the sholl shear zone west pilbara evidence for a domain boundary structure from integrated tectonostratigraphic analyses shrimp upb dating and isotopic and geochemical data of granitoids abstract the pilbara block provides a record of archaean continental growth involving the tectonic accretion of outboard island arcs and collisions with other continental scale fragments this record of continental growth is balanced by breakup and strike slip dismemberment of the continent new shrimp u pb in zircon ages and sm nd data provide evidence in the west pilbara which demonstrates that subduction related and tectonic accretion processes at the western margin of that ancestral continent between 3 15 2 78 ga were coeval with and genetically related to crustal scale tectonics and basin formation inboard of that margin the tectonic division of the west pilbara is defined by integrated tectonic analyses geochronology geochemistry and isotopic analyses geochronological studies clearly indicate that the western pilbara comparises two domains with different recorded geohistories whereas geochemistry and isotopic systematics reflect the changing tectonic regimes through time in combination these studies allow the development of a reconstruction of the relative positions of the domains through time on the western margin of the pilbara block the supracrustal rocks of the northern roebourne lithotectonic complex domain 6 in a pilbarawide scheme were formed in an island arc setting facing an ocean to the north west prior to 3260 ma the time of emplacement of voluminous granitoids into the complex in contrast the supracrustal rocks of the southern sholl belt pilbara domain 5 were formed in a back arc setting behind a north west facing arc between 3125 and 3112 ma with more or less synchronous granite emplacement at about 3115 ma the two domains were tectonically juxtaposed between 2991 and 2925 ma by the sholl shear zone a largely sinistral shear zone with subsequent volcanism in both domains to about 2925 ma the roebourne lithotectonic complex domain 6 is interpreted to be an allochthonous terrane which formed north east relative to its present position but indigenous to the pilbara block rather than an exotic terrane the east pilbara is interpreted to have acted as a cratonic hinterland during the convergent margin tectonics that affected the two west pilbara domains

environmental problems at the nevsehir kozakli geothermal field central turkey the kozakli nevsehir geothermal field extends a long a nw se direction at se of the centrum of kozakli the area is not rugged and average elevation is 1 000 m the kozanozu creek flows towards north of the area in the kozakli thermal spa area thermal waters are manifested along a valley with a length of 1 5 km and 200 m width in this resort some hot waters are discharged with no use the thermal water used in the area comes from wells drilled by mta in addition these waters from wells are also utilized by hotels baths and motels belonging to city private management municipality and private sector the measured temperature of kozakli waters ranges from 43 51 c in springs and 80 96 c in wells waters are issued in a wide swampy area as a small group of springs through buried faults electrical conductivity values of thermal spring and well waters are 1 650 3 595 s cm and ph values are 6 72 7 36 kozakli cold water has an electrical conductivity value of 450 s cm and ph of 7 56 all thermal waters are dominated by na and cl so4 while cold waters are dominated by ca 2 and hco3 the aim of this study was to investigate the environmental problems around the kozakli geothermal field and explain the mechanisms of karstic depression which was formed by uncontrolled use of thermal waters in this area and bring up its possible environmental threats at the kozakli geothermal field a sinkhole with 30 m diameter and 15 m depth occurred in january 17th 2007 at the recreation area located 20 m west of the geothermal well which belongs to the government of nevsehir province the management of the geothermal wells should be controlled by a single official institution in order to avoid the creation of such karstic structures affecting the environment at the source area

late archaean deep marine volcaniclastic sedimentation in an arc related basin the kalgoorlie sequence of the eastern goldfields superterrane yilgarn craton western australia abstract the kalgoorlie sequence 2658 ma is a 3000 m thick succession of volcaniclastic sedimentary rocks and subordinate rhyolite dacite andesite and basalt spatially and temporally associated with subvolcanic sills and dykes of rhyolite and dacite gabbro sills and i type granitoids although basalts are tholeiitic the felsic rocks have ttd affinity the sequence comprises mostly deep marine channel levee turbidite complexes and hemipelagites resedimented syneruptive volcaniclastic deposits are associated with coherent lavas but almost all of the sedimentary fill was recycled from prior cycle volcanic and volcaniclastic sources provenance was mainly dacitic rhyolitic with minor andesitic basaltic and polymictic compositions volcano bound and fault bound architectures and two styles of basin filling are identified progradational or aggradational transverse fans and slope aprons and retrogradational longitudinal fans of a linear trough retrogradation in longitudinal systems is consistent with basin lengthening and deepening six depositional sequences are grouped in four unconformity bounded tectonic stages that record uplift subsidence cycles coeval mafic and felsic magmatism indicate that the tectonic stages represent extensional tectonic settings whereas volcanogenic provenance spatially linked volcanism and plutonic magmatism and deep marine environments support an intra arc site cyclic uplift subsidence and basin lengthening are more consistent with strike slip controls on basin formation than with orthogonal extension the tectonic setting is interpreted to have been a pull apart basin associated with strike slip faulting and amalgamating arc related terranes similar to the modern philippines archipelago the strong similarity between archaean volcaniclastic and modern arc related volcaniclastic environments implies comparable tectonic settings and therefore comparable controlling tectonic factors

