geochemical and mineralogical control of different genetic types of deep sea nodules from the pacific ocean deep sea nodules from the northeast pacific nodule belt and the southeast pacific sonne basin being formed in areas bordering the equatorial zone of high biological productivity accumulate by two basically different growth processes a early diagenetic growth by supply from pore water and b hydrogenetic growth by supply from near bottom sea water these growth processes lead to different genetic types of nodules early diagenetic type a hydrogenetic type b and mixed type ab a further type ac very rich in mn is being formed by increasing influence of early diagenesis these types can clearly be distinguished by their shapes surface textures mineral constituents of oxide fraction internal microstructures and geochemistry a genetical classification is being proposed on the basis of statistically computed interelement relationships todorokite very poor in fe is the main mn phase in the early diagenetic substance mno2 intimately intergrown with feooh xh2o is the main phase in the hydrogenetic substance consequently an important difference can be pointed out the metal supply for the growth of the early diagenetic nodules is based on an ionic solution of me2 e g mn2 ni2 cu2 zn2 whereas the supply for the hydrogenetic nodules is caused by transport of colloidal particles mobilization of mn2 and fractionation from fe is controlled by the amount of decomposing organic matter in the peneliquid layer of the sediments the main factor controlling the intensity of early diagenesis is the biological productivity in surface waters the crucial point of reversal at a mn fe ratio of about 5 obtained by hyperbolical regression of the analyses of nodules from the southeast pacific represents best concentrations in ni and cu mn fe quotients greater than 5 cause a decrease of ni and cu content nodules from the northeast pacific nodule belt generally contain higher concentrations in cu than nodules from the southeast pacific this can be explained by an additional supply of cu transported below ccd by siliceous plankton

separation of iron from manganese and growth of manganese nodules as a consequence of diagenetic ageing of radiolarians abstract 111 samples of diagenetically aged radiolarians sampled in the central pacific manganese nodules belt were investigated chemically and microscopically authigenic clays of the smectite group are precipitated in the cavities of radiolarian tests metal oxides are precipitated on the surfaces of radiolarian tests during these processes a separation of iron from manganese takes place about 96 of the iron is bound to smectites and all of the manganese is bound to the oxide coatings of the radiolarians with further diagenesis radiolarian tests are dissolved together with their oxide coatings this dissolution of the oxide coatings provides material for the growth of manganese nodules material which is depleted in fe and enriched in mn cu and zn the smectite aggregates that fill the cavities of radiolarian tests contain iron bound to their crystal lattice whereas radiolarian tests are dissolved during the diagenesis these smectite aggregates do not dissolve and thus become enriched in older samples

dispersal and deposition of eolian and fluvial sediments off peru and northern chile relative abundances of quartz and feldspar in fine grained terrigenous sediments have been used to recognize specific continental sediment sources along northwestern south america and to trace the dispersal of specific grain size fractions from these sources to adjacent continental margin and deep sea sedimentary environments quartz feldspar ratios are low 0 6 for all fractions of sediments derived from southern peru and northern chile but such ratios increase systematically in central and northern peru as the importance of granitic and related intrusives increases relative to more basaltic extrusives and gabbroic equivalents limited published analyses of dusts collected offshore prospero and bonatti 1969 are also consistent with a latitudinally varying continental sediment source we find that clay

variations in os isotope ratios of pyrrhotite as a result of water rock and magma rock interaction constraints from virginia formation duluth complex contact zones abstract os isotope ratios in pyrrhotite bearing pelitic rocks of the 1 85 ga virginia formation are variable with perturbations linked to the emplacement of the 1 1 ga duluth complex pyrrhotite in footwall rocks of the contact aureole show evidence for a mixing event at 1 1 ga involving a low 187 os 188 os fluid however because rocks with perturbed pyrrhotite os isotope ratios occur 1 km or more from the duluth complex the fluid is unlikely to have been of magmatic origin fluid inclusions in layer parallel quartz veins provide evidence of the involvement of a boiling fluid at temperatures between 300 and 400 c analyses of fluid inclusions via la icp ms show that the fluids contain up to 1 7 wt na 1 1 wt k 4330 ppm fe 2275 ppm zn and 415 ppm mg the veins also contain pyrite or pyrrhotite plus minor amounts of chalcopyrite bornite pentlandite and sphalerite the re os isotopic ratios of pyrite from the veins indicate that they crystallized from low 187 os 188 os fluids 18 o values of vein quartz range from 7 7 to 9 5 consistent with an origin involving fluid with a relatively low 18 o value between 2 and 5 meteoric water with such a low 18 o value could have interacted with the igneous rocks of the complex and would have acquired os with a low 187 os 188 os ratio strongly serpentinized olivine rich rocks of the complex are commonly characterized by such low 18 o values and we propose that the fluid involved in serpentinization was also responsible for the perturbation of the os isotopic system recorded by pyrrhotite in the virginia formation two important observations are that only pyrrhotite bearing assemblages in the contact aureole show isotopic perturbation and that intervals showing os exchange are spatially restricted and not uniformly distributed os exchange and mixing has occurred only where temperatures were sufficient to convert pyrite to pyrrhotite and where time integrated water rock ratios in the aureole were high enough to provide a supply of os troctolitic and gabbroic rocks of the partridge river intrusion duluth complex are characterized by os isotope ratios that are indicative of variable degrees of crustal contamination os values of 0 543 xenoliths of carbonaceous and sulfidic pelitic rocks of the virginia formation found in the igneous rocks provide evidence that os was released by organic matter and pyrite in the sedimentary rocks and assimilated by mantle derived magma however residual pyrrhotite produced as a result of pyrite breakdown in the xenoliths is characterized by 187 os 188 os ratios that are much lower than anticipated and similar to those of pyrrhotite in the contact aureole the os exchange and addition shown by pyrrhotite in the xenoliths highlight an unusual cycle of re os liberation during devolatilization kerogen maturation and pyrite to pyrrhotite conversion processes that contribute to magma contamination followed by os uptake by pyrrhotite during back reaction involving magma and or fluid characterized by a relatively low 187 os 188 os ratio the extreme os uptake recorded by pyrrhotite in the xenoliths as well as the lesser degree of uptake recorded by pyrrhotite in the contact aureole is in line with the high os diffusivity in pyrrhotite experimentally determined by brenan et al 2000 our data confirm that os isotope ratios in pyrrhotite bearing rocks may be readily perturbed for this reason caution should be exercised in the interpretation of os isotope ratios in rocks where pyrrhotite may be the primary host of os

