avo and devonian reef exploration difficulties and possibilities although avo has proven useful in hydrocarbon exploration in shallow gas sands there are few examples of its application to carbonate exploration this paper presents a conjecture that avo can help differentiate between shale and porous dolomite in devonian reefs a critical problem in canada where oil production from nisku reefs in the devonian formation accounts for a large part of industry activity devonian formations have generated 60 of canadian oil production and 25 of gas production

the impact of hydrothermal mineral replacement reactions on the formation and alteration of carbonate hosted polymetallic sulfide deposits a case study of the artemis prospect queensland australia abstract hydrothermal sulfidation of carbonate rocks and the reverse replacement of sulfides by carbonates are important processes responsible for the formation and subsequent alteration of ore deposits these processes have been recognized in the case study of the artemis zn cu au prospect which is located in the cloncurry district within the eastern succession of the mount isa inlier nw queensland australia the high grade polymetallic mineralization displays a complex association of massive sulfides and carbonates hosted in a vertical marble lens adjacent to garnet bearing schist staurolite muscovite schist and quartzo feldspathic psammite petrographic analyses of drill core specimen by optical and electron microscopy micro x ray florescence elemental maps electron probe microanalyses cathodoluminescence and bulk geochemistry suggested three major stages of mineralization i pre ore stage marble calcite 0 ii ore stage involving sulfidation of the marble and precipitation of calcite 1 and spherical sulfide inclusions in the first episode and the formation of calcite 2 and massive sulfide in the second episode and iii post ore stage involving replacement of sulfides by calcite 3 and garnet mineral replacement reactions are dominant processes in rocks of ore stage and post ore stage the ore stage involved the dissolution of coarse and pristine calcite 0 ca0 95mn0 3fe0 2co3 and the precipitation of sulfides and calcite 1 ca0 96mn0 3fe0 1co3 and calcite 2 ca0 96mn0 3fe0 1co3 the sulfide assemblage consists of pyrrhotite sphalerite chalcopyrite galena arsenopyrite cobaltite costibite bi cubanite ag sulfides and au in decreasing order of abundance in episode 1 calcite 1 contains spherical sulfide inclusions while in episode 2 calcite 2 envelopes calcite 1 the replacement of co rich arsenopyrite fe0 75co0 26as1 13s0 83 by relatively co poor arsenopyrite fe0 86co0 15as0 99s0 99 via a coupled dissolution precipitation reaction occurred in episode 2 based on arsenopyrite geothermometry the temperatures for the first and second episode are 650 50 and 450 70 c respectively micro xrf elemental maps of the garnet bearing schist adjacent to the sulfidized marble revealed the sulfidation front where pre ore garnet and amphibole were replaced by pyrrhotite chalcopyrite au biotite and muscovite in the post ore stage calcite 2 was partially replaced by siderite and calcite 3 ca0 94mn0 4fe0 2mg0 1co3 which shows sectoral and oscillatory zoning galena was replaced by calcite 3 as documented by embayed lobate grain boundaries between these minerals and pyrrhotite fe 1 x s x 0 091 0 119 was pervasively replaced by garnet mn1 2fe1 2ca0 6 al2si3o12 the microscale investigations of the mineralization processes in the artemis orebody document the impact of hydrothermal mineral replacement reactions on metal sequestration mineral replacement reactions facilitate the formation of ore deposits and subsequent alteration processes which may lead to the loss of economic value of the deposit

ava analysis and interpretation of a carbonate reservoir northwest java basin indonesia a detailed analysis is performed of amplitude variation with angle ava observations in six common midpoint gathers with reflection points that are over and beside carbonate reefs in the parigi formation in the northwest java basin both empirical analysis and full wavefield modeling of the ava data suggest that the presence of gas affects ava by reducing the bulk density of the reservoir decreasing of the overburden vp vs ratio and by local attenuation caused by gas sieving through the overlying sediments the slopes of ava curves for reflections from the top of the parigi are negative for brine saturation and strongly positive for gas saturation

part i decrepitation and degassing behaviour of quartz up to 1560 c analysis of noble gases and halogens in complex fluid inclusion assemblages stepped heating and crushing experiments have been used to investigate the noble gas and halogen degassing behaviour of quartz in detail samples with diverse character were selected from the eloise and osborne iron oxide copper gold iocg ore deposits and the railway fault 13 km south of the mt isa mine in the proterozoic mt isa inlier of northeast australia quartz has been shown to have a bimodal degassing profile the first degassing mode at temperatures of 700 c is caused by thermally induced mechanical decrepitation of fluid inclusions changes in the br cl i cl ar cl and 40 ar 36 ar composition of gas released at different temperatures up to 700 c can be related to the decrepitation of different types of fluid inclusion observed by microthermometry these variations with temperature permit deconvolution of the complex fluid inclusion assemblages associated with the iocg samples the ultra high salinity multi solid ms and liquid vapour daughter lvd fluid inclusions with a predominantly primary origin decrepitate at higher temperatures than lower salinity liquid vapour lv and monophase m fluid inclusions that have a predominantly secondary origin three of the iocg samples have primary ms and lvd fluid inclusions characterized by molar br cl values of between 0 25 10 3 and 0 66 10 3 i cl between 0 37 10 6 and 5 0 10 6 40 ar 36 ar values of 1000 and low 36 ar concentrations of 0 7 1 0 10 6 cm 3 cm 3 h2o these low values are most easily explained by the involvement of halite dissolution water in iocg genesis one of the iocg samples has br cl of 1 3 2 0 10 3 and i cl of 10 10 6 similar to juvenile magmatic fluids in phanerozoic porphyry copper deposits this sample also has a higher 36 ar concentration of 3 5 10 6 cm 3 cm 3 h2o and a slightly elevated 40 ar 36 ar of 2236 step heating reveals limited and nonsystematic variation within the more homogenous population of lv fluid inclusions from the railway fault the samples have mean values of 8 1 10 3 for br cl 9 4 12 10 6 for i cl 2000 for 40 ar 36 ar and 4 7 4 8 10 6 cm 3 cm 3 h2o for 36 ar concentration the br cl values are similar to those previously reported for basinal brines present in silicic alteration at the mt isa mine and the additional data can be explained by interaction of such a bittern brine with fine grained sedimentary rocks in the sub surface the second mode of quartz degassing occurs between 1200 and 1450 c and releases a greater volume of gas than the first degassing mode several lines of evidence including microscope observations indicate that the gas released at high temperature is also from the fluid inclusion reservoir however its release may be triggered by a metastable phase transition of quartz 1200 c and caution is required in interpretation of the fluid compositions obtained at these temperatures the data provide an improved understanding of fluid inclusion decrepitation behaviour that is different to that obtained in lower temperatures experiments designed by other workers to investigate h isotope fractionation

the guelb moghrein cu au deposit neoarchaean hydrothermal sulfide mineralization in carbonate facies iron formation abstract the guelb moghrein copper gold deposit in the islamic republic of mauritania reopened in 2006 and has produced copper concentrate and gold since then the deposit is hosted in neoarchaean palaeoproterozoic fe mg carbonate dominated metamorphic rocks interpreted as carbonate facies iron formation it forms tabular orebodies controlled by shear zones in the hanging wall and footwall of this meta iron formation copper and gold are hosted in a complex sulfide ore in tectonic breccia replacing fe mg carbonate and magnetite hydrothermal monazite dates the mineralization at 2492 9 ma two types of aqueous fluid inclusions suggest fluid mixing at 0 75 1 80 kbar and 410 c as the mineralization and precipitation mechanism which is temporally coincident with regional retrograde metamorphism at 410 30 c garnet biotite distal alteration zones are enriched in k rb and cu whereas orebodies are depleted in k rb sr and ba the copper gold mineralization at guelb moghrein formed during retrograde shearing in metamorphic rocks and contemporaneous hydrothermal alteration the stable isotope signature of alteration and ore minerals suggest an external crustal fluid source fluids were focused in the reactive and competent meta iron formation potassium alteration magnetite and copper gold mineralization suggest an iocg mineral system akin similar deposits in australia and brazil

modeling the role of sodic alteration in the genesis of iron oxide copper gold deposits eastern mount isa block australia liberation of iron and potassium by widespread postmetamorphic albitization of country rocks was one of the likely contributing processes in the formation of both barren and mineralized magnetite chalcopyrite biotite gold hematite clinopyroxene actinolite apatite ironstones in the cloncurry district of the proterozoic mount isa block whole rock geochemical data indicate nearly immobile al ga ti zr during transformation of a variety of least altered rocks toward albitite the data indicate that the addition of na from a brine to the rock accompanied the loss of fe k ba rb ca sr co v mn pb and zn from those altered rocks and enrichment in the brine but that cu was not systematically stripped from a variety of wall rocks during albitization conversely the formation of metasomatic ironstones the immediate hosts to some cu au ores involves addition of most of the same elements that were lost during albitization the correlation between intensity of alteration its distribution and timing e g in breccias cored by ca 1530 1500 ma granitoids and convergence of all rock types toward magmatic stable isotope values provides strong evidence for a substantial component of igneous derived fluid simulations of the albitization process were carried out isothermally at 550 c and 350 mpa and polythermally from these conditions down to 400 c and 200 mpa using the gibbs minimization method with hch software and the unitherm database both simple fluid rock mixing models and more complicated reactor style algorithms used a range of input fluids from fluids equilibrated fluid with two feldspar granite through to na k ratios consistent with fluid inclusion results and geochemical data for initially unaltered wall rocks the apparent paradox of widespread albitization resulting from fluid released by two feldspar granites can be explained by relatively small shifts away from the k feldspar albite equilibrium curve and even isothermal model fluids derived from two feldspar granites produce albitites in calc silicate rocks outboard of granite proximal k feldspar clinopyroxene skarns matching field patterns those models with fluid na k ratios similar to those of fluid inclusions produced the most realistic alteration assemblages dominated by albite for both isothermal conditions and decreasing temperature which approximate those observed in the field pixe and microthermometric data on fluid inclusions from quartz in two feldspar quartz monzonite and pegmatite at the top of the mount angelay pluton indicate bulk na k molar ratios in the fluid of between 10 and 20 considerably higher than our thermodynamically calculated values for fluid in equilibrium with two feldspar granite of around 3 at 550 c 350 mpa such shifts may have been attained by admixture of magmatic hydrothermal fluid with small amounts of nacl brines trapped along grain boundaries in scapolite bearing calc silicate wall rocks by fluid immiscibility due to high initial co2 contents in the felsic intrusions by contributions from mafic magmas or from dissolution of salt rich layers into the intrusions prior to crystallization and fluid release with increasing amounts of fluid rock interaction in the models the fluids were enriched in k fe and ca approaching compositions observed in fluid inclusions in the ore deposits these fluids reacted with pelitic rocks which are common ore hosts would produce magnetite clinopyroxene biotite actinolite alteration at high temperature similar to the proximal alteration around ore deposits we infer that precipitation of sulfides in the cu au deposits was the result of mixing of cu bearing brine of ultimately magmatic origin but modified extensively via albitization with sulfur bearing fluids or reaction of the brine with sulfur bearing rocks when cu was absent from the initial magmatic fluid barren ironstones may have been the result