a generalized genetic framework for the development of sinkholes and karst in florida u s a karst topography in florida is developed on the tertiary limestones of the floridan aquifer post depositional diagenesis and solution have made these limestones highly permeable t ca 50 000 m2 d zones of megaporosity have formed at unconformities and dissolution has enlarged joints and fractures erosion of the overlying clastic miocene hawthorn group strata on one flank of a structural arch has exposed the limestone the elevated edge of the hawthorn cover forms the cody scarp ubiquitous solution pipes have previously formed at joint intersections and are now filled downwashing of the fill deeper into solution cavities in the limestone and subsidence of the overlying unconsolidated sediments causes surface collapse a subsidence doline or sinkhole this process may penetrate up to 60 m of the semi consolidated hawthorn cover as occurred when the winter park sinkhole developed dense clusters of solution pipes may have formed cenotes which are now found on the exposed limestone terrain

physical volcanology and geochemistry of a late archaean volcanic arc kurnalpi and gindalbie terranes eastern goldfields superterrane western australia abstract late archaean 2715 2704 ma calc alkaline volcanic complexes in the kurnalpi terrane are identical in facies and geochemistry to modern intra arc volcanic complexes preserved volcanic rocks and associated feldspathic sedimentary rocks represent proximal to medial submarine facies of submarine to locally emergent intra oceanic arc related volcanoes the least altered volcanic rocks are dominantly andesite but range from basalt and basaltic andesite to rare rhyolite and are the product of magmas similar in composition to those of modern arcs intermediate magmas were most likely derived from large ion lithophile element lile enriched mafic magmas by fractional crystallisation with or without assimilation processes the kurnalpi terrane thus provides an example of a late archaean volcanic arc in which hydrated mantle wedge melting was the main mechanism for magma genesis ttd suite volcanism derived from slab melting was either absent or played a subordinate role the adjacent gindalbie terrane contains younger 2692 2680 ma bimodal basalt rhyolite volcanic complexes with associated quartz rich sedimentary rocks and calc alkaline intermediate silicic volcanic complexes volcanosedimentary basement to the gindalbie volcanic sequences is deeply eroded equivalents of the calc alkaline volcanic complexes their associated sedimentary rocks and younger basaltic sequences found in the kurnalpi terrane gindalbie basalt rhyolite successions locally contain volcanic hosted massive cu zn mineral deposits rhyolites derived by low pressure fractional crystallisation or melting of andesites are more abundant than in the kurnalpi volcanic complexes facies associations and the local occurrence of distinctive incompatible element enriched mildly peralkaline a type rhyolites are consistent with rifting of a mature arc system the two terranes most likely represent volcanic evolution of the same late archaean volcanic arc but are different tectonic fragments that were welded together by 2660 ma

