Genna D.,University of Quebec at Chicoutimi |
Genna D.,Experimental and Quantitative Metallogeny Research Laboratory LAMEQ at UQAC |
Gaboury D.,University of Quebec at Chicoutimi |
Gaboury D.,Experimental and Quantitative Metallogeny Research Laboratory LAMEQ at UQAC |
Ore Geology Reviews | Year: 2014
The distribution of rare earth elements (REE) in the alteration zones surrounding modern and ancient volcanogenic massive sulfide (VMS) deposits is often characterized by a wide range of variations comprising both gains and losses of light REE (LREE: La to Sm) and europium. The evolution of the hydrothermal system is recorded by mineral assemblages and their chemical composition. To address the behavior of the REE in such a context, the Bracemac-McLeod Archean VMS deposits of the Matagami district are used. There, mineralization was formed mainly by subsea-floor replacement along a tuffaceous marker unit (Key Tuffite) of homogenous andesitic composition, hence providing a single protolith to account for mineral and chemical variations in relation to ore position. We combine whole-rock and mineral REE data in both distal sericite and proximal chlorite alteration surrounding the mineralization. A model, integrating observed textural relationships, geochemical data and current understanding of mineral stabilities, is proposed to explain the redistribution of the REE during the evolution of the VMS hydrothermal system. The distal sericite zone represents the early, low temperature alteration. It is characterized by the destruction of volcanic glass and plagioclase leading to a negative Eu anomaly in the whole-rock analyses and the depletion of LREE. The proximal chlorite zone was formed during the thermal evolution of a fertile VMS hydrothermal system. It is generally characterized by gains of LREE and Eu, although some chloritized samples are depleted in LREE. Petrographic observations suggest that the coprecipitation of allanite with chlorite explains the increase of LREE, whereas a mass balance calculation indicates that the precipitation of apatite (±. carbonates) essentially controls the Eu. Local silicification, occurring as pulses during the hydrothermal system life, is also of interest because it could preserve an intermediate alteration state and thus provide additional information on the evolution of the hydrothermal system. The mobility of REE is indicative of specific hydrothermal conditions, which may reflect the efficiency of a mineralizing hydrothermal system. At Matagami, the mobility of LREE and Eu could be used for vectoring in exploration, especially Eu which has an anomalous behavior that extends far beyond the limit of the sulfide zone, into the distal sericitic low-temperature alteration (up to 400. m from the ore zones). © 2014 Elsevier B.V.
Genna D.,University of Quebec at Chicoutimi |
Gaboury D.,University of Quebec at Chicoutimi |
Mineralium Deposita | Year: 2014
The Key Tuffite is a stratigraphic marker unit for most of the zinc-rich volcanogenic massive sulfide deposits of the Matagami Camp in the Abitibi Greenstone Belt. This 2- to 6-m-thick unit was previously interpreted as a mixture of ash fall (andesitic to rhyolitic tuffaceous components) and volcanogenic massive sulfide (VMS)-related chemical seafloor precipitate (exhalative component). Previous attempts to develop geochemical exploration vectoring tools using metal content within the Key Tuffite were mostly inconclusive due to the complex nature of the Key Tuffite unit and a poor understanding of its composition, origin and relationship with the VMS-forming hydrothermal systems. Detailed mapping and thorough lithogeochemistry of the Key Tuffite in the vicinity of the Perseverance and Bracemac-McLeod deposits indicate that the Key Tuffite is a homogeneous calc-alkaline, andesitic tuff that was deposited before the VMS deposits were formed. The unit is mostly devoid of exhalative component, but it is strongly hydrothermally altered close to orebodies. This is characterized by a strong proximal chloritization and a distal sericitization, which grades laterally into the unaltered Key Tuffite. Neither the Key Tuffite nor the ore was formed by seafloor exhalative processes for the two studied deposits. This probably explains why previously proposed exploration models based on metal scavenging proved unsuccessful and suggests that a re-evaluation of the exhalative model should be done at the scale of the mining camp. However, as shown in this study, hydrothermal alteration can be used to vector towards ore along the Key Tuffite. © 2013 Springer-Verlag Berlin Heidelberg.
