19 research outputs found
A technical study of the digestibility of corn stover silage for beef cows
Cover title.Bibliography: p. 48
Paragenesis of the Paroo Fault, Mount Isa, Queensland, Australia
The sigmoidal 23km long Paroo Fault forms the footwall to the Mount Isa copper orebodies which lie within a silica and dolomite halo. Orebodies are predominantly located directly above the fault in the Proterozoic (c. 1650 Ma) Urquhart Shale which the fault juxtaposed against the\ud
metabasalts and psammites of the Haslingden Group (c.1750 Ma), though some are "perched" tens to hundreds of meters above the fault. The Paroo Fault is a probable conduit for ore-forming fluids but the paragenesis of the fault rocks has never been studied. Here we present results of\ud
transects across it from the basement to the overlying shales using petrography, microstructural analysis and cathodoluminescence (SEM-CL).\ud
The first generation of quartz (Q1) is brightly luminescent and consists of angular to sub-rounded clasts (10-100μm), formed during early faulting. A subsequent deformation caused fracturing and rounding of Q1 clasts. Then a weekly luminescent generation of quartz (Q2) formed angular to sub\ud
rounded clasts around Q1. Cross cutting Q2 are fine (10-30μm) veins of moderately luminescent quartz (Q3) containing sulphide. Coarse carbonate (C1) and some sulphide mineralisation formed (in the fault) and were subsequently deformed. Q4 is luminescent quartz which forms large veins (300-1000μm) and is cross cut by the final stage of quartz (Q5) comprising small (1-5μm) brightly\ud
luminescent veins. C2 carbonates form along the edge of the large recrystalised quartz (Q1-5) grain boundaries in association with microfracturing and grain size reduction. C2 is associated with chlorite and carbonaceous material and is prevalent at the edges of the Paroo Fault.\ud
Reverse movement is recognized on the Paroo fault from macro-scale observations and from fluid inclusion plane (FIP) analysis. Normal movement is recognized from gouge marks on graphitic mylonite and quartz fish, drag structures, and the FIPs. Normal postdates reverse movement as the lineations are best preserved. Although the reverse movement determined from FIPs postdates Q1-3, this movement is consistent with the flat part of the Paroo Fault acting as a dilatant bend. We therefore concluded that the quartz (Q3) and carbonate (C1) veins which are associated with sulphide mineralisation may have been caused by reverse movement creating a dilatational jog during D3
Orientations of fluid inclusion planes in the Paroo fault\ud and their relation to macro-scale structures at Mount Isa, northwest Queensland
The Paroo Fault is a prospective conduit for the oreforming\ud
fluids that created the Mt Isa copper deposit, but its kinematic history and relationship to copper mineralisation are unclear. Fluid inclusion planes in quartz from the fault zone occur in two prominent sets; one set dips more steeply, and the other set less steeply than the fault zone. They may indicate reverse and normal movements, which can potentially be timed with respect to ore-forming fluids. Different rock types within the fault and the different orientations of fluid inclusion planes are evidence of a complex history on the Paroo Fault, which may be the key to copper mineralisation
Orientations of fluid inclusion planes in the Paroo fault and their relation to macro-scale structures at Mount Isa, northwest Queensland
The Paroo Fault is a prospective conduit for the oreforming
fluids that created the Mt Isa copper deposit, but its kinematic history and relationship to copper mineralisation are unclear. Fluid inclusion planes in quartz from the fault zone occur in two prominent sets; one set dips more steeply, and the other set less steeply than the fault zone. They may indicate reverse and normal movements, which can potentially be timed with respect to ore-forming fluids. Different rock types within the fault and the different orientations of fluid inclusion planes are evidence of a complex history on the Paroo Fault, which may be the key to copper mineralisation
A technical study of the digestibility of corn stover silage for beef cows /
Cover title.Bibliography: p. 482Mode of access: Internet
Physical and chemical characteristics of the Ernest Henry iron oxide copper gold deposit, Australia; implications for IOGC genesis
The ~1530 Ma Ernest Henry IOCG deposit in the Cloncurry district of the Eastern Succession of the Mount Isa Inlier is one of the largest IOCG deposits in Australia. The deposit is hosted by brecciated and strongly K feldspar altered Mount Fort Constantine metavolcanics (~1740 Ma). Ore-bearing assemblages are dominated by magnetite, chalcopyrite, pyrite, carbonate, quartz and apatite. Most gold is present as electrum, in both pyrite and chalcopyrite. At shallow levels, the ore is dominantly infill between rounded clasts of K feldspar altered metavolcanics. In this setting, ore grade is inversely correlated with breccia clast abundance, reflecting the dominance of ore minerals as infill. At greater depths however, the boundary between clasts and infill becomes diffuse, and ore minerals are not restricted to the space between clasts, but are also present within clasts, indicating that replacement was a key process of ore deposition. At these greater depths, the relationship between grade and clast abundance breaks down, also consistent with ore precipitation by replacement as well as infill. Deep in the deposit, multiple generations of breccias are present, and late "second generation breccias" are iron-rich and contain coarse rounded and corroded fragments of pyrite, chalcopyrite and magnetite in a magnetite-rich matrix. The presence of clasts of ore-related minerals suggests that a feeder zone or region of pre-enrichment exists at depth, and may have been critical in localising ore. The Ernest Henry breccia is texturally similar to some regional unmineralised hydrothermal breccias, which are interpreted to have formed by fluidisation and particle transport over hundreds to thousands of metres by high energy fluids.\ud