detrital zircon age spectra for late archaean synorogenic basins of the eastern goldfields superterrane western australia abstract the kalgoorlie gindalbie kurnalpi duketon and burtville terranes were amalgamated by 2658 ma into the eastern goldfields superterrane which was later accreted cordilleran style onto the foreland of a pre existing continent late stage synorogenic basins developed within the eastern goldfields superterrane during the early stage of accretion the basins are similar to all late stage basins of archaean provinces developing late in the tectonic cycle in a strike slip regime they developed in two stages during the gap in granite emplacement between 2658 ma and 2648 ma basin analysis suggests that the bulk of sediments was derived from rocks readily identifiable today within the superterrane consistent with the provenance style of all late stage basins sediment derivation from the foreland occurred only during stage ii and is recorded only from basins proximal to the suture detrital zircon geochronology has corroborated those interpretations eleven new shrimp u pb detrital zircon datasets and 14 previously published datasets indicate that the bulk of zircon bearing sediment was derived from the 2715 ma to 2658 ma high ca ttg granites and volcanic rocks that define the terranes moreover primary modes in the detrital zircon age spectra of 2680 3 ma 2673 ma 2666 3 ma and 2660 3 ma coincide with the peaks of emplacement of high ca granites provenance from across the suture has also been corroborated with detrital zircon age spectra of the kurrawang basin a stage ii basin close to the suture having no match to rocks of the eastern goldfields superterrane defining modes of 2730 ma and 3000 ma some as old as 3750 ma and 3540 ma can be matched to an 2735 ma calc alkaline volcanic province and quartzites with 4350 3130 ma detrital zircon in the foreland the study shows that detrital zircon age spectra can be powerful supporters of tectonic analysis but for the study presented here their interpretation has been greatly assisted by prior basin analysis and a considerable geochronological database of source rock equivalents

archean gold mineralization synchronous with the final stages of cratonization yilgarn craton western australia sm nd ages of pegmatite dikes that crosscut gold bearing structures in the southern yilgarn craton western australia provide minimum age constraints of 2640 6 11 ma 2628 6 10 ma and 2620 6 36 ma for gold mineralization at the westonia and nevoria yellowdine terrane and scotia norseman terrane gold deposits respectively similarly a post gold mineralization dike at westonia has a u pb zircon age of 2637 68 ma theseconstraintsareconsistentwith andprovidefurthersupportfor suggestionsthatthe majority of gold deposits in the yilgarn craton formed during a regionally extensive gold mineralization event at ca 2630 ma i e 2630 6 10 ma in combination with recent geochronological results these data also provide further evidence that although mineralization appears to significantly postdate the majority of magmatic and metamorphic activity at higher crustal levels widespread thermal reworking of the lower middle crust involvingpartialmelting amphibolitetogranulitefaciesmetamorphism andlowercrustal granitoid intrusion occurred concurrently with gold mineralization at ca 2630 ma it is probable that the large scale hydrothermalfluidflow that produced widespread gold deposition was also part of this tectonothermal event models developed for other archean terranes whereby gold mineralization postdates formation and cratonization of host granite greenstone terranes and is therefore unrelated to these processes are not required to explain the timing of the majority of gold deposits in the yilgarn craton

late archaean felsic alkaline igneous rocks in the eastern goldfields yilgarn craton western australia a result of lower crustal delamination numerous felsic alkaline intrusions were emplaced in the granite greenstone terrain of the eastern goldfields yilgarn craton between c 2650 and 2630 ma intrusion coincided with the waning stages of voluminous regional granitic magmatism the alkaline rocks are localized along and adjacent to major crustal structures that separate lithostratigraphic greenstone terranes and are divided into four geographically and compositionally distinct suites viz the mount monger emu claypan and ninnis suites the rocks have features in common with a type granites including high total alkalis an anhydrous primary mineralogy an apparent anorogenic setting and enrichment in some hfse although they also have low concentrations of nb and y they show a range of features that together point to a crustal source e g the alkaline rocks are not associated with voluminous mafic magmatism they have high lile concentrations they carry zircon xenocrysts of similar age to whole rock sm nd model ages they show evidence for regional source heterogeneity suites have constant and distinct la y and nb y ratios and the rocks show many compositional similarities to the slightly older voluminous crust derived granites extreme enrichments in sr and ba in the mount monger suite however suggests that their source may have been metasomatized before or during melting intrusion of the alkaline rocks heralds a poorly recognized third tectonothermal event in the evolution of the eastern part of the yilgarn craton and was broadly synchronous with the intrusion of voluminous felsic fractionated granites crustal extension and widespread au mineralization the late archaean geology of the eastern goldfields shows many features in common with phanerozoic collisional belts thought to be profoundly influenced by processes of lithospheric delamination or convective thinning this newly recognized third tectonothermal event in the eastern goldfields may relate to the delamination or convective thinning of a dense garnet rich lower crust that resulted from extraction of earlier voluminous granite magma and it is possible that such processes have had a greater influence on late archaean crustal evolution than previously recognized