consolidation characteristics of sediments from the peru chile continental margin and implications for past sediment instability abstract one dimensional consolidation tests were performed on eight near surface samples 0 5 to 3 5 m from the peru chile continental margin these tests show that the consolidation behavior of these deposits is strongly influenced by the presence of high concentrations of organic matter resulting from the occurrence of coastal upwelling along this margin of south america organic carbon concentrations as high as 12 are found in samples from an upper slope mud lens between 10 5 to 13 6 s that lies beneath an area of intense upwelling with increasing organic content both the compressibility and rate of secondary compression are found to increase the increase in void ratio with increasing organic content and the ease by which organic matter is deformed appear responsible for these trends outside the mud lens the compressibility also increases as a result of increasing concentrations of clay size material and the abundance of smectite and illite all of the sediments along the margin behave as if they were consolidated under a pressure greater than the present effective overburden pressure evidence of erosion as a cause of the overconsolidation is present only on the upper slope mud lens at 13 6 s where 14 c dating verifies the erosion of 3 5 to 7 m of sediment numerous unconformities and intervals of deformed bedding in a core from 13 6 s attest to the past instability of sediments at this site at the other locations along the margin the increase in the overconsolidation ratio with increasing organic carbon content suggests that the bonding of sediment particles by organic matter may be responsible for the apparent overconsolidation low sedimentation rates on the slope off northern chile may also be a contributing factor to the apparent overconsolidation of sediments in this area

compositional variations of olivine from the jinchuan ni cu sulfide deposit western china implications for ore genesis the jinchuan ni cu sulfide deposit is hosted by an elongated olivine rich ultramafic body that is divided by subvertical strike slip faults into three segments central eastern and western the central segment is characterized by concentric enrichments of cumulus olivine crystals and interstitial sulfides pyrrhotite pentlandite chalcopyrite intergrowth whereas the eastern and western segments are characterized by an increase of sulfides toward the lower contacts in all segments sulfides are concentrated at the expense of intercumulus silicates olivine re crystallization is found to be associated with actinolite alteration in some samples the compositional variations of primary olivine from the sulfide poor samples can be explained by a small degree of olivine crystallization 50 modal and sulfide averaging 5 wt in the rocks are consistent with the interpretation that the jinchuan deposit was formed by olivine and sulfide laden magma successively ascending through a conduit to a higher now eroded level sulfide enrichment toward the center in the central segment and toward the lower contact in the eastern and western segments may have in part resulted from flow differentiation and gravitational settling during magma ascent respectively

small pressure drop triggered near a fault by small teleseismic waves abstract we describe a pressure transient triggered near an active fault by seismic waves generated more than 10 000 km away during the 2003 mw 7 8 rat island earthquake in contrast with previous similar observations the pressure drop occurs simultaneously with the arrival of s waves and not during the passage of the rayleigh waves that have larger amplitudes and smaller frequencies this small 60 pa drop is compatible with a small slip on the fault which induced either dilatant damage or a transient disruption in the impermeable barrier the fault constitutes

paragneiss assimilation in the genesis of magmatic ni cu co sulfide mineralization at voisey s bay labrador δ34s δ13c and se s evidence the voisey s bay ni cu co deposit is located in ca 1 33 ga troctolitic rocks of the nain plutonic suite northern labrador it is widely regarded as a prime example of sulfide mineralization associated with a magmatic conduit system previous geological and geochemical studies have indicated that the voisey s bay intrusion was contaminated by interaction with both sulfide poor archean gneisses and with paleoproterozoic sulfide bearing tasiuyak metasedimentary gneiss limited sulfur isotope data previously indicated that only one of the four ore zones at voisey s bay is characterized by 34s values outside the range considered normal for uncontaminated mantle derived mafic magmas 0 2 new s isotope data presented here extends the previously reported range in 34s values for the tasiuyak gneiss from 17 0 to 18 3 per mil with an average of 1 4 per mil assimilation of this sulfur followed by isotope homogenization in the magmatic system is consistent with the isotope data from the ore zones and in line with the wealth of evidence that suggests that interaction with tasiuyak gneiss was an essential ingredient for ore formation in all the zones se s values of sulfide minerals in the ore zones at voisey s bay are also in the same range as those of whole rock samples from the tasiuyak gneiss 13c values of both mineralized and nonmineralized parts of the voisey s bay intrusion are anomalous 18 3 to 24 8 and similar to values of graphite in the tasiuyak gneiss both s and c contamination of the voisey s bay intrusion via diffusive transfer in a fluid phase derived from inclusions and wall rocks are considered unlikely because the area had been subjected to granulite grade metamorphism prior to emplacement of the nain plutonic suite either fractional melting or total fusion of xenoliths is considered a more likely mechanism for s addition to the mafic magma via pyrrhotite melting and for c addition in the form of co2 and ch4 produced by reaction of graphite with o and h bearing melt species

