Lode–gold mineralization in the Tanami region, northern Australia     

David L. Huston  Leon Vandenberg  Andrew S. Wygralak  Terrence P. Mernagh  Leon Bagas  Andrew Crispe  Alexis Lambeck  Andrew Cross  Geoff Fraser  Nick Williams  Kurt Worden  Tony Meixner  Bruce Goleby  Leonie Jones  Pat Lyons  David Maidment 《Mineralium Deposita》2007,42(1-2):175-204

The Tanami region of northern Australia has emerged over the last two decades as the largest gold-producing region in the Northern Territory. Gold is hosted by epigenetic quartz veins in sedimentary and mafic rocks, and by sulfide-rich replacement zones within iron formation. Although limited, geochronological data suggest that most mineralization occurred at about 1,805–1,790 Ma, during a period of extensive granite intrusion, although structural relationships suggest that some deposits predate this period. There are three main goldfields in the Tanami region: the Dead Bullock Soak goldfield, which hosts the world-class Callie deposit; The Granites goldfield; and the Tanami goldfield. In the Dead Bullock Soak goldfield, deposits are hosted by carbonaceous siltstone and iron formation where a late (D₅) structural corridor intersects an early F₁ anticlinorium. In The Granites goldfield, deposits are hosted by highly sheared iron formation and are interpreted to predate D₅. The Tanami goldfield consists of a large number of small, mostly basalt-hosted deposits that probably formed at a high structural level during D₅. The D₅ structures that host most deposits formed in a convergent structural regime with σ ₁ oriented between E–W and ENE–WSW. Structures active during D₅ include NE-trending oblique thrust (dextral) faults and ESE-trending (sinistral) faults that curve into N- to NNW-trending reverse faults localized in supracrustal belts between and around granite complexes. Granite intrusions also locally perturbed the stress field, possibly localizing structures and deposits. Forward modeling and preliminary interpretations of reflection seismic data indicate that all faults extend into the mid-crust. In areas characterized by the N- to NW-trending faults, orebodies also tend to be N- to NW-trending, localized in dilational jogs or in fractured, competent rock units. In areas characterized by ESE-trending faults, the orebodies and veins tend to strike broadly east at an angle consistent with tensional fractures opened during E–W- to ENE–WSW-directed transpression. Many of these deposits are hosted by reactive rock units such as carbonaceous siltstone and iron formation. Ore deposition occurred at depths ranging from 1.5 to 11 km from generally low to moderate salinity carbonic fluids with temperatures from 200 to 430°C, similar to lode–gold fluids elsewhere in the world. These fluids are interpreted as the product of metamorphic dewatering caused by enhanced heat flow, although it is also possible that the fluids were derived from coeval granites. Lead isotope data suggest that lead in the ore fluids had multiple sources. Hydrogen and oxygen isotope data are consistent with both metamorphic and magmatic origins for ore fluids. Gold deposition is interpreted to be caused by fluid unmixing and sulfidation of host rocks. Fluid unmixing is caused by three different processes: (1) CO₂ unmixing caused by interaction of ore fluids with carbonaceous siltstone; (2) depressurization caused by pressure cycling in shear zones; and (3) boiling as ore fluids move to shallow levels. Deposits in the Tanami region may illustrate the continuum model of lode–gold deposition suggested by Groves (Mineralium Deposita 28:366–374, 1993) for Archean districts.  相似文献   

Evaluation of hydrologic impact of an irrigation curtailment program using Landsat satellite data     

Naga Manohar Velpuri  Gabriel B. Senay  Matthew Schauer  C. Amanda Garcia  Ramesh K. Singh  MacKenzie Friedrichs  Stefanie Kagone  Jonathan Haynes  Terrence Conlon 《水文研究》2020,34(8):1697-1713

Upper Klamath Lake (UKL) is the source of the Klamath River that flows through southern Oregon and northern California. The UKL Basin provides water for 81,000+ ha (200,000+ acres) of irrigation on the U.S. Bureau of Reclamation Klamath Project located downstream of the UKL Basin. Irrigated agriculture also occurs along the tributaries to UKL. During 2013–2016, water rights calls resulted in various levels of curtailment of irrigation diversions from the tributaries to UKL. However, information on the extent of curtailment, how much irrigation water was saved, and its impact on the UKL is unknown. In this study, we combined Landsat-based actual evapotranspiration (ETa) data obtained from the Operational Simplified Surface Energy Balance model with gridded precipitation and U.S. Geological Survey station discharge data to evaluate the hydrologic impact of the curtailment program. Analysis was performed for 2004, 2006, 2008–2010 (base years), and 2013–2016 (target years) over irrigated areas above UKL. Our results indicate that the savings from the curtailment program over the June to September time period were highest during 2013 and declined in each of the following years. The total on-field water savings was approximately 60 hm³ in 2013 and 2014, 44 hm³ in 2015, and 32 hm³ in 2016 (1 hm3 = 10,000 m³ or 810.7 ac-ft). The instream water flow changes or extra water available were 92, 68, 45, and 26 hm³, respectively, for 2013, 2014, 2015, and 2016. Highest water savings came from pasture and wetlands. Alfalfa showed the most decline in water use among grain crops. The resulting extra water available from the curtailment contributed to a maximum of 19% of the lake inflows and 50% of the lake volume. The Landsat-based ETa and other remote sensing datasets used in this study can be used to monitor crop water use at the irrigation district scale and to quantify water savings as a result of land-water management changes.  相似文献   

