope data and the characteristic zoning of ore minerals and alteration assemblages support a magmatic source for the hydrothermal fluids similarities in many of the isotopic signatures between peak hill and deposits such as northparkes support generation of the high sulfidation mineralisation during the late ordovician to earliest silurian possibly ca 440 ma metallogenic event the late ordovician to early silurian volcanic and sedimentary facies associations at peak hill are consistent with alteration and mineralisation occurring in rocks deposited in a submarine setting

footprints of storms on the sea a view from spaceborne synthetic aperture radar synthetic aperture radar sar on board seasat observed images of stormlike echoes on the sea in 1978 the core of these images is usually an echo free hole which is attributed to the damping of the short 30 cm radar detectable gravity waves by the intense rain in the storm core although the beating down of waves by rain is consistent with observations by seafarers and with the first scientific explanation of the phenomenon by reynolds 1875 neither theory nor experiment has provided definitive support one experiment appears to provide the key it shows that the kinetic energy of the rain produces sufficient turbulence in a thin fresh water layer to damp 30 cm waves in 10 20 s thus producing the echo free hole a sequence of positive feedbacks then serves to damp the longer waves the angular dependence of the sea surface echo cross sections seen by seasat sar outside the echo free hole indicates winds diverging from the downdraft induced by the intense rain core the wind generated waves and associated echoes extend out to a sharply defined gust front the sea surface footprint thus mimics the features of a storm microburst the variations in surface radar cross section due to a combination of rain and wind effects impacts spaceborne measurements of surface winds by scatterometry and rainfall measurements by radar portions of this synthesis remain speculative but serve as hypotheses for further research

the role of thermal stress fatigue in the breakdown of rock in cold regions abstract many geomorphological studies have ignored the role of thermal stress fatigue engineers have long maintained that thermal stress is an effective process physicists and the ceramics industry have provided a theoretical foundation to explain the nature and mode of operation of thermal breakdown recent geomorphological studies have shown the importance of thermal stress in cold regions by means of high frequency rock temperature data which can identify rates of temperature change in excess of 2 c min 1 the occurrence of weathered material in cold but dry regions can be explained by thermal stress shock differential radiation receipts on slopes of varying orientation and gradient can exert a very strong effect

thermal fatigue and thermal shock in bedrock an attempt to unravel the geomorphic processes and products widespread acceptance in science at large notwithstanding the ability of thermal stresses to produce thermal fatigue tf and or thermal shock ts in bedrock and coarse debris in the field is often doubted commonly called insolation weathering in geomorphology the results of questionable laboratory experiments have led many geomorphologists to consider terrestrial temperatures to be inadequate to generate thermally induced stresses leading to rock failure the exceptions are the action of fire or lightning we comprehensively survey the general scientific literature on tf and ts while rigorously scrutinizing that relating to geomorphology findings indicate theoretical and experimental information is adequate to establish the feasibility of tf and ts in rock stemming from rock temperatures monitored in the field while ts may exhibit fracture patterns that are uniquely diagnostic those of tf lack any such attributes it would appear unlikely that tf can prepare or weaken rock to increase the likelihood of ts the question of whether widespread polygonal versus rectilinear cracking is diagnostic of ts is presently an open one as possible explanations invoke process es and or host material s and consequently to assign palaeoenvironmental significance to such fracture patterns is premature at this time further geomorphological laboratory research into tf and ts is merited as sufficient theoretical underpinning already exists however laboratory experimentation needs to be much more rigorously defined and executed and is faced with significant hurdles if it is to be effectively linked to field observations