formation of clay minerals during early diagenesis of a calcareous ooze abstract deep sea sediments from a basin in the southeast pacific are described in which strong carbonate dissolution and strong diagenetic migration of metals can be observed clay minerals of smectite type are formed in large quantities during the early diagenesis of this sediment in a first stage as an x ray amorphous phase which later crystallizes to smectite rb sc na and k become enriched during the process of clay mineral formation probably due to uptake of these elements from sea water to interlayer positions of smectite the unsolved question is what sort of mechanism connects the calcite dissolution with the formation of smectite the source of the al necessary for the formation of smectite is also unknown

identification of earthquake signals from groundwater level records using the hht method summary coseismic signals of groundwater levels are generally obtained by subtracting the responses of atmospheric pressure earth tides and precipitation from the observed data however if the observations are conducted without nearby barometers pluviometers or earth tide data for correction coseismic signals are often difficult to extract in this case the hilbert huang transform hht is used to obtain the instantaneous frequencies and amplitudes for every point of the decomposed intrinsic mode functions imfs from groundwater level data for differentiating the related frequency dependent responses without a further auxiliary input the extracted coseismic signals show intense amplitude pulses that are clearly seen in the third imf in addition two types of coseismic signals can be readily distinguished in the results from the hht transform one is an instantaneous short time signal induced by the passing of seismic waves another coseismic signal is a sustained signal induced by the nearfield earthquake occurring near the hualien station taiwan and shows a positive correlation between the earthquake distance and magnitude our results generally show that using the hht transform improves our understanding of automatic detection of the coseismic signals from the groundwater level

critical factors for the formation of a nickel copper deposit in an evolved magma system lessons from a comparison of the pants lake and voisey s bay sulfide occurrences in labrador canada the voisey s bay nickel copper deposit and the pants lake sulfide occurrences are the most important mineral systems discovered to date within the nain plutonic suite in northern labrador there are many intriguing similarities at both locations both are hosted by relatively small troctolite gabbro bodies that intrude the sulfide bearing paragneiss of the churchill province and these intrusions contain inclusions of the paragneiss similar chemical reactions of the gneissic inclusions with the host magmas are observed at both locations the reactions resulted in the addition of sio2 k2o na2o and sulfur to the magmas and are responsible for sulfide saturation and resultant segregation of immiscible sulfide liquids from the magmas the initial sulfide liquids in both cases were relatively poor in metals containing 2 5 wt ni and 2 wt cu the sulfides at pants lake remained poor in metals because of a lack of subsequent interaction with new chalcophile undepleted magma at voisey s bay the initial sulfides segregated in a dynamic conduit and were subsequently upgraded in metals to 6 wt ni and 3 wt cu by a new surge of undepleted magma using the same conduit these sulfides were then concentrated to form large sulfide bodies in the wider parts of the conduit and its entry to an upper chamber in response to a sudden change of liquid velocity in these environments this study confirms three of the most important factors for the formation of magmatic sulfide deposits in an evolved magma system 1 contamination of magma with sulfide bearing country rock to achieve sulfide saturation 2 a dynamic magmatic system such as a magma conduit to transport large volume of sulfide liquid and to concentrate them in limited localities and 3 upgrading of metals in the sulfide by new chalcophile undepleted magma

nickeliferous gabbroic intrusions of the pants lake area labrador canada implications for the development of magmatic sulfides in mafic systems the pants lake intrusions are located some 80 kilometers south of the world class voisey s bay ni cu co sulfide deposit in labrador canada they are dominated by olivine gabbro with subordinate troctolite melagabbro peridotite and leucogabbro they form several sheet like bodies that were emplaced into metasedimentary gneisses that locally contain sulfides the largest of these termed the north and south intrusions have been dated by other workers at 1322 2 ma and 1337 2 ma respectively indicating that they formed in two discrete events the north intrusion is more varied petrologically and its three units show ambiguous contact relationships implying that they partly coexisted as liquids disseminated sulfide mineralization is widespread near the basal contacts of both intrusions but massive sulfide mineralization is rare in the older south intrusion sulfides are hosted by melagabbro and peridotite of cumulate origin and probably represent a gravitational accumulation in the younger north intrusion they are hosted by a complex mineralized sequence interpreted to represent two or more influxes of magma charged with sulfides and reacted country rock fragments the older south intrusion is geochemically distinct from the younger north intrusion and more closely resembles the voisey s bay intrusion mineralized rocks within both pants lake intrusions are geochemically similar to the associated unmineralized rocks and must be closer related to them the mafic rocks almost all have low ni contents and low cu zr ratios that imply extraction of metals by sulfide liquids this pervasive depletion signature coupled with consistent ni cu and ni co and clustering of sulfide metal contents suggests that sulfide liquids were developed on an intrusion wide scale probably at depth rather than by local processes sulfides at pants lake typically contain less than 2 percent ni and 2 percent cu these values agree with predictions from the low ni contents of silicate rocks and imply a low mass ratio r factor of silicate magma to sulfide liquid r 1000 the pervasive ni and cu depletion contrasts with the more localized metal depletion seen at voisey s bay this may indicate that the pants lake sulfide liquids were not as effectively upgraded by later batches of undepleted magma from the perspective of metallogenesis data from the pants lake intrusions support several key concepts proposed m models for the formation of the voisey s bay deposit suggesting that these may apply more widely as controls on the formation of magmatic sulfide deposits in broadly gabbroic magma systems