Gumede H.,Chamber of Mines RSA |
Blomerus K.,Chamber of Mines RSA |
Journal of the Southern African Institute of Mining and Metallurgy | Year: 2014
The challenges of noise emission in the mining industry are well known. These challenges are exacerbated by the increasing trend towards mechanized mining, and there is general consensus that an effective industry-wide Buy Quiet initiative (BQI) will significantly assist in reducing noise-induced hearing loss by minimizing noise at its source. In its endeavours to improve the health of workers, the MOSH Noise Team has facilitated development of a proposed strategy and structure for a BQI. Extensive consultation with stakeholders resulted in support for the initiative. The MOSH Noise Team was advised to solicit the contributions of consulting mechanical and electrical engineers (CM&EEs), whose support is viewed as critical for realization of the initiative, since elimination of noise at source is an engineering challenge, and most procurement standards and specifications are set and managed by engineers. A workshop with CM&EEs and their representatives, as well as group environmental engineers (GEEs), confirmed the urgent need for the initiative and provided valuable insights. The workshop used obstaclebased planning techniques to identify the factors on which the success of this BQI will depend. Most potential obstacles to the implementation revolved around proper scoping, leadership commitment, and companies' adherence to the initiative. Lack of involvement by the relevant stakeholders and economic issues were also identified as potential obstacles. Delegates at the workshop felt that the successful implementation of the industry-wide BQI, will depend on the mining industry addressing the specific obstacles. The most critical and urgent issue was identified as the formation of a properly constituted industry-wide BQI task team that includes representatives from critical stakeholder groups and which is mandated and empowered to drive the initiative. © The Southern African Institute of Mining and Metallurgy, 2014.
IMPC 2014 - 27th International Mineral Processing Congress | Year: 2014
The objective of this project was to investigate the application of Prompt Gamma Neutron Activation Analysis (PGNAA) technology to provide real-time on-belt elemental analysis of feed ore in base metal sulphide processing, in this case at the Mount Isa Mines Zinc-Lead Concentrator Heavy Medium Plant (HMP). After initial exploratory testwork proved successful, a Geoscan On-Belt Elemental Analyser was retrofitted onto the existing HMP feed conveyor. Dynamic calibration of the Geoscan was conducted based on laboratory XRF analysis results of the HMP feed conveyor hammer autosampler samples from May to November 2013. Comparison of the Geoscan results to the laboratory XRF analysis results during and after dynamic calibration indicated the technology had acceptable accuracy to be incorporated into HMP process control. The variation between the two sets of data includes all primary sampling, sample preparation and XRF analysis errors as well as the Geoscan errors themselves. The Geoscan instrument precision must be calculated separately through a duplicate sampling campaign and independent laboratory analysis before extending the scope of its range of application beyond HMP process control. The expected benefits of integrating the Geoscan real-time data into HMP process control are optimised HMP metal recovery, improved cost efficiency and improved stability of the downstream processes (milling and flotation). Utilisation of the Geoscan will also enable improved feedback to mines on grade control and dilution, and provide additional information on individual ore types when fed as campaigns to HMP.
News Article | March 31, 2015
As Comcast continues its attempt to purchase Time Warner Cable, another deal announced today would see the cable industry shrink even further. Charter Communications, the fourth-largest cable provider in the US, has agreed to purchase competitor Bright House Networks for $10.4 billion in cash and stock. Bright House is the sixth-largest US provider, but Charter says the merged company would become the second biggest cable operator by customer volume if the deal successfully closes. Charter had once signaled an interest in scooping up Time Warner Cable before Comcast came in with its own offer, which federal regulators are continuing to review (and Charter stands to gain from). This transaction will also require regulatory and shareholder approval, though it may not face quite the same level of scrutiny as Comcast's Time Warner Cable takeover or AT&T's current bid to buy DirecTV. Bright House serves approximately 2 million customers in central Florida, according to a press release, including Orlando and Tampa Bay, plus other markets in Alabama, Indiana, Michigan, and California. "Bright House has built outstanding cable systems in attractive markets that are either complete, or contiguous with the New Charter footprint," said Charter CEO Tom Rutledge. "This acquisition enhances our scale, and solidifies New Charter as the second largest cable operator in the US."