carbonate platform evolution from a bioconstructed platform margin to a sand shoal system devonian guilin south china the depositional organization and architecture of the middle late devonian yangdi rimmed carbonate platform margin in the guilin area of south china were related to oblique extensional faulting in a strike slip setting the platform margin shows two main stages of construction in the late givetian to frasnian with a bioconstructed margin evolving into a sand shoal system in the late givetian the platform margin was rimmed with microbial buildups composed mainly of cyanobacterial colonies mostly renalcis and epiphyton these grew upwards and produced an aggradational locally slightly retrogradational architecture with steep foreslope clinoforms three depositional sequences s3 s5 are recognized in the upper givetian strata which are dominated by extensive microbialites metre scale depositional cyclicity occurs in most facies associations except in the platform margin buildups and upper foreslope facies in the latest givetian at the top of sequence s5 relative platform uplift subaerial exposure and associated rapid basin subsidence probably a block tilting effect caused large scale platform collapse and slope erosion to give local scalloped embayments along the platform margin and the synchronous demise of microbial buildups subsequently sand shoals and banks composed of ooids and peloids and a little later stromatoporoid buildups on the palaeohighs developed along the platform margin from which abundant loose sediment was transported downslope to form gravity flow deposits another strong tectonic episode caused further platform collapse in the early frasnian at the top of sequence s6 leading to large scale breccia release and the death of the stromatoporoid buildups siliceous facies banded cherts and siliceous shales were then deposited extensively in the basin centre as a result of the influx of hydrothermal fluids the platform margin sand shoal bank system possibly with gullies on the slope persisted into the latest frasnian until the restoration of microbial buildups four sequences s6 s9 characterized by abundant sand shoal deposits on the margin and gravity flow and hemipelagic deposits on the slope are distinguished in the frasnian strata smaller scale depositional cyclicity is evident in all facies associations across the platform slope basin transect the distinctive depositional architecture and evolution of this yangdi platform are interpreted as having been controlled mainly by regional tectonics with contributions from eustasy environmental factors oceanographic setting biotic and sedimentary fabrics

inversion and interpretation of a 3d seismic data set from the ouachita mountains oklahoma acoustic impedance inversion ai and simultaneous angle dependent inversion sadi of a 3d seismic data set characterize reservoirs of mississippian morrowan age in the triangle zone of the frontal ouachita mountains oklahoma acoustic impedance of the near angle seismic data images the 3d spatial distributions of wapanucka limestone and cromwell sandstone lame parameters density and and sections are derived from the p wave and s wave impedance ip and is sections produced by the sadi lithology is identified from the gamma logs and the vp vs and are interpreted in terms of a hydrocarbon distribution pattern the ip is used to identify high ip regions that are consistent with high sand shale ratio the estimated impedances and derived lame parameter sections are consistent with the interpretation that parts of the wapanucka limestone and cromwell sandstone contain potential gas reservoirs in fault bounded compartments the cromwell sandstone contains the main inferred

the lightning creek sill complex cloncurry district northwest queensland a source of fluids for fe oxide cu au mineralization and sodic calcic alteration the lightning creek cu au prospect is hosted by a cogenetic suite of plutonic i type granitoids the dominant rock type is a porphyritic quartz monzodiorite that is intruded by more fractionated rocks including monzogranite and alkali feldspar granite a series of flat lying sills are interpreted to be late stage differentiates based on their timing mineralogy and chemistry in parts of the prospect there is pervasive sodic calcic alteration pyroxene after amphibole albite after k feldspar and oligoclase of the plutonic rocks this alteration predates sill emplacement and is unrelated to veining or fracturing of any kind the presence of small amounts of carbonate in the altered rocks suggests that the fluids were co2 bearing quartz and feldspar separates from these altered rocks have oxygen isotope compositions similar to those from fresh quartz monzodiorite suggesting that the fluids were hot and of magmatic composition sodium and ca were added and k fe cl and cu were stripped during what is interpreted as an autometasomatic event the sills display considerable textural and mineralogical complexity and evolved from equigranular quartzofeldspathic rocks aplites with magmatic chemistry to unusual fe rich rocks albite magnetite quartz that exhibit a range of bizarre spherulitic textures some of the albite and magnetite in the sills is secondary albite forms pseudomorphs after k feldspar na fe ca alteration along sill margins and within sills at the contacts between different textural zones halos of disseminated magnetite clinopyroxene fe ca na alteration are developed adjacent to early magnetite veins fluid inclusion studies indicate that these rocks crystallized at temperatures in excess of 500 c and at pressures in excess of 1 5 kbar the range of spherulitic textures is taken to indicate crystallization under hydrous conditions with the episodic release of a fluid phase this magmatic fluid phase was dominated by h2o co2 and chlorine and underwent phase separation into a co2 rich vapor and a hypersaline brine 33 55 wt nacl equiv the hypersaline fluid was enriched in fe 10 wt and cu 1 wt pixe analysis in addition to na k and ca where this fluid was retained within fe rich portions of the sills it caused ca fe na alteration pyroxene albite magnetite growth at the expense of quartz where the fluid was expelled from the sills it produced quartz magnetite clinopyroxene albite veins broadly coeval with the early magnetite veins although rich in cu these granitoid derived magmatic fluids did not generate significant cu au mineralization perhaps because of the high temperatures involved and or a lack of reduced sulfur in the fluids or host rock however the amount of iron present is estimated from the aeromagnetic anomaly to be in excess of 2 000 million tonnes mt a later generation of calcite chlorite pyrite chalcopyrite veins contain traces of cu au mineralization fluid inclusion and stable isotope work indicate that these veins probably crystallized from cooler 200 c more dilute 15 28 wt nacl equiv fluids perhaps generated by the admixture of a meteoric component the conclusions reached in this study have implications for understanding the genesis of fe oxide cu au deposits and related sodic calcic alteration the study indicates the potential for co2 rich granitoid magmas to evolve hypersaline fe and cu rich fluids capable of causing intense magnetite veining and cu au mineralization autometasomatic sodic calcic alteration of the granitoids may be an important precursor to mineralization contributing fe k cu and cl to the magmatic fluids

radiogenic and stable isotope constraints on the genesis of the eloise cu au deposit cloncurry district northwest queensland new radiogenic 40ar 39ar and stable oxygen hydrogen and sulfur isotope analyses of metamorphic and metasomatic minerals constrain the age metasomatic evolution and genesis of the eloise cu au deposit 3 1 mt 5 5 cu 1 4 g t au and 16 g t ag biotite from a pre to syn d2 stage vein has an 40ar 39ar age of 1555 4 ma which is interpreted to coincide with a regional metamorphic event synchronous with d2 six later stages of alteration and mineralization are recognized all of which postdate peak metamorphism and d2 stages i to iii are volumetrically the most significant and comprise early albitization stage i quartz hornblende biotite veins and alteration stage ii and cu au mineralization stage iii stages iv v and vi are localized vein events and postdate the main cu au mineralization stage ii vein and alteration hornblendes have 40ar 39ar ages of 1530 3 ma biotite from the same stage has an 40ar 39ar age of 1521 3 ma muscovite from a postore shear zone has an 40ar 39ar age of 1514 3 ma these results provide a maximum ca 1530 ma and minimum ca 1514 ma age for the mineralizing event however the intimate relationship between stage ii mafic silicate veins and alteration and the stage iii cu au event combined with fluid inclusion results which indicate that a cooling evolving high salinity fluid was responsible for both stages suggests that the older age is likely to be closer to the age of mineralization the stage ii biotite age of ca 1521 ma is interpreted to record thermal resetting during postore ductile deformation the results suggest that micas in the cloncurry district are more susceptible to later thermal resetting than amphiboles which may have significant implications for deposits which have only been dated by micas quartz from stages ii iii and iv have 18oquartz values ranging between 10 1 and 11 9 per mil stage ii biotite has a lower 18o composition 5 6 than biotite from a pre d2vein 6 9 but both have identical d compositions 84 stage ii hornblende has lower 18o 6 8 and 7 4 and d 88 and 90 values than does stage iii actinolite 8 0 and 84 respectively the 34s values for chalcopyrite pyrrhotite and pyrite fall in a narrow range between 0 0 and 2 3 per mil a distinct trend can be recognized with 34s values becoming progressively greater from south to north thus reflecting the zoned alteration system magnetite pyrite rich in the south through to pyrrhotite rich in the north the change in mineralogy and sulfur isotope values may be due to cooling and sulfidation processes which resulted in changes in oxygen and sulfur fugacities the oxygen hydrogen and sulfur isotope data combined with high temperature and high salinity fluid inclusion data indicate a predominantly magmatic origin for the ore forming fluids the deposit is interpreted to have formed from magmatic hydrothermal fluids which were tapped by deep seated crustal structures

local to regional scale structural controls on mineralisation and the importance of a major lineament in the eastern mount isa inlier australia review and analysis with autocorrelation and weights of evidence although major crustal lineaments may play an important role in mineralisation the relationship between lineaments and mineral deposits can be quite cryptic and structural controls may vary as a function of scale along lineaments major lineaments alone may be of limited use for detailed target generation the cloncurry lineament in the eastern part of the mount isa inlier is a crustal scale structure defined by potential field derived worms weights of evidence quantifies the association between mineral occurrences and this lineament autocorrelation is used to recognise structural controls on mineralisation at different scales by progressively limiting the lengths of the vectors between mineral occurrence points in the autocorrelation plot the weights of evidence analysis shows that au au cu cu au and cu deposits have a positive spatial correlation to the cloncurry lineament which suggests it that acted as a primary crustal scale control on the localisation of cu and au through focussing mineralisation systems on a broad scale however autocorrelation defines a variety of local structural controls which can be interpreted as shear zones variably oriented fault sets en echelon fault arrays and potentially the orientation of bedding and or iron formations which localise fluid flow and mineral deposition at finer scales the results suggest that major lineaments defined by geophysical contrasts can be used in conjunction with techniques of spatial analysis for targeting structurally controlled mineralisation in areas under thin cover adjacent to mineralised terrains such as the mt isa inlier

tectonic control on peritidal carbonate parasequence formation an investigation using forward tectono stratigraphic modelling studies of quaternary extensional faults indicate that they have instantaneous amounts of throw 0 4 to 4 m average slip rates 0 05 to 2 8 m kyr 1 and frequency of recurrence 40 000 years accounting for the accommodation space required for the accumulation of peritidal carbonate parasequences pcps hangingwall sites and graben are characterized by fault down dropping together with regional subsidence and footwall sites and horsts by fault related uplift alternating with periods of regional subsidence the relative sea level curves generated by these processes operating in a maritime rift setting are used as inputs to a forward stratigraphic modelling program sedtec2000 to simulate how fault related changes in accommodation space can account for high frequency pcp formation each instantaneous fault slip generates a flooding surface or aggradation in hangingwall and graben settings high frequency cycles in hangingwall sites are either symmetric deepening then shallowing upward or asymmetric shallowing upward the major factor controlling cycle types is the balance between rates of carbonate accumulation and generation of accomodation space high frequency cycles in footwall sites and horsts comprise shallow subtidal facies with no distinctive bathymetric trends capped by erosional boundaries generated by footwall uplift the modelled cycles are of the same thickness with bathymetric trends and frequency to cycles commonly interpreted to be due to orbitally driven eustatic sea level changes or autocyclic processes these numerical experiments demonstrate that high frequency pcps can be generated by tectonic fault related processes a hypothesis that is frequently discounted

architecture and depositional sequences of tertiary fault block carbonate platforms an analysis from outcrop miocene gulf of suez and computer modelling abstract this study combines outcrop with seismic data and tectonostratigraphic modelling to characterise the stratigraphy of tertiary fault block carbonate platforms seismic sections from the middle east and southeast asia indicate that carbonate platforms commonly develop on fault blocks in the late syn rift to post rift stage of basin evolution they are characterised by retrogradational or drowning morphologies with deep water clastics evaporites sealing the platforms a new tectono stratigraphic modelling program simulates the development of carbonate platforms on domino style fault blocks and predicts a distinctive tectonic control on the evolving syn rift stratigraphy detailed field work from a three dimensionally exposed miocene syn rift platform from the gulf of suez gebel abu shaar egypt shows the existence of unconformity bound depositional sequences which are predicted by the program and are interpreted to have formed in response to fault block rotation the sequences are characterised by synchronous hangingwall subsidence and footwall uplift and erosion the seismic images the modelling and the outcrop study provide different levels of information on fault block platforms and their characteristic stratigraphy the scale of the modelling is of particular value as it provides a link between the seismic scale imaging and outcrop data