Dust settling in magnetorotationally driven turbulent discs – I. Numerical methods and evidence for a vigorous streaming instability     

Dinshaw S. Balsara  David A. Tilley  Terrence Rettig  Sean D. Brittain 《Monthly notices of the Royal Astronomical Society》2009,397(1):24-43

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When the long run matters     

Terrence Iverson  Scott Denning  Sammy Zahran 《Climatic change》2015,129(1-2):57-72

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Recent changes in the Labrador Sea Water within the Deep Western Boundary Current southeast of Cape Cod     

Beatriz Peña-Molino  Terrence M. Joyce 《Deep Sea Research Part I: Oceanographic Research Papers》2011,58(10):1019-1030

Water properties measured by the central mooring in the Line W mooring array southeast of Cape Cod document a large character shift during the period of November 2001 to April 2008. The observed temperature, salinity and planetary potential vorticity (PPV) anomalies manifest changes in the formation region of the water masses present at Station W, specifically upper Labrador Sea Water (uLSW), deep Labrador Sea Water (dLSW) and Overflow Water (OW). During the observation period, the minimum in the PPV anomaly field relative to the record mean PPV profile migrated from 1500 m, where it was originally found, to 700 m. Temporal changes in the vertical distribution of temperature and salinity were correlated with the PPV changes. This suggests a dLSW-dominated first half of the record versus an uLSW-dominated second half. The structure of these anomalies is consistent with observations within the Labrador Sea, and their transit time to Line W agrees well with tracer-derived times for signals spreading along the western boundary. In that context, the observed water properties at Line W in the early 2000s reflected the intense deep convection in the Labrador Sea in the mid-1990s, with less intense convection subsequently affecting lighter isopycnals. The observed velocity field is dominated by high-frequency (periods of days to months) fluctuations, however, a fraction of the velocity variability is correlated with changes in water mass properties, and indicate a gradual acceleration of the southwestward flow, with a corresponding increase in Deep Western Boundary Current transport.  相似文献   

A Review of Fluid Inclusions in Diagenetic Systems     

Terrence P. MERNAGH 《《地质学报》英文版》2015,89(3):697-714

The study of fluid inclusions can help constrain the conditions at which diagenetic minerals precipitated, leading to a better understanding of the geologic controls and relative timing of changes in porosity and/or mineralising events. Many of the diagenetic minerals are easily deformed and it is important to check for any post-entrapment changes to the inclusions. Possible post-entrapment changes include reaction with the host crystal, necking down, nucleation metastability and thermal re-equilibration. The recommended method of detecting these problems is to examine individual fluid inclusion assemblages (FIAs) and report data for each individual FIA. These studies have been enhanced by the development of new micro-analytical techniques such as micro-fluorescence spectroscopy, micro-infrared spectroscopy, nuclear magnetic resonance, various mass spectrometry techniques and the analysis of individual fluid inclusions using laser ablation/decrepitation methods. Special techniques have been developed for hydrocarbon-bearing inclusions such as the Grains containing Oil Inclusions (GOI), Fluid Inclusion Stratigraphy (FIS), and the Molecular Composition of Inclusions (MCI) techniques. The fluid inclusions that form in some minerals during diagenesis provide the only direct means of examining the fluids present in these systems. They provide useful temperature, pressure, and fluid composition data that cannot be obtained by other means.  相似文献   

Physiological costs and effects on the immune system of sewage sludge exposure in dab, Limanda limanda (L.)     

D.F. Houlihan  C.J. Secombes  M.J. Costello  R. Stagg  T. Fletcher  J. Brechin 《Marine environmental research》1995,39(1-4)

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New constraints on fluid sources in orogenic gold deposits,Victoria, Australia     

Bin?FuEmail author  Mark?A.?Kendrick  Alison?M.?Fairmaid  David?Phillips  Christopher?J.?L.?Wilson  Terrence?P.?Mernagh 《Contributions to Mineralogy and Petrology》2012,163(3):427-447