influence of surface heterogeneities of building granite on its thermal response and its potential for the generation of thermoclasty surface properties especially albedo and aspect are widely accepted as strong influences on the surface thermal response of building stone to insolation however the influence that adjacent areas of stone with very different surface properties may have on the thermal response of a patch of stonework and the ways in which spatial variation in thermal characteristics might enhance stone decay has received relatively little attention this paper examines the differential thermal response of granite used in construction that results from the presence of dark coloured micro granular enclaves within a leucocratic host surface temperatures and temperature differences between enclaves exhibiting mico spalling enclaves with no spalling and the surrounding stone were measured for different aspects and seasons on a 20th century building in madrid these data were used to calculate a number of indices related to short term temperature cycling and temperature gradients that have the theoretical capability of generating irreversible deformation of the stone these indices suggest that micro spalling of enclaves compared to a lack of similar decay on the host rock is related to their differential thermal response to insolation most importantly the lower albedo and thermal conductivity values of the enclaves however these factors are not sufficient on their own to trigger spalling and breakdown was only observed where enclaves also experienced repeated short term surface temperature cycling caused by for example temporary shading by adjacent vegetation these rapid temperature reversals are identified as a key contributory factor to the thermally driven decay observed on some of the enclaves

high precision u pb zircon chronostratigraphy of the mount read volcanic belt in western tasmania australia implications for vhms deposit formation the middle cambrian mount read volcanics of western tasmania australia host several world class volcanic hosted massive sulfide vhms deposits representing a wide range of deposit styles although the deposits and their host sequences are variably deformed and locally preserve spectacular examples of primary textures and structures rapid lateral and vertical facies changes and faults with uncertain sense and magnitude of displacement have made it impossible to correlate stratigraphy across the belt previous dating studies in the area have yielded relatively imprecise crystallization ages we have employed the chemical abrasion isotope dilution thermal ionization mass spectroscopy id tims u pb zircon method to obtain highly precise crystallization ages for a total of 18 samples of volcanic and intrusive rock units from throughout the mount read volcanics and underlying mafic ultramafic complexes the new data permit detailed resolution of age relationships within the belt the study establishes an age of 516 0 0 9 ma for the mcivor hill gabbro which is part of a mafic ultramafic complex interpreted to underlie the mount read volcanics magmatism in the central mount read volcanics lasted at least 12 7 m y from 506 8 1 0 ma for a massive dacite unit in the lower part of the central volcanic complex to 496 0 0 9 ma for a welded ignimbrite in the lower tyndall group together with previous age constraints results of the study provide a precise chronostratigraphic framework for magmatism and vhms deposit formation within the mount read volcanics the precise age data indicate that north of the henty fault magmatism occurred in three discrete pulses at least two of which were separated by periods of sedimentation we demonstrate that vhms deposits in the mount lyell roseberry hercules and que hellyer districts comprising the majority of the known significant vhms deposits in the belt formed within a narrow time interval at 500 1 ma at a relatively late stage in the evolution of the belt some of the larger intrusions in the belt e g the bonds range porphyry 500 4 0 8 ma were emplaced contemporaneously with vhms deposit formation however other bodies such as the murchison granite 497 3 0 9 ma are younger than the deposits and are unlikely to have been involved in their genesis as has previously been suggested these conclusions will aid explorers in targeting vhms mineralization in the mount read volcanics

rock thermal data at the grain scale applicability to granular disintegration in cold environments consideration of the mechanisms associated with the granular disintegration of rock has been limited by available data in most instances both the size of the transducer and the nature of the study have negated any applicability of the resulting data to the understanding of grain to grain separation within rock the application of microthermocouples 0 15 mm diameter and high frequency logging 20 s intervals at a taffoni site on southern alexander island and from a rock outcrop on adelaide island antarctica provide new data pertaining to the thermal conditions at the grain scale of the rock surface the results show that thermal changes t t can be very high with values of 22 c min 1 being recorded although available data indicate that there can be differences in frequency and magnitude of uctuations as a function of aspect all aspects experienced some large magnitude 2 c min 1 uctuations further in many instances large thermal changes in more than one direction could occur within 1 min or in subsequent minutes these data suggest that the surface grains experience rapidly changing stress elds that may with time effect fatigue at the grain boundaries albedo differences between grains and the resulting thermal variations are thought to exacerbate this the available data failed to show any indication of water freezing an exotherm and thus it is suggested that microgelivation may not play as large a role in granular breakdown as is often postulated for cold regions and that in this dry antarctic region thermal stress may play a signi cant role copyright 2003 john wiley sons ltd