seismic impedance inversion and interpretation of a gas carbonate reservoir in the alberta foothills western canada acoustic and simultaneous elastic impedance inversions of a 2d land seismic data set are performed to characterize a carbonate reservoir of mississippian age in the turner valley formation in the rocky mountain foothills of western canada the inversions produce p wave and s wave impedance sections ip and is respectively from which lame parameter density and sections are derived the ip data provide a separation between the clastics and carbonates the data provide an estimate of porosity distribution within the dolomitized limestone target deviations from baseline curves for water saturated carbonates of versus porosity versus porosity and is versus ip are interpreted as indicators of gas potential these indicators all provide similar spatial patterns of areas of high gas potential and are consistent with the gas occurence observed in a well

reduced and oxidized au cu bi iron oxide deposits of the tennant creek inlier australia an integrated geologic and chemical model iron oxide associated au cu bi deposits of the tennant creek gold field range from magnetite pyrrhotite pyrite reduced cu rich deposits through sulfide poor magnetite rich high grade au bi intermediate f o2 deposits to hematite rich high grade au oxidized deposits discordant magnetite hematite chlorite quartz ironstone bodies that host the ore formed hydrothermally during the 1840 to 1860 ma barramundi orogeny at temperatures up to 350 to 400 c and 2 5 to 5 kbars deposition of ironstone minerals was localized by dilatency that was generated during d1 reverse shearing and folding a separate au cu bi hydrothermal stage overprinted selected ironstones during d2 at or before 1825 to 1830 ma where favorable d1 structures and fluid pathways were reactivated the extremes of the reduced to oxidized deposit spectrum represent divergent chemical conditions that cannot be reconciled by the action of a single fluid we have identified both reducing and oxidizing fluids that helped to form the au cu bi deposits at the west peko deposit which represents the reduced end member subtype constraints from oxide silicate sulfide mineral stabilities fluid inclusions and chlorite thermochemistry indicate that au cu bi ore was introduced into ironstone at 300 to 340 c by a reducing pyrrhotite stable weakly acidic sulfur rich and n2 ch4 rich aqueous fluid containing 3 to 10 wt percent nacl equiv an ore fluid source outside the relatively oxidized metasedimentary host sequence warramunga formation is implied we suggest similar ore fluids for other reduced cu and sulfide rich deposits in the district chemical mass transfer modeling of reactions between reducing fluid and ironstone incorporating estimated thermodynamic properties for aqueous bismuth complexes indicates that highly efficient gold and native bi deposition was predominantly in response to desulfidation and oxidation of the fluid chalcopyrite precipitated mainly in response to increased ph gold bismuth ore in the eldorado deposit an oxidized and hematitic end member is interpreted to have involved mixing of an oxidizing hematite stable ca na cl brine with an intermediate f o2 low to moderate salinity ore fluid as well as reaction of both fluids with ironstone furthermore the mass transfer modeling suggests that mixing of reducing and oxidizing fluids in the absence of ironstones could have resulted in high grade au deposits lacking fe oxides a subtype that has received comparatively little exploration attention in the tennant creek district

contrasting fluids and reservoirs in the contiguous marcona and mina justa iron oxide cu ag au deposits south central peru the marcona mina justa deposit cluster hosted by lower paleozoic metaclastic rocks and middle jurassic shallow marine andesites incorporates the most important known magnetite mineralization in the andes at marcona 1 9 gt at 55 4 fe and 0 12 cu and one of the few major iron oxide copper gold iocg deposits with economic cu grades 346 6 mt at 0 71 cu 3 8 g t ag and 0 03 g t au at mina justa the middle jurassic marcona deposit is centred in ica department peru and the lower cretaceous mina justa cu ag au prospect is located 3 4 km to the northeast new fluid inclusion studies including laser ablation time of flight inductively coupled plasma mass spectrometry la tof icpms analysis integrated with sulphur oxygen hydrogen and carbon isotope analyses of minerals with well defined paragenetic relationships clarify the nature and origin of the hydrothermal fluid responsible for these contiguous but genetically contrasted deposits at marcona early sulphide free stage m iii magnetite biotite calcic amphibole assemblages are inferred to have crystallized from a 700 800 c fe oxide melt with a 18o value from 5 2 to 7 7 stage m iv magnetite phlogopite calcic amphibole sulphide assemblages were subsequently precipitated from 430 600 c aqueous fluids with dominantly magmatic isotopic compositions 34s 0 8 to 5 9 18o 9 6 to 12 2 d 73 to 43 and 13c 3 3 stages m iii and m iv account for over 95 of the magnetite mineralization at marcona subsequent non economic lower temperature sulphide calcite amphibole assemblages stage m v were deposited from fluids with similar 34s 1 8 to 5 0 18o 10 1 to 12 5 and 13c 3 4 but higher d values average 8 several groups of lower 200 c fluids can be recognized in the main polymetallic cu zn pb sulphide stage m v and may record the involvement of modified seawater at mina justa early magnetite pyrite assemblages precipitated from a magmatic fluid 34s 0 8 to 3 9 18o 9 5 to 11 5 at 540 600 c whereas ensuing chalcopyrite bornite digenite chalcocite hematite calcite mineralization was the product of non magmatic probably evaporite sourced brines with 34s 29 18o 0 1 and 13c 8 3 two groups of fluids were involved in the cu mineralization stage 1 ca rich low temperature approx 140 c and high salinity plausibly a basinal brine and 2 na k dominant with a low temperature approx 140 c and low salinity probably meteoric water la tof icpms analyses show that fluids at the magnetite pyrite stage were cu barren but that those associated with external fluids in later stages were enriched in cu and zn suggesting such fluids could have been critical for the economic cu mineralization in andean iocg deposits

fluid inclusions with nacl cacl2 h2o composition from the cloncurry hydrothermal system nw queensland australia abstract fluid inclusions whose composition can be approximated by the ternary system nacl cacl 2 h 2 o are common in the fe oxide cu au deposits and associated alteration in the cloncurry hydrothermal system nw queensland australia detailed microthermometric work indicates that a multi staged cacl 2 bearing fluid trapping was involved during the formation of mineralization and alteration the fluid evolution history is characterized by early high temperature and low salinity to late low temperature and high salinity which is distinct from many intrusion related hydrothermal systems in the world the ubiquitous presence of low temperature t h 2 bearing inclusions is a remarkable feature of the mid proterozoic cloncurry hydrothermal system and it is interpreted to be a result of the interaction between evaporites and downward penetration of meteoric water the transition from early magmatic and or metamorphic fluids to late meteoric water is ascribed to the shift of the crustal level during exhumation despite the controversies over the mechanisms of mineralization fluid mixing demonstrated by the rapid drop in temperature through addition of cooler meteoric water into the hydrothermal system must have played a significant role with regard to the metal precipitation in some deposits of this type

petrogenesis of the squirrel hills granite and associated magnetite rich sill and vein complex lightning creek prospect cloncurry district northwest queensland the lightning creek fe oxide cu au prospect is hosted within a mesoproterozoic granitoid batholith composed dominantly of high k calc alkaline porphyritic quartz monzodiorite the quartz monzodiorite contains enclaves of quartz diorite and has been intruded by more felsic granitoids monzogranite and alkali feldspar granite and a series of subhorizontal sills the quartz monzodiorite crystallised at crustal depths in excess of 10 km pnot vert similar4 kb t 800 850 c melt xh2o 4 wt fo2not vert similarnno buffer and was probably fluid saturated xh2o xco2 of 0 5 as might be expected the more fractionated granitoids crystallised at progressively lower temperatures quartz monzonite not vert similar800 c alkali feldspar granite 2 5 kb and temperatures greater than 500 c phase separation occurred in the fluid phase producing in a co2 rich vapour and a metal rich fe cu brine

low latitude meteoric fluid flow along the cloncurry fault cloncurry district nw queensland australia geodynamic and metallogenic implications hydrothermal alteration within the mount isa block mib is typically largely to have ceased at the end of the isan orogeny ca 1 50 ga however late large brittle quartz rich vein systems including those of the cloncurry fault cut mesoproterozoic tectonic fabrics intrusions and products of regional na ca hydrothermal alteration associated features display affinities to iron oxide cu au ore deposits including specular hematite bearing veins and cu au u lree ba mineralization stable isotope data suggest late veins in the vicinity of the cloncurry fault eastern fold belt efb formed from fluids with 18oh2o and dh2o 250 c of 4 to 3 and 22 to 4 respectively the high dh2o moderate 18oh2o and cacl2 nacl rich character of the saline fluids indicates they were mixtures of low latitude meteoric fluids and evaporite derived basinal brines which with time became progressively dominated by meteoric water deposited barite and cooled the low latitude meteoric signature demonstrates that the fault fracture systems were active when in equatorial regions paleomagnetic data for the mib and the australian protocontinent together with structural and thermal considerations and geochronological arguments suggest the veins probably formed sometime after 1 10 ga and potentially as late as during the alice springs orogeny ca 0 34 ga the late quartz veining was unrelated to two phases of regional na ca alteration and economically significant fe oxide cu au mineralization at 1 60 1 58 and 1 53 1 50 ga

the aitik cu au ag deposit in northern sweden a product of high salinity fluids the aitik cu au ag deposit is located in northern sweden and is hosted by strongly deformed 1 9 ga svecofennian volcano sedimentary rocks the main copper mineralization which occurs as disseminations and veinlets is hosted by garnet biotite schist subeconomic mineralization in the footwall to the ore is hosted by feldspar biotite amphibole gneiss and porphyritic quartz monzodiorite the deposit has been affected by post mineralization metamorphic and igneous activity fluid inclusions in six samples of copper mineralized quartz veins record the presence of three different fluid populations the main ore was deposited from an aqueous highly saline 31 37 eq wt nacl cacl2 fluid this fluid was trapped in inclusions intimately associated with the main chalcopyrite mineralization later bornite deposition took place from a less saline 18 27 eq wt nacl cacl2 aqueous fluid a third fluid composed of almost pure co2 interacted with the copper rich system during a post ore event the aitik cu au ag deposit shares some features with both porphyry type and fe oxide cu au deposits a high calcium content of the ore fluids similar to other cu au deposits in northern scandinavia suggests a contribution to the salinity of the mainly magmatic hydrothermal fluids from evaporitic rocks in stratigraphically lower units

modification of a palaeoproterozoic porphyry like system integration of structural geochemical petrographic and fluid inclusion data from the aitik cu au ag deposit northern sweden the aitik cu au ag deposit in the gallivare area in northern sweden is sweden s largest sulphide mine with an annual production of 35 mt of ore and the biggest open pit operation in northern europ

