preface archaean geology of the eastern goldfields of western australia regional overview abstract the eastern goldfields region forms part of the yilgarn craton which after the superior province of canada is one of the largest fragments of archaean granite greenstone terrain exposed at the surface of the earth this craton has much in common with the more intensely studied superior province but there are also significant differences between these two cratons both cratons were assembled from numerous smaller crustal fragments in a relatively brief period during the late archaean the superior province was assembled between 2725 and 2695 ma card 1990 and the yilgarn craton was assembled between c 2670 and 2650 ma myers 1993 both cratons contain fragments of older continental crust and volcanic arcs that formed just prior to collision and cratonisation the superior province contains extensive belts of metasedimentary rocks interpreted as accretionary prisms card 1990 whereas metasedimentary rocks form only a minor component of the yilgarn craton and most appear to postdate accretion both cratons contain significant concentrations of gold and support thriving gold mining industries the most prominent difference between the cratons lies in the nature of the granitoid rocks the superior province is dominated by tonalite and granodiorite whereas the yilgarn craton largely consists of granite this applies to granitoid rocks of all ages in each craton granite studies form a major part of this special volume of precambrian research

re os ages for the erdenet and tsagaan suvarga porphyry cu mo deposits mongolia and tectonic implications the erdenet and tsagaan suvarga deposits are the two largest known porphyry cu mo deposits in mongolia replicate re os analyses of molybdenite from these deposits yield ages of 240 7 0 8 and 240 4 0 8 ma for erdenet and 370 1 1 2 and 370 6 1 2 ma for tsagaan suvarga 2 errors the re os age of erdenet is significantly older and that of tsagaan suvarga is slightly older than published 40ar 39ar ages for sericite associated with mineralization in these deposits 207 4 5 0 and 364 9 7 0 ma respectively these re os results suggest that in the hydrothermal environment 40ar 39ar ages may be partly to significantly reset whereas re os ages record and maintain the age of primary mineralization events these re os ages indicate that porphyry mineralization at erdenet and tsagaan suvarga are related to porphyritic intrusions representing the youngest event during regional magmatism in northern and southern mongolia respectively the re os age of erdenet marks the final stage of arc magmatism in northern mongolia followed by late permian collision between the mongolian north china and siberian blocks the re os age of tsagaan suvarga indicates that devonian arc magmatism in southern mongolia was active at the present latitude of 44 n at least until 370 ma

origin of the coastally trapped waves observed during the australian coastal experiment abstract freely propagatiug coastally trapped waves ctws dominated the large alongshore scale low frequency variability in the australian coastal experiment ace two analytical models are used to demonstrate that these waves are not due to wave energy propagating freely through bass strait from the southern australian wave guide but rather are largely generated by the very strong low frequency winds in bass strait the first model shows that the considerable ctw energy flux from the southern australian shelf wave guide does not propagate through bass strait it is either frictionally dissipated at the northwest entrance to bass strait or travels southward along the western bass strait escarpment as escarpment waves and then southward along tasmania s west coast as coastally trapped waves the second model is used to calculate the eastward energy flux at the eastern end of bass strait assuming that all of this flux is generated by the very strong winds in bass strait the calculations show that the

dating low grade metamorphic events by shrimp u pb analysis of monazite in shales although the u pb isotopic system is widely used to date magmatism and medium to high grade metamorphism dating low grade metamorphic events has been hampered by a scarcity of suitable minerals we show that monazite forms in shales during low grade metamorphism and can be dated by in situ u pb analysis providing precise ages for low temperature thermal events in proterozoic shales from the pine creek inlier of northern australia monazite and xenotime crystals that formed in a contact aureole yield ages synchronous with granite intrusion ca 1830 ma in the pilbara craton of northwestern australia monazite growth 2192 5 m y ago coincided with basaltic volcanism and rifting an event apparently responsible for hydrothermal iron oxide mineralization in a nearby giant iron ore deposit the mineralizing environment was highly oxic and bathed by meteoric fluids thus our results imply the existence of an oxygen rich atmosphere by 2200 ma given the abundance of shales in the stratigraphic record and the likely widespread distribution of monazite in such rocks in situ u pb dating of monazite may become an important chronometer for low grade metamorphic events

structural setting hydrothermal alteration and gold mineralisation at the archaean syenite hosted jupiter deposit yilgarn craton western australia the jupiter gold deposit in the northeastern eastern goldfields province of the yilgarn craton of western australia is hosted in greenschist facies metamorphosed tholeiitic basalt quartz alkali feldspar syenite and quartz feldspar porphyry syenite intrudes basalt as irregularly shaped dykes which radiate from a larger stock whereas at least three e w and ne sw striking quartz feldspar porphyries intrude both syenite and basalt brittle ductile shear zones are shallow dipping nw to ne striking or are steep dipping to the south and west quartz carbonate veins that host gold at jupiter occur in all lithologies and are divided into 1 veins that are restricted to the shear zones 2 discrete veins that are subparallel to shear zone hosted veins and 3 stockwork veins that form a network of randomly oriented microfractures in syenite wallrock proximal to shallow dipping shear zones the gold bearing veins comprise mainly quartz calcite ankerite and albite with minor sericite pyrite chalcopyrite galena sphalerite molybdenite telluride minerals and gold proximal hydrothermal alteration zones to the mineralised veins comprise quartz calcite ankerite albite and sericite high gold grades 2 g t au occur mainly in syenite and in the hanging walls to shallow dipping shear zones in syenite where there is a greater density of mineralised stockwork veins the jupiter deposit has structural and hydrothermal alteration styles that are similar to both granitoid hosted but post magmatic archaean lode gold deposits in the yilgarn craton and intrusion related syn magmatic syenite hosted gold deposits in the superior province of canada based on field observations and petrologic data the jupiter deposit is considered to be a post magmatic archaean lode gold deposit rather than a syn intrusion deposit

