mountain geomorphology a theoretical framework for measurement programmes abstract ten distinctive mountain geomorphic systems identified on the basis of structural elements and spatial scale are considered questions and approaches to measurement programmes that are most appropriate to each system are discussed with the aid of illustrative examples from the literature

a weathering intensity index for the australian continent using airborne gamma ray spectrometry and digital terrain analysis abstract weathering intensity largely controls the degree to which primary minerals are altered to secondary components including clay minerals and oxides as weathering intensity increases there are changes in the hydrological geochemical and geophysical characteristics of the regolith thus once calibrated weathering intensity can be used to predict a range of regolith properties a weathering intensity index wii over the australian continent has been developed at a 100 m resolution using regression models based on airborne gamma ray spectrometry imagery and the shuttle radar topography mission srtm elevation data airborne gamma ray spectrometry measures the concentration of three radioelements potassium k thorium th and uranium u at the earth s surface the total gamma ray flux dose is also calculated based on the weighted additions of the three radioelements regolith accounts for over 85 of the australian land area and has a major influence in determining the composition of surface materials and in controlling hydrological and geomorphological processes the weathering intensity prediction is based on the integration of two regression models the first uses relief over landscapes with low gamma ray emissions and the second incorporates radioelement distributions and relief the application of a stepwise forward multiple regression for the second model generated a weathering intensity index equation of wii 6 751 0 851 k 1 319 relief 2 682 th k 2 590 dose the wii has been developed for erosional landscapes but also has the potential to inform on deposition processes and materials the wii correlates well with site based geochemical indices and existing regolith mapping interpretation of the wii from regional to local scales and its application in providing more reliable and spatially explicit information on regolith properties are described

surface topography as key constraint on thermo rheological structure of stable cratons why some archean cratons survived for billions of years while the rest of the lithosphere has been reworked probably for several times is both enigmatic and fundamental for plate tectonics craton longetivity is mainly explained by their buoyancy and analyzed by testing gravitational stability of hardly detectable cratonic mantle keels as a function of a hypothesized thermo rheological structure destruction of some cratons suggests that buoyancy is not the only factor of their stability and many previous studies show that their mechanical strength is equally important the upper bounds on the integrated strength of cratons are provided by flexural studies demonstrating that te values equivalent elastic thickness in cratons are highest in the world 110 150 km yet the lower bounds on the integrated strength of stable cratons are still a matter of debate as well as the question on how this strength is partitioned between crust and mantle and which set of rheological parameters is most pertinent we show that primary observed cratonic features flat topography and frozen heterogeneous crustal structure represent the missing constraints for understanding of craton longevity the cratonic crust is characterized by isostatically misbalanced density heterogeneities suggesting that the lithosphere has to be strong enough to keep them frozen through time without developing major gravitational instabilities and topographic undulations hence to constrain thermo rheological properties of cratons one should investigate the stability of their topography and internal structure our free surface thermo mechanical numerical models demonstrate that craton stability cannot be warranted even by very high crustal strength so that dry olivine mantle and cold thick lithosphere are indispensable conditions we establish lower bound limits on the thermo rheological structure of cratons in particular we find that minimal te needed for long term stability of continents is approximately 90 110 km of which at least 70 km should be contributed by the lithosphere mantle

evidence of multiple halogen sources in scapolites from iron oxide copper gold iocg deposits and regional nacl metasomatic alteration norrbotten county sweden abstract scapolites from barren regional na cl metasomatic assemblages rm iron oxide copper gold deposits iocg scapolite altered metabasic rocks iocg m and from iocg proximal alteration na skarns iocg ps from norrbotten county in northern sweden have been analysed for halogen content and cl stable isotope composition the aim of the study was to constrain the source of halogens within alteration assemblages and to investigate the possible fractionation of cl isotopes between scapolite and the hydrothermal fluid scapolite separates were analysed for cl br and major oxide concentrations using electron probe micro analysis epma and micro x ray fluorescence xrfm spectrometry chlorine was extracted from the scapolite separates via pyrohydrolysis and then analysed for their stable cl isotope compositions by isotope ratio mass spectrometry irms all samples of scapolite investigated in this study are marialitic in composition one of the scapolites from the gruvberget deposit iocg ps had a cl br molar ratio of 2363 which is the highest amongst all scapolites reported in the literature to date cl br molar ratios lower than seawater 650 were identified in two iocg ps scapolite samples cl br 554 and 271 as well as in two iocg m scapolites cl br 393 and 565 three rm scapolites had cl br molar ratios very close to or slightly higher than seawater values 639 to 770 samples with cl br molar ratios less than seawater are inferred to have halogens derived from evaporative residual brines whereas samples with molar ratios higher than seawater may have halogens derived from fluids that have dissolved halite and or are from magmatic systems considering the wide variation of the cl br molar ratios in the iocg ps and iocg m scapolites compared to the restricted composition of the regional alteration rm it is proposed that the hydrothermal fluids interacted with several different protoliths to generate the iocg alteration rm alteration scapolites had 37 cl values from 0 1 to 0 3 two iocg m scapolites had values of 0 2 and iocg ps scapolites had 37 cl values from 0 1 to 1 0 using a previously published 37 cl value from fluid inclusion leachates 1 7 from the iocg m mineralisation at pahtohavare and the 37 cl value of co existing scapolite measured in this study 0 2 an empirical fluid scapolite fractionation factor was calculated to be 1 9 this large fractionation factor is not supported by previous predictions for monovalent chlorides and assuming equilibrium indicates that 37 cl was preferentially accommodated in the a site of the scapolite structure this indicates that either the stable cl isotope partitioning between the cacl 2 rich brine and the scapolite may differ from currently available estimates for nacl brines in equilibrium with silicate minerals or that the scapolite and brine are not in isotopic equilibrium overall the data in this study suggest that halogens in early scapolites were derived from residual brines and halite during metamorphism of evaporites linked to the rm alteration later in the history of the norrbotten district components of the rm alteration were recycled and mixed during magmatic and local metasomatic events to varying extents resulting in the brines associated with iocg alteration

the candelaria punta del cobre iron oxide cu au zn ag deposits chile several iron oxide rich cu au zn ag deposits define an approximately 5 km wide and at least 20 km long belt along the eastern margin of the coastal batholith near copiapo chile this belt includes the large candelaria mine and a group of middle and small sized mines in the punta del cobre district which is located about 3 km northeast of the candelaria deposit estimated geologic resources of the belt are on the order of 700 to 800 million metric tons mt at 1 0 percent cu the ore occurs in veins breccia and stringer bodies and in replacement bodies that are roughly concordant to bedding the orebodies are hosted mainly by volcanic and volcaniclastic rocks of the punta del cobre formation and in places also occur in volcaniclastic intercalations in the lower part of the overlying early cretaceous chanarcillo group most of the larger orebodies in the belt are located where northwest trending brittle faults intersect the contact between massive volcanic and volcaniclastic rocks these northwest faults and a major northeast trending ductile shear zone control portions of the ore of the candelaria deposit chalcopyrite is the only hypogene cu mineral the cu au ore is characterized by abundant magnetite and or hematite and by locally elevated concentrations of ag zn mo and light rare earth elements the ore is hosted mainly in zones with biotite potassium feldspar calcic amphibole epidote alteration at candelaria in the punta del cobre district ore in the deeper parts of the deposits is similarly associated whereas at shallow levels it occurs in zones of biotite potassium feldspar or albite chlorite calcite alteration mineralization at candelaria punta del cobre took place under relatively oxidized conditions manifested by the formation of specular hematite in parts of the district the pseudomorphic replacement of early specular hematite by magnetite during the main iron oxide formation marks a shift toward more reduced conditions or higher temperatures the bulk of the magnetite probably formed at temperatures of about 500 to 600 c the main sulfide stage followed with formation of pyrite and chalcopyrite at temperatures of 470 to 328 c subsequent martitization of the magnetite points to a temperature decrease cooling of the hydrothermal system is also indicated by the homogenization temperatures of 236 c of saline fluid inclusions in late stage calcite oxygen isotope combined with microthermometric data suggest that magmatic fluids or nonmagmatic fluids equilibrated with magmatic silicates were dominant during the main copper mineralization relatively light oxygen isotope signatures of fluids in equilibrium with late calcite suggest mixing with a nonmagmatic fluid e g basinal brines or meteoric waters during the late stages of hydrothermal activity sulfur isotope ratios of chalcopyrite pyrite pyrrhotite and sphalerite from the bronce candelaria las pintadas santos and socavon rampa deposits range from 34scdt values of 0 7 to 3 1 per mil this narrow range of sulfur isotope ratios near 0 per mil is consistent with sulfur of magmatic origin anhydrite from the candelaria mine paragenetically overlaps with chalcopyrite fluid inclusions in this anhydrite homogenize between 340 and 470 c and it has 34scdt values between 14 5 and 17 5 per mil a sulfate sulfide value of 13 4 per mil for a sample with coexisting anhydrite and chalcopyrite is consistent with sulfide sulfate fractionation at temperatures on the order of 400 c ore lead isotope signatures are homogeneous and similar to those of least altered volcanic host rocks and nearby intrusive rocks radiometric ages including new 40ar 39ar ages for hydrothermal alteration at candelaria point to a main cu au mineralization event at candelaria punta del cobre at around 115 ma the ages indicate that ore formation was broadly coeval with batholithic granitoid intrusions and with regional uplift they further imply that the cu au zn ag deposits formed at shallow crustal levels 3 km the stable isotope data the presence of previously reported hypersaline co2 rich fluid inclusions in the main cu ore stage and saline fluid inclusions in late stage calcite the oxidized character of the first ore fluid pulses and the mineralization age coeval with nearby intrusive activity are consistent with but not unequivocally evidence of magmatic fluid contribution into the hydrothermal system