chemical and stable isotopic characteristics of syn tectonic tourmaline from the western fold belt mount isa inlier queensland australia abstract understanding hydrothermal fluid flow events related to orogenic events is important because they provide large scale redistribution of metals which may become concentrated in ore deposits in this study we determine the origin of tourmaline bearing quartz veins and pegmatites in the western fold belt of the proterozoic mount isa inlier a region which host numerous syn orogenic cu deposits this paper uses tourmaline mineral chemistry and isotopic analyses in situ b and bulk o and h isotopes to fingerprint the fluid reservoirs that contributed to the fluid budget during the isan orogeny all the tourmaline samples have schorl dravite solid solution compositions quartz tourmaline 18 o 11 0 12 6 and 7 7 9 4 v smow respectively pairs yield equilibrium formation temperatures of 305 to 575 c with the higher temperatures related to pegmatitic tourmaline tourmaline d values have a relatively narrow range from 68 to 56 v smow in most cases calculated 18 o fluid and d fluid values are compatible with primary magmatic water with a small component of metamorphic 18 o enriched formation waters however there are large variations in tourmaline 11 b values which range from 10 7 to 17 0 with the majority of values between 10 and 15 variations in 11 b tur in the pegmatites suggest that boron degassing generated relative 11 b depletion during crystallization similar 11 b tur values in quartz tourmaline veins spatially associated with the pegmatites in cordierite and sillimanite bearing metamorphic rocks west of the mount isa fault demonstrate a similar origin for b in this tourmaline in contrast quartz tourmaline veins of similar timing hosted by greenschist grade metamorphic rocks east of the mount isa fault have much higher 11 b tur values 6 2 to 10 7 which reflect the involvement of a distinct b isotopic reservoir mostly likely a near surface derived evaporitic brine thus the b isotopic data reveal important differences in fluid origin that are not reflected in the 18 o values therefore at least two isotopically distinct fluids one sourced from fractionating anatectic pegmatites and the other from external basinal brines circulated contemporaneously in separate areas during the isan orogeny there is no evidence based on the tourmaline isotopic data to suggest that these fluids mixed which demonstrates that the hydrothermal plumbing system in the western fold belt during the isan orogeny was disconnected probably due to differences in thermal structure metamorphic grade across the western fold belt during orogenesis

mixed messages in iron oxide copper gold systems of the cloncurry district australia insights from pixe analysis of halogens and copper in fluid inclusions proterozoic rocks of the cloncurry district in nw queensland australia are host to giant tens to hundreds of square kilometers hydrothermal systems that include 1 barren regional sodic calcic alteration 2 granite hosted hydrothermal complexes with magmatic hydrothermal transition features and 3 iron oxide copper gold iocg deposits fluid inclusion microthermometry and proton induced x ray emission pixe show that iocg deposits and the granite hosted hydrothermal complexes contain abundant high temperature ultrasaline complex multisolid type 1 inclusions that are less common in the regional sodic calcic alteration the latter is characterized by lower salinity three phase halite bearing type 2 and two phase type 3 aqueous inclusions copper contents of the type 1 inclusions 300 ppm is higher than in type 2 and 3 inclusions 1 000 ppm are found both in the granite hosted systems and in inclusions with br cl ratios that are consistent with a magmatic source the br cl ratios of the inclusions with lower cu contents are consistent with an evaporite related origin wide ranges in salinity and homogenization temperatures for fluid inclusions in iocg deposits and evidence for multiple fluid sources as suggested by halogen ratios indicate fluid mixing as an important process in iocg genesis the data support both leaching of cu by voluminous nonmagmatic fluids from crustal rocks as well as the direct exsolution of cu rich fluids from magmas however larger iocg deposits may form from magmatic derived fluids based on their higher cu content

development and controlling factors of miocene carbonate platform in the nam con son basin southwestern south china sea miocene carbonate platforms are located on intrabasinal structural highs and along the southern margin of the nam con son basin also referred to as the wanan basin by chinese southwestern south china sea these isolated platforms together cover a gross area of over 25 000 km 2 we map the platforms reconstruct their evolution and evaluate the controls on platform growth and demise within the regional geological setting using available seismic and well data the platforms initiated in the late early miocene and reached their widest extent during the middle miocene the platform margins were controlled by synsedimentary faults associated with carbonate slope failure deposits and or reef talus the platforms formed as isolated platform platform growth history involves six phases start up second start up keep up exposure renewal and drowning phases quantitative analysis of the basin evolution indicates that tectonism eustasy the supply of both terrigenous sediment and nutrients were the dominant controls on platform development and demise c 2013 elsevier ltd all rights reserved

an unusual poriferan community in the albian of islares north spain palaeoenvironmental and tectonic implications abstract the discovery of a well preserved lower cretaceous siliceous sponge community in islares cantabria north spain is documented lower albian sponges crop out in great abundance as a rich necrocoenosis embedded in a marly matrix demosponges make up the bulk of an 11 m thick succession which is interpreted as having formed in a slope setting the sponges show body preservation and were buried in situ all types of growth forms are present they grew so tightly that they often fused secondarily shape polarity suggests steady low energy predominantly easterly palaeocurrents the main factor limiting the community seems to have been space competition a preliminary documentation of the systematic palaeontology is presented only taxa from the families tetracladinidae megamorinidae and corallistidae were found geometrical restoration of the platform basin transect allows estimation of a depth of approximately 40 m for the lithistid sponges sea level variations driven by block faulting controlled the available accommodation space sponges occur just below and above a sequence boundary and are associated with a major tectonic event linked with the opening of the bay of biscay

carbonate platform growth influenced by contemporaneous basaltic intrusion albian of larrano spain carbonate platform growth in active tectonic settings may be strongly influenced by the structural evolution of the basin including volcanic activity in this paper the sedimentary tectonic evolution of the duranguesado carbonate platform larrano in northern spain is described and an evolutionary depositional model is presented the albian duranguesado carbonate platform deposits are dominated by rudist and coral limestones with small intervening argillaceous limestone filled troughs 10 30 m deep the platform succession is divided into two parts the lower platform deposits were intruded by volcanics and tilted before the deposition of the upper platform succession a volcanic vent plug filling an upward flaring pipe occurs in the lower carbonate platform succession the timing of intrusion is well constrained to the early albian tectonic extension and active deep seated strike slip faults induced magma ascent at a fault intersection sedimentological analysis of these areas indicates that before volcanic intrusion they acted as weakened zones of extension and were slightly more subsident basinal areas these sites contain anomalous accumulations of siliceous sponge spicule deposits linked to the release of hydrothermal fluids on the sea floor after the phase of intrusion tilting and erosion of the platform and its associated volcanic products occurred as the intrusion cooled the platform downwarped leading to the formation of an overlying perched capping basin bordered by carbonate platforms over the volcanic plug carbonate mounds grew on local palaeohighs the presence of strike slip and magma emplacement in the duranguesado platform is related to movements between the iberian and european lithospheric plates which were accommodated by rotation and lateral movement of the crust along wrench faults

hydrothermal alteration associated with magnetite mineralization in the bafq iron deposits iran abstract bafq mining district bmd is an iron mineralization province that contains more than 2 gt of iron ore located in the early cambrian volcano plutonic arc known as the kashmar kerman zone the host rocks of the fe mineralization are granitic and microgranitic rocks and their extrusive equivalents field observations and petrographic studies showed that both sodic and calcic alteration are related to iron mineralization other alteration styles including silicic chlorite epidote and sericite alteration are less important and post dated the mineralization sodic alteration is associated with the formation of chessboard albite whereas the calcic alteration is featured by a mineral assemblage of actinolite tremolite magnetite apatite available evidence suggests that the involved metasomatic fluids could be mainly of evaporitic sources with a minor contribution from magmatic fluids we suggest that mineralization formed at the end of the precambrian in pull apart basins in a magmatic back arc region associated with subduction of the proto tethys oceanic crust under central iranian plate iron ore mineralization may be related to the interaction of granite derived hydrothermal fluids and brine derived fluids sourced from the latest precambrian rizu and dezu evaporitic sequences

a fluid inclusion study of the suicide ridge breccia pipe cloncurry district australia implication for breccia genesis and iocg mineralization abstract the suicide ridge barren breccia pipe 1527 4 ma is one of numerous breccia occurrences that characterize the cloncurry district australia interest in breccia systems in the cloncurry district is related to their possible link with iron oxide copper gold deposits the suicide ridge barren breccia pipe is temporally and spatially associated with a granite that outcrops at its southwestern boundary and which is ascribed to the williams and naraku magmatic event ca 1550 1500 ma the breccia is characterized by clasts of variable dimensions degree of rounding and composition that includes dominant calc silicate clasts of the corella formation that underlie rocks of the soldiers cap group that host the pipe indicating a dominant upward transport of the fragments other breccia fragments include granite bodies characterized by albite quartz mineralogy and textures typical of the magmatic hydrothermal transition these rocks are interpreted to have formed in a fractionated granite carapace during the exsolution and accumulation of volatiles associated with the cooling magma two dominant types of inclusions have been identified at the suicide ridge barren breccia pipe these include early primary and pseudosecondary carbonic fluid inclusions observed only in magmatic hydrothermal transitional textures of granite breccia clasts and secondary sodic calcic brine inclusions that occur in all the collected samples variable homogenization temperatures in the primary and pseudosecondary pure co2 fluid inclusions indicate that they were trapped under different pressure conditions pressures estimated from the primary co2 fluid inclusions suggest that they were trapped at 4 2 kbar at least 1 kbar above the inferred lithostatic pressure this likely represents the overpressuring produced by release of co2 rich volatiles during the crystallization of magma and which ultimately caused the subsequent brecciation estimated pressures for pseudosecondary co2 fluid inclusions indicate pressure entrapment conditions around 2 7 kbar similar to the lithostatic pressure and 1 5 kbar lower than pressures recorded by type ia fluid inclusions this significant drop of pressure likely represents the sudden pressure depression occurring in response to brecciation evidence from field relationships breccia characteristics mineralogy and textures of granite clasts within the pipe and fluid inclusion studies support an origin of the suicide ridge barren breccia pipe in response to overpressuring generated by the release expansion and possibly phase separation of fluids of dominant carbonic composition from a crystallizing magma beneath and adjacent to the pipe sodic calcic fluid inclusions represent a later influx of fluids in the breccia system that produced widespread albitization significantly high temperature ultrasaline multisolid fluid inclusions abundant in iocg deposits and considered to be samples of the mineralizing fluid were not observed at the suicide ridge breccia pipe their absence in the barren systems suggests that they were critical for the formation of iocg deposits

a dominant tectonic signal in high frequency peritidal carbonate cycles a regional analysis of liassic platforms from western tethys abstract meter scale peritidal carbonate cycles are a common feature of the geological record but debate continues about what processes lead to their formation three conceptual models or a combination thereof are commonly invoked to explain cycle formation eustasy tectonics or autocyclicity these three models are tested with a large new dataset from different early jurassic plate margins from western tethys study of seven logged sections from spain italy greece tunisia morocco and gibraltar enables an analysis of the possible roles of local versus regional patterns and controls on cyclicity within a sinemurian time slice cycle types are diverse and include shallowing upward cycles parasequences but also deepening upward and diagenetic cycles high frequency sequences and subtidal cycles numbers of cycles per section and cycle stacking patterns within this time slice vary from section to section statistical tests runs tests time series and bundling all indicate random stacking of cycles within sections and an absence of any bundling of thicknesses or of facies trends assessment of cycle types by their occurrence and stacking patterns indicates little support for either eustasy or autocyclicity being the dominant cycle forming mechanism however the variability in numbers of cycles per section thickness variations of the sections cycle type variability and randomness of stacking patterns all favor a pulsed tectonic control for the creation and filling of accommodation space this conclusion is further supported by evidence that has largely arisen during the course of this study of syndepositional extensional tectonics in the sinemurian on these rifted tethyan margins although tectonics appears to be the dominant control superimposed eustasy and or autocyclic processes cannot be discounted