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Potassic alteration that forms a halo to the deposit, extends for over a kilometre beyond the ore zone. This alteration zone overprints earlier regional sodic and sodic-calcic alteration, and is in turn overprinted by brecciation and copper-gold mineralisation. In addition to K, relative to the host rocks, the deposit is enriched in Ba, Mn, Cu, Au, Fe, Mo, U, Sb, W, Sn, Bi, Ag, F, REE, S, As, Co and Ca. Several lines of evidence, including C, O, and S isotopes, fluid inclusion halogen ratios and fluid inclusion Ar isotope ratios, are consistent with involvement of both magmatic and basinal fluid in the transport and precipitation of these elements. Fluid inclusions indicate that both hypersaline brines (~35 to 70 wt.% NaCl equiv) and CO2-rich fluids were abundant, although the role of each in the transport of ore-related elements is not clear. The deposit-wide correlation between copper and gold suggest that both travelled in the same fluid.\ud
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Pyrite at Ernest Henry is strongly zoned, with arsenic, nickel and cobalt all ranging from a few hundred ppm to a few wt.% within individual grains of pyrite. Such pyrite compositions are not unusual relative to other IOCG deposits or weakly mineralised IOCG-like magnetite-matrix hydrothermal breccias in the Eastern Succession. On the other hand, with up to 1 wt.% Mn, Ernest Henry magnetite is the most manganese-enriched hydrothermal magnetite identified in the Cloncurry region. Mn/Ti ratios in Ernest Henry and several other regional IOCG deposits are consistently greater than those in unmineralised IOCG-like magnetite-matrix breccias from the Eastern Succession. Apatite at Ernest Henry is unusually fluorine and arsenic-rich, and is zoned with variable concentrations of arsenic and sulphur. Around the world, arsenic (and fluorine)-rich apatite is common in iron-manganese-rich seafloor deposits. The strong enrichments of iron within the deposit, manganese in magnetite and arsenic in apatite, may indicate interaction of hydrothermal fluids with iron-manganese-rich seafloor sediments and banded iron formations, such as those in the Overhang Jaspilite, which may be present below the deposit.\ud
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We propose that the Ernest Henry IOCG deposit formed where mafic and felsic magmas of the ~1530 Ma Naraku batholith mingled, driving volatile exsolution. Extreme fluid overpressuring resulted, confined by an impermeable carapace formed by regional sodic and sodic-calcic alteration. The eventual failure of this seal led to a high-energy fluid-flow event forming hydrothermal breccias with upwardly transported and milled clasts. Mixing of basinal and magmatic fluids accompanied ore precipitation, although the source of the metals remains unclear. In the upper portions of the deposit, most ore was precipitated as hydrothermal infill between clasts of K feldspar-altered metavolcanics. At greater depths in the ore body, interaction between fluids and rocks was more prolonged, forming both infill and replacement-style ores
Syngenetic-remobilized versus epigenetic: why won't the Mount Isa copper controversy go away?
Over half a century of research on and mining of the Proterozoic, shale-hosted Mount Isa copper orebodies has not removed the shadows of doubt from genetic models for this\ud
deposit. The controversy stems from a broad range of seemingly conflicting datasets, and also the insistence by many researchers that a single model adequately describes the ore genesis. This contribution aims to present the different models with as little bias as possible, and attempts to come up with a more comprehensive explanation for the genesis of this extraordinary giant, both in its local and regional context
The Portland region: Where city and suburbs talk to each other ... and sometimes agree
Portland, OR, is often cited as an example of successful regional governance and planning. The metropolitan area appears to match many of the precepts of the popular compact city model of urban growth and to demonstrate the capacity of local and state government to shape growing metropolitan regions. Given this reputation, it is important to evaluate the relevance of the Portland experience for other communities, distinguishing unique local circumstances form generalizable characteristics. This analysis explores the spatial character of metropolitan Portland in the 1990s, summarizes the politics of regional planning, examines weaknesses in the Portland approach, and offers suggestions for other metropolitan areas. The study finds that many of Portland\u27s accomplishments center on urban design, but that the region\u27s most distinguishing characteristics is its attention to political process. The discussion concludes with suggestions about the value of extensive civic discourse,incremental policy making, and institution building