zircon titanite and apatite u th he ages and age eu correlations from the fennoscandian shield southern sweden craton cores far from plate boundaries have traditionally been viewed as stable features that experience minimal vertical motion over 100 1000 ma time scales here we show that the fennoscandian shield in southeastern sweden experienced several episodes of burial and exhumation from 1800 ma to the present apatite titanite and zircon u th he ages from surface samples and drill cores constrain the long term low temperature history of the laxemar region single grain titanite and zircon u th he ages are negatively correlated 104 838 ma for zircon 160 945 ma for titanite with effective uranium eu u 0 235 th a measurement proportional to radiation damage apatite ages are 102 258 ma and are positively correlated with eu these correlations are interpreted with damage diffusivity models and the modeled zircon he age eu correlations constrain multiple episodes of heating and cooling from 1800 ma to the present which we interpret in the context of foreland basin systems related to the neoproterozoic sveconorwegian and paleozoic caledonian orogens inverse time temperature models constrain an average burial temperature of 217 c during the sveconorwegian achieved between 944 ma and 851 ma and 154 c during the caledonian achieved between 366 ma and 224 ma subsequent cooling to near surface temperatures in both cases could be related to long term exhumation caused by either post orogenic collapse or mantle dynamics related to the final assembly of rodinia and pangea our titanite he age eu correlations cannot currently be interpreted in the same fashion however this study represents one of the first examples of a damage diffusivity relationship in this system which deserves further research attention

rates and timing of earth surface processes from in situ produced cosmogenic be 10 beryllium 10 is the longest lived of the seven known unstable isotopes of be it results mostly from the interaction of cosmic radiation primarily neutrons with a variety of target atoms by spallation the splitting of nuclei lal 1988 it can also be produced at very low levels by radio disintegration of u and th sharma and middleton 1989 although all radioactive be isotopes are produced in the atmosphere via cosmic ray reactions arnold 1956 lal and peters 1967 morris et al chapter 5 this volume in this paper we are most interested in 10be produced in rock which we refer to as in situ produced such in situ produced 10be is a cosmic ray dosimeter functioning as a quantitative monitor of near surface residence time in some geologic situations 10be can be used as a chronometer allowing one to estimate the duration of surface exposure in other settings 10be can be used as a tracer allowing one to estimate the rate distribution and behavior of earth surface processes rates of 10be production are very low in rocks exposed at earth s surface 102 atoms g 1 y 1 resulting in typical in situ produced 10be concentrations termed activities of 103 to 107 atoms g 1 the development of accelerator mass spectrometry ams in the 1980s allowed routine measurement of 10be at levels typical of rocks exposed near earth s surface elmore and phillips 1987 analytical refinements in the 1990s lowered detection limits by an order of magnitude allowing dating of exposure periods 103 years in favorable geologic and geographic situations simple exposure histories at high altitude and latitude most in situ 10be is measured in quartz mineral separates where the primary spallation target is o lal and arnold 1985

a fluid inclusion and stable isotope o h s and c study of the archean iocg cristalino deposit carajas mineral province brazil implications to ore genesis abstract the hydrothermal history of the archean cu au cristalino deposit is recorded in moderately to intensely altered host rocks which evolved from 550 c to 150 c distal sodic and proximal calcic ferric potassic and propylitic alterations developed successively with variable intensity two main mineralization types are also recognized an earlier one characterized by a chalcopyrite pyrite magnetite au association that occurs as disseminations and breccias in calcic ferric zones and a later one represented by a chalcopyrite pyrite hematite au association that occurs as breccias and veins mainly in potassic and propylitic zones estimated pressures 0 6 to 2 6 kbar are consonant with brittle and ductile brittle deformational environments where both alteration and mineralization took place the ore bearing fluid was hot t as high as 550 c acidic and hypersaline 55 1 wt nacl equiv and chemically approached by the h2o nacl cacl2 co2 mgcl2 fecl2 system salinity might have exceeded 55 wt nacl equiv in the early alteration stages but decreased progressively to 7 9 wt nacl equiv from 250 c onwards due to incursion of surficial water into the deposit site the fluid was initially 18o enriched and d depleted 18ov smow 9 73 to 6 48 dv smow 30 17 to 40 25 and most likely derived from magmatic sources as result of dilution caused by mixing with meteoric water the fluid became relatively 18o depleted and d enriched 18ov smow 5 57 to 0 28 dv smow 19 15 to 22 24 the 13cv pdb values for vein and breccia calcite 6 5 to 3 8 are consistent with a deep source for co2 likely of mantellic origin most 34sv cdt values for chalcopyrite show narrow variation 1 6 to 3 5 and could indicate a homogeneous reservoir for sulfur however a few samples reveal significant influence of sedimentary rocks on their isotope composition 34sv cdt 32 6 showing that sulfur may have been sourced from various reservoirs it is inferred that most cu and au were transported as chloride complexes 350 c and precipitated in response to decrease in temperature and cl activity and increase in ph the formation of the chalcopyrite pyrite hematite au association was especially favored by an oxygen fugacity increase during the late stages of the hydrothermal alteration secondary fluid inclusions reveal that an aqueous colder 200 150 c and relatively less saline 21 3 1 wt nacl equiv fluid of uncertain origin circulated in the cristalino deposit area which is likely related to a nearby paleoproterozoic granitic intrusion in comparison with other archean carajas iocg deposits particularly those that lie in the southern sector of the carajas domain the cristalino deposit shows similar structural styles hydrothermal assemblages and ore fluid composition and evolution the data presented here support previous interpretations that consider cristalino as of iocg typology

mineralization and ore genesis of the qiaoxiahala fe cu au deposit in the northern margin of east junggar terrane central asian orogenic belt constraints from fluid inclusions and stable isotopes abstract the qiaoxiahala fe cu au deposit 1 44 mt ore 43 53 fe 0 55 2 21 cu and 0 13 2 4 g t au is located in the northern margin of east junggar terrane nw china the deposit is hosted in the upper part of the middle devonian beitashan formation mafic and felsic volcanic rocks and sedimentary interbeds and is spatially closely related to local fractures six hypogene hydrothermal stages have been identified including stage i early skarn stage ii late skarn stage iii magnetite mineralization stage iv magnetite pyrite mineralization stage v chalcopyrite mineralization and stage vi late veins these six stages include three major mineralization events as represented by the stage iii magnetite epidote k feldspar quartz calcite stage iv magnetite pyrite garnet quartz calcite and stage v chalcopyrite chlorite assemblages the stage iii magnetite mineralization fluids were likely of high temperature 354 386 c low medium salinity 9 9 14 7 wt nacl equiv mg fe rich and organic rich with lithostatic pressure of 1 3 1 5 kbar and corresponding depth of 4 3 4 8 km oxygen and hydrogen isotopes showed that the 18o rich 9 7 11 2 and d rich 26 3 fluids were possibly modified from the early carboniferous seawater interacting with the beitashan formation organic rich limestone or tuff in comparison the stage iv magnetite pyrite mineralization fluids were likely of medium high temperature 272 453 c low medium salinity 2 9 19 5 wt nacl equiv mg fe rich with pressure of 0 8 1 2 kbar and corresponding depth of 2 6 4 0 km the stage v chalcopyrite mineralization fluids were likely of low medium temperature 186 270 c low medium salinity 1 4 21 8 wt nacl equiv ca or na rich with pressure of 0 4 0 6 kbar and corresponding depth of 1 2 km hydrogen and oxygen isotopic compositions stage iv dwater 141 to 92 18owater 8 9 11 1 stage v dwater 104 18owater 7 2 suggest that the ore fluids were of connate marine origin furthermore stage iv 13cwater values 0 6 to 0 also indicate interactions between seawater and sedimentary wall rocks the negative sulfur isotopic compositions of chalcopyrite and pyrite 4 2 to 0 2 may demonstrate a biogenic sulfur source compared with the arc related iocg deposits in the central andean orogen the qiaoxiahala fe cu au deposit shares many common features in geology mineralization alteration and various sources of fluids indicating a possible iocg like mineralization style and potential to discover other late paleozoic arc related iocg deposits in east junggar

a shared borehole approach for coal bed methane drainage and ground stabilization with grouting abstract in underground longwall coal mines the risks of surface subsidence and coal bed methane cbm emission are generally controlled separately e g subsidence mitigation by overburden stabilization using grout injection and pressure relief cbm drainage using surface boreholes however some longwall panels require both gas drainage and ground stabilization for this purpose we propose a shared borehole approach for ground stabilization grouting and adjacent seam pressure relief cbm drainage by using mining induced fractures and voids in this method overlying seam pressure relief cbm is drained through a surface borehole during extraction of a longwall panel whereas grout injection is applied to stabilize the ground using the same borehole following drainage a combined drainage injection model that determines the allowable lag distance for grout injection is proposed the effectiveness of the shared borehole approach was tested at a longwall panel in a chinese coal mine no obvious interactions between the injection and drainage processes were detected during the case study verifying the effectiveness of the shared borehole approach

an intrusion related origin for cu au mineralization in iron oxide copper gold iocg provinces major cu au deposits of iron oxide copper gold iocg style are temporally associated with oxidized potassic granitoids similar to those linked to major porphyry cu au deposits stable and radiogenic isotope evidence indicates fluids and ore components were likely sourced from the intrusions iocg deposits form over a range of crustal levels because co2 rich fluids separate from the magmas at higher pressures than in co2 poor systems thereby promoting partitioning of h2o cl and metals to the fluid phase at deep levels the magma fluid system cannot generate sufficient mechanical energy to fracture the host rocks as in porphyry systems and the iocg deposits therefore form in a variety of fault related structural traps where the magmatic fluids may mix with other fluids to promote ore formation at shallow levels the iocg deposits form breccia and fracture hosted mineralization styles similar to the hydrothermal intrusive breccias and sulphide vein systems that characterize many porphyry cu au deposits the fluids associated with iocg deposits are typically h2o co2 salt fluids that evolve by unmixing of the carbonic phase and by mixing with fluids from other sources in contrast fluids in porphyry systems typically evolve by boiling of moderate salinity fluid to produce high salinity brine and a vapor phase commonly with input of externally derived fluids these different fluid compositions and mechanisms of evolution lead to different alteration types and parageneses in porphyry and iocg deposits porphyry cu au deposits typically evolve through potassic sericitic and intermediate and or advanced argillic stages while iocg deposits typically evolve through sodic calcic potassic and carbonate rich stages and at deeper levels generally lack sericitic and argillic alteration the common association of porphyry and iocg cu au deposits with potassic oxidized intermediate to felsic granitoids together with their contrasting fluid compositions alteration styles and parageneses suggest that they should be considered as part of the broad family of intrusion related systems but that they are typically not directly related to each other