tectono stratigraphy of late archaean greenstone terranes in the southern eastern goldfields western australia abstract late archaean greenstone terranes in the southern part of the eastern goldfields are regionally extensive faultbounded entities defined on the basis of small but distinct differences in stratigraphy and structure the greenstones comprise volcano sedimentary successions that were all deposited at the same time c 2720 2675 ma on sialic crust hence the terranes are interpreted to represent contemporaneous probably adjacent basins these basins were affected by the same history of granite plutonism and regional deformation c 2675 2620 ma early subhorizontal deformation is poorly understood but includes at least locally significant thrust stacking d1 with a south to north movement direction this was followed by regional east west extension affecting all supracrustal successions above a province wide detachment now lying at depths between 4 and 7 km this detachment may have evolved from the greenstone basement contact but only after extensive reworking clastic basins developed along or above major extensional faults but no volcanism is associated with this extension subsequent east west d2 shortening resulted in regional scale thrusting folding and associated late stage transcurrent fault movements the d2 event is contemporaneous with a major thermal event represented by voluminous granite emplacement c 2660 ma and associated peak regional metamorphism in the greenstone succession predominantly monzo granite derived from older sialic crust was emplaced throughout the period of basin formation and deformation early synvolcanic granite c 2719 2710 ma is a minor component late synvolcanic granite c 2685 2675 ma is widespread and syn d2 granite c 2660 ma is abundant there are a few small late tectonic intrusions c 2640 ma to 2600 ma the lateral lithostratigraphic persistence of the contemporaneous basins the syn d2 low pressure regional metamorphism and the province wide monzo granite magmatism suggest that the greenstone basins possibly developed in a tectonic setting similar to that of failed rifts above aborted spreading centres the basins closed in response to far field compressional stresses

age constraints on recycled crustal and supracrustal sources of archaean metasedimentary sequences eastern goldfields province western australia evidence from shrimp zircon dating abstract shrimp u pb zircon dating of sedimentary volcanic and subvolcanic intrusive rocks from unconformity bounded sequences in the eastern goldfields province defines maximum depositional ages for those sequences the kambalda sequence which records a backarc basin was deposited prior to 2700 ma and from at least 2715 ma the spargoville sequence which records an arc adjacent volcano bound basin was deposited between 2700 and 2683 ma the kalgoorlie sequence which records an intra arc rift basin comprises two tectonic stages with depositional ages of 2681 2670 and 2661 2655 ma deposition of the spargoville and kalgoorlie sequences overlapped with the intrusion of granitoids and subvolcanic porphyries thereby indicating that those granitoids were emplaced during crustal extension younger submarine fan kurrawang sequence and braided fluvial merougil and jones creek sequences deposits of a remnant ocean basin were deposited at when coupled to palaeocurrent data provenance dating of detrital zircon suites fingerprints southeast oriented amalgamation of felsic detritus from multiple sources within longitudinal depositional systems and longitudinal reworking of felsic detritus from single sourced transverse systems most felsic detritus was recycled from coeval volcanoplutonic arcs and the orogen to the remnant ocean basin sequences with zircon ages ranging from 2730 to 2660 ma older felsic sources with age ranges of 3570 3130 3030 2900 2870 2770 and 2760 ma could have been structural enclaves within the volcanoplutonic arcs or orogen but were more likely within a distant cratonic basement when coupled with stratigraphic data it is concluded that detrital zircon age distributions preserve evidence for the sedimentary recycling of coeval volcanoplutonic arc or orogenic sources uplifted basin floor and dissected arc successions and cratonic basement virtually all source terrains have apparently vanished presumably through the combination of tectonic and sedimentary recycling and tectonic severance increased use of detrital zircon suites from archaean sedimentary sequences is advocated in order to quantify the balance between sedimentary recycling of felsic rocks from contemporaneous volcanoplutonic sources which themselves document crustal growth in arc environments and from relict volcanoplutonic and crustal basement sources which document the degree of crustal recycling