an overview of the relationship between granitoid intrusions and gold mineralisation in the archaean murchison province western australia in the archaean murchison province of western australia granitoid batholiths and plutons that intruded into the ca 2 7 2 8 ga and ca 3 0 ga greenstone belts can be divided into three major suites suite i is a ca 2 69 ga monzogranite granodiorite suite which was derived from anatexis of old continental crust and occurs as syn tectonic composite batholiths over the entire province suite ii is a trondhjemite tonalite suite termed i type derived from partial melting of subducted basaltic crust which intruded as syn to late tectonic plutons into the greenstone belts in the northeastern part of the province where most of the major gold deposits are situated one of the suite ii trondhjemite plutons has a pb pb isochron age of 2641 36 ma and one of the structurally youngest tonalite plutons has a minimum pb pb isochron age of 2630 1 4 3 ma suite iii is a ca 2 65 2 62 ga a type monzogranite syenogranite suite which is most abundant in the largely unmineralised southwestern part of the province gold deposits in the province are mostly hosted in brittle ductile shear zones and were formed at a late stage in the history of metamorphism deformation and granitoid emplacement at one locality mineralisation has been dated at 2636 8 4 2 ma through a pyritetitanite pb pb isochron lead and sr isotope studies of granitoids and gold deposits indicate that although most gold deposits have initial pb isotope compositions most closely similar to those of suite ii intrusions both suite i and suite ii intrusions or their source regions could have contributed solutes to the ore fluids these preliminary data suggest that gold mineralisation in the murchison province was temporally and spatially associated with suite ii i type granitoids in the northeastern part of the province this association is consistent with the concept that archaean gold mineralisation was related to convergent style tectonic settings as generation of both suite ii i type granitoids and hydrothermal ore fluids could have been linked to the dehydration and partial fusion of subducted oceanic crust and old sialic crust or its anatectic products may also contribute solutes to the ore fluids integration of data from this study with other geological and radiogenic isotope constraints in the yilgarn block argue against direct derivation of gold ore fluids from specific i type granitoid plutons but favour a broad association with convergent tectonics and granitoid magmatism in the late archaean

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

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

constraints on the age of granitoid emplacement metamorphism gold mineralization and subsequent cooling of the archean greenstone terrane at big bell western australia the big bell gold deposit 40 t au produced is located in a narrow terrane of the meekatharra wydgee greenstone belt in the murchison province of the yilgarn craton western australia at the mine site the greenstones consist of amphibolites and metakomatiites of the 3 0 ga gabanintha formation rotated into a subvertical position and foliated parallel to stratigraphic contacts the amphibolite metakomatiite sequence is intruded parallel to foliation by swarms of granodiorite tonalite dikes the largest dike exposed in the big bell open pit and dated at 2737 or 4 ma u pb zircon is surrounded by a zoned contact metamorphic aureole 1 km wide of amphibolite facies grade the dikes represent the oldest and outermost intrusive phase of the batholith to the southeast where the border granodiorite pluton has been dated at 2700 or 7 ma u pb zircon the gold bearing metasomatic rocks at big bell are subdivided into central muscovite microcline and biotite plagioclase gneisses and into outer calcic skarns both gneisses and skarns form steeply dipping zones bound to the contacts of altered granodiorite dikes the timing of main gold sulfide scheelite mineralization is constrained by a concordant u pb almandine age of 2662 or 5 ma from a low grade cummingtonite hornblende contact skarn main mineralization in the mine area thus postdates amphibolite facies metamorphism by about 80 m y muscovite from the main lode microcline gneiss yielded an ar ar plateau age of 2639 or 16 ma interpreted as reset by the thermal effect of the granite pluton at the northwestern margin of the greenstone terrane the granite u pb zircon age 2627 or 8 ma agrees within error with the ar ar muscovite age metamorphic recrystallization related to granite intrusion was of very limited extent