geology geochronology and hf and pb isotope data of the raul condestable iron oxide copper gold deposit central coast of peru raul condestable is a 32 million metric ton mt iron oxide copper gold iocg deposit located on the peruvian coast 90 km south of lima the ore occurs as veins replacement mantos and disseminations consisting of a chalcopyrite pyrite pyrrhotite magnetite amphibole mineral association the geology of the studied area comprises a series of superposed volcanic edifices of late jurassic to early cretaceous age which are part of a larger volcanic island to continental arc system particularly good exposures of the tilted host sequence allow the mapping of the raul condestable iocg deposit in a nearly complete oblique cross section from its associated volcanic edifice down to a paleodepth of about 6 km u pb zircon ages indicate that in the deposit area felsic magmatic activity took place between 116 7 0 4 and 114 5 1 ma defining a new raul condestable superunit the oldest so far of the peruvian coastal batholith this superunit is located west of the main part of the batholith and includes a dacite andesite volcanic dome and a subvolcanic quartz diorite porphyry sill dike complex that were emplaced at 116 7 0 4 and 116 4 0 3 ma respectively followed by tonalite stocks and dikes emplaced between 115 1 0 4 and 114 5 1 ma all these rocks contain hornblende and or biotite but no pyroxene and correspond to silica and water rich magmas following a calcic differentiation trend hf isotope data on zircons ehf 115 ma 5 2 7 5 and pb isotope data on whole rock combined with lithogeochemical results suggest that magmas were generated by partial melting of the upper mantle enriched through hydrous metasomatism and or melting of subducted pelagic sediments the lack of zircon inheritance suggests that there was no direct involvement of continental crust the raul condestable iocg deposit is connected in space and time with the magmatism of the raul condestable superunit the mineralization was emplaced in the core of the dacite andesite volcanic dome at a paleodepth of 2 to 3 km surrounding two tonalitic intrusions formed at 115 1 0 4 and 114 8 0 4 ma the u pb age of hydrothermal titanite from iocg veins at 115 2 0 3 ma indicates that the mineralization was coeval with or more probably just followed the emplacement of the tonalites re os geochronology on molybdenite did not yield reliable ages due to apparent re loss copper ore is associated with a zoned alteration pattern which surrounds the tonalite intrusions it consists of a core of biotite alteration and quartz stockwork grading outward to actinolite magnetite chlorite titanite scapolite albite epidote and upward to sericite fe chlorite alteration an upper distal alteration halo consisting of hematite chlorite surrounds the sericite fe chlorite and actinolite alterations laterally most of the ore is spatially associated with the actinolite alteration and to a lesser extent with the sericite fe chlorite alteration the results of this study confirm that the 110 to 120 ma age range was a productive time period for andean iocg deposits the characterization of the hydrous intermediate magmatism related to the mineralization as well as the subvolcanic position of the deposit and its related alteration pattern provides further criteria that may be used when exploring for iocg deposits in a convergent plate tectonic setting

pre quaternary landforms in the low latitude context the example of australia abstract direct effects of quaternary glaciation and periglacial activity affected only comparatively small areas of southeastern australia certainly volcanicity continued in a few districts extensive new planation surfaces were formed dunefields were widely developed and there were important developments at the coastline and offshore during this period but many pre quaternary terrains persist in the contemporary landscape tertiary volcanic plains and plateaux are widespread in the eastern uplands and duricrusted ferruginised silicified remnants some of them folded are characteristic of many parts of the central and western sectors of the continent drainage systems of similar age are also increasingly recognised older gondwanan elements also feature prominently but especially in the eastern uplands and on the craton some of these ancient elements are exhumed but others are epigene and etched though the so called epigene surfaces are mostly of etch type the survival of the ancient epigene and etch forms is attributed to resistance of bedrock through drainage unequal activity and reinforcement mechanisms

gondwanan late jurassic and cretaceous palaeosurfaces of the australian craton abstract cretaceous and especially early cretaceous marine transgressions played an important part in the evolution of the australian landscape they covered at least 40 of the present australian craton and about 45 of the entire present continent in so doing they preserved in unconformity extensive areas of the pre existing or gondwana landscape though substantial gondwana elements have been ehumed at the margins of the depositional basins as a result of the cainozoic stripping of the sedimentary cover clear examples are demonstrated in the isa highlands the peake and davenport ranges and the northermost flinders ranges the basinal areas subsided under the weight of water and sediment while adjacent land areas were uplifted flexure continentale or randschwelle those that were already of low relief were dissected and regoliths were eroded but substantial areas of the gondwana plains in etch form were preserved on divides as in the gawler and hamersley ranges others were reduced to low relief by rivers graded to cretaceous shorelines as in the southern and central flinders ranges elsewhere the gondwana landscapes were preserved more or less intact as in the western yilgarn craton the mt lofty ranges and possibly the higher ridges of the macdonnell ranges the nature of the gondwana landscape varied according to structure but inselberg landscapes were widely developed and have been exhumed for instance in the western pilbara and in the eastern musgrave block kulgera region the gondwana landscape was already complex with stratigraphic conditions suitable for the exhumation of archaean preterozoic and cambrian forms for instance already in place re exposure later took place so that very old elements form integral parts of the present landscape exhumed gondwana landscapes have been preserved by burial and the stripping of some of the etch forms may have taken place in the later cainozoic so that their survival poses few difficulties other etch surfaces like those of the gawler and the hamersley ranges demonstrably were stripped in the early cretaceous and eocene respectively and they like epigene earliest tertiary and mesozoic features call for explanation various factors like resistant bedrock unequal erosion surfaces which stand high and dry interior situation and reinforcement effects go some way to relieving though they do not resolve the problem

eroding australia rates and processes from bega valley to arnhem land we report erosion rates determined from in situ produced cosmogenic 10 be across a spectrum of australian climatic zones from the soil mantled se australian escarpment through semi arid bedrock ranges of southern and central australia to soil mantled ridges at a monsoonal tropical site near the arnhem escarpment climate has a major effect on the balance between erosion and transport and also on erosion rate the highest rates averaging 35 m ma 21 were from soil mantled transport limited spurs in the humid temperate region around the base of the se escarpment the lowest averaging about 1 5 m ma 21 were from the steep weathering limited rocky slopes of kings canyon and mt sonder in semi arid central australia between these extremes other factors come into play including rock type slope and recruitment of vegetation we measured intermediate average erosion rates from rocky slopes in the semi arid flinders and macdonnell ranges and from soil mantled sites at both semi arid tyler pass in central australia and the tropical monsoonal site at soil mantled sites in both the se and tropical north soil production generally declines exponentially with increasing soil thickness although at the tropical site this relationship does not persist under thin soil thicknesses and the relationship here is humped results from tyler pass show uniform soil thicknesses and soil production rates of about 6 5 m ma 21 supporting a longstanding hypothesis that equilibrium soil mantled hillslopes erode in concert with stream incision and form convex up spurs of constant curvature moreover weathering limited slopes and spurs also occur in the same region the average erosion rate for rocky sandstone spurs at glen helen is 7 m ma 21 similar to the tyler pass soil mantled slopes whereas the average rate for high quartzite spurs at mount sonder is 1 8 m ma 21 the extremely low rates measured across bedrock dominated landscapes suggest that the ridge valley topography observed today is likely to have been shaped as long ago as the late miocene these rates and processes quantified across different undisturbed landscapes provide critical data for landscape evolution models

the emplacement of the granitic las tazas complex northern chile the relationship between local and regional strain abstract the coastal batholith of northern chile grew under transtensional extensional conditions that prevailed along the andean margin during the mesozoic the batholith hosts the atacama fault zone a major arc parallel fault system which was characterised by sinistral transtensional shearing during the early cretaceous the las tazas complex is a composite granitoid intrusion that was emplaced syntectonically along the atacama fault zone at 130 ma syntectonic emplacement is indicated by a consistent kinematic history between the complex and its wall rocks together with synchronous crystallisation and shearing ages in contrast to regional patterns the las tazas complex was emplaced during a local change from vertical east side down to dextral transcurrent displacement along the fault zone during intrusion strain was partitioned between non coaxial simple shearing within country rock mylonites and a flattening strain across the crystallising complex this combination indicates that the pluton was emplaced under temporary transpressive conditions that were localised around the pluton probably induced by magma emplacement such a difference between local and regional strain suggests that emplacement related structures should only be related to regional strain states with great care

the marcona magnetite deposit ica south central peru a product of hydrous iron oxide rich melts marcona the preeminent andean magnetite deposit 1 9 gt 55 4 fe and 0 12 cu is located in the iron oxide copper gold iocg subprovince of littoral south central peru fe oxide and cu zn pb sulfide mineralization was controlled by northeast striking faults transecting a middle jurassic aalenian to oxfordian andesitic shallow marine arc and a succession of contiguous plate boundary parallel late jurassic to mid cretaceous volcanosedimentary basins at marcona hydrothermal activity was initiated in the earliest middle jurassic 161 177 ma by high temperature mg fe metasomatism represented by cummingtonite and phlogopite magnetite assemblages subsequently during the terminal eruptions 156 162 ma of the arc widespread albite marialite alteration na cl metasomatism was followed by the emplacement of an en echelon swarm of massive magnetite ore bodies with subordinate overprinted magnetite sulfide assemblages hosted largely by paleozoic metasilici clastics the magnetite orebodies exhibit abrupt smoothly curving contacts dike like to tubular apophyses and intricate amoeboid interfingering with dacite porphyry intrusions there is no convincing megascopic or microscopic evidence for large scale fe metasomatism associated with the main sulfide poor mineralization the largest 400 mt minas 2 3 4 orebody is interpreted as a bimodal magnetite dacite intrusion comprising commingled immiscible melts generated through the dissolution of metasedimentary quartz in parental andesitic magma oxygen and sulfur stable isotope geothermometry indicates that the evolution at ca 159 ma from magnetite biotite calcic amphibole phlogopite fluorapatite to magnetite phlogopite calcic amphi bole pyrrhotite pyrite assemblages coincided with quenching from above 800 c to below 450 c and the concomitant exsolution of dilute aqueous brines subsequently chalcopyrite pyrite calcite pyrrhotite sphalerite galena assemblages in part metasomatic were deposited from lower temperature 360 c brines the cu poor marcona kiruna type magnetite and cu rich iocg deposits in the district therefore although spatially contiguous represent contrasting ore deposit types the former are interpreted as the product of fe oxide melt coexisting with dacite magma within an andesitic arc which failed during the closure of a back arc basin the weak associated magmatic hydrothermal cu sulfide mineralization at marcona was generated through melt vesiculation and contrasts with the considerably higher grade cu and ag rich orebodies of the major cu rich iocg deposits in the central andes e g la candelaria punta del cobre mantoverde raul condestable and mina justa which were the products of cool oxidized hydrothermal fluids plausibly expelled from the adjacent basins during tectonic inversion