phosphate regeneration from sediments of the peru continental margin by dissolution of fish debris generally oxidative regeneration of phosphate from anoxic sediments is by microbially mediated sulfate reduction processes stoichiometric modelling of such reactions takes into consideration varying proportions of decomposable organically bound p to account for the ratios among nutrients in depth concentration profiles of near surface sediments new results of interstitial water composition from sediments underlying the water masses influenced by coastal upwelling of the eastern boundary current system off peru indicate that dissolution of phosphatic fish debris represents a mechanism for remineralization of phosphate comparable to or larger in magnitude than that by oxidative regeneration of organically bound p dissolved interstitial phosphate from fish debris is revealed by an excess amount of phosphate over that predicted from a simple stoichiometric oxidative regeneration model and by anomalously high dissolved interstitial fluoride concentrations phosphate flux estimates based on diffusion from the sediment suggest that this mechanism may generate up to 10 of the nutrient pool in the waters of the peru undercurrent partitioning of p among the two sources reveals further that fish debris phosphate is about four times more important than organically bound p in nutrient generation from sediments of the peru continental margin not only does this mechanism of regeneration affect the nutrient cycling but may also control widespread phosphorite formation in this area

earthquake source scaling relationships from 1 to 5 ml using seismograms recorded at 2 5 km depth the scaling relationships of earthquake sources less than about magnitude 3 have been the subject of considerable controversy over the last two decades studies of such events have shown a tendency for the constant stress drop self similarity of larger earthquakes to breakdown at small magnitudes and an apparent minimum source dimension of about 100 m has been observed other studies showed that this apparent breakdown in scaling could be an artifact of severe near surface attenuation limiting the spatial resolution of surface data in this study source parameters are determined for over 100 nearby tectonic earthquakes from recordings at a depth of 2 5 km in granite in the cajon pass scientific drill hole southern california comparison of the seismograms recorded at this depth with those at the wellhead clearly demonstrates the effect of the severe attenuation in the upper kilometers of the earth s crust source parameters are calculated by spectral modeling of three component p and s waves assuming four source models based on the brune 2 n 2 model in model l n 2 is fixed and q of p and s waves is determined to be 912 581 1433 and 1078 879 1323 respectively the numbers in parentheses are 1 standard deviation in model 2 qp qs 1000 is assumed and n is allowed to vary the 2 model is a good average for the data set but there is some real scatter supported by the data in model 3 qp qs 1000 is also assumed and 2 is constrained and in model 4 attenuation is ignored and n is allowed to vary source dimensions of less than 10m are observed for all four models 10 times smaller than the proposed minimum no breakdown in constant stress drop scaling is seen in the downhole data approximately ml 1 to 5 5 m0 109 1016 nm the ratio between radiated seismic energy estimated by integrating the velocity squared spectra with adequate signal bandwidth and seismic moment appears to decrease gradually with decreasing moment in the magnitude range 1 to 7 this is not incompatible with a constant stress drop but could result from errors in calculating energy the ratio of the s wave energy to that radiated by the p waves is about 14 after correction for attenuation this low value is consistent with the corner frequency shift of about 1 3 this corner frequency shift is observed for all four source models and therefore is interpreted as being source controlled

geochemical and sedimentological studies of a box core from the western sector of the peru basin abstract the distribution of sediments micronodules and manganese nodules which has been studied in a number of cores from the peru basin is clearly related to the proximity of the basin to the c c d and to the equatorial high productivity zone one core from the peru basin has been looked at in considerable detail in this core an extensively bioturbated calcareous siliceous rich upper sedimentary unit is underlain by an overconsolidated dark brown clay characteristic differences in mineralogy and chemistry are observed in the composition of these sediment types with the dark brown clays having higher contents of mn fe co ni cu zn and p than the sediments of the upper horizon in addition these dark brown clays contain montmorillonite as the principal clay mineral whereas the sediments of the upper sediment horizon consist of montmorillonite kaolinite and illite micronodules are much more abundant in the coarse fraction 40 m of the dark brown clay horizon than in the upper sedimentary unit and are characterized by higher mn fe ratios and higher ni and cu contents than those from the upper sediment horizon this reflects the fact that these overconsolidated sediments are well oxidized and that element remobilization from the micronodules has not taken place within this sediment type in the upper sedimentary unit there is a sharp drop in the mn fe ratio and ni and cu contents of the micronodules immediately beneath the sediment surface reflecting the selective migration of mn and other transition elements such as ni and cu from the micronodules buried managanese nodules are found at two horizons within the sediment column these nodules show characteristic differences in their surface texture compared to surface nodules but no marked difference in composition the buried nodules are not associated with any well defined feature such as a sedimentary hiatus it is suggested that nodules are maintained at the sediment surface by bioturbation buried nodules are simply those nodules that have failed to be maintained at the sediment water interface