the granny smith gold deposit the role of heterogeneous stress distribution at an irregular granitoid contact in a greenschist facies terrane the granny smith gold deposits formed late in the structural history of the yilgarn block at a high crustal level in a largely brittle structural regime gold mineralisation is located along a n s striking fault which wraps around the contact of a small granitoid intrusion in different sections of the fault mineralisation may be developed in the granitoid in the adjacent sedimentary sequence and or along the contact between them in the granitoid gold mineralisation is in conjugate networks of thin carbonate quartz veins and their alteration halos small displacements along veins are common in contrast veins and faults in the sedimentary rocks are subparallel to bedding spatial variations in the conjugate vein orientations indicate that the local stress field was heterogeneous and controlled by the shape of the granitoid contact the greatest variations in vein and implied stress orientations occur in zones where the contact is most irregular these are also the areas of richest mineralisation fluid flow was thus focused in a regional scale low mean stress region created by the geometry of the granitoid intrusion its irregular contact caused deposit scale variations in fluid flow and resulted in heterogeneous gold grades along the contact zone

retrieving root zone soil moisture profile from p band radar via hybrid global and local optimization we propose an inversion model for retrieving the root zone soil moisture profile using the p band radar observations and validate it using data collected during the airborne microwave observatory of subcanopy and subsurface airmoss mission the forward model utilized in this article uses an existing small perturbation method spm to calculate the electromagnetic wave scattered from multilayered rough surface dielectric structures to solve the inverse problem which is formulated as a least squares problem we utilize a novel global optimization technique that takes the advantage of the speed of a local optimization method while ensuring convergence to the global minimum we present the numerical results to demonstrate significant improvements in the inversion results and computational speed compared to the previously used airmoss baseline inversion algorithm the presented method is validated with in situ soil moisture measurements finally by utilizing a closed form analytical solution to richards equation we demonstrate improvements in the accuracy of our soil moisture retrieval results

evidence for diachronous archean lode gold mineralization in the yilgarn craton western australia a shrimp u pb study of intrusive rocks the currently accepted model for the archean lode gold deposits of the yilgarn craton postulates that they represent a coherent group of epigenetic deposits the majority of which formed during a craton scale broadly synchronous hydrothermal event late in the tectonothermal evolution of the granite greenstone terranes at ca 2640 to 2630 ma felsic rocks from the southern eastern goldfields which host or are cut by gold mineralization have shrimp ii u pb zircon ages of 2673 or 3 ma at mount charlotte 2669 or 17 ma at mount percy 2663 or 3 ma at racetrack and 2657 or 8 ma at porphyry all these ages are consistent with gold mineralization at ca 2640 to 2630 ma intermediate to felsic dikes cut typical syn to postmetamorphic lode gold mineralization at the mount mcclure and jundee deposits in the yandal greenstone belt in the north of the kurnalpi terrane the dikes give ages of 2656 or 4 2663 or 4 and 2668 or 10 ma from mount mcclure and 2656 or 7 ma from jundee requiring that mineralization and peak regional metamorphism in the belt occurred prior to ca 2660 ma however both the characteristics of the jundee and mount mcclure deposits and the relative timing of mineralization with respect to the metamorphic and structural history of the belt are similar to that seen for gold deposits elsewhere in the yilgarn craton this implies that mineralization at jundee and mount mcclure was produced prior to 2660 ma by similar processes to those seen elsewhere in the yilgarn at 2640 to 2630 ma peak metamorphism in the western higher metamorphic grade terranes of the yilgarn was not reached until ca 2630 ma some 10 to 30 m y after peak metamorphism in the kalgoorlie terrane and more than 30 m y after metamorphism in the yandal belt in addition almost all of the published robust ages supporting gold mineralization at ca 2640 to 2630 ma are from the west of the craton consideration of the new data from the yandal belt in conjunction with previously published geochronology throws doubt on the hypothesis that lode gold mineralization occurred approximately synchronously across the yilgarn craton rather it suggests that mineralization along with regional metamorphism is earlier by at least 30 m y in the northeastern yilgarn craton

geochronological constraints on pre syn and postmineralization events at the world class cleo gold deposit eastern goldfields province western australia recent geological and geochronological studies have led to a reevaluation of whether or not the majority of the lode gold deposits of the yilgarn craton formed nearly synchronously during an archean craton wide hydrothermal event as previously proposed the majority of reliable data indicate that gold mineralization took place at ca 2640 to 2625 ma however recent work in the far north of the eastern goldfields province provides structural evidence for instances of earlier gold mineralization and geochronological data for interpreted postore rocks that are considerably older than 2640 ma the documentation of xenotime and monazite in association with ore minerals at the cleo deposit provides a valuable means of determining the absolute age of gold mineralization at the cleo deposit high grade western lodes veins crosscut the sunrise shear zone at a high angle with only centimeter scale offset given that the stratigraphic sequence indicates at least several hundred meters offset across the shear zone the minimal offset of the western lodes veins indicates that gold mineralization was late in the history of movement in the shear zone the absolute ages of pre syn and postmineralization elements in the mine stratigraphic succession have been determined using a variety of geochronological techniques fuchsite micas formed in the sunrise shear zone yield an 40ar 39ar isochron age of 2667 19 ma rhyodacite porphyry dikes postdate the formation of the shear zone but predate the main phase of gold mineralization dike intrusion is constrained to 2674 3 ma by shrimp ii u pb analysis of zircons from these dikes rhenium os analysis of molybdenite from quartz chalcopyrite molybdenite veins that crosscut the porphyry dikes gives an age of formation at 2663 11 ma consistent with their relationship to the porphyry dikes both the dikes and these veins are crosscut by gold bearing western lodes veins mutually crosscutting relationships with ore minerals indicate that microscopic xenotime and monazite grains were deposited during ore formation in the western lodes ore zones shrimp ii u pb analyses of xenotime and monazite grains indicate that western lodes mineralization took place at 2654 8 ma at least 9 m y after the intrusion of the porphyry dikes 95 confidence evidence for substantial temporal separation between intrusive activity and gold mineralization is recorded by other researchers for other deposits associated with granitic intrusions in the leonora laverton area phlogopitic micas from a lamprophyre that crosscuts the whole succession including the sunrise shear zone yield an ar ar plateau age of 2080 4 ma this study constrains the timing of multiple events at cleo including the main phase of gold mineralization during a relatively short span of time however in the context of the larger debate about the existence of a dominant 2640 to 2625 ma period of gold mineralization and the extent of a proposed widespread pre 2660 ma mineralization event in the yilgarn craton the data from cleo are equivocal the 2654 8 ma age for mineralization being significantly older than 2640 ma but not significantly pre 2660 ma even if the maximum possible age is accepted