the wangkathaa orogeny an example of episodic regional d2 in the late archaean eastern goldfields province western australia abstract the eastern goldfields province egp is a late archaean orogenic belt located on the eastern margin of the yilgarn craton the egp is characterised by a prominent nnw trending tectonic grain developed largely during regional e w oriented shortening a simplistic sequence of largely progressive compressional deformation events d 1 to d 4 has been used by previous workers to explain the development of the egp regional d 2 was thought to be responsible for most of the finite strain and therefore a reliable marker event for correlating deformation histories across the region a re examination of the deformation history has shown that d 2 kalgoorlie orogen of weinberg et al precambrian res 120 2003 219 239 was not a single progressive event rather it was episodic and involved several stages of switching of the tectonic mode compression extension switching between 2665 and 2655 ma the sequence of events during d 2 was an early stage of e w shortening d 2a followed by extension with basin formation and normal fault movement d 2e and finally a second stage of e w compression d 2b we introduce this sequence of events as the wangkathaa orogeny more complex in tectonics and broader in geographical scope than the kalgoorlie orogen features of the wangkathaa orogeny are well illustrated by the geometry and geological relationships that occur in the kurnalpi terrane welcome well area and the kalgoorlie terrane ora banda kambalda and the boorara domains of the central and southern egp available geochronology indicates that this sequence of events was likely to have been diachronous across the entire egp and the eastern southern cross province of the yilgarn craton recognition of these separate episodic stages of e w oriented compression and extension is important in our understanding the tectonic evolution of the egp switching tectonic mode between compression and extension will change the state of mean stress in a rock mass e g from net dilation to net constriction and vice versa and is an effective method in transporting and trapping mineral rich fluids the paradox of the different timings established for d 2 across the province are explained by the wangkathaa orogeny especially if it were diachronous as different workers dated different phases of an episodic orogeny

the influence of urbanization of sinkhole development in central pennsylvania the karsted limestone valleys of central pennsylvania contain two populations of sinkholes solution sinkholes occur in the champlainian limestone units along the margins of the valleys solution sinkholes are permanent parts of the landscape and although a nuisance to construction do not present other problems the second population is the suffosional or soil piping sinkholes these occur on all carbonate rock units including the beekmantown and gatesburg dolomites that comprise the two principal carbonate aquifers in the valley suffosional sinkholes are the principal land use hazard suffosional sinkholes are transient phonomena they occur naturally but are exacerbated by runoff modifications that accompany urbanization suffosional sinkholes are typically 1 5 2 5 m in diameter depending on soil thickness and soil type the vertical transport of soil to form the void space and soil arch that are the precursors to sinkhole collapse is through solutionally widened fractures and cross joints and less often through large vertical openings in the bedrock the limited solution development on the dolomite bedrock combined with soil thickness seldom greater than 2 m limits the size of the sinkholes all aspects of suffosional sinkhole development are shallow processes transport piping void and arch formation and subsequent collapse take place usually less than 10 m below the land surface factors exacerbating sinkhole development include pavement street and roof runoff which accelerates soil transport such seemingly minor activities as replacing high grass and brush with mowed grass is observed to accelerate sinkhole development dewatering of the aquifer is not a major factor in this region

land subsidence and caprock dolines caused by subsurface gypsum dissolution and the effect of subsidence on the fluvial system in the upper tigris basin between bismil batman turkey abstract karstification based land subsidence was found in the upper tigris basin with dimensions not seen anywhere else in turkey the area of land subsidence where there are secondary and tertiary subsidence developments reaches 140 km 2 subsidence depth ranges between 40 and 70 m the subsidence was formed as a result of subsurface gypsum dissolution in lower miocene formation although there are limestones together with gypsum and eocene limestone below them in the area a subsidence with such a large area is indicative of karstification in the gypsum the stratigraphical cross sections taken from the wells and the water analyses also verify this fact the lower miocene gypsum which shows confined aquifer features was completely dissolved by the aggressive waters injected from the top and discharged through by zellek fault this resulted in the development of subsidence and formation of caprock dolines on loosely textured upper miocene pliocene cover formations the tigris river runs through the subsidence area between batman and bismil there are four terrace levels as t1 40 m t2 30 m t3 10 m and t4 4 5 m in the tigris river valley it was also found that there were some movements of the levels of the terraces in the valley by subsidence the subsidence developed gradually throughout the quaternary however no terrace was formed purely because of subsidence

a mechanical analysis of the keystone muddy mountain thrust sheet in southeast nevada abstract the keystone muddy mountain thrust sheet was displaced for several tens of kilometres across the land s surface in cretaceous times its movement is related to the emplacement of the sierra nevada batholith which provided a source of compressive stress over a period of about 140 ma the mechanical analysis presented here examines the stresses operating throughout the whole thrust sheet i e the toe ramp and main thrust block which extends for approximately 200 km from front to rear frictional sliding can explain only the motion of the toe the ramp and perhaps part of the main thrust block a composite model involving elastic upper and viscous lower layers is used to account for the movement of most of the main thrust block