mechanisms of continental growth in extensional arcs an example from the andean plate boundary zone during the late triassic jurassic and early cretaceous an extensional magmatic arc was formed in the andean margin of northern chile plutons emplaced at ramps within a hinterland propagating extensional duplex were fed by dikes that transferred magma through the lower crust from a reservoir in the mantle phases of volcanism separated phases of plutonism and our model demonstrates that plutonism was favored only when upper plate extensional fault systems were active when they were not dikes cut across inactive faults and magma rose directly to the surface during volcanic phases of arc growth

a study of surface subsidence and coal pillar safety for strip mining in a deep mine some villages and bridges are located on the ground surface of the working district no 7 in the wanglou coal mine if longwall mining is adopted the maximum deformation of the ground surface will exceed the safety value strip mining is employed for the working district no 7 which is widely used to reduce surface subsidence and the consequent damage of buildings on the ground surface to ensure the safety of coal pillars and improve the recovery coefficient theoretical analysis and numerical simulation flac 3d were adopted to determine the coal pillar and mining widths and to discuss the coal pillar stress distribution and surface subsidence for different mining scenarios the results revealed that the width of coal pillars should be larger than 162 m and the optimized mining width varies from 150 to 260 m as the coal seam is exploited vertical stress is mainly applied on the coal pillar inducing stress changes on its ribs the coefficient of mining induced stress varies from 2 02 to 2 62 for different mining scenarios the maximum surface subsidence and horizontal movement increase as the mining width increases however when the mining width increases to a certain value increasing the pillar width cannot significantly decrease the maximum subsidence to ensure the surface subsidence less than 500 mm the mining width should not be larger than 200 m considering the recovery coefficient and safety of the coal pillar a pillar width of 165 m is suggested

environmentally sustainable mining a case study on surface subsidence control of grouting into overburden this paper presents an investigation on the effect of grouting into multi bed separation to control mining induced surface subsidence in the overburden without obvious thick and hard strata for generating large scale bed separation overburden grouting is carried out by increasing the number of boreholes and grouting strata the scale model test numerical simulation and field measurements are used to study distribution and process of bed separation and to compare the overburden failure with surface subsidence due to pre and post overburden grouting with a case study of the qi nan coal mine anhui province china the scale model test and numerical simulation results of the overburden grouting process are in close agreement with those obtained from the field measurements filling masses with different diffusion radii are commonly formed in the different bed separation which are overlaid to control the surface subsidence it is proven that overburden grouting can successfully mitigate overburden failure and subsidence without obvious hard strata and bed separations this provides an effective and cost efficient approach for addressing the surface subsidence and overburden deformation problems due to mining

co2 storage potential of south african coals and gas entrapment enhancement due to igneous intrusions abstract methane outburst events have occurred in some underground coal mines of south africa such as those in twistdraai mine in the highveld coalfield in the early 1990s occurrences of methane outbursts suggest that high gas content in adsorbed and free phase might be present in some sections of the coal seams coal seams might also be friable in those sections allowing pulverisation during outburst the survey of gas outburst events indicates that the locations of high gas emissions were mainly in the vicinity of the igneous intrusions mainly dolerite intrusions these intrusions are a result of post depositional volcanism into coal seams in some major coalfields of south africa such as the highveld coalfield this study was undertaken firstly to investigate potential locations for the occurrence of coal seam gas in south african coal seams with respect to the igneous intrusions and their enhancement effect on gas release and storage of these coals secondly it was thought that as the metamorphosed coals with high ash content were not economically viable for mining they might be potentially suitable for co 2 disposal measurements on 14 coal samples taken in an underground coal mine at various distances from a dolerite dyke show that the adsorption and porosity properties of metamorphosed coals have been enhanced thus increasing their gas storage capacity diffusivity results show that dolerite intrusions would act as enclosures and gas traps for storage of gas gas diffusivity was greater in coals near the dyke by a factor of two in general it is expected that the co 2 storage and gas flow properties of such coals be enhanced due to the heating effect of intrusions making the coals more appealing for possible future sequestration of co 2 from anthropogenic sources

long term landscape evolution in australia the main features of the australian physical landscape are of the order of 107 108 years old this contradicts the widely held view that little of the earth s topography predates the quaternary and that erosion cycles are carried to planation within tens of millions of years much of the australian landscape must have developed over similar timescales to that of the tectonic evolution of the continent itself the study of the geomorphology of such ancient terrains may therefore be seriously deficient unless it is considered within the context of continental scale tectonic development application of this approach shows that there are strong links between the geomorphology of australia and plate movements ocean spreading plate convergence tectonostratigraphic terranes orogenesis and epeirogenesis the most important factor contributing to the survival of ancient landscapes in australia is the low rate of denudation which the continent has experienced during the mesozoic and cenozoic this is largely a consequence of orogenic stability although the absence of significant quaternary glaciation may also be of importance however in order for landforms to have survived over such timespans denudation must not only have been low but must also have been highly localized over space and time this has been the case both on a regional scale with long term denudation rates of 0 2 m ma 1 in central australia contrasting with higher rates along the continental margins and on a local scale with denudation confined to valleys leaving divides and interfluves almost unscathed

sources of mineralising fluids for the olympic dam deposit south australia smnd isotopic constraints abstract the olympic dam cu u au ag deposit south australia is hosted by the olympic dam breccia complex a high level hematite rich hydrothermal breccia system the deposit is characterised by extreme enrichments of ree which are a product of the ore forming process therefore making the sm nd isotopic system an ideal tool for clarifying the complex relationships between the different ore and breccia types pyrite chalcopyrite and bornite chalcocite rich hematitic ores share an initial end signature of 2 5 which suggests that these ore types are cogenetic these ores together with sulphide poor hematitic breccias yield a 14 point sm nd isochron age of 1572 99 ma the host roxby downs granite has an initial nd of 5 and therefore cannot alone have been the source of the mineralising fluids for the hematitic ores in contrast to hematitic rocks volumetrically minor magnetite rich assemblages have the same initial nd signature as the host granite suggesting that they are cogenetic assuming that both hematite and magnetite were precipitated from solution their contrasting isotopic signatures require that ore deposition involved two distinct fluids the isotopic data do not allow the distinction between a model involving concurrent activity of such fluids in a mixing regime and a model involving temporally separate overprinting of magnetite by hematite cu sulphides the ore signature of nd 2 5 cannot have been derived solely from pre existing crustal rocks of the gawler craton it must have involved a contribution from a mantle derived source rock or magma the most likely source of this nd component are the mantle derived rocks produced during the gawler range volcanics event e g altered alkaline mafic ultramafic dykes within the deposit which have initial isotopic signatures as high as nd 4 assuming end member compositions equivalent to these dykes and the roxby downs granite the ore signature implies that 30 of the nd in the ores was derived from the mafic ultramafic source if nd was leached from source rocks rather than derived from magmatic volatiles the inferred rock fractions contributing ree to the deposit are 13 mafic ultramafic rocks and 87 roxby downs granite or its volcanic equivalent massbalance calculations indicate that 13 rock fraction of mafic ultramafics can account for 50 of the cu contained in the deposit the involvement of mafic ultramafic rocks is therefore inferred to have been crucial to the genesis of the cu enriched ores at olympic dam

iron oxide copper gold mineralization of the devonian laoshankou deposit xinjiang nw china in the central asian orogenic belt abstract the laoshankou iron oxide cu au iocg deposit 41 km southwest of qinghe city xinjiang nw china is the most important magnetite deposit with economic cu and au metal reserve 3 26 mt fe 33 5 36 4 9 8 kt cu 0 2 0 4 and 0 14 t au 0 5 1 3 g t in the east junggar terrane of the central asian orogenic belt caob the deposit is hosted by volcanic rocks of the middle devonian beitashan formation in this study four hypogene hydrothermal alteration stages have been identified including the ca silicate alteration stage i amphibole epidote magnetite alteration mineralization stage ii pyrite chalcopyrite mineralization stage iii and late hydrothermal veining stage iv mineralogical fluid inclusion including laser raman spectroscopy and mineral sulfur oxygen hydrogen and carbon isotope analyses were carried out to elucidate the nature and origin of the hydrothermal fluids at laoshankou stage i hydrothermal fluids were likely derived from a 590 c magmatic fluid with 18 o water 9 2 9 7 subsequently the magnetite epidote amphibole assemblage may have precipitated from the fluids 530 c formed by the mixing of high temperature magmatic fluids with the seawater that reacted with 18 o rich wall rocks the fluid rock reactions are reflected from the 18 o water 9 6 10 7 and d water 25 5 23 8 values the sub economic stage iii a pyrite epidote quartz garnet mineralization likely occurred at 415 c and was formed by fluids with 34 s fluid 3 7 0 5 d water 110 94 and 18 o water 7 92 8 9 the lower temperature and presence of organic matter of the stage iii a fluids may have reflected the involvement of meteoric water and organic matter from the wall rocks the economic cu mineralization stage iii b was probably formed by the mixing of a meteoric water dominated fluid medium temperature low salinity and na dominated and a ca rich formation water in equilibrium with the volcanic wall rocks medium temperature medium salinity and ca fe mg dominated with 34 s fluid 2 6 18 o water 5 6 5 8 13 c water 3 3 3 1 and d water 92 95 towards the end of the fluid evolution meteoric water incursion may have continued and generated the ore barren low temperature low salinity and na dominated fluids although the laoshankou deposit contains distinct skarn alteration the ore mineral assemblage and ore fluid features indicate that it is not a typical skarn deposit but share many similarities with many central andean iocg deposits we conclude that the iocg ore forming setting in the devonian east junggar was analogous to the cretaceous central andes in that they both occurred during basin inversion in a volcanic arc setting