evolution of the archaean granite greenstone terranes of the eastern goldfields western australia shrimp upb zircon constraints abstract thirty five high precision shrimp u pb zircon dates with an average 95 confidence error of 6 ma have been obtained from the granite greenstone terranes in the southern part of the eastern goldfields of western australia these dates establish the timing of major deformation metamorphism and granite intrusion events and test inferred stratigraphic relationships within the greenstones these new data reveal that felsic volcanic rocks were erupted throughout the southern part of the eastern goldfields between c 2713 and c 2672 ma analytically indistinguishable dates of c 2705 ma were obtained for felsic volcanic rocks interbedded with komatiitic lavas at three sites dates on felsic volcanic rocks within tectonostratigraphic packages that include komatiites are also consistent with an inferred eruption age for these komatiites of c 2705 ma komatiitic lavas in the southern part of the eastern goldfields were probably emplaced during a single voluminous eruption that resulted in the flooding of a vast area of the late archaean landscape filling the topographic lows around older felsic volcanic vents the stratigraphic complexity within tectonostratigraphic domains is attributed to the existence of an undulating topography during the eruption of the mafic and ultramafic lavas and to the rapid and localized deposition of felsic volcanic rocks close to a number of isolated volcanic centres prior to and after the komatiite lava eruption event between c 2685 and c 2675 ma early pre d2 intrusive equivalents of the felsic volcanic rocks were emplaced as thick granite sheets into the base of the greenstone sequences regional east west compression between c 2675 and c 2657 ma reactivated early extensional structures and resulted in the stacking of the greenstones this was accompanied by further intrusion of granite within developing antiforms burial of greenstone slices by stacking and the effect of hydrothermal fluids emanating from both the granites and buried greenstones resulted in regional metamorphism to greenschist facies prior to c 2640 ma monzogranite and granodiorite emplaced near the western southern and eastern margins of the greenstones were deformed and metamorphosed to upper amphibolite facies and converted into gneisses during d2 and d3 compression events movement along large scale transcurrent d3 shear zones had ceased by c 2635 ma remnants of a c 2958 to c 2930 ma greenstone sequence preserved near norseman and ravensthorpe in the southeastern yilgarn craton and xenocryst zircons ranging in age from c 2910 2730 ma in the c 2713 2672 ma felsic volcanic rocks indicate that the exposed greenstone sequences were deposited on continental basement the eastern goldfields granite greenstone terranes were formed by the closure of a series of narrow back arc rift basins that developed along a continental margin and above an active subduction zone located to the east of the rift basins

a study of low frequency wind driven coastal trapped waves along the southeast coast of australia abstractcoastal trapped waves ctws along the southeast coast of australia were investigated based on a frictional wind driven long wave theory it was found that low frequency sea level anomalies slas were continuously propagating from the south coast up along the east coast as ctws mainly forced by the alongshore wind stress three main subinertial peaks existed in the spectral characteristics of the slas with periods of 14 2 10 2 and 7 8 days respectively power spectral density distributions of the peaks showed that the ctw amplitudes varied significantly along the southeast coast for idealized linear and exponential shelves a theoretical analysis indicated that the fundamental factor influencing the eigenvector of mode 1 and therefore the ctw amplitude was the offshore water depth this theoretical work was well supported by eight sensitivity cases four additional cases were conducted and time averaged energy fluxes were calculated to identify the energy source of the ctws in the austr