magma generation and sulfide saturation of permian mafic ultramafic intrusions from the western part of the northern tianshan in nw china implications for ni cu mineralization compared to permian magmatic ni cu sulfide deposits in the eastern part of the northern tianshan such as huangshan and huangshandong those in the western part e g baixintan and lubei are poorly documented zircon id tims u pb age data 279 7 0 2 ma of lherzolite and la icpms u pb age data 277 8 3 4 ma of a hornblende gabbro suggest the lubei intrusion was emplaced in the early permian the baixintan and lubei mafic ultramafic intrusive rocks are characterized by enrichments of large ion lithophile elements and th and u relative to the high field strength elements as well as depletion of nb and ta relative to mid ocean ridge basalt the 87sr 86sr t 0 70354 0 70713 end t 2 80 to 7 05 and ehf t 2 50 18 4 values for the intrusions indicate that they have assimilated tianshan basement rocks whereas the se s ratios 181 10 6 418 10 6 and 34scdt values 0 13 to 0 90 of the sulfides suggest that crustal sulfur has not been incorporated into the magma the decrease in pd zr with increasing th nb pm indicates that sulfide saturation accompanied crustal contamination the olivine compositions and whole rock chalcophile elements of the baixintan and lubei intrusions imply that the parental magma of the intrusive rocks in the west contains higher chalcophile elements than those in the east which suggests that the mafic ultramafic intrusions in the western part of the northern tianshan should be regarded as favorable ni cu sulfide exploration targets

re os geochronology on sulfides from the tudun cu ni sulfide deposit eastern tianshan and its geological significance the tudun deposit is a medium sized cu ni sulfide deposit located at the westernmost edge of the huangshan jing erquan belt in the northern part of eastern tianshan nw china sulfide separates including pentlandite pyrrhotite and chalcopyrite from the tudun deposit contain re common os and 187os ranging from 40 46 to 201 2 0 8048 to 6 246 and 0 1709 to 0 9977 ppb respectively they have very low 187os 188os ratios of 1 224 2 352 the sulfides yield a re os isochron age of 270 0 7 5 ma mswd 1 3 consistent within uncertainty with the shrimp zircon u pb age for the tudun mafic intrusion gabbro of 280 0 3 0 ma the calculated initial 187os 188os ratio is 0 533 0 022 and os values range from 283 to 307 with a mean of 297 indicating significant crustal contamination of the parent melt prior to sulfide saturation the tudun deposit shares the same age and re os isotopic compositions with other orthomagmatic cu ni sulfide deposits in huangshan jing erquan belt suggesting that they have formed in early permian

thorium and uranium isotopes in a manganese nodule from the peru basin determined by alpha spectrometry and thermal ionization mass spectrometry tims are manganese supply and growth related to climate thorium and uranium isotopes were measured in a diagenetic manganese nodule from the peru basin applying alpha and thermal ionization mass spectrometry tims alpha counting of 62 samples was carried out with a depth resolution of 0 4 mm to gain a high resolution230thexcess profile in addition 17 samples were measured with tims to obtain precise isotope concentrations and isotope ratios we got values of 0 06 0 59 ppb 230th 0 43 1 40 ppm 232th 0 09 0 49 ppb 234u and 1 66 8 24 ppm 238u the uranium activity ratio in the uppermost samples 1 6 mm and in two further sections in the nodule at 12 5 1 0 mm and 27 3 33 5 mm comes close to the present ocean water value of 1 144 0 004 in two other sections of the nodule this ratio is significantly higher probably reflecting incorporation of diagenetic uranium the upper 25 mm section of the mn nodule shows a relatively smooth exponential decrease in the230thexcess concentration tims the slope of the best fit yields a growth rate of 110 mm ma up to 24 5 mm depth the section from 25 to 30 3 mm depth shows constant230thexcess concentrations probably due to growth rates even faster than those in the top section of the nodule from 33 to 50 mm depth the growth rate is approximately 60 mm ma two layers in the nodule with distinct laminations 11 15 and 28 33 mm depth probably formed during the transition from isotopic stage 8 to 7 and in stage 5e respectively the mn fe ratio shows higher values during interglacials 5 and 7 and lower ones during glacials 4 and 6 a comparison of our data with data from adjacent sediment cores suggests a a variable supply of hydrothermal mn to sediments and mn nodules of the peru basin or b suboxic conditions at the water sediment interface during periods with lower mn fe ratios

petrologic evolution of gneissic xenoliths in the voisey s bay intrusion labrador canada mineralogy reactions partial melting and mechanisms of mass transfer nickel copper cobalt sulfide ores in the voisey s bay intrusion are closely associated with troctolitic to gabbroic rocks that contain abundant country rock xenoliths potential sources of the xenoliths include pelitic paragneiss enderbitic orthogneiss and mafic to quartzofeldspathic gneisses that form immediate country rocks to different parts of the intrusion regardless of location all xenoliths have a similar refractory mineral assemblage composed of hercynite magnetite ca rich plagioclase and corundum the refractory mineral assemblage formed via partial melting immediately after xenoliths were engulfed by magma rapid thermal equilibration allowed the xenoliths to survive prolonged interaction with magma corundum was formed by the incongruent melting of na rich plagioclase in pelitic and quartzofeldspathic gneisses corundum and ca rich plagioclase assemblages are aluminous their origin involved either multistage melting of protoliths where the production of a granitic minimum melt was followed by the liberation of a more silica rich and al poor melt or one stage disequilibrium melting density differences between the xenoliths restite assemblages and enclosing mafic magma facilitated the separation of partial melt from restite no evidence for the melts in the form of channels or interstitial glass is observed in the restite flow of mafic magma in the conduit system is thought to have dispersed the si and alkali rich melts derived from the xenoliths the only record of the xenolith derived melts is in the form of concentric rims of plagioclase and biotite which crystallized from a hybrid melt in boundary layers around most xenoliths hercynite in the restitic assemblage was produced either by partial melting involving fe and mg bearing minerals such as garnet and pyroxene or by replacement of corundum feo and mgo that were excluded from the boundary layer diffused inward and reacted with corundum to form hercynite the thickness of the hercynite bands suggests formation times between 3 000 and 23 000 years where the insulating rims of plagioclase and biotite were not present diffusion of feo and mgo from the surrounding crystal mush continued resulting in near complete conversion of corundum to hercynite the highly refractory mineral assemblages which characterize xenoliths present in the voisey s bay intrusion provide evidence for a complex history of magma country rock interaction the transfer of xenomelts and sulfur to flowing magma may have been essential for the formation of the magmatic sulfide ores