weathering of granite in antarctica i light penetration into rock and implications for rock weathering and endolithic communities where rocks are composed of translucent minerals light penetrates the rock and in so doing impacts on the thermal conditions where minerals are not translucent all the heat transformation must be at the rock surface and steep thermal gradients can occur where light does penetrate a component of the incoming radiation is transformed to heat at differing depths within the rock thereby decreasing the thermal gradient equally light transmissive minerals facilitate endolithic communities which can also play a role in rock weathering the attribute of light transmission within rock and the impact this has on the resulting thermal conditions has not been considered within rock weathering studies an attempt was made to monitor the amount of light penetrating the outer 2 mm of coarse granite under antarctic summer conditions and to evaluate the thermal impact of this it was found that the amount of light penetration at this site exceeded modeled or postulated values from biological studies and that it could significantly impact the thermal conditions within the outer shell of the rock although the resulting data highlighted a number of flaws in the experimental procedure sufficient information was generated to provide the first assessment of the range of thermal responses due to light transmissive minerals in rock copyright 2007 john wiley sons ltd

evidence for freeze thaw events and their implications for rock weathering in northern canada ii the temperature at which water freezes in rock many undertakings have used either a single value or a narrow window of temperatures as a threshold for the freezing of water within rock these temperatures vary from 0 to 5 c with most windows being in the range 1 to 4 c based on thermal data these thresholds are commonly used to count the number of freeze thaw events as a basis for determining freeze thaw weathering data collected from northern canada indicate that the temperature at which freezing occurs can vary substantially even for the same site using exotherm and zero curtain observations from bricks at angles of 90 and 45 aligned to the four cardinal aspects the various temperatures at which water froze are shown bricks on the north and east commonly did exhibit freezing based on exotherms within the window 1 to 5 c while data for the south and west aspects showed substantial variation with freezes sometimes between 6 4 and 8 9 c the data were evaluated for evidence of zero curtain effects indicative of water freezing but no unequivocal events could be found and it is suggested that at the scale of observation used here they are unlikely it would therefore appear that the use of thermal thresholds may not be meaningful for evaluation of freeze thaw events the available data also indicate many instances when temperatures went substantially sub zero e g 20 c and yet no indication of water freezing occurred most likely because there was no water available to freeze this indicates that any form of freeze thaw event counting in the absence of some indicator of the presence of water and that it actually froze is flawed as thermal conditions alone are not adequate to indicate the occurrence or not of actual freeze thaw weathering events these data suggest that evaluations of freeze thaw occurrence based simply on thermal thresholds may be substantially in error copyright 2006 john wiley sons ltd

the effect of rain in calming the sea abstract the effect of rain in damping surface waves appears to be significant in the estimation of wind speed from the backscatter of radar signal from the sea surface the radar backscatter depends on the small scale roughness of the sea surface this is modified by the generation of capillary and gravity capillary ripples by raindrops and by the increased damping of the wavelengths of 10 cm scale the phenomenon is also important in wave generation and wave breaking since in both cases the short wavelengths play a key role a laboratory experiment has been performed to investigate the damping of water waves by rain in the absence of wind rain of intensity of 300 mm h 1 falls on mechanically generated progressive waves the wave amplitude is measured before the wave enters and after it exits the rain section of a tank 2 35 m long on the assumption of exponential damping it is found that the effect of rain can be described by an eddy viscosity e 0 3 cm2 s 1 the major part of the damping is attrib