structure of the isan orogeny under cover to the east of the mount isa inlier revealed by multiscale edge analysis and forward and inverse modelling of aeromagnetic data aeromagnetic data reveals the presence of three north south orientated tens of kilometre scale elliptical structures under cover to the east of the mount isa inlier in queensland australia the holy joe creek boot creek and nora creek structures are typically defined by three narrow continuous magnetic ridges highly magnetically susceptible amphibolite bodies similar to those exposed in the inlier are probably the source of most of these magnetic anomalies multiscale edge analysis 2d forward modelling and 3d inverse modelling methods have been used to resolve the geometry and near surface dip of the structures these techniques indicate that the structures dip moderately to steeply around their edges the holy joe creek structure exhibits sub vertical to steeply west dipping sides and a moderate plunge around the northern closure the boot creek and nora creek structures are more complex magnetically but their eastern edges also have sub vertical to steep westerly dips diapirism and domes in an egg box style type 1 fold interference pattern are considered as possible origins for the elliptical structures however disparity between the shape of the structures and possible diapiric bodies and the lack of complementary basin structures to the domes makes these two explanations unlikely a more plausible alternative is that the structures are the result of deformation in a single phase producing folds with a variable hinge line plunge these results indicate that east west shortening during the d2 event of the isan orogeny was the major deformation in the buried rocks of the study area suggesting a shared structural history with the mount isa inlier to the west

growth of syndepositional faults in carbonate strata upper permian capitan platform new mexico usa abstract the upper permian capitan platform new mexico is cut by syndepositional faults and fractures these are parallel to platform margin and cluster within strata that steepen and thicken abruptly into the basin faults are steep dip slip have measurable displacements of up to 24 m are typically associated with growth strata and mostly tip out blindly within the platform basinward throwing faults are typically reverse and are steeper than shelfward throwing faults which have normal geometry the sense of displacement across some initially basinward throwing faults changed as they developed these patterns indicate that faults were rotated as they grew synkinematic rotation of faults is interpreted to have occurred due to syndepositional compaction driven down to basin tilting of the capitan platform faults grew through interaction with inherited fractures and by segment linkage vertically separated fault segments had a tendency to grow downward to link with underlying segments thus promoting accumulation of displacement across faults without vertical propagation of fault tips four fault types are distinguished on the basis of structures associated with their upper terminations i faults breaking free surface ii faults tipping out within non folded growth strata iii faults tipping out below growth monoclines and iv buried faults with no expression on free surface fault tips evolved from one type into another in response to variations in the rates of fault growth and deposition fault tip structures also vary laterally over distance of 750 1400 m inferably as a result of variable distances from fault centres

metamorphic fluid origins in the osborne fe oxide cu au deposit australia evidence from noble gases and halogens the osborne iron oxide copper gold iocg deposit is hosted by amphibolite facies metasedimentary rocks and associated with pegmatite sheets formed by anatexis during peak metamorphism eleven samples of ore related hydrothermal quartz and two pegmatitic quartz feldspar samples contain similarly complex fluid inclusion assemblages that include variably saline 12 65 wt salts aqueous and liquid carbon dioxide varieties that are typical of iocg mineralisation the diverse fluid inclusion types present in each of these different samples have been investigated by neutron activated noble gas analysis using a combination of semi selective thermal and mechanical decrepitation techniques ore related quartz contains aque ous and carbonic fluid inclusions that have similar 40 ar 36 ar values of between 300 and 2 200 the highest salinity fluid inclusions 47 65 wt salts have calculated 36 ar concentrations of approximately 1 5 ppb which are more variable than air saturated water asw 1 3 2 7 ppb these fluid inclusions have extremely variable br cl values of between 3 8 10 3 and 0 3 10 3 and i cl values of between 27 10 6 and 2 4 10 6 all ratios are molar fluid inclusions in the two pegmatite samples have similar 40 ar 36 ar values of 1 700 and an overlapping range of br cl and i cl values high salinity fluid inclusions in the pegmatite samples have 2 5 21 ppb 36 ar that overlap the range determined for ore related samples in only one case the fluid inclusions in both sample groups have 84 kr 36 ar and 129 xe 36 ar ratios that are mainly in the range of air and air saturated water and are similar to mid crustal rocks and fluids from other settings the uniformly low 40 ar 36 ar values 2 200 and extremely variable br cl and i cl values do not favour a singular or dominant fluid origin from basement or mantle derived magmatic fluids related to a type magmatism instead the data are compatible with the involvement of metamorphic fluids that have interacted with anatectic melts to variable extents the metamorphic fluids probably represent a mixture of 1 inherited sedi mentary pore fluids and 2 locally derived metamorphic volatilisation products the lowest br cl and i cl values and the ultra high salinities are most easily explained by the dissolution of evaporites the data demonstrate that externally derived magmatic fluids are not a ubiquitous component of iocg ore forming systems but are com patible with models in which iocg mineralisation is localised at sites of mixing between fluids of different origin

depositional architecture of a rimmed carbonate platform albian gorbea western pyrenees a lower cretaceous carbonate platform depositional system with a rimmed margin and an adjacent oversteepened slope was analysed in order to determine its depositional architecture and major depositional controls the platform is made up of coral rudist orbitolinid and algal limestones and in a 12 km dip transect there is a gradation from lagoon to platform margin slope and basin environments each characterized by distinctive sedimentological features and facies associations the rimmed platform is an aggradational system developed during approximately 4 2 million years of fluctuating relative sea level rise and it is bounded by unconformities at its base and top internal cyclicity in the construction of the system is evident mainly in platform interior and slope settings the seven recognized sequences average 0 6 million years in duration and are related to minor relative sea level changes carbonate deposition occurred in shallow and deep water settings during periods of high relative sea level reduced rates of sea level rise led to the development of shallowing upward sequences and eventually to the exposure of the shallowest parts of the platform during relative sea level falls during low relative sea level erosion surfaces developed on the slope and gravitational resedimentation occurred at the toe of slope basinwards resedimented units pinch out over distances of a few hundred metres active faults controlled sedimentation at the platform margin promoting the development of steep slopes up to 35 and preventing progradation of the shallow water platform despite high sediment production rates the development of sequences is interpreted to be related to tectonic activity

mid crustal fluid mixing in a proterozoic fe oxide cu au deposit ernest henry australia evidence from ar kr xe cl br and i fluid inclusions in six quartz veins associated with cu au mineralisation at the giant ernest henry iron oxide copper gold deposit 167 mt 1 1 cu 0 54 ppm au in northwest queensland have been analysed for naturally occurring and neutron produced noble gas isotopes of ar kr and xe a combination of thermal and mechanical decrepitation methods enables distinction between four types of fluid inclusion ultra high salinity 30 to 70 wt nacl eq fluid inclusions have compositions that define two end members that are variably mixed in different samples the first end member has a 40 ar 36 ar value of 29 000 a 40 are cl value of 3 10 3 and mantle like br cl and i cl values of 1 2 10 3 and 11 10 6 respectively the second end member has a much lower 40 ar 36 ar value of less than 2500 a 40 are cl value of 10 6 low br cl values of 0 4 10 3 and i cl values of 1 2 10 6 all ratios are molar carbon dioxide and later lower salinity liquid vapour fluid inclusions have similar 40 ar 36 ar values of less than 2500 in all samples these data are compatible with genetic models in which cu au mineralisation formed at a depth of 6 10 km from circulation of magmatic fluids derived from regionally abundant a type granites and a high salinity halite dissolution brine generated from sedimentary formation waters in the upper crust the largest source of co2 was probably carbonate rich lithologies in the midcrust later lower salinity fluids with a surficial origin diluted the mineralising brines and are preserved in the latest secondary fluid inclusions these data provide insight on the composition of crustal fluids during the proterozoic furthermore the magmatic fluid endmember derived from melts generated by re melting lower crustal paleoproterozoic igneous rocks with a mantle source preserves mantle like br cl and i cl these geochemical characteristics are interpreted to provide insight on i recycling at subduction zones and the composition of seawater in the paleoproterozoic 2007 elsevier b v all rights reserved

part ii evaluation of 40ar 39ar quartz ages implications for fluid inclusion retentivity and determination of initial 40ar 36ar values in proterozoic samples the argon isotope systematics of vein quartz samples with two different k reservoirs have been evaluated in detail potassium is hosted by ultra high salinity fluid inclusions in quartz samples from the eloise and osborne iron oxide copper gold iocg deposits of the mt isa inlier australia in contrast k is hosted by accidentally trapped mica within lower salinity fluid inclusions of a sample selected from the railway fault 13 km south of the mt isa copper mine australia imprecise apparent ages have been obtained for all of the samples studied and conclusively demonstrate that quartz fluid inclusions are retentive to ar and have not leaked over billions of years iocg samples that host k in fluid inclusions only have k cl values of 1 and the ages obtained represent the maximum ages for mineralization in contrast the railway fault samples that include accidentally trapped mica have k cl values of 1 excess 40 are plus cl hosted by fluid inclusions and radiogenic 40 arr plus k are strongly correlated in these samples and define a plane in 3d 40 ar 36 ar k cl space in this case the plane yields an excess 40 are corrected age of 1030 ma that is 100 s of ma younger than nearby cu mineralization at mt isa the age is interpreted to reflect 40 ar loss from the accidentally trapped mica into the surrounding fluid inclusions and is not related to the samples age of formation the initial 40 ar 36 ar value of fluid inclusions is widely used to provide information on fluid origin for the iocg samples that host k in fluid inclusions only the initial 40 ar 36 ar values are close to the measured values at every temperature of stepped heating experiments for samples that include accidentally trapped mica the correction for post entrapment radiogenic 40 arr production is significant furthermore because 39 ark present in accidentally trapped mica crystals is released at different temperatures to radiogenic 40 arr lost to the surrounding fluid inclusions intra sample 40 ar 36 ar variation cannot be reliably documented the results demonstrate that noble gas analysis is readily applicable to proterozoic or older samples but that if k mineral impurities are present within quartz the abundance of k must be determined before calculation of mean 40 ar 36 ar values that are

fluid inclusion and isotopic constraints on the origin of the paleoproterozoic yinachang fe cu ree deposit southwest china the yinachang deposit in the kangdian fe cu metallogenic province southwest china contains approximately 20 mt ore 41 9 to 44 5 wt fe and 15 mt ore 0 85 to 0 97 wt cu with potentially significant rees orebodies are hosted in the late paleoproterozoic dongchuan group and consist mainly of massive and banded replacement ores the paragenetic sequence of this deposit includes pre ore na fe alteration stage i fe ree mineralization dominated by magnetite and siderite with subsidiary apatite and fluorite stage ii and cu ree mineralization with chalcopyrite ankerite biotite and subordinate apatite fluorite allanite and synchysite stage iii this sequence is similar to those of many iron oxide copper gold iocg deposits elsewhere there are two distinct types of fluid inclusions within apatite of both stages ii and iii type 1 fluid inclusions with liquid and vapor phases have relatively low homogenization temperatures 98 345 c and salinities 4 7 16 2 wt nacl equiv whereas type 2 fluid inclusions with one or more solid phases a liquid phase and a vapor phase have higher homogenization temperatures 273 500 c and salinities 36 2 59 8 wt nacl equiv fluids in sulfur isotope equilibrium with chalcopyrite of stages iii have 34 s cdt values ranging from 2 8 to 2 7 consistent with a magmatic origin for the sulfur thus sulfur isotopie compositions imply that magmatic hydrothermal fluids probably represented by the hot and saline type 2 fluid inclusions were involved in the ore forming process although 34 s close to 0 might also mean that sulfur was leached from igneous rocks by nonmagmatic fluids siderite of stage ii and ankerite of stage iii have 13 c pdb values ranging from 12 4 to 7 5 and from 8 5 to 4 4 respectively the large variation of 13 c pdb values reveals a strong interaction between the magmatic hydrothermal fluids and the dolostone in the ore hosting sequence calculated 18 o smow values of the fluids in stages ii and iii are broadly similar and vary from 11 1 to 17 1 avg 13 5 such values are higher than that of magmatic hydrothermal fluids and thus may indicate extensive fluid wall rock interaction and or mixing of magmatic hydrothermal fluids with shallow level nonmagmatic fluids this interpretation is consistent with the radiogenic sr isotope compositions of bulk ores 87 sr 86 sr i 0 710404 0 734034 and fluorite separated from ores 87 sr 86 sr i 0 709851 0 723658 these nonmagmatic fluids are probably representative of the type 1 fluid inclusions bulk ores and mineral separates have nd t values ranging from 8 1 to 0 4 mostly 0 9 to 0 4 similar to the coeval mafic intrusions in the region 2 0 to 2 8 this similarity suggests that rees in the yinachang deposit might have been derived dominantly from mantle derived magmas on the other hand relatively low nd t values 5 5 and 8 1 of some samples indicate insignificant ree contributions from wall rocks the yinachang deposit is temporally associated with regional mantle derived mafic magmatism and may have a genetic relationship with it fluids derived from deep seated magmas may have supplied abundant sulfur and carbon as well as some of the ore metals in this deposit the mafic magmatism could also have provided heat to induce the shallow level nonmagmatic fluids to interact with the sedimentary volcanic sequence thus leaching additional ore metals into the ore forming system fluid mixing can effectively trigger saturation and deposition of ore minerals our work highlights that nonmagmatic fluids are not a prerequisite for cu au ree mineralization but may facilitate metal deposition in magmatic hydrothermal iocg systems