a thrust ramp model for gold mineralization at the archean trondhjemite hosted tarmoola deposit the importance of heterogeneous stress distributions around granitoid contacts the trondhjemite hosted tarmoola gold deposit is situated in the leonora district in the eastern goldfields province and is the largest granitoid hosted gold deposit in the yilgarn craton of western australia 100 t au the massive trondhjemite pluton intrudes a northwest striking shallowly northeast dipping supracrustal sequence that comprises greenschist facies metamorphosed basalt komatiite chloritic siltstones and a volcani clastic unit several east northeast striking quartz diorite dikes cut the trondhjemite and supracrustal sequence major ore zones 1 g t au occur 1 within the trondhjemite as discontinuous west northwest striking zones 2 along the steeply dipping eastern trondhjemite contact in the supracrustal and trondhjemite rocks and 3 subparallel to the shallowly dipping western trondhjemite margin in supracrustal rocks ore zones in the trondhjemite are controlled by west northwest striking steeply south west and northeast dipping conjugate quartz carbonate veins that contain minor pyrite chalcopyrite sphalerite galena gold and rare scheelite gold bearing veins in supracrustal rocks have a similar vein mineralogy and timing to that of the auriferous veins in trondhjemite deformation at tarmoola occurred during progressive regional east west directed shortening the first deformation event d 1 caused early barren isoclinally folded quartz carbonate veins and a pervasive foliation in supracrustal rock to be aligned subparallel to the steeply dipping eastern margin of the pluton during the gold mineralization event d 2 the trondhjemite pluton acted as a competent body within ductile supracrustal country rocks subhorizontal northwest southeast shortening caused auriferous conjugate veins in trondhjemite and the reactivation of the eastern contact and a preexisting subparallel foliation in the supracrustal rock the reverse movement of supracrustal rock along the sheared western trondhjemite contact caused the formation of west dipping gold bearing shear zones in the overlying supracrustal sequence the reactivation of the eastern trondhjemite contact caused the development of low mean stress zones adjacent to the contact hy drothermal ore fluids were focused into these regions to form ore zones the third deformation event d 3 produced brittle ductile shear zones quartz carbonate veins and brittle faults that offset lithological contacts and gold bearing veins

synmetamorphic lode gold deposits in high grade archean settings lode gold deposits that formed under conditions of the middle to upper amphibolite and granulite facies have been identified in the yilgarn block of western australia these deposits which form a continuum with lower metamorphic grade mesothermal gold depos its show that at least some of the fluids responsible for mesothermal gold deposits originated in or below the middle crust studies of 18 o suggest that fluid compositions were controlled by the wall rocks at least for some elements these more proximal gold deposits provide more information about deep fluid sources than do investigations of higher level mineralization deposited from fluids strongly modified by wall rock interaction during the early part of their ascent

re os ages for archean molybdenite and pyrite kuittila kivisuo finland and proterozoic molybdenite kabeliai lithuania testing the chronometer in a metamorphic and metasomatic setting seven 187re 187os ages were determined for molybdenite and pyrite samples from two well dated precambrian intrusions in fennoscandia to examine the sustainability of the re os chronometer in a metamorphic and metasomatic setting using a new 187re decay constant 1 666 10 11y 1 with a much improved uncertainty 0 31 we determined replicate re os ages for molybdenite and pyrite from the kuittila and kivisuo prospects in easternmost finland and for molybdenite from the kabeliai prospect in southernmost lithuania these two localities contain some of the oldest and youngest plutonic activity in fennoscandia and are associated with newly discovered economic au mineralization ilomantsi finland and a cu mo prospect kabeliai lithuania two re os ages for vein hosted kabeliai molybdenite average 1486 5 ma in excellent agreement with a 1505 11 ma u pb zircon age for the hosting kabeliai granite pluton the slightly younger age suggests the introduction of cu mo mineralization by a later phase of the kabeliai magmatic system mean re os ages of 2778 8 ma and 2781 8 ma for kuittila and kivisuo molybdenites respectively are in reasonable agreement with a 2753 5 ma weighted mean u pb zircon age for hosting kuittila tonalite these re os ages agree well with less precise ages of 2789 290 ma for a rb sr whole rock isochron and 2771 75 ma for the average of six sm nd tdm model ages for kuittila tonalite three re os analyses of a single pyrite mineral separate from the same sample of kuittila pluton that yielded a molybdenite separate provide individual model ages of 2710 27 2777 28 and 2830 28 ma re 17 4 12 1 and 8 4 ppb respectively with a mean value of 2770 120 ma in agreement with the kuittila molybdenite age the re and 187os abundances in these three pyrite splits are highly correlated r 0 9994 and provide a 187re 187os isochron age of 2607 47 ma with an intercept of 21 ppt 187os mswd 1 1 it appears that the re os isotopic system in pyrite has been reset on the millimeter scale and that the 21 ppt 187os intercept reflects the in situ decay of 187re during the 160 to 170 m y interval from 2778 ma time of molybdenite pyrite deposition to 2607 ma time of pyrite resetting when the re os data for molybdenites from the nearby kivisuo prospect are plotted together with the kuittila molybdenite and pyrite data a well constrained five point isochron with an age of 2780 8 ma and a 187os intercept 2 4 3 8 ppt of essentially zero results mswd 1 5 we suggest that the pyrite isochron age records a regional metamorphic and or hydrothermal event possibly the time of au mineralization a proposed re os age of 2607 ma for au mineralization is in good agreement with radiometric ages by other methods that address the timing of archean au mineralization in deposits worldwide so called late au model molybdenite in contrast provides a robust re os chronometer retaining its original formation age of 2780 ma despite subsequent metamorphic disturbances in archean and proterozoic time