contrasts in morphogenesis and tectonic setting during contemporaneous emplacement of s and i type granitoids in the eastern lachlan fold belt southeastern australia

structural evolution of auriferous veins at the endeavour 42 gold deposit cowal mining district nsw australia polyphase veins at the low grade structurally controlled epithermal gold deposit endeavour 42 in the junee narromine volcanic belt of the ordovician to silurian macquarie arc central new south wales australia record multiple tectonically driven fluid flow events during the mid paleozoic ordovician host rocks consist of a volcano sedimentary succession intruded by trachyandesite and andesitic lavas and intrusions as well as a volumetrically significant ordovician diorite sill the entire succession was tilted and faulted prior to the emplacement of multiple mafic to intermediate dike phases commonly localized along faults gold bearing veins cut all lithologic units at the endeavour 42 deposit with the exception of rare late stage intrusions economic gold is restricted to faults fault hosted breccias and veins with two distinct populations 1 an older steeply dipping conjugate vein set cut by 2 two younger moderately dipping vein sets both steep and inclined moderately dipping vein sets contain a similar mineral assemblage implying formation during a single epithermal system veins are generally 1 to 10 mm thick commonly straight walled but locally form overlapping veins with hard linkages the steep veins reactivated two sets of older faults fault parallel fractures and dike contacts and accommodated subhorizontal extension high gold grade hydrothermally cemented breccias are associated with early gold bearing veins and localized along deposit scale faults crosscutting the early steep gold bearing vein sets are inclined gold bearing veins with moderate dips to the southwest and west these opened as a new vein set and as veins localized along and at a slight angle to westward dipping bedding planes respectively the geometry of the inclined moderately dipping veins either represents a sudden change in the far field stress state to near vertical minimum compressive stress thereby suggesting a change from an extensional to a contractional environment or it may reflect local changes in the differential stress state with subhorizontal northeast southwest tension late veins and thrust faults in the deposit indicate a postmineral contractional environment the endeavour 42 deposit underwent tectonic burial until it was exhumed in the early carboniferous as indicated by 40ar 39ar plateau ages of 362 7 2 1 356 3 1 8 and 344 5 2 1 ma toward the end of the kanimblan cycle

schmidt hammer studies in the maritime antarctic application to dating holocene deglaciation and estimating the effects of macrolichens on rock weathering in order to contribute to the reconstruction of the deglaciation history of the marguerite bay area 68 s maritime antarctic and to estimate the rock weathering rate in this antarctic sector 28 sites 7 on rothera point and 21 on anchorage island were characterised using schmidt hammer values the weathering effect of two of the most widespread species of macrolichens in this area usnea sphacelata and umbilicaria decussata was tested at 5 different sites on rothera point schmidt hammer data in conjunction with recent 14c age suggest a deglaciation age for the marguerite bay area of around 12 ka and an average uplift rate of 5 4 mm year 1 on anchorage island for the period between 3 3 and 5 2 ka the weathering rates are extremely slow e g three times slower than reported in norway our data confirm that lichens exert a strong impact on weathering decreasing the schmidt hammer r values on lichenised surfaces by a factor of 3 4 compared to bare rock surfaces the effect of lichens on weathering is mainly due to edaphic conditions and the type of the lichen involved rather the period of exposure