mineralogical and chemical evolution of the ernest henry fe oxide cu au ore system cloncurry district northwest queensland australia the ernest henry cu au deposit was formed within a zoned post peak metamorphic hydrothermal system that overprinted metamorphosed dacite andesite and diorite ca 1740 1660 ma the ernest henry hydrothermal system was formed by two cycles of sodic and potassic alteration where biotite magnetite alteration produced in the first cycle formed ca 1514 24 ma whereas paragenetically later na ca veining formed ca 1529 11 8 ma these new u pbtitanite age dates support textural evidence for incursion of hydrothermal fluids after the metamorphic peak and overlap with earlier estimates for the timing of cu au mineralization ca 1540 1500 ma a distal to proximal potassic alteration zone correlates with a large up to 1 5 km k fe mn ba enriched alteration zone that overprints earlier sodic alteration mass balance analysis indicates that k fe mn ba alteration largely produced during pre ore biotite and magnetite rich alteration is associated with k rb cl ba fe mn and as enrichment and na ca and sr depletion the aforementioned chemical exchange almost precisely counterbalances the mass changes associated with regional na ca alteration this initial transition from sodic to potassic alteration may have been formed during the evolution of a single fluid that evolved via alkali exchange during progressive fluid rock interaction cu au ore dominated by co precipitated magnetite minor specular hematite and chalcopyrite as breccia matrix forms a pipe like body at the core of a proximal alteration zone dominated by k feldspar alteration both the core and k feldspar alteration overprint na ca alteration and biotite magnetite k fe alteration ore was associated with the concentration of a diverse range of elements e g cu au fe mo u sb w sn bi ag f ree k s as co ba and ca mineralization also involved the deposition of significant barite k ba feldspar calcite fluorite and complexly zoned pyrite the complexly zoned pyrite and variable k ba feldspar versus barite associations are interpreted to indicate fluctuating sulphur and or barium supply together with the alteration zonation geochemistry and overprinting criteria these data are interpreted to indicate that cu au mineralization occurred as a result of fluid mixing during dilation and brecciation in the location of the most intense initial potassic alteration a link between early alteration na ca and k fe and the later k feldspathization and the cu au ore is possible however the ore related enrichments in particular elements especially ba mn as mo ag u sb and bi are so extreme compared with earlier alteration that another fluid possibly magmatic in origin contributed the diverse element suite geochemically independently of the earlier stages structural focussing of successive stages produced the distinctive alteration zoning providing a basis both for exploration for similar deposits and for an understanding of ore genesis

c o h n fluids circulations and graphite precipitation in reactivated hudsonian shear zones during basement uplift of the wollaston mudjatik transition zone example of the cigar lake u deposit abstract graphitic shear zones are spatially associated with unconformity related uranium deposits that are located around the unconformity between the strata of the paleo to mesoproterozoic athabasca basin saskatchewan canada and its underlying archean to paleoproterozoic basement the present study focuses on basement hosted ductile brittle graphitic shear zones near the cigar lake u deposit one of the largest unconformity related u deposits the goal of the study is to decipher the pre athabasca basin fluid migration history recorded within such structures and its potential role on the formation of such exceptional deposit dominantly c o h n metamorphic fluids have been trapped in fluid inclusion planes fips in magmatic quartz within ductile brittle graphitic shear zones active during retrograde metamorphism associated with the formation of the wollaston mudjatik transition zone wmtz between ca 1805 and 1720 ma such fluids show a compositional evolution along the retrograde path from a dense and pure co2 fluid during the earliest stages through a lower density co2 ch4 n2 h2o fluid and finally to a very low density ch4 n2 fluid statistical study of the orientation distribution proportion and chemical characterization of the fips shows that i co2 13cco2 around 9 pdb from decarbonation reactions and or partial water metamorphic graphite equilibrium initially migrated regionally and pervasively under lithostatic conditions at about 500 to 800 c and 150 to 300 mpa such p t conditions attest to a high geothermal gradient of around 60 to 90 c km probably related to rapid exhumation of the basement or a large scale heat source ii later brittle reactivation of the shear zone at around 450 c and 25 50 mpa favored circulation of co2 ch4 n2 h2o fluids in equilibrium with metamorphic graphite 13cco2 around 14 under hydrostatic conditions and only within the shear zones cooling of these fluids and the water uptake linked to fluid basement rock reactions led to the precipitation at around 450 c of poorly crystallized hydrothermal graphite this graphite presents isotopic 13c 30 to 26 pdb and morphological differences from the high t metamorphic graphite 600 c 29 to 20 13c derived from metamorphism of c rich sedimentary material the brittle structural reactivation and the related fluid migration and graphite precipitation were specifically focused within the shear zones and related damage zones the brittle reactivation produced major changes in the petro physical mineralogical and chemical characteristics of the structures and their damage zones it especially increased the fracture paleoporosity and rock weakness toward the fault cores these major late metamorphic modifications of the graphitic shear zones were likely key parameters favoring the enhanced reactivity of these basement zones under tectonic stress following deposition of the athabasca basin and so controlled basinal brine movement at the basin basement interface related to the formation of the unconformity related uranium deposits this relationship consequently readily explains the specific spatial relationships between unconformity related u deposits and the ductile brittle graphitic shear zones

genesis of palaeoproterozoic iron skarns in the misi region northern finland sodic alteration is widespread in palaeoproterozoic greenstone and schist belts of the northern fennoscandian shield in the misi region that forms the easternmost part of the perapohja schist belt several small magnetite deposits show intimate spatial relationships with intensely albitised gabbros raising the possibility that regional sodic alteration released iron which was subsequently accumulated into deposits two of these magnetite deposits raajarvi and puro display a typical paragenesis as follows from oldest to youngest 1 diopside 2 actinolite tremolite magnetite chlorite biotite and 3 serpentine hematite chlorite mass balance calculations suggest that significant amounts of fe ca mg k cu v and ba were lost and na and si gained during the albitisation of the gabbro at near constant al ga ti and zr significant amounts of si ca fe and na were enriched in the formation of skarn related to magnetite deposits fe and v leached from country rocks deposited during the skarn alteration and formed the vanadium rich iron deposits while cu passed through the system without significant precipitation due to low sulphur fugasity variations in na ca mg k and ba contents reflect the composition of the infiltrating fluid during alteration conventional heating freezing measurements and proton induced x ray emission pixe analyses of the fluid inclusions related to actinolite tremolite magnetite stage alteration indicate that the fluids that caused the alteration and the fe mineralisation were complex oxidised highly saline h2o co2 fluids that contained high amounts of na ca k fe and ba as well as elevated concentrations of cu zn and pb the oxygen isotope thermometry suggest that temperature during the fe mineralisation stage was between 390 and 490 c calculated 18ofluid values of 6 1 9 8 smow and 13c values of calcites in the ores and skarns were between 7 7 and 10 9 pdb and most likely reflect admixture of 13c depleted possibly magmatic fluids with the marble wall rocks that show 13ccalcite values of 13 pdb the sims u pb data on the zircons in the albitised gabbro next to the raajarvi and puro deposits suggest that intrusion of the gabbro took place at 2123 7 ma and was accompanied by the formation of diopside skarn the tims data on the metasomatic titanites related to sodic alteration yielded ages of 2062 3 and 2017 3 ma iron was probably stripped from the mafic country rocks by sodic alteration between 2123 and 2017 ma driven by repeated brine influxes subsequently the metal rich brine was focused by a fault system and the iron was precipitated from this fluid by a combination of wall rock reaction fluid mixing and a drop in the temperature

alteration mineralization and fluid evolution at the eloise cu au deposit cloncurry district northwest queensland australia the eloise deposit 3 1 million metric tons mt 5 5 cu 1 4 g t au and 16 g t ag is hosted by proterozoic rocks of the soldiers cap group in the eastern fold belt of the mount isa inlier the deposit is characterized by very high grade chalcopyrite pyrrhotite rich mineralization hosted by mafic silicate alteration alteration and mineralization lie within and adjacent to a major shear zone the main metasomatism comprised three stages early pervasive albite alteration stage i was overprinted by stage ii hornblende biotite quartz veins and alteration stage iii chalcopyrite pyrrhotite magnetite pyrite calcite quartz chlorite and actinolite replaced and brecciated the earlier mafic silicates the lodes occupy a narrow portion of a zoned mineralized system that is at least 2 km in length magnetite pyrite rich mineralization occurs in the south with chalcopyrite pyrrhotite rich mineralization in the central lode zone and pyrrhotite rich mineralization in the north the system has a distinct chemistry with enriched cu au ag co ni and zn fluid inclusions in pre syn and late to postmineralization veins indicate an evolving fluid history primary inclusions and associated hornblende biotite assemblages in premineralization veins indicate a high temperature fluid 450 degrees 600 degrees c and salinity estimates suggest it was an ultrasaline brine 32 68 wt total salts fluid inclusions in stage iii quartz in mineralized veins display a wide range of homogenization temperatures approximately 100 degrees 500 degrees c and gangue assemblages actinolite chlorite muscovite suggest mineralization was a cooler event 200 degrees 450 degrees c inclusions associated with the mineralization have a lower salinity 30 47 wt total salts than do premineralization inclusions and variable fluid inclusion types occur within the same clusters which may reflect fluid mixing the ultrasaline nature of the fluids and preliminary sulfur isotope results 0 4 2 0ppm suggest the ore fluid was predominantly magmatic metals were carried as chlorocomplexes and h 2 s was the dominant sulfur species important factors in ore deposition were a decrease in temperature and salinity and sulfidation of fe silicates eloise is interpreted to be a structurally controlled distal magmatic hydrothermal vein deposit