shrimp u pb geochronological constraints on archean volcanic hosted massive sulfide and lode gold mineralization at mount gibson yilgarn craton western australia the base metal rich mount gibson gold deposits are hosted within the ductile mount gibson shear zone in the retaliation greenstone belt of the murchison province of the archean yilgarn craton the deposits are unique in the context of the yilgarn as they exhibit two main styles of hydrothermal alteration and sulfide mineralization consistent with overprinting of synvolcanic volcanic hosted massive sulfide style mineralization by synorogenic shear hosted lode gold mineralization on the basis of model ages based on sulfide pb isotope ratios these two events are separated by approximately 300 m y subvolcanic intrusive rocks from within the host sequence to mineralization at the orion two and hornet deposits have shrimp ii zircon u pb ages of crystallization of 2929 or 3 and 2934 or 6 ma respectively these ages are within error and provide a minimum age for the host sequence and consequently the volcanic hosted massive sulfide mineralizing event at mount gibson on the basis of geochemical evidence the intrusions are interpreted to have been derived from the same parent magma as the rocks they intrude and consequently ca 2930 ma is probably the approximate age of the host rocks to mineralization the regional granitoid which intrudes the base of the greenstone belt has a crystallization age of 2935 or 3 ma a post tectonic granite porphyry which crops out approximately 25 km north northeast of the mount gibson mine site has a shrimp ii zircon u pb crystallization age of 2623 or 7 ma this granitoid has identical field relationships similar whole rock geochemistry and similar pb isotope ratios to those of an internal granitoid which cuts gold mineralization in the deep south pit and is consequently interpreted to be cogenetic and contemporaneous the 2623 or 7 ma date is therefore interpreted to be a minimum age for synorogenic gold mineralization at mount gibson a morphologically and chemically distinctive population of zircons extracted from the sample of 2934 ma altered felsic schist from the hornet deposit gives a shrimp ii zircon u pb age of 2627 or 13 ma these zircons have characteristics which are consistent with a hydrothermal origin and the age is interpreted to represent the timing of synorogenic gold mineralization at mount gibson the interpreted mineralization age is within error of the inferred age of the postmineralization post tectonic granitoid the age is also within error of the majority of absolute ages for gold mineralization from across the yilgarn craton which generally fall in the range 2630 or 10 ma shrimp zircon u pb geochronology thus provides strong support for the two stage model proposed for mineralization at mount gibson synvolcanic volcanic hosted massive sulfide style mineralization occurred at ca 2930 ma and was overprinted by lode gold mineralization some 300 m y later at ca 2630 ma

propagation characteristics of coastally trapped waves on the australian continental shelf 1 coastally trapped waves ctws are investigated around the australian coast based on their signature in the sea surface height ssh field using independent data from coastal tide gauge observations and the bluelink ocean forecasting system from 2009 a high correlation correlation coefficients from 0 6 to 0 9 between the model and observational data is demonstrated for locations between hillarys in the south west of the continent and cape ferguson in the north east this justifies the use of bluelink data for the rest of the investigation and enables coastal locations between tide gauge stations to be included spectrum analysis shows that ctws have periods of between 10 and 25 days with the 10 day period dominating along the south coast and greater energy around the 20 day period on the east coast the greatest spectral power is located around the great australian bight after filtering to isolate these ctw frequencies phase speeds are estimated using two methods and are consistent with earlier studies there is a close correlation between the standard deviation of the filtered ssh data and the width of the continental shelf indicating that ctw amplitudes are strongly modulated by the local shelf width contrary to earlier studies a complex empirical orthogonal function analysis shows that the majority of the variance propagates as continuous features between the south west and north east and although modulated by the shelf width it is unaffected by the sharply changing coastline orientation shallow bass strait or wind forcing regions

observational evidence from direct current measurements for propagation of remotely forced waves on the shelf off the west coast of india 1 we use data from six acoustic doppler current profiler adcp moorings deployed during march september 2008 on the continental shelf and slope off bhatkal goa and jaigarh on the central west coast of india to present evidence for poleward propagation of shelf or coastal trapped waves ctws wave propagation is seen on the shelf in the 20 40 day 10 14 day and 3 5 day period bands the lag from south to north indicates that remote forcing is important even at periods as short as 4 days using quikscat wind data we show that the contribution of remote forcing to the shelf west indian coastal current wicc is significant even when the local alongshore wind is strong as during the summer monsoon onset during may june and forces a strong local response that masks the effect of remote forcing forced wave calculations using ctw theory show that remote forcing of the wicc is present at all times but is most striking when the local winds are weak as during march april the ctw calculations show that the source region for the remote forcing may extend beyond the west coast into the gulf of mannar between india and sri lanka on the slope propagation is seen only at the 4 day period at higher periods the slope wicc decorrelates rapidly along the coast but upward phase propagation implying downward propagation of energy associated with poleward propagation is evident even at these higher periods