chilean earthquakes aquifer responses at the russian platform we studied hydrogeological responses to the passage of seismic waves from the chilean earthquakes with ms 7 6 at epicentral distances of about 126 the variation in the levels of confined and unconfined aquifers was analyzed under platform conditions at the mikhnevo geophysical observatory near moscow russia synchronous recording of seismic and hydrogeological data enabled us to evaluate the amplitude frequency response of aquifers the study shows that medium response to dynamic impact depends on various physical parameters of the aquifers

growth history of manganese nodules and crusts of the peru basin abstract in the nodule field of the peru basin situated south of the zone of high bioproductivity a relatively high flux of biogenic matter explains a distinct redox boundary at about 10 cm depth separating very soft oxic surface sediments from stiffer suboxic sediments maximum abundance 50 kg m 2 of diagenetic nodules is found near the calcite compensation depth ccd currently at 4250 m there the accretion rate of nodules is much higher 100 mm ma 1 than on ridges 5 mm ma 1 highest accretion rates are found at the bottom of large nodules that repeatedly sink to a level immediately above the redox boundary there distinct diagenetic growth conditions prevail and layers of dense laminated mn oxide of very pure todorokite are formed the layering of nodules is mainly the result of organisms moving nodules within the oxic surface sediment from diagenetic to hydrogenetic environments the frequency of such movements is much higher than that of climatic changes two types of nodule burial occur in the peru basin large nodules are less easily moved by organisms and become buried consequently buried nodules generally are larger than surface nodules this type of burial predominates in basins at ridges where smaller nodules prevail burial is mainly controlled by statistical selection where some nodules are not moved up by organisms

carbonate preservation history in the peru basin paleoceanographic implications we studied preservation dissolution cycles and paleoproductivity in eight sediment cores from the peru basin south of the highly productive surface waters of the eastern equatorial pacific stratigraphy is based on stable oxygen isotopes and on combined magnetostratigraphy and biostratigraphy sediment cores which span the last 8 m y were retrieved during cruise 79 with rv sonne close to the carbonate compensation depth ccd in general sediments show pacific type carbonate cycles we interpret a pronounced carbonate peak between 6 and 7 ma as the result of a western and northern extension of the highly productive peru current decreased carbonate contents from the late miocene to the late pliocene might be associated with a slow contraction of the latitudinal extent of the high productivity belt north of the study areas during the pliocene carbonate variations showed 400 kyr cycles indicating the growth and decay of ice sheets which should have been associated with pulsations of the antarctic ice cap an abrupt collapse of the carbonate system occurred at 2 4 ma higher frequency variations of the carbonate record indicate the major increase of the northern hemisphere glaciation during the quaternary carbonate fluxes are high during glacials and low during interglacials large amplitude variations with long broad minima and maxima associated with small migrations of the lysocline and the ccd 200 m are indicative of the preservation dissolution history in the peru basin during the early pleistocene climatic forcing by the 41 kyr obliquity cycle is not observed in the carbonate record during the last 800 kyr variability in the carbonate record was dominated by the 100 kyr eccentricity cycle fluxes of biogenic material calcium carbonate organic carbon opal and barium were greatest during glacials which imply higher productivity and export production of the peru current during cold climatic periods dissolution was greatest during interglacials as inferred from the relatively poor preservation of planktonic foraminifera and from the low accumulation rate of carbonate after the mid brunhes event 400 ka we observe a plateaulike shift to enhanced dissolution and to intensified productivity