geometry and kinematics of large arcuate structures formed by impingement of rigid granitoids into greenstone belts during progressive shortening regional scale arcuate structures in the central part of the archean yilgarn craton western australia were generated by impingement of competent granitoid blocks into less competent greenstone belts during progressive east west shortening sinistral shear zones developed along northwest trending margins of the granitoid blocks whereas dextral shear zones developed along northeast trending margins in apex regions these northeast and northwest trending shear zones are linked by north trending contractional zones along which shortening was accommodated by the formation of folds and reverse faults in the greenstone belts and a coaxial flattening fabric in granitoid rocks lateral escape of the greenstone belts is indicated by the progressive rotation of early macroscopic folds into parallelism with the strike slip shear zones during granitoid impingement this recently recognized deformation style may have important tectonic implications for other archean granite greenstone terranes and where rock heterogeneity and competency differences are significant

u pb ages constraining batholith emplacement contact metamorphism and the formation of gold and w mo skarns in the southern cross area yilgarn craton western australia gold mines in the archean southern cross greenstone belt central yilgarn craton have produced more than 220 metric tons t of gold the deposits are characterized by a pyroxene rich gangue and have been interpreted as synmetamorphic amphibolite facies replacement deposits and as postmetamorphic intrusion related skarns we present ion microprobe u pb zircon data constraining the age of amphibolite facies contact metamorphism in the aureole of the ghooli dome the largest granitoid batholith intruding the southern cross belt drill cores from the copperhead gold mine provided zircons from an altered quartz porphyry sill located 300 m southwest of the ghooli dome and zircons from the monzogranite gneiss at the border of the batholith the porphyry sill contains embayed igneous zircons dated by a concordant u pb age of 2912 5 ma and euhedral zircons of metamorphic crystal habitus dated by a second concordant age of 2772 5 ma the igneous zircons are slightly younger than those recovered from another sill of quartz porphyry sampled at the southern star mine which define a single concordant u pb age of 2934 7 ma the metamorphic zircons in the porphyry at copperhead record the same age as the igneous zircons 2775 10 ma in the monzogranite gneiss of the ghooli dome this pluton extends more than 40 km to the southeast of copperhead and also forms the batholith border at the corinthian and fraser s mines these gold deposits too are hosted by amphibolite facies greenstones contact metamorphosed at 2772 5 ma the corinthian skarn 2620 6 ma formed 150 m y after high grade metamorphism and consequently cannot be classified as synmetamorphic or metamorphogenic a review of field relationships and of published geochronometric data suggests that the gold skarns in the southern cross area are related in space and time to a suite of magnetite series granite pegmatite complexes these granites dated regionally at 2 66 to 2 60 ga are also associated with gold bearing w mo skarn greisen or skarn systems of up to 6 km strike length the numerous skarns exposed in the deeply eroded 14 km paleodepth central yilgarn craton are members of a recently recognized group of intrusion related gold deposits which are part of continental margin tungsten tin provinces

the role of hydrogeology in solution subsidence development and its environmental impacts a case study for sazlica nigde turkey solution subsidence and other types of collapse failures developed in the vicinity of sazlica have been a major source of environmental problems such as groundwater pollution soil erosion and foundation failures extensive pumping of water from the lake dipsiz during irrigation seasons creates landslide developments at the shores of the lake five stages of landslide development were observed in the unconsolidated soils around lake dipsiz bowl shaped solution subsidence features with depths from 1 to 3 m and diameters between 1 and 60 m were formed due to excess pumping and recharge and discharge features of unconfined aquifer the pumping activities must be controlled to prevent further environmental problems lake dipsiz and other subsidence developments are the groundwater exposure areas highly vulnerable to contamination the proposed remedies for overcoming the environmental problems are the establishment of conservation areas around such natural features ceasing the removal of top soil controlling the urbanization and keeping the livestock farming away from the areas susceptible to pollution