40 ar 39 ar and u pb age constraints on the timing of gold mineralization in the kalgoorlie gold field western australia the 40 ar 39 ar ages of three hydrothermal muscovite samples associated with auriferous gold stockwork systems at the mount charlotte deposit in the kalgoorlie gold field have a weighted mean of 2602 or 8 ma 40 ar 39 ar age errors are 2sigma at the nearby golden mile deposit 40 ar 39 ar ages from two muscovite samples associated with shear hosted lode gold mineralization have a weighted mean of 2629 or 9 ma on the balance of available evidence these ages are interpreted to represent the timing of gold mineralization in the two deposits these data indicate that formation of auriferous gold stockwork systems at mount charlotte occurred at least 10 million years after formation of the gigantic golden mile lode system this is consistent with geologic relations between the two different styles of mineralization and suggests that separate hydrothermal episodes were responsible for stockwork and shear hosted gold mineralization a weighted mean 207 pb 206 pb zircon age for a postregional metamorphism biotite porphyry intrusion of 2674 or 6 ma 95 confidence limits provides a minimum estimate for the timing of regional metamorphism of the surrounding greenstone sequence and associated compressive deformation hypotheses for the formation of archcan gold deposits which invoke fluids that are derived from regional metamorphic devolatilization of upper middle crustal greenstone sequences or from intrusion of spatially related porphyries cannot account for the gold mineralization in the kalgoorlie gold field these data indicate that the events occurred 30 to 40 and 60 to 70 million years prior to mineralization at the golden mile and mount charlotte respectively formation of the golden mile appears to have been part of a widespread gold mineralizing event at ca 2630 to 2640 ma supporting models in which crustal scale hydrothermal circulation at this time is used to explain archcan gold mineralization within the yilgarn block however such models must now contain the caveat that discrete younger episodes of mineralization such as that responsible for mount charlotte may also produce significant gold deposits with features similar to typical archcan gold deposits

a generalized radar backscattering model based on wave theory for multilayer multispecies vegetation a generalized radar scattering model based on wave theory is described the model predicts polarimetric radar backscattering coefficients for structurally complex vegetation comprised of multiple species and layers compared to conventional two layer crown trunk models modeling of actual forests has been improved substantially allowing better understanding of microwave interaction with vegetation the model generalizes an existing single species discrete scatterer model and by including scattering and propagation effects through judiciously defined vegetation layers enables its application to an arbitrary number of species types the scatterers within each layer are modeled as finite cylinders or disks having arbitrary size density and orientation as in the predecessor model the distorted born approximation is used to represent the propagation through each layer while scattering from each is modeled as a linear superposition of scattering from its respective random collection of scatterers interactions of waves within and between each layer and direct scattering from the ground are accounted for validation of the model is presented based on its application to 23 wooded savanna sites located in queensland australia and comparison with advanced land observing satellite alos phased arrayed l band synthetic aperture radar palsar and national aeronautics and space administration nasa jet propulsion laboratory jpl airborne synthetic aperture radar airsar data results indicate good agreement between simulated and actual backscattering coefficients particularly at hh and vv polarizations more discrepancies are found at hv polarizations and can be explained by uncertainties in the knowledge of input parameters such as inaccuracies in the surface model surface roughness parameterization and soil moisture

geological setting and shrimp u pb geochronological evidence for ca 2680 2660 ma lode gold mineralization at jundee nimary in the yilgarn craton western australia the 7 million oz jundee nimary lode gold deposit occurs in the northern portion of the yandal greenstone belt in the northeastern part of the archean yilgarn craton of western australia gold mineralization at jundee nimary is similar in structural style mineralogy geochemistry and relative timing with respect to deformation and metamorphism to other western australian archean greenstone hosted gold deposits but is unusual in the fact that mineralized structures are crosscut by structurally late intermediate to felsic dykes within the deakin south open cut gold mineralization is hosted in brittle ductile shear zones primarily developed within the dacitic mitchell porphyry the moore porphyry a broad dyke of porphyritic granodiorite intrudes the mitchell porphyry crosscutting and post dating gold mineralization analytically indistinguishable shrimp u pb zircon ages of 2678 5 ma for the mitchell porphyry and 2669 7 ma for the moore porphyry require that gold mineralization at jundee nimary occurred at ca 2680 2660 ma approximately 40 million years earlier than the majority of published robust ages for gold mineralization in the yilgarn craton which mostly overlap at ca 2640 2630 ma the close spatial and temporal relationship between gold mineralization and felsic to intermediate magmatism at jundee nimary also raises the possibility of a genetic link between hydrothermal and igneous activity however additional work is required to establish a firm connection current research on lode gold mineralization in archean paleozoic and phanerozoic terranes suggests a model which postulates that these deposits formed during transpressional to compressional deformation in accretionary and collisional orogens and that their formation is intimately related to orogenic processes consequently mineralization and regional metamorphism are expected to be diachronous as terranes are accreted and the front of orogenesis migrates consideration of the new data presented in this paper in conjunction with previously published dates supports the hypothesis that gold mineralization along with regional metamorphism was generally diachronous from northeast to southwest across the yilgarn craton over a period of approximately 40 million years from ca 2680 2660 ma to ca 2640 2630 ma this is directly analogous to the accepted model for the timing of orogenic lode gold mineralization in other provinces and therefore provides further support for a unified model for this style of deposit through geological time