tracing the fluid evolution of the kiruna iron oxide apatite deposits using zircon monazite and whole rock trace elements and isotopic studies the ore genesis of the paleoproterozoic iron oxide apatite deposits in the vicinity of kiruna in northern sweden is poorly understood despite a century long mining history and 2500 mt of iron ore with grades of 30 to 70 wt fe produced in the region to date zircon grains from the ore recently dated at ca 1874 ma show very different appearances compared to zircon from surrounding host rocks ca 1880 ma and related intrusions ca 1880 and ca 1874 ma particularly an inclusion rich rim in contrast zircon from the host rocks and a proximal granite intrusion exhibit typical igneous growth zoning electron microprobe results show near stoichiometric composition for zr si and hf in the host rock zircon grains the ore zircon crystals have low analytical totals with significant concentrations of ca fe y and p and infrared spectroscopy showed several weight percent of water these ore zircon grains further show fe rich inclusions zones and or veins in elemental x ray maps and light rare earth elements lree enrichment transmission electron microscopy tem shows that the lree are not due to micro or nano inclusions in the zircon but are likely hosted as lree oxides in amorphous regions of the grains based on these characteristics the rims on ore zircon grains are interpreted to be of hydrothermal origin uranium pb in monazite from the ore measured by sims suggests a secondary event influencing the area at ca 1624 ma a period of known geologic activity in fennoscandia electron microprobe x ray mapping of these monazite grains shows no zoning and relatively low u and th concentrations stark contrasts are visible between the ore depleted mantle influence and host rocks crustal influence in the whole rock lu hf and sm nd data the depleted mantle signature of the ore could be related to the kiruna greenstone group as a potential source region for the iron the sm nd isotopic composition of monazite from the ore shows a crustal influence and indicates that the younger event has not disturbed the whole rock sm nd signature of the ore the hydrothermal nature of the ore zircon grains and the isotopic signatures point to a hydrothermal influence on the ore formation with a high temperature magmatic fluid related to the intrusions as most likely heat and fluid source

early proterozoic cu au and fe ore deposits associated with regional nacl metasomatism in northern fennoscandia scapolite is widely distributed in 1 9 2 5 ga volcano sedimentary rocks and 1 77 2 2 ga igneous rocks over several hundred square kilometres in northern fennoscandia comprising northern sweden no

displacement history of the atacama fault system 25 00 s 27 00 s northern chile in the cordillera de la costa of the central andes in northern chile mesozoic arc complexes are cut by a trench parallel strike slip fault system the atacama fault system brittle faulting in the atacama fault system is superposed on steeply dipping foliations in ductile shear belts between 25 s and 27 s the western part of the fault system was active in early cretaceous time as an upper amphibolite facies down to the east dip slip ductile shear zone in the eastern part of the fault system ductile deformation is of similar early cretaceous age but occurred under lower grade metamorphic conditions at the greenschist lower amphibolite facies transition the mylonites in the eastern part of the fault system were formed by sinistral strike slip displacement the dip slip and sinistral strike slip displacements are contemporary with the development of a magmatic arc and they imply that the tectonic environment in this part of the arc was transtensional the ductile deformation was partitioned spatially into a dip slip component associated with the emplacement of magmas and a sinistral strike slip component brittle fault zones in the el salado segment of the atacama fault system define large scale sidewall ripout structures subhorizontai slickenlines ripout asymmetry and s c type fabrics in fault gouge indicate that brittle deformation involved sinistral strike slip displacements the transition from ductile to brittle sinistral strike slip displacements may have occurred due to cooling in mid cretaceous time when the magmatic arc was abandoned

the tropezon cu mo au deposit northern chile the missing link between iocg and porphyry copper systems this study has been supported by the project cicyt feder cgl2006 0378 of the spanish government and by internal funds of the igme

mesozoic magmatic and tectonic events within the andean plate boundary zone 26 27 30 s north chile constraints from 40 ar 39 ar mineral ages in north chile jurassic cretaceous arc magmatism is represented by several narrow belts of plutons and two separate volcanic sequences new 40 ar 39 ar mineral ages confirm five distinct episodes of magma emplacement as plutonic complexes c 202 188 ma c 160 153 ma c 142 138 ma c 130 127 ma and c 106 103 ma conjugate dike sets were emplaced immediately before periods of plutonism and each distinct episode of magmatism prior to c 127 ma was located successively eastward inboard from the subduction boundary features interpreted to result from regional extension within the magmatic arc steeply dipping ductile mylonitic shear zones were developed in wall rocks along western contacts of late jurassic and early cretaceous plutons steeply plunging mineral stretching lineations and a variety of kinematic indicators record an east side down extension along eastern faults of the atacama fault system steeply dipping ductile mylonitic shear zones display subhorizontal mineral stretching lin

cambrian river terraces and ridgetops in central australia oldest persisting landforms fluvial sediments in paleovaileys cut in the ashburton surface of the davenport province of central australia form terrace remnants that appear to retain their original depositional tops and have probably existed as subaerial landforms since their inception marine fossils in sediments conformable with the fluvial sediments near the southeast margin of the province give a cambrian age for the terraces the ashburton surface forming the ridgetops between the paleovalleys is cambrian or older

investigation of fill distribution in post injected longwall overburden with implications for grout take estimation abstract in civil and mining engineering grout injection technology which involves the injection of grout into the bedding separation zone or other voids through surface boreholes is used to stabilize the ground above underground excavations the injected fill at the targeted void space mitigates the deformation of overlying strata thus reducing surface subsidence when applying this technology it is important to determine the distribution of the injected fill in the overburden as it affects grout take estimation evaluation of subsidence control effectiveness etc in this paper we present theoretical and physical models of the distribution of the injected fill according to previous borehole data the location of the injected fill is assumed to be a single horizon based on the characteristic of the main injection horizon and geological features of the surrounding strata an easy to use theoretical model of injected fill distribution is proposed which quantifies the fill thickness at different locations along the main injection horizon the proposed model is verified using a physical model of overburden grout injection in addition to the injection parameters such as the horizon depth and ratio of injection a site specific geological parameter namely the angle of full subsidence as well as the underground opening width play a vital role in governing the fill distribution using the proposed model we develop a method for estimation of grout take which may facilitate the injection design thus improving the effectiveness of ground stabilization

pre quaternary landscape inheritance in australia palaeogeographic reconstructions indicate that parts of the australian continent have been subaerially exposed for hundreds of millions of years some landforms and regolith are demonstrated to be at least 300 million years old but their persistence at or near the surface is inconsistent with long term denudation rate estimates based on cosmogenic nuclides and apatite fission track thermochronology burial and exhumation are suggested as significant preservation factors in conjunction with prolonged tectonic stability and a shift to more arid climatic regimes in the cenozoic copyright 2007 john wiley sons ltd

iron oxide copper gold deposits an andean view iron oxide copper gold iocg deposits defined primarily by their elevated magnetite and or hematite contents constitute a broad ill defined clan related to a variety of tectono magmatic settings the youngest and therefore most readily understandable iocg belt is located in the coastal cordillera of northern chile and southern peru where it is part of a volcano plutonic arc of jurassic through early cretaceous age the arc is characterised by voluminous tholeiitic to calc alkaline plutonic complexes of gabbro through granodiorite composition and primitive mantle derived parentage major arc parallel fault systems developed in response to extension and transtension induced by subduction roll back at the retreating convergent margin the arc crust was attenuated and subjected to high heat flow iocg deposits share the arc with massive magnetite deposits the copper deficient end members of the iocg clan as well as with manto type copper and small porphyry copper deposits to create a distinctive metallogenic signature

effects of arch structure in unconsolidated layers on fracture and failure of overlying strata abstract the conventional model for bearing structures was established based on the assumption that the effect of unconsolidated layers can be assumed to be similar to uniformly distributed loading while ignoring the variations in the loading stress imposed on the strata owing to an arch structure in the unconsolidated layers asul in order to make up for this deficiency in this study a mechanical model of the arch structure in the unconsolidated layers was established and the conditions for the formation of the arch structure in the unconsolidated layers were derived the evolution of the arch structure in the unconsolidated layers during excavation was simulated using two dimensional physical simulations mechanical models of the fractural characteristics of the key stratum ks and the voussoir beam structure vbs based on the arch structure in the unconsolidated layers were also developed the simulation results showed that when the thickness of the unconsolidated layers is larger than the critical thickness corresponding to the formation conditions an arch structure in the unconsolidated layers can form the critical thickness is affected by the mining width and the thickness of the bedrock strata in the absence of the arch structure in the unconsolidated layers the loading stress applied on the underlying strata can be assumed to correspond to uniformly distributed loading as is the case in the traditional model when affected by the arch structure in the unconsolidated layers the loading stress of the overlying strata is transferred to the abutment of the arch structure in the unconsolidated layers there is a stress decreased zone under the arch structure in the unconsolidated layers which can decrease the loading stress on the underlying strata in longwall face lw 7130 of the qidong coal mine in an area affected by an arch structure in the unconsolidated layers the fractural interval of the key stratum will increase and the key strata will be fractured successively upward however the sliding and rotational failures of the voussoir beam structure will not occur under the arch structure in the unconsolidated layers in the absence of the arch structure in the unconsolidated layers the fractural interval of the primary key stratum will decrease resulting in the complete breakage of the overlying strata and the sliding of the voussoir beam structure the results of the theoretical calculations were verified through field observations performed in longwall face 7130

new constraints on the timing of host rock emplacement hydrothermal alteration and iron oxide apatite mineralization in the kiruna district norrbotten sweden high spatial resolution zircon u pb geochronological data obtained directly on the kiirunavaara iron oxide apatite ioa deposit related orebodies and host rocks provide new constraints on the timing of mineralization in these deposits these data raise new arguments in the debate of a magmatic versus hydrothermal metasomatic genesis of these major 2 500 mt 30 70 wt fe paleoproterozoic deposits the main orebody at kiirunavaara contains ti poor magnetite and minor 0 05 5 wt p apatite located between a trachyandesite footwall and a rhyodacite hanging wall which also hosts smaller orebodies nukutus rektorn and tuolluvaara the pervasive na and k metasomatism in the host rock is documented by whole rock geochemical data and cathodoluminescence cl microscopy zircon u pb data for the metavolcanic rocks in the footwall and hanging wall cluster between 1884 4 and 1880 3 ma in the footwall a syenite aplite system yields ages of 1880 7 and 1881 4 ma a granite pluton exposed underground has an age of 1874 4 ma zircons in two ore samples never directly dated before this study yield ages of 1877 4 and 1874 7 ma brecciation at the contacts between the ore and host rocks the tight age at ca 1880 ma for most volcanic and plutonic rocks in the footwall and hanging wall and the marginally younger age for ore at ca 1877 to 74 ma matching the age of the spatially related granite pluton suggest a magmatic hydrothermal emplacement model for the kiruna area ioa ores