multi element variations in olivine as geochemical signatures of ni cu sulfide mineralization in mafic magma systems examples from voisey s bay and pants lake intrusions labrador canada olivine from the olivine gabbro to troctolite intrusions at voisey s bay and at pants lake labrador was analyzed for multiple elements ca sc mg si ti v cr mn fe co ni cu zn sr y and zr with secondary ion mass spectrometry sims both intrusions have similar lithologies and petrographic characteristics and are approximately coeval 1 34 and 1 32 ga respectively members of the mesoproterozoic nain plutonic suite the voisey s bay intrusion hosts a producing economic ni cu sulfide deposit whereas the pants lake intrusion displays evidence of ni cu sulfide mineralization but to date a viable ore deposit has not been discovered olivine from both barren and mineralized lithologies was analyzed to assess the potential of the olivine composition for providing a record of silicate melt evolution and sulfide saturation related to formation of a massive sulfide deposit two detailed transects were sampled using five diamond drill holes that laterally approach the basal massive sulfide in the eastern deeps portion of the voisey s bay intrusion from the barren central part olivine displays distinct trace element distributions that vary coherently with host lithology and proximity to sulfide mineralization in particular olivine shows an increase in fe fo80 to fo60 mn 2500 to 5000 ppm and zn 280 to 700 ppm generally coupled with a decrease in ni 1600 to 900 ppm co 270 to 190 ppm and cr 110 to 45 ppm from barren troctolite normal troctolite nt and weakly mineralized troctolite variable textured troctolite vtt towards the heavily mineralized brecciated basal succession basal breccia sequence bbs the enrichment in fe mn zn is most pronounced in samples that laterally approach but do not directly intersect the massive sulfide deposit at the base of the intrusion particularly in samples from the lower variable textured troctolite and the basal breccia olivine from gabbro lithologies within the basal gabbro bg and upper gabbro ug of the pants lake intrusion is fairly homogeneous fo60 4300 ppm mn 460 ppm zn 340 ppm ni 50 ppm cr with a more evolved composition 2100 ppm ca 20 ppm sc 300 ppm ti 4 ppm y than the average olivine of the voisey s bay intrusion 570 ppm ca 6 ppm sc 65 ppm ti 0 3 ppm y pants lake olivine also commonly lacks the mutually mn zn rich signature of olivine from the basal breccia at voisey s bay that is characteristic of contamination of the parent magma by country rock gneiss and there reflects a close proximity to massive sulfides in conjunction with petrographic observation and the stratigraphic context a multiple element v cr mn fe co ni zn regression can be applied to calculate a lateral proximity of olivine to massive sulfide mineralization in the eastern deeps part of the voisey s bay intrusion over a distance exceeding 150 m the compositional variations in olivine from the economic voisey s bay intrusion bimodal and primitive and the mainly barren pants lake intrusion homogeneous and evolved provide potential as a regional scale mineralogical fertility indicator for mafic intrusions with comparable types of sulfide mineralization

reevaluation of the role of external sulfur addition in the genesis of ni cu pge deposits evidence from the nebo babel ni cu pge deposit west musgrave western australia the nebo babel ni cu pge sulfide deposit located in the west musgrave block western australia is hosted within a tube like concentrically zoned gabbronorite magma conduit emplaced at 1068 ma the nebo babel deposit is associated with the ca 1078 ma giles complex which is part of the warakurna large igneous province previous geologic and geochemical studies have shown that the nebo babel consists of chemically related but temporally distinct magma pulses the initial magma pulses which were the most primitive and the most contaminated formed the marginal units of the conduit the later pulses were emplaced into the core of the conduit the chilled margin rocks contain sulfide globules mineralization is confined to the early magma pulses and consists of massive sulfide breccias and stringers and disseminated gabbronorite hosted sulfides the ni tenor of the massive sulfides which have undergone sulfide liquid fractionation and the disseminated sulfides are almost the same indicating that both formed at similar r factors the whole rock massive and disseminated sulfides contain 650 ppb and 60 to 500 ppb total pge respectively all of the nebo babel rock units are slightly pge depleted with cu pd ratios higher than primitive mantle indicating early saturation and segregation of a sulfide and or pgm rocks with trace cumulus sulfides have the lowest cu zr and highest cu pd ratios and the most fractionated metal patterns indicating that these units have undergone the highest degrees of ni cu and pge depletion the average 34s value of all nebo babel disseminated and massive sulfides is 0 4 0 2 per mil which is consistent with the s originating in the mantle sulfur saturation did not occur in situ and is inferred to have been triggered by assimilation of felsic orthogneiss perhaps in the parental magma chamber this initial magma pulse with entrained sulfides formed marginal units of the nebo babel intrusion some of the entrained sulfides accumulated within physical traps on the way into the conduit and or at the exit from the chamber these sulfides were later emplaced along the footwall contact as massive and or marginal fragment laden sulfide liquid distribution of the disseminated sulfides was influenced by the conduit geometry and magma flow dynamics the final and volumetrically dominant barren magma pulse underwent crystal fractionation and oxide precipitation in the core of the nebo babel intrusion which in turn caused sulfide saturation and formed trace but pge depleted sulfides in these units the nebo babel deposit has a number of features in common with other ni cu pge deposits hosted in dynamic magma conduits e g voisey s bay such as multiple magma pulses and sulfide entrainment from depth rather than in situ sulfide segregation however si addition was the primary cause of sulfide saturation and external s addition did not play a role in the genesis of the nebo babel deposit

sediments and micronodules in the northern and central peru basin the mineralogy and composition of sediments and manganese micronodules from the northern and central sectors of the peru basin are discussed because of the proximity of the basin to the carbonate compensation depth c c d surface sediments vary between calcareous oozes and siliceous muds besides biogenic components clay minerals are important by far the most abundant clay mineral is smectite which is thought to be of diagenetic origin on a carbonate free basis the surface sediments are rather uniform in composition throughout the basin and are similar in composition to those of the equatorial pacific sedimentation rates for the uppermost core sections are in the range of 3 to 5 mm 1000 yr

periodic events of bottom transport of peru basin sediment during the late quaternary 230th and 231pa depth profiles in cores from the peru basin suggest that the sediment accumulation during the late quaternary was characterized by a sequence of periods with normal slow accumulation of siliceous rich muds that were interrupted by shorter periods of up to one order of magnitude higher accumulation of carbonate rich sediments faster sediment accumulation is caused by deposition of miocene carbonate rich sediments eroded in the southern regions of the peru basin the periods of faster accumulation occurred at 70 000 161 000 181 000 and 294 000 314 000 a and coincide with periods of global climatic cooling