late kinematic timing of orogenic gold deposits and significance for computer based exploration techniques with emphasis on the yilgarn block western australia abstract orogenic gold deposits are a widespread coherent group of epigenetic ore deposits that are sited in accretionary or collisional orogens they formed over a large crustal depth range from deep seated low salinity h2o co2 ch4 n2 ore fluids and with au transported as thio complexes regional structures provide the main control on deposit distribution in many terranes first order faults or shear zones appear to have controlled regional fluid flow with greatest ore fluid fluxes in and adjacent to lower order faults shear zones and or large folds highly competent and or chemically reactive rocks are the most common hosts to the larger deposits focusing of supralithostatic ore fluids into dilatant zones appears to occur late during the evolutionary history of the host terranes normally within d3 or d4 in a d1 d4 deformation sequence reactivation of suitably oriented pre existing structures during a change in far field stress orientation is a factor common to many deposits and repeated reactivation may account for multiple mineralization episodes in some larger deposits absolute robust ages of mineralization support their late kinematic timing and in general suggest that deposits formed diachronously towards the end of the 100 to 200 m y long evolutionary history of hosting orogens for example in the yilgarn block a region specifically emphasised in this study orogenic gold deposits formed in the time interval between 40 and 90 m y with most about 60 to 70 m y after the youngest widespread basic ultrabasic volcanism and towards the end of felsic magmatism the late timing of orogenic gold deposits is pivotal to geologically based exploration methodologies this is because the present structural geometries of i the deposits ii the hosting goldfields and iii the enclosing terranes are all essentially similar to those during gold mineralization at least in their relative position to each other thus interpretation of geological maps and cross sections and three dimensional models can be used to accurately simulate the physical conditions that existed at the time of ore deposition it is particularly significant that the deposits are commonly related to repetitive and predictable geometries such as structural heterogeneities within or adjacent to first order structures around rigid granitoid bodies or in specific locked up fold thrust structures importantly the two giant greenstone hosted goldfields kalgoorlie and timmins show a remarkably similar geometry at the regional scale computer based stress mapping and gis based prospectivity mapping are two computer based quantitative methodologies that can utilize and take advantage of the late timing aspect of this deposit type to provide important geological aids in exploration both in broad regions and more localized goldfields both require an accurate and consistent solid geology map stress mapping requires knowledge of the far field stresses during mineralization and the empirical prospectivity mapping requires data from a significant number of known deposits in the terrane the kalgoorlie terrane in the yilgarn block meets these criteria and illustrates the potential of these methodologies in the exploration for orogenic gold deposits low minimum stress anomalies interpreted to represent dilational zones during gold related deformation coincide well with the positions of known goldfields rather than individual gold deposits in the terrane and there are additional as yet unexplained anomalies the prospectivity analysis confirms that predictable and repetitive factors controlling the siting of deposits are i proximity to and orientation and curvature of granitoid greenstone contacts ii proximity to segments of crustal faults which strike in a preferred direction iii proximity to specific lithological contacts which have similar preferred strike iv proximity to anticlinal structures and v the presence of preferred reactive host rocks e g dolerite the prospectivity map defines a series of anomalous areas which broadly conform to those of the stress map 78 correspondence the most prospective category on this map covers less than 0 3 of the greenstone belts and yet hosts 16 of the known deposits which have produced 80 of known gold thus it discriminates in favour of the larger economically more attractive deposits in the terrane the successful application of stress mapping and prospectivity mapping to geology based exploration for orogenic gold deposits indicates that more quantitative analysis of geological map data is a profitable line of research the computer based nature of these methodologies is ideal for the production of an ultimate integrated deposit target map which can be compared to other more conventional targeting parameters such as geophysical and geochemical anomalies such an integrated strategy appears the way forward in the increasingly difficult task of cost effective global exploration for orogenic gold deposits in poorly exposed terranes

retrieval of permafrost active layer properties using time series p band radar observations we propose a method to estimate the active layer properties including soil dielectric profiles and active layer thickness alt in permafrost regions using time series p band polarimetric synthetic aperture radar sar observations the active layer and underlying permafrost are modeled as a three layer dielectric structure with the layer dielectric constants representing the soil moisture and freeze thaw state of the layer to resolve the ambiguity of the retrieved layer thicknesses an approach of finding the largest possible depths lpds is combined with time series observations where the alt is assumed time invariant between the maximum thaw and before the upward freezing front rises significantly from the permafrost table the lpd assisted time series retrieval algorithm is applied to the radar data acquired by the airborne microwave observatory of subcanopy and subsurface airmoss p band sar in august and october 2014 and 2015 over the alaska north slope the results show that the retrieved alt values are generally underestimated for the sites where the in situ alt is larger than the p band sensing depth with a retrieval bias ranging from 0 05 to 0 24 m as validated against the in situ alt collected at circumpolar active layer monitoring calm sites for the sites where the in situ alt is smaller than 0 55 m the retrieval errors are generally less than 0 1 m the retrieval results also show that the active layer properties are strongly influenced by the land cover types at the regional scale and not as much by the north south temperature gradient across a 180 km long transect along the deadhorse flight line