The effects of amphibolite facies metamorphism on the trace element composition of pyrite and pyrrhotite in the Cambrian Nairne Pyrite Member, Kanmantoo Group, South Australia

The trace element composition of pyrite has been used to explore for hydrothermal ore deposits and to understand ore-forming processes. However, the effects of metamorphism on the trace element distribution in pyrite have received relatively limited attention. In this study, laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) analyses of pyrite and pyrrhotite, along with minor amounts of sphalerite, chalcopyrite, and galena, are used to evaluate the effects of amphibolite facies metamorphism on the trace element distribution and remobilization of metals in iron sulfides in the clastic sediment-hosted Cambrian Nairne Pyrite Member (NPM), South Australia. The NPM and the Mt. Torrens Pb-Zn-Ag prospect, which occur near the base of the Kanmantoo Group, preserve irregularly zoned subhedral to euhedral metamorphic pyrite (Py1) and anhedral pyrrhotite (Po1), along with relatively minor quantities of remobilized anhedral pitted and cataclastic pyrite (Py2a) in quartzofeldspathic rocks and anhedral inclusion-poor pyrite (Py2b) in calc-silicate rocks that armor or cross-cut earlier formed Py1. Rare anhedral secondary melnikovite pyrite (Py3) locally formed on the margins of Py1 and Py2a. Trace element studies show that Py1 in the NPM at Brukunga and Ironstone Ridge contains mean values of 1254 ppm Co, 123 ppm Ni, 2167 ppm As, 16 ppm Se, 10 ppm Cu, 25 ppm Zn, and 15 ppm Pb, whereas Py1 in the Mt. Torrens prospect contains mean values of 2312 ppm Co, 263 ppm Ni, 1835 ppm As, 95 ppm Se, 9 ppm Cu, 6 ppm Zn, and 9 ppm Pb. Rare inclusion-rich cores of Py1 show higher concentrations of trace elements than inclusion-free rims with minor amounts of chalcopyrite, galena, and sphalerite forming along grain boundaries or in fractures within pyrite. This is interpreted to be the result of the release of Cu, Pb, and Zn from pyrite as it recrystallized. Remobilization of these elements then formed discrete sulfides at the millimeter to centimeter scale, with some exceptions at the meter scale where chalcopyrite, sphalerite, and galena, along with other sulfides and sulfosalts, formed in veins and tension gashes. These observations suggest that remobilization of trace metals, including Cu, Pb, and Zn, did not migrate more than a few meters at most. Moreover, despite the recrystallization of pyrite and pyrrhotite and subsequent remobilization of some trace elements (i.e., Co, Ni, As), which were structurally bound in these Fe sulfides, still retain elevated concentrations at amphibolite facies conditions. Remobilization of metals from the NPM during metamorphism to form Cu-Au (e.g., Kanmantoo) and Pb-Zn- Ag-(Cu-Au) (e.g., Angas, Wheal Ellen) deposits in the Tapanappa Formation stratigraphically higher in the Kanmantoo Group seems unlikely. However, it is possible that one source of metals for these deposits could have been leached from the NPM and carried in large hydrothermal cells prior to metamorphism. Such a scenario is consistent with previously published sulfur isotope data for sulfides from the NPM, and Cu-Au and Pb-Zn-Ag- (Cu-Au) deposits, which indicate that sulfur derived from the NPM and pyritic schists in the Kanmantoo Group was a likely source of sulfur for the base and precious metal deposits

Cross standard form : a solution to improve a given controller with H2 or Hoo specifications

This paper introduces in cross standard form (CSF) as a solution to the inverse optimal control problem. That is, the CSF is a canonical standard problem whose unique H1 or H2 optimal controller is a given controller. From the control design point of view, the general idea is to apply the CSF to a given controller in order to set up a standard problem which can be completed to handle frequency domain H2 or H1 specification. The analytical formulation of the CSF proposed in this paper can be applied to reduced-, full- or augmented-order compensators or two-degree of freedom compensations. Numerical and academic examples are given

Albiglutide and cardiovascular outcomes in patients with type 2 diabetes and cardiovascular disease (Harmony Outcomes): a double-blind, randomised placebo-controlled trial