alteration paragenesis and mineral chemistry of the tjarrojakka apatite iron and cu au occurrences kiruna area northern sweden the northern norrbotten area in northern sweden is an important mining district and hosts several deposits of fe oxide cu au type one of the best examples of spatially and possibly genetically related apatite iron and copper gold deposits in the region is at tjarrojakka 50 km wsw of kiruna the deposits are hosted by strongly sheared and metamorphosed intermediate volcanic rocks and dolerites and show a structural control the tjarrojakka iron deposit is a typical apatite iron ore of kiruna type and the tjarrojakka copper occurrence shows the same characteristics as most other epigenetic deposits in norrbotten the host rock has been affected by strong albite and k feldspar alteration related to mineralisation resulting in an enrichment of na k and ba fe and v were depleted in the altered zones and added in mineralised samples ree were enriched in the system with the greatest addition related to mineralisation y was also mobile associated with albite alteration and copper mineralisation the tjarrojakka iron and copper deposits show comparable hydrothermal alteration minerals and paragenesis which might be a product of common host rock and similarities in ore fluid composition or overprinting by successive alteration stages mineralogy and mineral chemistry of the alteration minerals apatite scapolite feldspars amphiboles and biotite indicate a higher salinity and ba k ratio in the fluid related to the alterations in the apatite iron occurrence than in the copper deposit where the minerals are enriched in f and s the presence of hematite barite and in so4 in scapolite suggests more oxidising rich conditions during the emplacement of the tjarrojakka cu deposit from existing data it might be suggested that one evolving system created the two occurrences with the copper mineralisation representing a slightly later product

mineral chemistry of ore and hydrothermal alteration at the sossego iron oxide copper gold deposit carajas mineral province brazil abstract the sossego iron oxide copper gold deposit in the carajas mineral province comprises two major orebodies sequeirinho and sossego sodic alteration albite hematite and sodic calcic alteration zones represented by albite ferro edenite hastingsite up to 3 8 wt cl actinolite magnesiohornblende magnetite titanite epidote and calcite are predominant at sequeirinho magnetite bodies with envelopes of apatite rich actinolitite were formed with the sodic calcic event at high temperatures 500 c at 1 4 kbar in the sossego orebody potassic alteration with orthoclase and cl rich biotite up to 3 1 wt and chloritization are the main alteration types mineralized breccias in both orebodies have coarse grained zoned actinolite ferro actinolite cl apatite and magnetite within the matrix sulfides occur in equilibrium with a paragenetically late calcite quartz chlorite epidote allanite assemblage the al iv contents of the chlorite indicate crystallization at temperatures below 300 c chalcopyrite occurs associated with pyrite up to 2 3 wt co and 0 2 wt ni native gold up to 14 9 wt ag siegenite millerite vaesite pd melonite and hessite dilution and cooling of the hot metalliferous fluid 500 c by mixing with meteoric fluids may have been the main mechanisms responsible for the deposition of metals transported as metal chloride complexes in both orebodies of the sossego deposit

the noble gas systematics of late orogenic h2o co2 fluids mt isa australia abstract the noble gases he ne ar kr and xe are powerful geochemical tracers because they have distinctive isotopic compositions in the atmosphere crust and mantle this study illustrates how noble gases can be used to trace fluid origins in high temperature metamorphic and mineralising environments and at the same time provides new information on the composition of noble gases in deeper parts of the crust than have been sampled previously we report data for h2o and co2 fluid inclusions trapped at greenschist to amphibolite facies metamorphic conditions associated with three different styles of mineralisation and alteration in the proterozoic mt isa inlier of australia sulphide fluid inclusions are dominated by crustal 4he however co variations in fluid inclusion 20ne 22ne 21ne 22ne 40ar 36ar and 136xe 130xe indicate noble gases were derived from three or more reservoirs in most cases the fluid inclusions elemental noble gas ratios e g ne xe are close to the ranges expected in sedimentary and crystalline rocks however the elemental ratios have been modified in some of the samples providing evidence for independent pulses of co2 and interaction of co2 with high salinity aqueous fluids compositional variation is attributed to mixing of i magmatic fluids or deeply sourced metamorphic fluids characterised by basement derived noble gases with 20ne 22ne 8 4 21ne 22ne 0 4 40ar 36ar 40 000 and 136xe 130xe 8 ii basinal metamorphic fluids with a narrow range of compositions including near atmospheric values and iii noble gases derived from the meta sedimentary host rocks with 20ne 22ne 8 9 8 21ne 22ne these data provide the strongest geochemical evidence available for the involvement of fluids from two distinct geochemical reservoirs in mt isa s largest ore deposits in addition the data show how noble gases in fluid inclusions can provide information on fluid origins the composition of the crust s major lithologies fluid rock interactions and fluid fluid mixing or immiscibility processes

tertiary syntectonic carbonate platform development in indonesia cenozoic tropical carbonate sedimentation was strongly influenced by local and regional tectonics in se asia this paper outlines the evolution of the syntectonic eocene to middle miocene tonasa formation of south sulawesi evaluating controls on sedimentation facies distribution and sequence development development of a facies model for this cenozoic tropical carbonate platform provides a meaningful analogue for similar less well studied se asian carbonates which commonly comprise targets for hydrocarbon exploration this study also has considerable implications for the study of syntectonic carbonates controls on carbonate sedimentation carbonate platform development in backarc areas and se asian tectonics detailed facies mapping logging petrographic and biostratigraphic analyses indicate that the tonasa formation was deposited initially as part of a transgressive sequence in a backarc setting by late eocene times shallow water carbonates were being deposited over much of south sulawesi forming a widespread 100 km long platform area shallow water sedimentation continued unabated in some areas of the platform until the middle miocene elsewhere active normal faulting resulted in fault block platforms with local subaerial exposure of footwall blocks and the formation of basinal graben in adjacent hangingwall areas platform top facies were aggradational and dominated by larger benthic foraminifera low angle slopes particularly hangingwall dip slopes were characterized by the development of ramps faults controlled in part by pre existing structures were periodically active and formed steep escarpment margins variable regional subsidence strongly influenced the development of the tonasa carbonate platform whereas platform wide effects caused by regional eustacy have not been identified computer modelling of the tonasa platform confirms that the accommodation space and sedimentary geometries observed can be produced by block faulting and regional subsidence alone modelling also reveals that regional subsidence and extension oblique to the main stretching direction were low on the margins of the backarc basin shallow water accumulation rates for this foraminifera dominated tropical carbonate platform were an order of magnitude lower than those for modern warm water platforms dominated by corals or ooids

ore genesis of the duotoushan fe cu deposit eastern tianshan nw china constraints from ore geology mineral geochemistry fluid inclusion and stable isotopes abstract the duotoushan fe cu deposit is located in the western segment of the aqishan yamansu metallogenic belt in eastern tianshan xinjiang china magnetite orebodies are mainly developed in the upper carboniferous volcano sedimentary rocks and are mostly stratabound pyrite re os dating has yielded an isochron age of 312 24 ma mswd 1 5 five hydrothermal and one supergene alteration mineralization stages have been recognized from the spatial distribution of alteration zoning mineral assemblages and textural relationships the earliest alteration of albite ab84 98or2 16 amphibole was related to the nearby albitization granite porphyry prograde alteration was developed on the footwall of the intermediate mafic volcanic rocks and formed a garnet ad60 95gr5 40 clinopyroxene hd0di93jo7 to hd10di83jo7 assemblage alteration associated with magnetite can be further divided into three sub stages consisting of magnetite amphibole titanite stage iii a magnetite amphibole epidote stage iii b and epidote magnetite quartz amphibole titanite pyrite stage iii c mineral assemblages the secondary amphibole is dominantly actinolite pyrite with minor chlorite chalcopyrite veins cut the magnetite ore followed by later quartz calcite hematite veinlets based on fluid inclusions fis and stable isotopes studies the pre ore stage stage ii was formed at high temperature 500 c and originated from magmatic hydrothermal fluids 18 o h 2 o 7 1 d h 2 o 85 two garnet samples have similar 18 o h 2 o values 5 6 and 6 4 but considerably lower d h 2 o values 134 and 139 indicating the overprinting by late meteoric water iron ore and hydrous minerals assemblages and the associated fluids had overprinted the early anhydrous minerals early magnetite mineralization stage stage iii a shows clear magmatic water input as constrained from the 18 o h 2 o 6 9 to 7 8 and d h 2 o 85 to 72 values later magnetite stage was magmatic hydrothermal fluid dominated but with mixing of heavy d h 2 o as indicated by stable isotope compositions 18 o h 2 o 6 1 to 7 8 d h 2 o 47 to 32 sulfur isotope values of the stage iv pyrite give a 34s interval of 8 8 to 12 1 suggesting significant addition of external basin fluid seawater or evaporite sulfur source to magmatic fluid the low temperatures 83 213 c average 135 c generally medium high but variable salinities 9 9 27 2 wt nacl equiv average 21 3 wt and ca mg rich components of stage v fluids show clear features of involvement of basinal brines seawater and minor meteoric water in the late hydrothermal stages we infer that the temperature drop of the hydrothermal fluids may have been the main cause of massive magnetite precipitation at the duotoushan deposit whereas increasing ph values decreasing temperature and fluid mixing maybe responsible for cu precipitation ore deposit geology mineral geochemistry and fluid evolution confirm that the duotoushan fe cu deposit is different from typical skarns and may represent a distinct group of fe cu deposits formed during the aqishan yamansu back intra arc basin inversion which show many similarities with the central andean iocg deposits

noble gas and halogen constraints on regionally extensive mid crustal na ca metasomatism the proterozoic eastern mount isa block australia fluid inclusions in late isan quartz veins associated with regional na ca alteration albitisation in the mary kathleen fold belt and the cloncurry district of the eastern mt isa block have been analysed for naturally occurring and neutron produced isotopes of ar kr and xe the noble gases have been extracted using a thermal decrepitation procedure that enables partial deconvolution of the different fluid inclusion types including variably saline aqueous liquid carbon dioxide and mixed aqueous carbonic varieties the variably saline 5 65 wt aqueous fluid inclusions dominate and have 40ar 36ar values of less than 2700 in most of the samples from across the region these fluid inclusions have extremely variable molar br cl values of 0 3 4 10 3 and i cl values of 0 2 35 10 6 and the fluids are interpreted to represent sedimentary formation waters derived from the upper crust that have dissolved variable quantities of halite or scapolite to achieve their ultra high salinity fluid inclusions in a sample from the snake creek anticline in the cloncurry district have the highest 40ar 36ar value of 25 000 demonstrating a deep magmatic or metamorphic fluid origin in this case a magmatic origin is favoured because this fluid is very similar to a fluid involved in iron oxide copper gold iocg mineralization at ernest henry that was also interpreted to have a magmatic origin and because the aqueous fluid inclusions have br cl of 1 2 10 3 and i cl of 10 10 6 that are similar to mantle derived igneous rocks carbon dioxide fluid inclusions dominate samples from the knobby quarry in the mary kathleen fold belt and have a maximum 40ar 36ar value of 6000 7000 these fluid inclusions are estimated to have a 36ar concentration of 1 4 ppb that is similar to the range determined for aqueous fluid inclusions in all the other samples in addition aqueous and carbonic fluid inclusions in all the samples have similar 129xe 36ar plus 84kr 36ar values that are unfractionated and close to the air air saturated water asw range these data are interpreted to indicate an independent and dominantly metamorphic origin for co2 and the presence of mixed aqueous carbonic fluid inclusions are attributed to fluid mixing and or mingling rather than fluid unmixing however the data do not preclude the presence of a minor magmatic co2 component in the samples from the knobby quarry fluid inclusions in most of the samples from the mary kathleen fold belt have higher br cl and i cl values higher 36ar concentrations and lower maximum 40ar 36ar values than fluid inclusions in samples from the cloncurry district this suggests na ca alteration in these different parts of the eastern mt isa block occurred independently however fluid inclusions associated with na ca alteration in the cloncurry district have a very similar composition to fluid inclusions in iocg mineralization stage quartz veins from ernest henry these data are therefore compatible with a genetic relationship between regional na ca alteration and iocg mineralization in the cloncurry district in both cases the ultra saline hydrothermal fluids had a dominant origin from sedimentary formation water but are interpreted to contain a magmatic component sourced from the late isan williams naraku batholiths which may have driven fluid convection