controls on skarn mineralization and alteration at the cadia deposits new south wales australia the cadia fe cu au skarns in eastern new south wales australia are associated with the late ordovician shoshonitic cadia intrusive complex which hosts the largest mineralized intrusion related system in eastern australia both the big cadia and little cadia skarns are developed within a 40 m thick volcanic derived calcareous sandstone and adjacent units which represent the most important control on skarn formation the ore zones have undergone postore displacement along steeply dipping predominantly reverse faults without significant remobilization of ore chalcopyrite and minor native gold formed in intimate association with epidote chlorite quartz calcite and in the interstices of bladed hematite and magnetite aggregates the age of the au cu mineralizing event at cadia is constrained by 40ar 39ar dating of accompanying muscovite at 438 2 4 2 ma 1 gold to copper ratios within the skarns are generally lower than for porphyry au cu deposits at cadia particularly the high tonnage low grade cadia hill deposit ore and calc silicate gangue mineralogy are similar to other oxidized fe cu au skarns associated with porphyry deposits iron skarn at big cadia occurs several hundred meters distant from the margin of a mineralized intrusion of quartz monzonite porphyry magmatic dominated fluids reacted with carbonate in the wall rocks and produced classic skarn zonation over an 800 m interval from the intrusive contact located at cadia quarry toward more distal environments at big cadia skarn zonation comprises 1 proximal garnet pyroxene 2 intermediate garnet pyroxene scapolite and 3 distal fe au cu skarn alteration of noncalcareous metavolcanic rock units fine grained pyroxene phyric volcanic rocks and volcaniclastic rocks adjacent to the mineralizing quartz monzonite porphyry includes hydrothermal biotite k feldspar quartz hornfels and magnetite quartz biotite hornfels gold copper mineralization formed adjacent to garnet bearing veins peripheral to the main garnet rich zone indicating that garnet forming fluids carried the ore metals at little cadia and cadia east mineralization and skarn zonation similar to big cadia developed above additional intrusions of quartz monzonite porphyry retrograde hydrous alteration replaced much of the prograde garnet dominant mineralogy at cadia with the strongest overprint at little cadia the styles and distribution of alteration and mineralization suggest that the big cadia skarn formed from fluids that migrated laterally within calcareous units from strongly altered quartz monzonite phases of the cadia intrusive complex at cadia quarry at little cadia skarn formation was probably related to fluids derived from the cadia intrusive complex that migrated vertically and laterally within permeable calcareous units structural controls were important in focusing fluids and localizing the emplacement of late mineralizing phases of the cadia intrusive complex

rain footprints on c band synthetic aperture radar images of the ocean revisited abstract it is well known that rain leaves footprints on the sea surface that sometimes become visible on synthetic aperture radar sar images rain cells can easily be detected on sar images at all radar frequencies when they are associated with a downdraft pattern but rain cells are not always associated with downdraft and rain can also occur in other forms as stratified rain rain bands and squall lines it turns out that radar signatures of rain at c band are much more complex than at l or x band radar and that it is particularly difficult to identify unambiguously rain events on c band sar images acquired over the ocean this is because c band lies in the transition region where raindrops impinging onto the sea surface can increase usually or decrease the backscattered radar power and where volume scattering and attenuation by rain drops in the atmosphere are not always negligible at very high rain rates in order to get an insight into the physical mechanisms causing the c band radar signatures of rain we first revisit results obtained from historic laboratory and field experiments and multi frequency multi polarization sar data acquired during the sir c x sar spaceshuttle mission in 1994 then we analyze several c band sar images acquired by the european satellites envisat and sentinel 1a and the canadian satellite radarsat 2 and compare them whenever possible with quasi coincident and collocated weather radar images the observational data show that at low to medium rain rates the main physical mechanism causing c band radar signatures of rain is bragg scattering at ring waves generated by the rain drops impinging onto the sea surface which increase the radar backscatter however areas of increased radar backscatter are often accompanied by adjacent areas of decreased radar backscatter which is due to attenuation of the bragg waves by turbulence also generated by the impinging rain drops furthermore we present a full polarimetric radarsat 2 sar image of a rain cell together with a polarimetric decomposition analysis which shows that the c band radar signature of a rain cell is caused by surface scattering the observation show that radar signatures of rain cells often contain segments where the co polarized as well the cross polarized radar backscatter are strongly enhanced which indicates non bragg scattering contributions to the scattering process furthermore the polarimetric decomposition analysis shows that the c band radar signature of a rain cell is dominated by surface scattering possible mechanisms like scattering at splash products are discussed whether the normalized radar cross section nrcs due to rain is increased or decreased depends on rain rate wind speed incidence angle and history of the rain event at low to moderate wind speeds 10 m s 1 and low to high rain rates but