alteration patterns and structural controls of the el espino iocg mining district chile the el espino iocg mining district is characterized by several mineralized bodies the largest of which is the el espino deposit which has an estimated geologic resource of 123 mt at 0 66 cu and 0 24 g t au mineralized bodies are distributed in a 7 10 km2 area throughout a 1 000 m vertical section they range from single veins to stockworks and breccias to manto type deposits the ore bodies are hosted primarily by volcanic volcaniclastic and sedimentary rocks of the early cretaceous arqueros and quebrada marquesa formations with a few mineralized zones within late cretaceous dioritic intrusions the fault and vein architecture shows that el espino iocg system was localized within a dilatational jog along a major transtensional dextral fault system sodic alteration albite is the most extensive style of alteration in the district and it is bounded by major ns nne trending faults sodic calcic epidote albite alteration occurs at deep to medium elevations 1 000 500 m and grades inward into calcic alteration calcic alteration surrounds dioritic intrusions of the llahuin plutonic suite significant iron oxides are associated with later calcic alteration associations actinolite epidote hematite the upper portions of the alteration system 0 500 m display hydrolytic alteration associations with abundant hematite hydrolytic veins are feeders to zones of manto type alteration and mineralization within favorable volcano sedimentary lithologies that formed el espino deposit sulfides are largely confined to calcic and hydrolytic alteration associations hydrothermal fluids responsible for hematite and sulfide mineralization had salinities between 32 and 34 wt nacleq and temperature of approximately 425 c at an estimated depth of 3 4 km geochronological u pb and 40ar 39ar data indicate that hydrothermal alteration was coeval with magmatic intrusive activity one particular dioritic intrusion 88 5 ma preceded the calcic stage 88 4 ma which was accompanied by iron oxide copper and gold mineralization hydrolytic alteration related to economic iron oxide copper and gold mineralization came immediately after at 87 9 ma

long hole destress blasting for rockburst control during deep underground coal mining abstract the lazy colliery in the ostrava karvina coalfield of the upper silesian coal basin adopted modern longwall technology for an underground extraction of coal seam no 504 this coal seam is located at a cover depth of around 700 m the seam thickness varied from 3 1 m to 5 0 m in the selected longwall panel two overlying coal seams nos 512 and 530 experienced mining at average heights of 58 m and 75 m respectively from the planned working horizon of the seam no 504 the proposed longwall panel was adversely situated below goaf edges of the workings in these two overlying extracted seams an analysis of the inter burden rock mass among these coal seams showed the presence of strong massive strata of sandstones and conglomerates with uniaxial compressive strength values between 70 mpa and 120 mpa the stress is measured at different mining stages by compact conical ended borehole monitoring ccbm a simple laboratory test of the coal sample found a high value of the ratio of the elastic deformation to the total deformation 0 8 indicating the energy storing characteristic prone to burst bump of the coal seam under the existing geo mining conditions of the site a suitable destress blasting long hole drilling and blasting design is adopted to pre fracture the identified competent strata from both gate roads in advance the total length of the panel could be extracted without any bump rockburst after the destress blasting the efficiency of the adopted destress blasting at the different mining stages is evaluated in terms seismic effect se which is calculated through the available seismic monitoring data and weight of the charged explosive a systematic adoption of the destress rock blasting led the 300 m long longwall panel to be smoothly extracted without any further rockbursts

recognizing propylitic alteration associated with porphyry cu mo deposits in lower greenschist facies metamorphic terrain of the collahuasi district northern chile implications of petrographic and carbon isotope relationships the collahuasi district is a porphyry cu mo subprovince located on the andean high plateau of northern chile late eocene early oligocene mineralization in the district involved hydrothermal alteration of the upper paleozoic to lower triassic collahuasi group granodiorites diorites andesites dacites and rhyolites which had previously experienced regional lower greenschist facies metamorphism as well as uneconomic porphyry style mineralization and associated sericitic alteration alteration mapping represents an effective technique for prospecting for hydrothermal deposits but in low grade metamorphic terrains recognition of propylitic assemblages that represent the boundary of the mineralizing system is hampered by their resemblance to metamorphic mineral assemblages our results from collahuasi indicate that petrographic criteria can distinguish propylitic alteration from the effects of lower greenschist facies metamorphism but distinctions vary with rock type mafic intermediate and felsic rocks with varying degrees of propylitic alteration can be distinguished from background metamorphism mainly by the presence of calcite however propylitic alteration can also be distinguished by high whole rock 13c values and carbon contents 19 1 to 1 4 and up to 0 79 wt respectively that result from the incorporation of magmatic co2 during the mineralizing events lower 13c values 32 7 to 13 1 and carbon contents 0 09 wt were recorded in other types of hydrothermal alteration intermediate argillic sericitic and potassic alteration and associated with background metamorphism they reflect a dominantly 13c depleted carbon component that remains in the rocks after extensive co2 degassing during emplacement alteration by hydrothermal fluids or contamination by organic carbon carbon and oxygen isotope compositions of calcite from propylitic alteration which range from 12 to 0 3 and 6 6 to 25 9 respectively are consistent with a predominantly magmatic origin for the carbonates although subsequent resetting of the oxygen isotopes by local ground water and minor contributions of organic carbon are recorded in some samples spatial variation in 13c values and carbon contents of outcrop samples from the collahuasi district delineate zones of high magmatic co2 component that correspond exclusively to propylitic alteration surrounding economic deposits

noble gas and halogen constraints on fluid sources in iron oxide copper gold mineralization mantoverde and la candelaria northern chile the noble gas ar kr xe and halogen cl br i composition of fluid inclusions in hydrothermal quartz and calcite related to the hypogene iron oxide copper gold iocg mineralization at mantoverde and candelaria chile have been investigated to provide new insights of fluid and salinity sources in andean iocg deposits a combination of mechanical extraction by crushing and thermal decrepitation methods was applied and collectively indicate that fluid inclusions with salinities ranging from 3 4 up to 64 wt nacl equivalent have molar br cl and i cl ratios of between 0 5 10 3 and 3 0 10 3 and i cl of between 8 10 6 and 25 10 6 in the majority of samples with maximum values of 5 2 10 3 obtained for br cl and 64 10 6 for i cl in fluid inclusions within individual samples the fluid inclusions have age corrected 40ar 36ar ratios ranging from the atmospheric value of 296 up to 490 45 indicating the presence of crustal or mantle derived excess 40ar in the fluid inclusions of most samples the fluid inclusions have 84kr 36ar and 130xe 36ar ratios intermediate of air and air saturated water however 40ar 36ar is not correlated with either 84kr 36ar or 130xe 36ar and the fluid inclusion 36ar concentrations of 0 2 3 5 10 10 mol g calculated from measured cl 36ar and thermometric salinity measurements extend below the seawater value of 0 34 10 10 mol g suggesting that contamination with modern air is a minor artifact the range of fluid inclusion br cl and i cl ratios overlap those previously documented for the mantle and magmatic hydrothermal ore deposits and the fluids unusually low 36ar concentration is consistent with the involvement of magmatic hydrothermal fluids input of additional non magmatic fluid components is suggested by the spread in br cl and i cl to values characteristic of bittern brine sedimentary formation waters and near atmospheric 40ar 36ar these data are compatible with mixing of magmatic hydrothermal fluids and evaporated seawater which was modified by interaction with back arc basin sediments as the major control on ore formation low br cl 0 5 10 3 and i cl 5 0 10 6 values that would provide evidence for evaporite dissolution as an important source of fluid salinity were not detected

oxygen isotope dating of the australian regolith australia has had a long and complex history of intense surficial weathering and this has led to the extensive development of laterites bauxites and deeply weathered profiles of a variety of ages across the continent1 2 a detailed knowledge of the age s of such weathering phenomena is of great importance for the reconstruction of australia s post palaeozoic geomorphic and palaeoclimatic history however in many instances absolute geo chronological information is not obtainable using conventional techniques here we describe and evaluate a new method that can provide an estimate of the age of intensely weathered profiles based on the oxygen isotope composition of minerals developed by deep weathering lateritization processes this method allows the definition of four ages of weathering in eastern australia from the late palaeozoic to the present and suggests that some profiles previously thought to be late cretaceous or tertiary in age may be of pre late mesozoic age the oxygen isotope data indicate that the minerals used in this study have retained their original isotopic composition for periods of up to 250 million years despite the continued presence of meteoric waters of progressively higher 18o content during this interval

the kinematic and geodynamic significance of the atacama fault zone northern chile abstract the atacama fault zone afz is the dominant feature in the structure of the north chilean coastal cordillera left lateral displacement took place along its system of longitudinal faults during the jurassic and early cretaceous this development was contemporaneous with arc magmatism and was later reactivated resulting in a steep normal fault strike slip movements along the afz consist of two sets of ductile shear zones of different ages one jurassic formed under amphibolite facies conditions the other early cretaceous with greenschist facies mylonites structural asymmetries point to a sinistral sense of shear in both sets the afz can be interpreted as a magmatic arc structure which accommodated the oblique subduction of an oceanic plate trench linked strike slip fault the sinistral sense of shear is consistent with reconstructions of late jurassic to early cretaceous plate configurations in the se pacific

