Hydrothermal Alteration and Cu-Au Mineralization at Nena High Sulfidation-type Deposit, Frieda River, Papua New Guinea     

Joseph Onglo Espi    Yoshimichi Kajiwara    Mike A. Hawkins  Tony Bainbridge 《Resource Geology》2002,52(4):301-313

Abstract. The Nena Cu‐Au deposit, located in the Frieda River mineral district of northwestern mainland Papua New Guinea, is a composite structurally‐lithologically controlled high sulfidation (HS) system. Its hydrothermal alteration and Cu‐Au mineralization are presented in this paper. Initially propylitized andesitic volcanics veined by epithermal quartz were pervasively superimposed by zoned HS alteration. The zonation grades from vuggy silica core to sulfur‐rich, pyritic silica‐alunite halo followed by pyrophyllite‐dickite‐kaolinite interval and finally to thin illite‐smectite margin, suggesting progressive decrease in temperature and increase in pH. This zonation is enveloped by chlorite‐epidote‐calcite‐gypsum alteration. The acid altered rocks were then invaded by multiple phases of pyrite, subsequently crosscut by quartz, vein alunite and barite. Then sequential deposition of bladed covellite, enargite, luzonite and stibioluzonite occurred from the NW to the SE portions of the deposit, forming a zonation suggestive of progressive decrease in temperature, sulfur fugacity and sulfidation stage. Most ore mineralization occurs in the vuggy silica core. Gold mineralization commenced from the transition of enargite to luzonite and continued throughout the stibioluzonite stage. Associated with gold deposition are Au‐rich pyrite, tennantite‐tetrahedrite, chalcopyrite‐bornite, native tellurium, electrum, calaverite, bismuthinite and galena. Native sulfur occupied the remaining cavities and represents the waning stage of the hydrothermal system. Fluid inclusions studies distinguished magmatic (>300–350d?C, 9–15 wt% NaCl equiv.) and meteoric (<150–200d?C, 1–2 wt% NaCl equiv.) fluids (Holzberger et al., 1996). Temperatures and salinities of fluid inclusions from barite associated with Cu sulfides show a general decrease from NW (330d?C, 9–15 wt% NaCl equiv.) to SE (172d?C, 10 wt% NaCl equiv.) parts of the deposit, indicating gradual entrainment of ground water (Hitchman and Espi, 1997). Interaction of magmatic fluids with meteoric water accompanied by changes in temperature, salinity, acidity and oxidation state of the resultant fluids is interpreted to have been the main cause of metal precipitation. Finally, supergene processes generated Au zone with an underlying chalcocite‐covellite‐digenite blanket over the primary sulfides at depth. Gold occurs as lattice constituent in scorodite, limonite‐goethite and jarosite. Chalcocite is more abundant and widespread than other Cu sulfides. Acidic fluids deposited powdery alunite and kaolinite, vein alunite and amorphous silica. Weakly secondary biotite‐quartz altered porphyry located below the known HS Cu‐Au deposit contains chalcopyrite‐bornite and is overprinted by quartz‐alunite‐pyro‐phyllite‐pyrite assemblage. This feature indicates close temporal, spatial and genetic relation between the two deposit types.  相似文献   

Numerical modelling of mechanical controls on coeval steep and shallow dipping auriferous quartz vein formation in a thrust zone,Macraes mine,New Zealand     