the age of the kambalda greenstones resolved by ion microprobe implications for archaean dating methods abstract a chert horizon within the archaean basalt pile at kambalda western australia contains zircons from air fall tuffs erupted as the sediment was laid down ion microprobe analyses of these magmatic zircons constrain the long sought age of the kambalda lavas to 2692 4ma 2 and show that regional metamorphism and deformation of the greenstone pile occurred within 30 ma of deposition rare zircon xenocrysts are evidence of pre greenstone crust as old as 3450 ma exposed remnants of which are yet to be identified subsets of both the magmatic and xenocryst zircons show evidence of hitherto unsuspected low temperature u and or pb mobility in the proterozoic long after stabilisation of the craton the ion microprobe data unravel complexities of isotopic inheritance and alteration illustrating the hazards of using bulk or whole rock samples in archaean isotopic investigations identification of interflow cherts as a precisely dateable rock type opens the way to direct ion probe dating of mafic ultramafic piles and close numerical age control of the complex but ill exposed stratigraphic and structural relations in this richly mineralised greenstone belt

environmental and engineering problems of karst geology in china karst terrane is generally regarded as a fragile and vulnerable environment its underground drainage system can aggrevate both drought and flood problems the lack of filtration in an underground conduit makes waste disposal more difficult and the lack of soil cover in bare karstland can enhance deforestation moreover karst terranes are quite often haunted by a series of engineering problems such as water gushing into mines or transportation tunnels leakage from reservoirs and failure of building foundations in china there are more than 200 cases of karst collapse which include many thousands of individual collapse points some of these are paleo and natural collapses but most of them are modern collapses induced by human activities and they have caused serious damage many factors such as geologic structure overburden thickness and character lithologic features of karstified rock and intensity of karstification are related to development and distribution of modern collapses however china s karst is mainly developed in pre triassic old phase hard compact carbonate rock consequently most modern collapses have occurred only in the overlying soil so it is understandable that the fluctuation of the water table in the underlying karstified strata plays an important role in the process of collapse nevertheless there are different explanations as to how the groundwater activities can induce collapse

climatic and tectonic influences on fan deltas and wave to tide controlled shoreface deposits evidence from the archaean keskarrah formation slave province canada the 2 6 ga keskarrah formation located in the central slave province northwest territories canada is a late orogenic tectonically controlled sedimentary sequence that developed under unusual climatic and depositional conditions the formation is adjacent to the crustal scale north trending beniah lake fault and overlies the 3 15 ga augustus granite the 2 69 2 7 ga mafic volcanic peltier formation and the turbiditic contwoyto formation unconformably principal lithofacies in the keskarrah formation include conglomerate sandstone and siltstone sandstone the conglomerate lithofacies represents coalescing gravelly streamflow dominated fan deltas adjacent to topographic highs up section quartz rich arenites and quartz arenites of the sandstone lithofacies are interpreted to be shallow water shoreface deposits influenced by wave action and tides the overlying feldspathic litharenites of the siltstone sandstone lithofacies are consistent with a lower shoreface to proximal offshore environment dominated by wave and tide interaction tidal influence in both sandstone dominated lithofacies is inferred from the presence of mudstone laminae between bedforms and on foresets of cross beds as well as from abundant reactivation surfaces with local mudstone drapes intense chemical weathering during the archaean resulting from elevated atmospheric co2 levels higher temperatures and moist climatic conditions played an important role in the development of quartz rich arenites that appear to be first cycle deposits few lithic fragments and feldspar grains are preserved due to in situ host rock weathering chemical weathering during transport and wave and tide action hydraulic sorting and abrasion in the shoreface environment contributed to the continued breakdown and transport of labile minerals increased proportions of lithic fragments in sandstone beds of the conglomerate lithofacies are the result of shorter transport distances from source areas to the depositional environment abundant conglomerate with up to 4 m large granitic boulders derived from the adjacent augustus granite and mafic clasts from the peltier formation indicate high relief and fault related uplift and subsidence the intimate association of fan deltas and wave and tide influenced shallow marine deposits in association with quartz rich sandstones forming in a high relief area make the keskarrah formation remarkable in the rock record

structural control of sinkholes and subsidence hazards along the jordanian dead sea coast for about four decades the dead sea ds level and the surrounding water table has been dropping dramatically at least from the eighties the direct vicinity of the lisan peninsula lp jordan has been facing high rates of subsidence and sinkhole hazards between 2000 and 2002 the arab potash company apc lost two salt evaporation ponds resulting in a loss of 70 million in the fertile plain of ghor al haditha gah three deep and wide bowl shaped subsidence areas threaten human activities and infrastructures over the part of the lisan peninsula that emerged before the 1960s relict fossil sinkholes occurred everywhere whereas new collapses constantly appear in the southern area only in this paper we have integrated 15 years of field observations related to sinkholes and subsidence with interpretation of space borne radar interferometric outputs aerial photographs and satellite images this has helped to place hazardous areas in their geological context and to clarify them within the framework of the general tectonic setting of the area