the raul condestable iron oxide copper gold deposit central coast of peru ore and related hydrothermal alteration sulfur isotopes and thermodynamic constraints the iron oxide copper gold iocg raul condestable deposit is located 90 km south of lima peru and approximately 5 km from the pacific coast mineralization consists mainly of replacement mantos and disseminations within permeable volcaniclastic and carbonate rich rocks and structurally controlled veins surrounding a coeval and apparently causative intrusion of tonalitic composition emplaced in the core of a dacitic volcano potassic biotite grading upward to sericite chlorite alteration and a poorly developed almost sulfide free quartz stockwork closely border the tonalite affecting the basaltic to dacitic lower cretaceous volcano sedimentary host sequence ore is associated with a hydrated calc silicate mainly amphiboles alteration that surrounds the biotite alteration a hematite chlorite albite epidote calcite alteration affects the periphery of the system the main ore stage is characterized by two end member mineral associations that were formed according to 1 an oxidized deposition sequence hematite magnetite pyrite chalcopyrite occurring in and near feeder structures and 2 a reduced deposition sequence pyrrhotite pyrite chalcopyrite found in volcaniclastic rocks and veins early specular hematite of the oxidized sequence is transformed to magnetite mushketovite the main ore stage mineralization is cut by minor late stage calcite sulfide veins main ore stage sulfides have 34s values asymmetrically distributed from 1 0 to 26 3 per mil with a median at 6 6 per mil n 51 similar values are observed for pyrrhotite pyrite and chalcopyrite the 34s values depend on the stratigraphic position with deep seated vein samples normally distributed between 1 0 and 6 3 per mil avg about 3 5 n 13 and shallower samples from 2 7 to 26 3 per mil median around 7 5 n 39 sulfides found in late stage calcite sulfide veins show strongly negative 34s values ranging between 32 7 and 22 9 per mil n 6 indicating a possible biogenic source because no rock unit is known to occur in the internal parts of the deposit that could have oxidized fluids to the point of hematite stability the oxidized mineral sequence is best explained by magmatic brines following the so2 h2s gas buffer at high temperature 350 c and fluid rock ratio this is supported by the close to magmatic 34s values of sulfides from the deep parts of feeder veins mass balance calculation based on sulfur isotope data suggests that at the deposit scale the bulk of the sulfides is dominated by magmatic sulfur with sulfides of the oxidized minerals association having a larger component of magmatic sulfur than those of the reduced mineral association the deposition sequence from hematite to chalcopyrite reflects the cooling of the magmatic fluid and redox and ph buffering by the basaltic andesitic volcano sedimentary host rocks thus the occurrence of magnetite pseudomorphous after early hematite mushketovite paragenetically followed by iron bearing sulfides is interpreted to be direct field evidence for precipitation from oxidized magmatic brines the same sequence has been described in many iocg skarn and some porphyry copper deposits worldwide 34s values of sulfides ranging up to 26 3 per mil are found in what corresponded to a relatively shallow aquifer filled with evolved reduced seawater heavy sulfur in h2s was produced through thermochemical reduction of aptian seawater sulfate 34s 14 in the recharge zone which is interpreted to correspond to the hematitechlorite albite epidote calcite alteration present at the upper flanks of the hydrothermal system adjacent to the causative intrusion hematitization through oxidation resulted from the high fo2 of seawater and from the reduction of its sulfate to h2s by the fe2 contained in the rock in the core of the system the seawater derived fluids reached near chemical equilibrium with their actinolitized host rock at about 300 to 350 c in reduced rock dominated conditions mixing of these fluids with magmatic brines already partially or totally reduced through reaction with wall rock at medium to low magmatic fluid rock ratio can explain the large positive 34s scatter observed in sulfides of the reduced mineral association at stratigraphically shallow positions

lithological and structural controls on the genesis of the candelaria punta del cobre iron oxide copper gold district northern chile abstract the candelaria punta del cobre district is the largest iron oxide cu and au iocg district in the chilean iocg belt with more than 13 mt of contained copper candelaria is the most important deposit in the district which includes seven other smaller producers carola punta del cobre mantos de cobre candelaria norte granate alcaparrosa atacama kozan las pintadas the district which is characterized by an early cretaceous volcanic sedimentary arc sequence 135 132 ma punta del cobre formation overlain by the marine sedimentary chanarcillo group formed in an extensional back arc basin 132 130 ma the copiapo batholith which occupies the western side of the district was emplaced between 118 and 110 ma during the change from extensional to transpressional tectonics mineralization is hosted predominately in the upper part of the lower andesite member and the overlying volcano sedimentary and dacite members all within the punta del cobre formation mineralization is hosted by fault zones breccias and specific lithologies north northwest faults are the dominant host for vertically extensive orebodies stratigraphically controlled mineralization forms extensive stratabound ore bodies mantos textural evidence suggest that the hydrothermal system evolved and advanced upwards over time the earliest event was dominated by magnetite actinolite in stratigraphically controlled mantos and extensive zones of disseminated magnetite actinolite below candelaria which were subsequently overprinted by chalcopyrite dominant mineralization with magnetite actinolite biotite k feldspar alteration in addition to magnetite iron oxides include widespread mushketovite and hematite in the upper part of some deposits geochronological data suggest that the main phase of mineralization occurred between 122 ma and 115 ma u pb in zircon overlapping in age with the two major early phases of the copiapo batholith there is no field evidence to indicate that exposed phases of the batholith were the source of mineralizing fluids alteration and mineralization in the earliest phase of the batholith la brea occurs in structures and is minor compared to mineralization in the punta del cobre formation later phases of the batholith cut the main stage of mineralization the extent of iocg mineralization in the candelaria punta del cobre district reflects a combination of factors including changing regional kinematics and related fault architecture multiple intrusive events fluid access to permeable and reactive lithologies vertical changes in redox conditions and the potential role of multiple fluids

geochemical and isotopic signature of pyrite as a proxy for fluid source and evolution in the candelaria punta del cobre iron oxide copper gold district chile

the antiquity of landscapes on the north australian craton and the implications for theories of long term landscape evolution the longevity of landscapes on cratons has set them apart from those in other tectonic settings this is exemplified over much of the north australian craton where landscapes that have for over half a century been argued to be largely the product of cycles of erosion throughout the cainozoic are in fact composed mainly of ranges valleys and plains which pre date the cretaceous valleys incised into upland plateaus and graded to lowland plains are in numerous places filled with cretaceous sediments many of the lowland plains are exhumed proterozoic and pre late jurassic features and appear to be older than neighboring areas of upland plateaus which were likely graded to the cretaceous sea the antiquity of these landscapes and the disparity in age between higher and lower elevation planation surfaces highlights the inadequacy of global applications of existing models of long term landscape evolution and theories concerned with the preservation of paleoforms in cratonic settings

evaporitic source model for igneous related fe oxide ree cu au u mineralization we propose that many igneous related fe oxide rich ree cu au u bearing deposits form by hydrothermal processes involving evaporitic ligand sources either coeval salars or older evaporites these deposits are abundant in both phanerozoic and proterozoic extensional continental and continent margin settings they commonly form in global arid zones but they also occur where magmatism is superimposed upon older evaporites magmatic compositions exert only second order control mainly on alteration mineralogy and on element abundances hot s poor brines generated by interaction with evaporitic materials are consistent with geologic settings and help rationalize the distinctive element enrichments siderophile lithophile and hydrothermal alteration sodic locally alkaline found in these systems this model contrasts with immiscible oxide melt and magmatic hydrothermal origins commonly proposed for these deposits although all three mechanisms can occur 31 refs 3 figs 1 tab

surface subsidence characteristics of grout injection into overburden case study of yuandian no 2 coalmine china a study on the surface subsidence characteristics is essential for evaluating the effects of subsidence control technologies and improving such technologies one such technology is grout injection into overburden gio which is used in coal mining areas in the past the subsidence reduction ratio a single index was often used to evaluate the final amount of subsidence control achieved by gio however little research has been conducted on the dynamic process of surface subsidence in this study the surface subsidence characteristics of gio on the side of a stopping line ssl of a longwall were examined through in situ monitoring and the characteristics of areas with grouting were compared with those without the final maximum subsidence horizontal displacement and subsidence rate decreased considerably 70 2 80 4 and 77 5 respectively with the use of gio however 4 6 of the mining height subsided at a certain surface point on the ssl before gio controlled subsidence at that point compared with the duration of the active period without grouting that with grouting and the corresponding subsidence decreased considerably 44 2 and 87 1 respectively generally it is quite difficult to control the surface subsidence when gio is implemented on the ssl of a longwall because the surface and subsurface are already affected by the coal extraction without grouting on the side of the open off cut thus the success of gio technology in the case study described in this paper demonstrates its effectiveness in controlling the surface subsidence in coal mining areas

magmatic arc fault systems deformation partitioning and emplacement of granitic complexes in the coastal cordillera north chilean andes 25 30 s to 27 00 s three fault systems were responsible for permian to late cretaceous deformation of the overriding plate of the andean convergent margin in the coastal cordillera of northern chile 25 30 to 27 00 s displacements were linked to crustal growth expressed by the emplacement of a sequence of magmatic arcs the tigrillo fault system active from triassic to early cretaceous time was characterized by arc normal extension with increasing left oblique extension transtension from early jurassic to early cretaceous time stretching of the crust created space for triassic early jurassic and early cretaceous arc basins where epiclastic volcaniclastic and volcanic sequences accumulated in continental to shallow marine environments tabular plutonic complexes were emplaced by roof uplift floor subsidence that allowed a vertical transfer of material in the crust without significant horizontal extension the atacama fault system was initiated at c 132 ma as a mainly left strike slip fault during left oblique extension of the margin elongate tabular plutonic complexes were emplaced within the atacama fault system between c 132 and c 106 ma again by roof uplift floor subsidence mechanisms ductile brittle transitions in synplutonic mylonitic rocks of the atacama fault system provided the setting for kiruna type fe apatite and fe oxide with cu and or au ores the chivato fault system was active as an extensional fault system at the eastern side of the coastal cordillera during displacement on the tigrillo fault system and later between c 125 and c 93 ma as a partitioned left oblique extensional fault system in post early cretaceous time the chivato fault system was inverted by left oblique contraction transpression when nw trending transfer faults some probably reactivated lateral ramps in the tigrillo fault system accommodated clockwise vertical axis rotations of 35 45 contraction inverted the atacama fault system and tigrillo fault system and was responsible for west vergent thin skinned fold thrust deformation in stratified rocks throughout the margin

aftershocks of the 1988 january 22 tennant creek australia intraplate earthquakes evidence for a complex thrust fault geometry summary on 1988 january 22 three earthquakes of ms 6 3 6 7 occurred in a 12 hr period near tennant creek northern territory in the proterozoic north australian craton and produced 32 km of surface rupture on two main scarps the lake surprise scarp is shaped like a boomerang with the east arm trending ese and the west arm wsw the kunayungku scarp lies 7 km to the northwest and trends ese locations of 211 aftershocks determined using data from portable seismograph arrays define a 10 km by 40 km aftershock zone elongated parallel to the trend of the surface ruptures in the western and eastern part of the fault zone aftershocks occur only south of the kunayungku and eastern lake surprise scarps respectively in the central section in contrast aftershocks lie primarily to the north of the western arm of the lake surprise scarp focal depths range from the surface to 8km in all sections the shallowest earthquakes lie closest to the scarps whereas deeper events lie further away in cross section the aftershocks lie in three distinct inclined zones which delineate fault surfaces ruptured by the main shocks aftershocks are concentrated near the edges of the inferred fault surfaces suggesting that stress was relieved in the centre of the faults by rupture during the main shocks the inferred fault plane dips are 45 to the ssw for the kunayungku fault 55 to the nnw for the western lake surprise fault and 35 to the ssw for the eastern lake surprise fault these dip directions are consistent with the sense of thrust movement inferred from surface deformation the reversal of fault dip and sense of movement between the central and end segments requires a complicated fault geometry the aftershock data would allow a second south dipping plane in the central section that does not intersect the surface this blind fault may be responsible for much of the moment release interpreted from the modelling of broad band teleseismic waveforms choy bowman 1989 rupture of the north dipping plane may have been controlled by a pre existing fault marked at the surface by a quartz ridge 5 km long and may be of secondary importance although the quartz ridge suggests previous faulting the absence of significant topographic relief together with estimates of erosion rates suggest an average repeat time in excess of 104yr preliminary interpretation of water withdrawal histories and water level data from a borefield adjacent to the eastern lake surprise scarp does not support a causal relationship between the borefield and the occurrence of the earthquakes the nearby warramunga wra seismic array provides a record of local earthquake activity from 1965 to the present the fault area was essentially aseismic until two small earthquakes in 1986 february and a series of six magnitude 4 5 earthquakes in 1987 january which were followed by more than 1000 aftershocks the frequency of occurrence of aftershocks declined very slowly in 1987 with p 0 2 in the modified omori formula whereas for the 1988 aftershock sequence p 1 the low p during 1987 may have been diagnostic of high stress in the source and water authority provided partial financial support for j r b and g g