linking mineral deposit models to quantitative risk analysis and decision making in exploration this paper describes a methodology of translating mineral deposit models into flexible probabilistic structures based on 1 extraction of ore components fluids metals and ligands from crustal or mantle sources or both 2 fluid or melt assisted transport of ore components from source to trap zones 3 formation of trap zones i e effective melt or fluid channels that can focus melt or fluid migration and accommodate large amounts of metal and 4 operation of the physicochemical processes that promote and sustain the deposition of metal from fluids or melts passing through a particular trap site our approach integrates these critical mineralization processes and conditions with concepts of probability theory decision analysis and financial modeling the principal objective is to make mineral deposit models amenable to financial risk and value analysis and suitable for communication of value creating geologic concepts to financial stakeholders in economic terms a case study based on an actual porphyry copper project illustrates how the resulting probabilistic mineral systems model can generate a measure of the probability of ore occurrence as an input for exploration decision trees and simulations to calculate the expected value of an exploration project and the probability distribution of all possible surrounding net present values npvs within a minimum and maximum range formulation of the probabilistic model closely follows and combines principles of the well established petroleum and mineral systems approaches and makes use of excel based model templates with decision tree and simulation add in software packages

evidence suggesting fluid flow beneath japan due to periodic seismic triggering from the 2004 sumatra andaman earthquake 1 we show that very large surface waves from the 2004 sumatra andaman earthquake m9 2 triggered deep low frequency dlf seismic tremors beneath japan over a 500 km wide region the triggered seismicity was periodically excited synchronized with the amplitudes and phases of the oscillatory surface waves incident on the region periodic excitation implies that the specific phase of the surface waves plays an important role for the triggering estimation of stress changes in the source regions showed that the volumetric dilatation larger than 10 8 was the predominant factor for triggering thereby strongly supporting the hypothesis that dlf events are caused by processes related to fluid flow

the distribution of rare earth elements in manganese micronodules and sediments from the equatorial and southwest pacific abstract thirty three manganese micronodules and 38 associated sediments from selected areas in the equatorial and southwest pacific have been analyzed for ree significant variations in composition of both micronodules and sediments between the areas are observed in general the avarage ree abundance in manganese modules in a given area is higher than that of the associated micronodules but the ce la ratio of the micronodules is in some cases higher than that of the nodules the avarage ce la ratio of the micronodules is always higher than that of the associated sediment but the ree abundance is lower in several cases the ce anomaly is dominantly positive for micronodules and negative for sediments negative ce anomalies are however found in micronodules from the crest of the east pacific rise epr where metallogenesis is taking place positive ce anomalies occur in sediments from the southwestern pacific basin between the epr and new zealand the highest ce la ratios of both micronodules and sediments are found in this region reflecting the well oxidized conditions prevailing there

sequential leaching of peru basin surface sediment for the assessment of aged and fresh heavy metal associations and mobility abstract sequential leaching experiments were carried out using the upper 25 cm of oxic to suboxic sediment from the peru basin and ferromanganese nodules in order to assess potential mobility and the associations of heavy metals in the mineral phases the general leaching pattern confirmed that in the nodules as well as in the upper dark brown sediment layer significant proportions of heavy metals like mn co ni zn cu and cd are associated with mno2 and would be released under reducing conditions in the underlying mn poor layers mn oxide hosted metals are minor to distinguish the leaching behaviour of aged and fresh sorbents radiotracers were adsorbed on the solids before leaching the dominant role of the mn oxide phase for scavenging dissolved heavy metals was confirmed for the upper sediment layer and the nodules for sorption equilibration times of 5 h and 7 days respectively the sorption process was rapid freshly sorbed metals were leached mostly in the same fractions as those in aged sorbents and little difference was found for sorption times of 5 h and 7 days in contrast in the mn poor sediment layers a significant amount of adsorbed radiotracers was easily remobilised by simple ion exchange especially cs and cd and an ageing effect shift to less easily leachable fractions was observed after 7 days when surface sediment is resuspended into the bottom water the mn oxide rich surface layer and nodule particles represent a much more effective heavy metal scavenger under oxic conditions compared to other mn poor sediment phases however at the same time the mn rich particles are a stronger potential source of toxic heavy metals in a shift to more reducing conditions

fe mn micronodules born in the metalliferous sediments of two spreading centres the east pacific rise and mid atlantic ridge abstract a geochemical study of fe mn micronodules associated with the metalliferous sediments at two spreading centres has shown that their composition depends on the site of micronodule formation close to the hydrothermal mounds they exhibit significant variation in elemental content related to the type of hydrothermal discharge low or high temperature the nature of primary hydrothermal matter plume fall out oxidised sulfides and the extent of diagenesis in this environment three types of micronodules can be distinguished although not observed as pure end members 1 diagenetic micronodules 2 micronodules formed generally from the plume fall out of oxyhydroxide matter and 3 micronodules grown on the oxidised sulfide grains supplied to the sediments by slumping or fall out of nearby buoyant plume away from the active spreading centre the hydrothermal signatures of primary precipitates are gradually masked and hydrogenous diagenetic processes lead the micronodule formation composition of micronodules becomes less variable well pronounced deep rift valleys confine the hydrothermal plume which brings the hydrothermal suspension into contact with restricted volumes of seawater and consequently weakens the hydrogenous influence on the primary hydrothermal matter shallow rift valleys do not confine hydrothermal plumes which are scattered over hundreds of kilometres by bottom currents this brings the hydrothermal suspended matter into contact with large volumes of seawater extensive scavenging occurs which masks the hydrothermal signal away from the spreading axis and enhances the hydrogenous one thus the ridge crest morphology defined by the spreading rate is supposed to play a certain role though indirect in the chemical composition of the primary precipitates and consequently in the composition of the micronodules formed