Phaedra Upton  Mike Begbie  Dave Craw 《Mineralium Deposita》2008,43(1):23-35

The Hyde-Macraes Shear Zone (HMSZ) is a regionally continuous, low-angle, NE dipping (~15°) late-metamorphic thrust zone in the Mesozoic Otago Schist. The shear zone, which is host to large volumes of mineralised schist, consists of foliated fissile schist with some massive schist pods. Two sets of quartz veins are found within the HMSZ: thrust-related, shallowly dipping veins that were emplaced parallel or sub-parallel to the shears and swarms of steeply dipping extensional veins, which cut across the metamorphic foliation. The latter are restricted to the massive schist pods. Mutual cross-cutting relationships occur between steep extensional veins and shallow-dipping veins, suggesting that they formed contemporaneously. The co-existence of these two vein types locally implies local rotation of the principal stress axes to produce extensional veins within a regional thrust setting. The steep extensional veins are spatially related to lateral and oblique ramps within the HMSZ. Three-dimensional mechanical models show that these lateral or oblique ramps can produce favourable conditions for extensional vein formation when combined with a high fluid pressure and oblique convergence. Mechanical requirements include a reduced differential stress, a positive volumetric strain and an increase in the horizontal shear stress. Our models show that under certain conditions, it is possible for extension-related structures to form during shortening because of local changes in the stress state without the need for a regional scale switch in the imposed stress field. The convergence direction across the HMSZ during formation of the steep extensional veins was ~WNW.  相似文献   

Quantifying the relationship between structural deformation and the morphology of submarine channels on the Niger Delta continental slope     

W. Hamish Mitchell  Alexander C. Whittaker  Mike Mayall  Lidia Lonergan  Marco Pizzi 《Basin Research》2021,33(1):186-209

The processes and deposits of deep‐water submarine channels are known to be influenced by a wide variety of controlling factors, both allocyclic and autocyclic. However, unlike their fluvial counterparts whose dynamics are well‐studied, the factors that control the long‐term behaviour of submarine channels, particularly on slopes undergoing active deformation, remain poorly understood. We combine seismic techniques with concepts from landscape dynamics to investigate quantitatively how the growth of gravitational‐collapse structures at or near the seabed in the Niger Delta have influenced the morphology of submarine channels along their length from the shelf edge to their deep‐water counterpart. From a three dimensional (3D), time‐migrated seismic‐reflection volume, which extends over 120 km from the shelf edge to the base of slope, we mapped the present‐day geomorphic expression of two submarine channels and active structures at the seabed, and created a Digital Elevation Model (DEM). A second geomorphic surface and DEM raster—interpreted to closer approximate the most recent active channel geometries—were created through removing the thickness of hemipelagic drape across the study area. The DEM rasters were used to extract the longitudinal profiles of channel systems with seabed expression, and we evaluate the evolution of channel widths, depths and slopes at fixed intervals downslope as the channels interact with growing structures. Results show that the channel long profiles have a relatively linear form with localized steepening associated with seabed structures. We demonstrate that channel morphologies and their constituent architectural elements are sensitive to active seafloor deformation, and we use the geomorphic data to infer a likely distribution of bed shear stresses and flow velocities from the shelf edge to deep water. Our results give new insights into the erosional dynamics of submarine channels, allow us to quantify the extent to which submarine channels can keep pace with growing structures, and help us to constrain the delivery and distribution of sediment to deep‐water settings.  相似文献   

Taking the pulse of hydrology education     

Thorsten Wagener  Markus Weiler  Brian McGlynn  Mike Gooseff  Tom Meixner  Lucy Marshall  Kevin McGuire  Mike McHale 《水文研究》2007,21(13):1789-1792

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The AAT/WFI survey of the Monoceros Ring and Canis Major dwarf galaxy – I. From l= (193–276)°     

Blair C. Conn  Richard R. Lane  Geraint F. Lewis  Rodrigo Gil-Merino  Mike J. Irwin  Rodrigo A. Ibata  Nicolas F. Martin  Michele Bellazzini  Robert Sharp  Artem V. Tuntsov  Annette M. N. Ferguson 《Monthly notices of the Royal Astronomical Society》2007,376(3):939-959

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Improved NLDAS‐2 Noah‐simulated hydrometeorological products with an interim run          下载免费PDF全文

Youlong Xia  Christa D. Peter‐Lidard  Maoyi Huang  Helin Wei  Mike Ek 《水文研究》2015,29(5):780-792