transition from diagenesis to metamorphism in extensional and collision settings areas in which there is a transition from diagenesis to metamorphism occur in a variety of tectonic settings some of which are of an extensional character rather than the collision setting normally associated with regional metamorphism in collision settings the diagenetic to metamorphic transition is typically followed by a continuum into the highest grades of metamorphism the baric type is usually of an intermediate pressure variety and metamorphism occurs at a late stage in the tectonic cycle in extensional settings such as marginal basins a restricted facies series is developed that ranges from diagenetic levels up to a low greenschist facies maximum the metamorphism is normally of a low pressure type and develops early in the tectonic cycle these characteristics suggest that it is possible to subdivide broadly the field of low grade regional metamorphism into compressional orogenic and extensional settings

localization of mining induced horizontal fractures along rock layer interfaces in overburden field measurements and prediction the locations of mining induced horizontal fractures along rock interfaces in the overburden of donetsk coal basin were identified using an original experimental device the device traps methane from horizontal fracture zone 100 fold coal seam thickness over an active longwall mining excavation presence or absence of horizontal fractures along rock layer interfaces is correlated with physical characteristics of the overburden such as thickness uniaxial compressive strength of overburden rock layers location of rock layer interfaces and thickness of extracted coal seams as a result a combined criterion based on these physical characteristics is proposed to predict the presence of overburden horizontal fracturing in coal mine operations

quantitative resolution of the debate over antiquity of the central australian landscape implications for the tectonic and geomorphic stability of cratonic interiors we report the first measure of long 100 myr and short 1 myr term denudation rates from key geologically stable landforms in the davenport range central australia these landforms have previously been assigned a cambrian age which arguably places them amongst the oldest persistent landforms on the continent if not on earth our results from combined apatite fission track thermochronology and in situ cosmogenic radionuclide analyses using 10 be and 26 al show that while average exhumation rates are low the denudation history for this cratonic region is incompatible with extreme sub aerial longevity and long term tectonic and geomorphic stability our revised model for the landscape evolution of this region is consistent with one of maximum burial prior to and during the mesozoic followed by a phase of kilometre scale exhumation that was largely complete by the beginning of the cainozoic we suggest that a similar process of burial and exhumation has probably been responsible for the sub aerial preservation of seemingly ancient landforms elsewhere in australia

a new petrogenetic grid for low grade metabasites abstract we have used internally consistent thermodynamic data to present calculated phase equilibria for the system na2o cao mgo al2o3 sio2 h2o ncmash in the range 0 500 c and 0 1 10 kbar involving the phases anorthite glaucophane grossular heulandite jadeite laumontite lawsonite paragonite prehnite pumpellyite stilbite tremolite wairakite zoisite with excess albite clinochlore quartz and pure water average activity terms derived from published mineral chemical data were included for clinochlore glaucophane prehnite pumpellyite tremolite and zoisite the new petrogenetic grid delineates stability fields and parageneses of common index minerals in zeolite prehniteactinolite prehnite pumpellyite pumpellyite actinolite blueschist and greenschist facies metabasites the stability fields of mineral assemblages containing prehnite pumpellyite epidote actinolite albite chlorite quartz were analysed in some detail using activity data calculated from five specific samples for example the prehnite actinolite facies covers a p t field ranging from about 220 to 320 c at pressures below 4 5 kbar the transition from the prehnite actinolite and pumpellyite actinolite to greenschist facies occurs at about 250 300 c at 1 3 kbar and at about 250 350 c at 3 8 kbar p t fields of individual facies overlap considerably due to variations in chemical composition

cosmogenic exposure and erosion history of australian bedrock landforms exceptionally high activities of in situ produced 1 0 be and 2 6 al indicate that australian bedrock surfaces are some of the most stable in the world these cosmogenic nuclides demonstrate that australian granite exposed and sampled at 10 sites along a transect from the eyre peninsula 33 s to the kakadu area in the northern territory 14 s has in some places eroded only decimeters over the past million years however nuclide activities are not saturated in any of the 61 exposed samples we analyzed mandating that the surfaces we sampled are losing mass albeit slowly over time such mass loss indicates that inselbergs are dynamic landforms confounding the assignment of discreet ages to inselberg surfaces nevertheless the differential between slow rates of erosion measured on the very stable uppermost parts of these landforms and the more rapid rates measured below their flanks and below the adjacent grus covered planes suggests that the forms of many large inselbergs which stand meters to tens of meters high must be at least tertiary in age and possibly much older activities of 1 0 be and 2 6 al in 61 exposed australian samples range from 5 1 0 1 10 6 to 5 3 0 6 x 10 5 atoms g 1 and 2 1 0 1 x 10 7 to 3 4 0 5 x 10 6 atoms g 1 respectively normalized to sea level at latitudes of 60 using only neutron scaling activities of 1 0 be and 2 6 al in seven shielded samples 3 5 13 m below the surface are much lower ranging from 3 4 0 2 x 10 4 to 7 0 0 1 x 10 4 atoms g 1 and 1 6 0 1 x 10 5 to 2 8 0 2 x 10 5 atoms g 1 respectively 2 6 al 1 0 be ratios of exposed samples range from 3 89 0 19 to 6 29 0 82 if 2 uncertainty ranges and a nominal sea level high latitude 1 0 be production rate of 5 17 atoms g 1 yr 1 are considered ratio data for all but one surface sample are consistent with continuous surface or near surface exposure and or erosion rock surfaces farther north in australia where the climate is more humid have lower nuclide activities thus we infer that surface stability is inversely related to mean annual precipitation from 61 exposed samples we calculated maximum limiting single nuclide model erosion rates of 0 3 0 1 to 5 7 1 0 m m y and minimum limiting single nuclide model exposure ages of 105 16 to 1310 190 ka by assuming a sea level high latitude 1 0 be production rate of 5 17 atoms g 1 yr 1 seven shielded samples in which the nuclide inventory is muon generated also have nuclide activities consistent with similarly low rates of erosion but over even longer time scales it appears that the eyre peninsula inselbergs have been and are eroding so slowly that they may well be direct descendents of cenozoic and perhaps even mesozoic forms

the regolith in australia abstract australian regolith materials are described many of which are complex much australian regolith dates back to the tertiary mesozoic or earlier there is a progressive change in the nature of alluvium through the tertiary aridity revealed through sand dunes and evaporites is confined to the quaternary ferricretes and silcretes are formed on lower slopes often followed by inversion of relief tectonic isolation of australia as well as climatic change is responsible for the change in the nature of terrestrial sediments since the cretaceous

ediacaran and cambrian paleosols from central australia abstract ediacaran to cambrian red sandstones of the northern territory including arumbera sandstone and grant bluff and central mount stuart formations have been reexamined and sampled in order to reconstruct paleoenvironments from sedimentary facies and paleosols sedimentary facies include green gray calcareous sandstone member iii of arumbera sandstone only red siltstone with calcareous nodules also only member iii and also non calcareous red green siltstone interbedded red siltstone and sandstone and trough bedded sandstone the green gray facies has diverse and distinctive cambrian marine trace fossils not found in the red beds which have instead an assemblage of problematic body fossils including arumberia noffkarkys hallidaya ernietta trepassia and dickinsonia the red facies are interpreted as fluvial paleochannels trough cross bedded fluvial levees interbedded siltstone and sandstone poorly drained floodplain red green siltstone and well drained floodplain or low terrace calcareous nodular the carbonate nodules have micritic replacive fabrics and a significant positive correlation of 13c and 18o characteristic of pedogenic carbonate of calcid soils other red beds have pseudomorphous sand crystals after gypsum like those of gypsid soils individual red beds show negative strain and mass transfer for cationic bases typical of soils as well as gradational alteration down from fossiliferous tops characteristic of soils their varied degree of pedogenic differentiation is identified as psamment aquent and ochrept paleosols phosphorus depletion in the paleosols is evidence that organisms lived in the paleosols and were not introduced by transient marine incursions the problematic quilted fossils arumberia noffkarkys and hallidaya formed a distinctive inland terrestrial polsterland during the ediacaran and early cambrian

dynamic disaster control under a massive igneous sill by grouting from surface boreholes abstract an overlying 140 m thick massive igneous sill has adversely affected mining activities considerably in the haizi coal mine china a coal and gas outburst disaster occurred during the drivage for a subsequent longwall after the extraction of two faces in the ii102 mining area the massive sill was determined to be primarily responsible for this outburst owing to the bed separation that occurred below the sill due to the sill s large span this is because such separation meant the massive sill was not supported by the gob as in a general case but it was supported by the solid coal instead resulting in a long load transfer distance that caused the drivage gate to collapse unexpectedly into the abutment thus it was determined that the high abutment pressure primarily triggered the outburst such disaster risk would have remained had the drivage in the gate continued and a wide area and sudden roof fall could have occurred during the extraction of the next longwall had the igneous sill broken suddenly as the critical span was reached with these risks in mind a field trial of a method of grouting into the overburden of the abandoned faces from surface boreholes was conducted for dynamic disaster control this technique alleviates the abutment pressures and restrains the igneous sill deflection by eliminating fractures and voids in the overburden using grouting the adoption of this grouting method led to the subsequent drivage and mining of a further 510 m without occurrence of any further dynamic disasters