endolithic microorganisms in the antarctic cold desert in the frigid desert of the antarctic dry valleys there are no visible life forms on the surface of the soil or rocks yet in certain rock types a narrow subsurface zone has a favorable microclimate and is colonized by microorganisms dominant are lichens of unusual organization they survive not by physiological adaptation to lower temperatures but by changing their mode of growth being able to grow between the crystals of porous rocks their activity results in mobilization of iron compounds and in rock weatherning with a characteristic pattern of exfoliation this simple ecosystem lacks both higher consumers and predators

the palaeozoic tectono metallogenic evolution of the northern tasman fold belt system australia interplay of subduction rollback and accretion abstract the tasman fold belt system in eastern australia provides a record of the palaeozoic geological history and growth of the australian continent along the proto pacific margin of gondwana inboard of an extensive and long lived subduction system the hodgkinson and broken river provinces represent prominent geological elements of this system and together form the northern tasman fold belt system geochronological age dating of the timing of gold formation in the amanda bel goldfield in the broken river province and the hodgkinson goldfield in the hodgkinson province provides constraints on the occurrence of a deformation and mineralisation episode in the late devonian early carboniferous integration of these newly obtained data with petrogenetic constraints and a time space evaluation of the geological evolution of the hodgkinson and broken river provinces as well as other terranes in the northern tasman fold belt system allows for the development of a geodynamic model for the palaeozoic evolution of the northern tasman fold belt system our model indicates that three cycles of extension contraction occurred during the palaeozoic evolution of the northern tasman fold belt system episodes of extension were controlled by rollback of the subduction system along the proto pacific margin of gondwana whereas episodes of contraction resulted from accretion following the arrival of positively buoyant segments i e micro continental blocks oceanic plateaus at the subducting trench our composite interpretative model on the geodynamic evolution of the northern tasman fold belt system integrates the timing of the development of mineral deposits throughout this part of the system and provides a significant advancement in the understanding of palaeozoic geodynamics along the margin of gondwana in northeast australia and allows comparison with the southern part of the tasman fold belt system

the historical legacy of spatial scales in freeze thaw weathering misrepresentation and resulting misdirection discussion of weathering in cold regions has historically been dominated by widespread acceptance of the significance of the freeze thaw concept among periglacial geomorphologists and an essentially universal acceptance by those geomorphologists not directly involved in researching the topic debris produced by freeze thaw is frequently deemed to be angular in form and the observation of such debris has been used to identify the former or present operation of this weathering mechanism large debris blocks and small debris grains or flakes have been recognised as the outcome of the two scales of freeze thaw weathering macrogelivation and microgelivation respectively however the fusion of climatic geomorphology and process geomorphology in the ongoing development of the freeze thaw concept has resulted in the confusion of product with process whereby microgelivation producing small products and macrogelivation producing large products are seen due to the product dichotomy as distinctly different processes despite the recent highly sophisticated laboratory experimentation on freeze thaw weathering this historical process scale dichotomy still pervades thinking and experimental evaluation here we consider the historical development of microgelivation macrogelivation and outline what are thought to be fundamental flaws with the concepts and their underpinnings built within the two notions are elements of rock properties hard and soft and scale issues regarding rock attributes solid rock and existing weaknesses in rock that serve only to confuse the process and scale issues even more the whole notion of frost weathered debris having a specific form is also highly spurious there being no shape attribute that is uniquely diagnostic of frost action and this in turn leads to the further problem of process synergy or other processes entirely being the cause of rock failure in cold regions ultimately we argue that while there may be a range of product sizes and shapes resulting from frost weathering per se the widely invoked scale concepts are fraught with problems and are best dropped as too are any process shape connotations