dead sea sinkholes an ever developing hazard sinkhole development along the western shore of the dead sea became a major concern in 1990 with the appearance of a series of holes 2 15 m diameter and up to 7 m deep in the newe zohar area one of these sinkholes below the asphalt surface of the main road along the western shore of the dead sea was opened by a passing bus repeated infilling and collapse of these holes indicated the extent of this ongoing process and the significance of this developing hazard since then sinkholes have developed in other areas including qalia ein samar ein gedi and mineral beach

late archaean synorogenic basins of the eastern goldfields superterrane yilgarn craton western australia part iii signatures of tectonic escape in an arc continent collision zone abstract siliciclastic supersequences in the eastern goldfields superterrane are remnants of basins that were linear zones of subsidence between intra terrane faults fluvial deposits record proximal to medial braid plains deep marine canyon and fan deposits were linked across intra terrane compartments only by mud rich deposits axial depositional systems dominate with only minor evidence for slope aprons although transverse and axial systems are preserved in some fluvial deposits basin development occurred during two stages separated by an inversion event with the kalgoorlie terrane recording change from a fluvial to a deep marine basin and the kurnalpi terrane change from distal to proximal deep marine facies tracts sparse palaeocurrents establish that uplift to the north controlled sediment dispersal lithofacies stacking is aggradational whereas abrupt upwards change in facies tracts is back stepping within depositional sequences and between depositional sequence sets but forward stepping between depositional sequences the stratigraphic architecture is atypical of synorogenic basins but consistent with a strike slip regime characterised by pulsed uplift subsidence steady state basin lengthening and subsidence punctuating catastrophic subsidence and lengthening and tectonic anchoring the basins are interpreted to have been similar to graben and half graben of the western anatolian extensional province of turkey with linear zones of subsidence developing adjacent to strike slip oblique slip or normal dip slip faults controls on stratigraphic patterns are considered to have been regional rather than at the scale of each basin the envisaged tectonic setting is similar to projected collision between the philippine archipelago west of the philippine fault and continental crust of the south china sea but the orogenic architecture is similar to that of accreted superterranes in the canadian cordillera interpreted north or northwest convergence between the burtville terrane to the east and the ancestral yilgarn continent to the northwest produced a south propagating orogen with the kalgoorlie gindalbie and kurnalpi terranes trapped between in a tectonic escape corridor tectonic escape to the south between bounding strike slip faults produced back stepping of facies tracts that simulated basin lengthening whereas forward stepping of facies tracts was the response to south propagating uplift

time transgressive archean unconformities underlying molasse basin fill successions of dissected oceanic arcs superior province canada abstract late archean diachronous unconformities underlying tectonically controlled coarse clastic successions are located throughout the superior province of canada examples studied in detail include hiatuses at the base of the timmins and kirkland basins in the abitibi greenstone belt and the crowduck and stormy basins in the wabigoon subprovince the timmins molasse basin fill succession overlies a high angle subaerial unconformity separating deepwater turbiditic deposits from fluvial conglomerates a subaerial erosional unconformity defines the contact between mafic flows and overlying felsic volcaniclastic deposits and fluvial conglomerates of the kirkland basin the crowduck and stormy successions are characterized by shallow water and subaerial unconformities between quartz feldspar porphyry stocks and clastic deposits the pronounced characteristics of the molasse basins which include 1 basal unconformities with older sedimentary volcanic or plutonic rocks 2 bounding fault systems 3 ba

hydrogeologic role in sinkhole development in the desert of kuwait sinkhole development is unlikely in desert areas with very low precipitation however a few cases of land subsidence and sinkhole development took place within the suburbs of kuwait city a few sinkholes developed in a sudden and rapid way leading to great economic losses in this paper the mechanism and causes of such a land subsidence are described decline in groundwater level and downward infiltration of excess irrigation are suggested to be the main factors in the development of the land subsidence in kuwait urbanization and excessive garden irrigation are most probably the triggers of the sudden and rapid land subsidence