diagenesis and fracturing of a large scale syntectonic carbonate platform abstract the influence of coeval tectonics on carbonate platform development is widely documented yet the diagenesis of such syntectonic platforms is barely evaluated an outcrop petrographic and geochemical study details here for the first time the diagenesis of the tonasa limestone formation developed in an extensional regime in central indonesia this equatorial carbonate system was affected by block faulting tilt block rotation differential uplift and subsidence throughout its eocene to early miocene history wilson 1999 wilson et al 2000 the tonasa carbonate platform is dominated by alteration in shallow to deeper burial depths by fluids with predominantly marine precursor origins mechanical and chemical compaction features are common as are a range of mainly burial related granular mosaic blocky and equant calcite cements earlier marine cements and meteoric influences are rare being highly localised to block faulted highs and or bathymetrically upstanding platform margin areas early marine micritisation of allochems was common on the platform top tectonic uplift together with a major oceanic throughflow current are thought to be key influences on localised karstification meteoric diagenesis and marine cementation the distribution and orientation of faults fractures and calcite veins together with evidence for their relative timing are the strongest manifestation of tectonism coeval with diagenesis there is concordance in the orientation and timing of structures affecting the tonasa platform with those basin wide with the potential for reactivation of pre existing basement fabrics tectonic subsidence including fault associated differential subsidence controlled the degree of burial diagenesis impacting different areas of the platform a predominance of burial diagenetic features and dearth of earlier marine or meteoric cementation is seen in other tertiary equatorial platforms and is partly attributed to 1 predominance of non framework building larger benthic foraminifera and or algae that are prone to remobilisation have low production rates and limited potential to build to sea level and 2 high runoff due to the equatorial humid climate contributing to lowered marine salinities in se asia underlying tectonic reasons for the preponderance of a regional diagenetic signature over a syntectonic one fracturing excepted are 1 development on the flanks of a backarc basin not on typical continental crust 2 key platform influencing structures are oblique to the main extensional direction in the basin and 3 development in an overall subsiding tectonic regime post dating basin initiation the aim here is that this study will contribute to understanding diagenetic alteration of syntectonic carbonate platforms and those from equatorial regions

carbonate depositional sequence development on active fault blocks the albian in the castro urdiales area northern spain the aptian to lowermost albian carbonate platform of castro urdiales cantabria northern spain was broken up by extensional tectonic movements shortly after the beginning of the albian block faulting characterized this rifting episode the effects of which waned during the albian in crestal locations tilting of the fault blocks caused the subaerial exposure of parts of the older platform resulting in intense karst diagenesis differential subsidence of the blocks controlled the development of a crestal residual carbonate platform arenillas which was surrounded by deeper water on both sides seven unconformities related to platform exposure and karstification are identified on the arenillas platform and form the basal boundaries of seven depositional sequences s1 s7 on the platform lowstand systems tract deposits consist of breccias filling caves and grainstones and debris flow deposits filling incised canyons transgressive plus highstand systems tracts consist of rare marls plus shallow water rudistid coral and chondrodontid limestones in the basin the unconformities are erosional surfaces at the base of resedimented limestones marls or sandy or silty siliciclastics lowstand systems tracts transgressive plus highstand systems tracts in this setting consist of marls and hemipelagic marly limestones tectonism is believed to be the main control on sequence formation and only a few sequence boundaries e g the base of s6 in the upper albian inflatum zone can be correlated with eustatic events

paragenesis stable isotopes and molybdenite re os isotope age of the lala iron copper deposit southwest china the lala fe cu deposit in the kangdian iron oxide copper gold iocg metallogenic province sw china is hosted in the paleoproterozoic hekou group this volcanic sedimentary sequence has undergone upper greenschist lower amphibolite facies metamorphism at 850 ma the deposit contains more than 200 million metric tons mt of fe cu ores with an average grade of 13 wt fe and 0 92 wt cu orebodies are roughly strata bound but occur along foliation lithologic contacts and shear zones the paragenetic sequence of the lala deposit includes metamorphosed i ii and iii and unmetamorphosed iv and v stages stage i is characterized by extensively pervasive na alteration forming abundant albite but minor scapolite stage ii occurs as massive and banded replacements consists of ti v poor magnetite and apatite with minor disseminated sulfide minerals and was associated with pervasive k fe alterations forming k feldspar chlorite and actinolite stage iii occurs predominantly as bands and disseminations confined along foliations with minor veinlets cross cutting hosting rocks this stage is characterized by abundant fe cu mo sulfides intergrown with angular magnetite and minor titanite and allanite and is associated with alteration of carbonate quartz fluorite and mica stage iv has an assemblage dominated by chalcopyrite with variable pyrite and bornite occurring as veins of sulfides quartz calcite biotite muscovite fluorite stage v occurs chiefly as veins of hematite calcite quartz and also results in extensive hematization stages ii and iii have fluids with high 18 o 7 2 11 7 and 34 s values 0 4 indicative of a magmatic hydrothermal origin however the stage iii fluids have 34 c values 0 5 close to the least altered marble 0 2 of the hosting rocks indicating a possible contribution of strata sourced carbon the stage iv fluids have 34 c values similar to and 18 o 4 1 6 7 lower than the stage iii fluids and a wider range of 34 s values 9 0 to 10 5 consistent with significant contributions of strata sourced sulfur fluids of the late barren vein stage v have relatively low 34 c 4 0 to 2 4 and 18 o values 2 9 to 0 6 indicative of significant contributions of meteoric and oxidized fluids molybdenite from stage iii has an re os isotope age of 1086 8 ma providing tight constraints on the timing of the main stage of mineralization this age indicates that the lala deposit is coeval with the 1100 ma intraplate magmatism in the western yangtze block we propose that the majority of the fe cu deposits in the kangdian iocg metallogenic province may have formed in an intraplate extensional setting although it is possible that some of the deposits may have involved in multiple events including modification by the neoproterozoic metamorphism forming the mineral assemblages of stage iv

geology and geochemistry of the reocin zinc lead deposit basque cantabrian basin northern spain the reocin zn pb deposit 30 km southwest of santander spain occurs within lower cretaceous dolomitized urgonian limestones on the southern flank of the santillana syncline the reocin deposit is one of the largest known strata bound carbonate hosted zinc lead deposits in europe the total metal endowment of the deposit including past production and remaining reserves is 62 mt of ore grading 8 7 percent zn and 1 0 percent pb the epigenetic mineralization consists of sphalerite and galena with lesser marcasite and trace pyrite with dolomite as gangue microprobe analyses of different generations of dolomite revealed nonstoichiometric compositions with various amounts of iron up to 14 mol of feco3 replacement of host dolomite open space filling of fractures and cementation of breccias derived from dissolution collapse are the principal types of ore occurrence detailed cross section mapping indicates a stratigraphic and structural control on the deposit a stratiform morphology is present in the western part of the orebody capa sur whereas mineralization in the eastern part is highly discordant but strata bound barrendera stratigraphic studies demonstrate that synsedimentary tectonic activity related to the rifting of the north atlantic bay of biscay was responsible for variation in sedimentation presence of unconformities including paleokarsts local platform emergence and dolomitization along the n60 fault trend in the reocin area two stages of dolomitization are recognized the first stage is a pervasive dolomitization of the limestone country rocks that was controlled by faulting and locally affected the upper part of the aptian and the complete albian sequence the second dolomitization event occurred after erosion and was controlled by karstic cavities this later dolomitization was accompanied by ore deposition and locally filling of dolomite sands and clastic sediments in karstic cavities the circulation of hydrothermal fluids responsible for sulfide deposition and the infilling of karst cavities were broadly contemporaneous indicating a post albian age vitrinite reflectance data are consistent with previously measured fluid inclusion temperatures and indicate temperatures of ore deposition that were less than 100 c carbon and oxygen isotopic data from samples of regional limestone host rock dolostone and ore stage dolomite suggest an early hydrothermal alteration of limestone to dolostone this initial dolomitization was followed by a second period of dolomite formation produced by the mixing of basinal metal rich fluids with local modified seawater both dolomitization events occurred under similar conditions from fluids exhibiting characteristics of basinal brines the 34s values of sulfides are between 1 8 and 8 5 per mil which is consistent with thermochemical sulfate reduction involving organic matter as the main source of reduced sulfur galena lead isotope compositions are among the most radiogenic values reported for zn pb occurrences in europe and they are distinct from values reported for galena from other basque cantabrian deposits this suggests that a significant part of the lead was scavenged from the local underlying asturian sediments the stratigraphic and structural setting timing of epigenetic mineralization mineralogy and isotopic geochemistry of sulfide and gangue minerals of the reocin deposit are consistent with the features of most of mississippi valley type ore deposits

systems tracts and depositional sequences in a carbonate setting a study of continuous outcrops from platform to basin at the scale of seismic lines abstract the application of sequence stratigraphy concepts to carbonates is feasible and this paper presents an example of its successful application the continuity and lateral extent of outcropping sedimentary sections observed at the scale of a seismic line from platform to basin in the southern vercors plateau western alps france confirm the validity of sequence stratigraphy concepts when applied to carbonate depositional systems from the stratal patterns displayed in outcrop we determined that carbonate lowstand systems tracts are major components in the basin even in the deep pelagic realm transgressive and highstand systems tracts are very thin a response to starvation in contrast on the shelf transgressive and highstand systems tracts are the major components carbonate lowstand and shelf margin systems tracts pinch out in the vicinity of the offlap break it clearly appears that the stratal patterns and stratal termination patterns of carbonate systems tracts especially of carbonate lowstand systems tracts are basically similar to those of siliciclastic systems tracts this study documents that carbonate platforms may provide the basin with carbonate clastics during periods of relative sea level falls and lowstand this is one of the most controversial aspects of the application of sequence stratigraphy concepts in carbonate environments a second controversial aspect of the application of sequence stratigraphy concepts to carbonate rocks is the distinction between transgressive and regressive facies cycles and depositional sequences and systems tracts this paper demonstrates that the shoreline position for carbonates which indicates the facies transgression or regression is independent of prograding or retrograding shelf breaks the stratal pattern and facies within systems tracts vary depending on the overall evolution of the accommodation space i e on their position within the transgressive and regressive cycles

retrograde mineral reactions in saline fluid inclusions the transformation ferropyrosmalite clinopyroxene evidence is presented for retrograde reaction of silicate minerals with saline brine inside fluid inclusions during post entrapment cooling ferropyrosmalite fe mn 8si6o15 oh cl 10 where fe mn has previously been interpreted as a daughter mineral in saline inclusions in magmatic quartz from altered granodiorite associated with the vyhne klokoc fe skarn deposit of slovakia based on combined raman spectroscopic microthermometric and sem edx techniques this phase is shown to react on heating above 450 c with a ca enriched saline inclusion fluid to form clinopyroxene this suggests that clinopyroxene was originally present in the inclusions at high temperature and then underwent retrograde reaction with the saline fluid on cooling to form ferropyrosmalite in its simplest form the equilibrium reaction for this transformation is formula 1 in practice the reaction is complicated by the presence of mn and mg the resulting daughter mineral assemblage observed at room temperature is actually a low temperature equilibrium assemblage very different to that originally present at high temperature although silicate daughter minerals such as clinopyroxene are rarely if ever described in fluid inclusions they may have originally been present but underwent similar retrograde reactions ferropyrosmalite itself is likely to be frequently overlooked as in the absence of raman spectroscopic analyses it may be mistaken for one of a range of possible hydrated iron chloride minerals improved raman spectra for ferropyrosmalite are presented which will make future identification easier failure to recognize intra inclusion retrograde reactions such as this may lead to misinterpretation of fluid inclusion chemistry including metal and silica solubilities 1 embed tex math 1 gif