Background: Glucagon-like peptide 1 receptor agonists differ in chemical structure, duration of action, and in their effects on clinical outcomes. The cardiovascular effects of once-weekly albiglutide in type 2 diabetes are unknown. We aimed to determine the safety and efficacy of albiglutide in preventing cardiovascular death, myocardial infarction, or stroke. Methods: We did a double-blind, randomised, placebo-controlled trial in 610 sites across 28 countries. We randomly assigned patients aged 40 years and older with type 2 diabetes and cardiovascular disease (at a 1:1 ratio) to groups that either received a subcutaneous injection of albiglutide (30–50 mg, based on glycaemic response and tolerability) or of a matched volume of placebo once a week, in addition to their standard care. Investigators used an interactive voice or web response system to obtain treatment assignment, and patients and all study investigators were masked to their treatment allocation. We hypothesised that albiglutide would be non-inferior to placebo for the primary outcome of the first occurrence of cardiovascular death, myocardial infarction, or stroke, which was assessed in the intention-to-treat population. If non-inferiority was confirmed by an upper limit of the 95% CI for a hazard ratio of less than 1·30, closed testing for superiority was prespecified. This study is registered with ClinicalTrials.gov, number NCT02465515. Findings: Patients were screened between July 1, 2015, and Nov 24, 2016. 10 793 patients were screened and 9463 participants were enrolled and randomly assigned to groups: 4731 patients were assigned to receive albiglutide and 4732 patients to receive placebo. On Nov 8, 2017, it was determined that 611 primary endpoints and a median follow-up of at least 1·5 years had accrued, and participants returned for a final visit and discontinuation from study treatment; the last patient visit was on March 12, 2018. These 9463 patients, the intention-to-treat population, were evaluated for a median duration of 1·6 years and were assessed for the primary outcome. The primary composite outcome occurred in 338 (7%) of 4731 patients at an incidence rate of 4·6 events per 100 person-years in the albiglutide group and in 428 (9%) of 4732 patients at an incidence rate of 5·9 events per 100 person-years in the placebo group (hazard ratio 0·78, 95% CI 0·68–0·90), which indicated that albiglutide was superior to placebo (p<0·0001 for non-inferiority; p=0·0006 for superiority). The incidence of acute pancreatitis (ten patients in the albiglutide group and seven patients in the placebo group), pancreatic cancer (six patients in the albiglutide group and five patients in the placebo group), medullary thyroid carcinoma (zero patients in both groups), and other serious adverse events did not differ between the two groups. There were three (<1%) deaths in the placebo group that were assessed by investigators, who were masked to study drug assignment, to be treatment-related and two (<1%) deaths in the albiglutide group. Interpretation: In patients with type 2 diabetes and cardiovascular disease, albiglutide was superior to placebo with respect to major adverse cardiovascular events. Evidence-based glucagon-like peptide 1 receptor agonists should therefore be considered as part of a comprehensive strategy to reduce the risk of cardiovascular events in patients with type 2 diabetes. Funding: GlaxoSmithKline

The effects of amphibolite facies metamorphism on the trace element composition of pyrite and pyrrhotite in the Cambrian Nairne Pyrite Member, Kanmantoo Group, South Australia

The trace element composition of pyrite has been used to explore for hydrothermal ore deposits and to understand ore-forming processes. However, the effects of metamorphism on the trace element distribution in pyrite have received relatively limited attention. In this study, laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) analyses of pyrite and pyrrhotite, along with minor amounts of sphalerite, chalcopyrite, and galena, are used to evaluate the effects of amphibolite facies metamorphism on the trace element distribution and remobilization of metals in iron sulfides in the clastic sediment-hosted Cambrian Nairne Pyrite Member (NPM), South Australia. The NPM and the Mt. Torrens Pb-Zn-Ag prospect, which occur near the base of the Kanmantoo Group, preserve irregularly zoned subhedral to euhedral metamorphic pyrite (Py1) and anhedral pyrrhotite (Po1), along with relatively minor quantities of remobilized anhedral pitted and cataclastic pyrite (Py2a) in quartzofeldspathic rocks and anhedral inclusion-poor pyrite (Py2b) in calc-silicate rocks that armor or cross-cut earlier formed Py1. Rare anhedral secondary melnikovite pyrite (Py3) locally formed on the margins of Py1 and Py2a. Trace element studies show that Py1 in the NPM at Brukunga and Ironstone Ridge contains mean values of 1254 ppm Co, 123 ppm Ni, 2167 ppm As, 16 ppm Se, 10 ppm Cu, 25 ppm Zn, and 15 ppm Pb, whereas Py1 in the Mt. Torrens prospect contains mean values of 2312 ppm Co, 263 ppm Ni, 1835 ppm As, 95 ppm Se, 9 ppm Cu, 6 ppm Zn, and 9 ppm Pb. Rare inclusion-rich cores of Py1 show higher concentrations of trace elements than inclusion-free rims with minor amounts of chalcopyrite, galena, and sphalerite forming along grain boundaries or in fractures within pyrite. This is interpreted to be the result of the release of Cu, Pb, and Zn from pyrite as it recrystallized. Remobilization of these elements then formed discrete sulfides at the millimeter to centimeter scale, with some exceptions at the meter scale where chalcopyrite, sphalerite, and galena, along with other sulfides and sulfosalts, formed in veins and tension gashes. These observations suggest that remobilization of trace metals, including Cu, Pb, and Zn, did not migrate more than a few meters at most. Moreover, despite the recrystallization of pyrite and pyrrhotite and subsequent remobilization of some trace elements (i.e., Co, Ni, As), which were structurally bound in these Fe sulfides, still retain elevated concentrations at amphibolite facies conditions. Remobilization of metals from the NPM during metamorphism to form Cu-Au (e.g., Kanmantoo) and Pb-Zn- Ag-(Cu-Au) (e.g., Angas, Wheal Ellen) deposits in the Tapanappa Formation stratigraphically higher in the Kanmantoo Group seems unlikely. However, it is possible that one source of metals for these deposits could have been leached from the NPM and carried in large hydrothermal cells prior to metamorphism. Such a scenario is consistent with previously published sulfur isotope data for sulfides from the NPM, and Cu-Au and Pb-Zn-Ag- (Cu-Au) deposits, which indicate that sulfur derived from the NPM and pyritic schists in the Kanmantoo Group was a likely source of sulfur for the base and precious metal deposits.This article is published as Conn, C. Dakota, Paul G. Spry, Dan Layton-Matthews, Alexandre Voinot, and Alan Koenig. "The effects of amphibolite facies metamorphism on the trace element composition of pyrite and pyrrhotite in the Cambrian Nairne Pyrite Member, Kanmantoo Group, South Australia." Ore Geology Reviews 114 (2019): 103128. doi:10.1016/j.oregeorev.2019.103128.</p