Fluid inclusion microthermometry, Raman spectroscopy and noble gas plus halogen geochemistry, complemented by published stable isotope data, have been used to assess the origin of gold-rich fluids in the Lachlan Fold Belt of central Victoria, south-eastern Australia. Victorian gold deposits vary from large turbidite-hosted ‘orogenic’ lode and disseminated-stockwork gold-only deposits, formed close to the metamorphic peak, to smaller polymetallic gold deposits, temporally associated with later post-orogenic granite intrusions. Despite the differences in relative timing, metal association and the size of these deposits, fluid inclusion microthermometry indicates that all deposits are genetically associated with similar low-salinity aqueous, CO₂-bearing fluids. The majority of these fluid inclusions also have similar ⁴⁰Ar/³⁶Ar values of less than 1500 and ³⁶Ar concentrations of 2.6–58 ppb (by mass) that are equal to or much greater than air-saturation levels (1.3–2.7 ppb). Limited amounts of nitrogen-rich fluids are present at a local scale and have the highest measured ⁴⁰Ar/³⁶Ar values of up to 5,700, suggesting an external or distinct source compared to the aqueous fluids. The predominance of low-salinity aqueous–carbonic fluids with low ⁴⁰Ar/³⁶Ar values, in both ‘orogenic’ and ‘intrusion-related’ gold deposits, is attributed to fluid production from common basement volcano-sedimentary sequences and fluid interaction with sedimentary cover rocks (turbidites). Aqueous fluid inclusions in the Stawell–Magdala deposit of western Victoria (including those associated with N₂) preserve mantle-like Br/Cl and I/Cl values. In contrast, fluid inclusions in deposits in the eastern structural zones, which contain more abundant shales, have elevated molar I/Cl ratios with maximum values of 5,170 × 10⁻⁶ in the Melbourne Zone. Br/I ratios in this zone range from 0.5 to 3.0 that are characteristic of fluid interaction with organic-rich sediments. The maximum I/Cl and characteristic Br/I ratios provide evidence for organic Br and I released during metamorphism of the shales. Therefore, the regional data provide strong evidence for the involvement of sedimentary components in gold mineralisation, but are consistent with deeper metamorphic fluid sources from basement volcano-sedimentary rocks. The overlying sediments are probably involved in gold mineralisation via fluid–rock interaction.  相似文献   

Introductory perspective on the COREF Project     

Yasufumi  Iryu  Hiroki  Matsuda  Hideaki  Machiyama  Werner E.  Piller  Terrence M.  Quinn  Maria  Mutti 《Island Arc》2006,15(4):393-406

Abstract Coral reefs are tropic to subtropic, coastal ecosystems comprising very diverse organisms. Late Quaternary reef deposits are fossil archives of environmental, tectonic and eustatic variations that can be used to reconstruct the paleoclimatic and paleoceanographic history of the tropic surface oceans. Reefs located at the latitudinal limits of coral‐reef ecosystems (i.e. those at coral‐reef fronts) are particularly sensitive to environmental changes – especially those associated with glacial–interglacial changes in climate and sealevel. We propose a land and ocean scientific drilling campaign in the Ryukyu Islands (the Ryukyus) in the northwestern Pacific Ocean to investigate the dynamic response of the corals and coral‐reef ecosystems in this region to Late Quaternary climate and sealevel change. Such a drilling campaign, which we call the COREF (coral‐reef front) Project, will allow the following three major questions to be evaluated: (i) What are the nature, magnitude and driving mechanisms of coral‐reef front migration in the Ryukyus? (ii) What is the ecosystem response of coral reefs in the Ryukyus to Quaternary climate changes? (iii) What is the role of coral reefs in the global carbon cycle? Subsidiary objectives include (i) the timing of coral‐reef initiation in the Ryukyus and its causes; (ii) the position of the Kuroshio current during glacial periods and its effects on coral‐reef formation; and (iii) early carbonate diagenetic responses as a function of compounded variations in climate, eustacy and depositional mineralogies (subtropic aragonitic to warm‐temperate calcitic). The geographic, climatic and oceanographic settings of the Ryukyu Islands provide an ideal natural laboratory to address each of these research questions.  相似文献   

A large marine ecosystem governance framework     

Lucia Fanning  Robin Mahon  Patrick McConney  Jorge Angulo  Felicity Burrows  Bisessar Chakalall  Diego Gil  Milton Haughton  Sherry Heileman  Sergio Martínez  L’ouverture Ostine  Adrian Oviedo  Scott Parsons  Terrence Phillips  Claudia Santizo Arroya  Bertha Simmons  Cesar Toro 《Marine Policy》2007

A large marine ecosystem (LME) governance framework, developed from a need to effectively address the sustainable management of the shared living marine resources of the Caribbean, is proposed. The framework is based on four propositions and focuses on a linked examination of two well-known components of LME-level governance: the policy cycle process by which decisions are made and the multi-level nature of LMEs. It accommodates the diversity of policy cycles at multiple levels and the linkages among them required for effective governance of LMEs. The framework takes into account of factors such as context, purpose, jurisdictional scale, capacity and complexity and provides a means to identify critical areas for intervention.  相似文献