In North American Land Data Assimilation System Phase 2 (NLDAS‐2) Noah simulation, the NLDAS team introduced an intermediate ‘fix’ to constrain the surface exchange coefficient when the atmospheric boundary layer is stable. In the current NLDAS‐2 Noah version, this fix is used for all stable cases including snow‐free grid cells. In this study, we simply apply this fix to the grid cells in which both stable atmospheric boundary layer and snow exist simultaneously, excluding the snow‐free grid cells as we recognize that the fix in NLDAS‐2 is too strong. We conduct a 31‐year (1979–2009) NLDAS‐2 Noah interim (Noah‐I) run and use observed streamflow, evapotranspiration, land surface temperature, soil temperature, and ground heat flux to evaluate the results, including comparisons with the original NLDAS‐2 Noah run. The results show that Noah‐I has the same performance as NLDAS‐2 Noah for snow water equivalent; however, Noah‐I significantly improved the simulation of other hydrometeorological products as noted earlier when compared with NLDAS‐2 Noah and the observations. This simple modification is being included in the next Noah version used in NLDAS. The hydrometeorological products from the improved NLDAS‐2 Noah‐I are being staged on the National Centers for Environmental Prediction public server. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

Development and Implementation of a National Groundwater Monitoring Network          下载免费PDF全文

Mike Wireman 《Ground Water Monitoring & Remediation》2015,35(2):21-22

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Biodegradation of Simazine and Diuron Herbicides under Aerobic and Anoxic Conditions Relevant to Managed Aquifer Recharge of Storm Water          下载免费PDF全文

Ali Shareef  Declan Page  Joanne Vanderzalm  Mike Williams  V. V. S. R. Gupta  Peter Dillon  Rai Kookana 《洁净——土壤、空气、水》2014,42(6):745-752

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Episodic post‐rift deformation in the south‐eastern Australian passive margin: evidence from the Lapstone Structural Complex          下载免费PDF全文

Andrew McPherson  Dan Clark  Mike Macphail  Matthew Cupper 《地球表面变化过程与地形》2014,39(11):1449-1466

Identifying the influence of neotectonics on the morphology of elevated passive margins is complicated in that major morpho‐structural patterns might plausibly be explained by processes related to late Mesozoic to early Cenozoic rifting and/or differential erosion induced by Cenozoic epeirogenic uplift. The proportional contribution of each process can vary from continent to continent, and potentially even within the same passive margin. In the passive margin setting of the southeast Australian highlands the documented occurrence of neotectonic deformation is rare, and accordingly its role in landscape evolution is difficult to establish. The results of investigations within the Lapstone Structural Complex, which forms the eastern range front of the Blue Mountains Plateau, provide evidence for two periods of Cenozoic neotectonic uplift in this part of the highlands. The first, demonstrated by seismic and structural evidence, is suggested to have occurred in the Paleogene, and is thus unrelated to Cretaceous rifting. The second period, demonstrated by evidence from the Kurrajong Fault (presented herein) suggests that uplift occurred in both the Mio‐Pliocene and the Middle Pleistocene. The cumulative Neogene and younger uplift of ~15 m determined for the Kurrajong Fault is less than 10% of the 130 m of total measured throw across the fault. The apparently minor contribution of neotectonism to the current elevation of the Blue Mountains Plateau supports a predominantly erosional exhumation origin for the topographic relief at the plateau's eastern edge. This finding contrasts with evidence from fault complexes associated with similar topographic relief elsewhere in the south‐eastern highlands, indicating that present‐day topography cannot be directly related to relief generated by Neogene and younger uplift, even from relatively closely‐spaced (< 150 km) structures within the same passive margin. These findings have implications for understanding the spatio‐temporal variability of post‐rift faulting in continental passive margin settings and the evolution of landscapes therein. © Commonwealth of Australia. Earth Surface Processes and Landforms © 2014 John Wiley & Sons, Ltd.  相似文献   

Emulator-assisted data assimilation in complex models   总被引：1，自引：1，他引：0  

Nugzar Yu Margvelashvili  Mike Herzfeld  Farhan Rizwi  Mathieu Mongin  Mark E. Baird  Emlyn Jones  Britta Schaffelke  Edward King  Thomas Schroeder 《Ocean Dynamics》2016,66(9):1109-1124

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