417 research outputs found
Determining the cooling history of in situ lower oceanic crust - Atlantis Bank, SW Indian Ridge
No full textBarbara E. John, David A. Foster, John M. Murphy, Michael J. Cheadle, A. Graham Baines, C. Mark Fanning, Peter Copelandhttp://www.elsevier.com/wps/find/journaldescription.cws_home/503328/description#descriptio
Emplacement and temporal constraints of the Gondwanan intrusive complexes of northern Patagonia: La Esperanza plutono-volcanic case
No full textTwo main lines of evidence disagree whether or not the Patagonian blocks collided with Gondwana. All models invoke the voluminous magmatism of the La Esperanza Complex as evidence for active subduction magmatic arc or to a postcollisional setting. The evolution of this bimodal igneous suite is reassessed with field, geochronological (SHRIMP U-Pb zircon and K-Ar mica) and petrophysical data. Emplacement of high-K calk-alkaline granitic magmas occurred at shallow crustal levels (2–8 ± 2 km depth) related to the development and collapse of a caldera associated with a regional NW-SE structural trend. Magmatism involved intermediate hybrid pulses at 273 ± 2 Ma and 255 ± 2 Ma (Prieto Granodiorite) that shifted like a yo-yo to acidic magmas at 260 ± 2 Ma and 250 ± 2 Ma (Donosa and Calvo granites). Absence of solid-state deformation features and the low anisotropy degrees in the granites indicate that its fabric is magmatic in origin. Magnetic fabric in granodiorites displays a concentrical pattern with subhorizontal foliations and lineations. Parallel to the volcanic axis, magnetic foliations and moderately plunging lineations indicate a common feeder system for plutonics and volcanics. Donosa Granite shows a discordant pattern with WNW-ESE ENE-WSW trending low plunging lineations and foliations. The plutono-volcanic system construction (273–255 Ma) followed NW-SE and NE-SW diamond shape faults trends and supracrustal discontinuities. Magmatic Climax is bracketed at 260 Ma. The collapse of the edifice is evidenced by the intrusion of acid magma plugs and dike swarms between 250 and 246 Ma. A similar age range was identified in other areas of Patagonia related to syn and postcollisional tectonic events. No evidence of tectonic activity such as major uplift, metamorphism or thrusting was found excepting regional strike-slip faulting and extension. Therefore, La Esperanza Complex is a high crustal level episode, and as such may not have structurally recorded an active collision during its crystallization and cooling.Fil: Martínez Dopico, Carmen Irene. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Geocronología y Geología Isotopica. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Geocronología y Geología Isotópica; ArgentinaFil: Lopez, Monica Graciela. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Geocronología y Geología Isotopica. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Geocronología y Geología Isotópica; ArgentinaFil: Rapalini, Augusto Ernesto. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Geociencias Basicas, Aplicadas y Ambientales de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Geociencias Basicas, Aplicadas y Ambientales de Buenos Aires; ArgentinaFil: Wemmer, Klaus. Universität Göttingen; AlemaniaFil: Fanning, Mark. Australian National University; AustraliaFil: Basei, Miguel A. S.. Universidade de Sao Paulo; Brasi
Evidence from detrital zircons for recycling of Mesoproterozoic and Neoproterozoic crust recorded in Paleozoic and Mesozoic sandstones of southern Libya
No full textThe geodynamic history of the Precambrian basement in central North Africa as well as the age and provenance of its sedimentary cover sequence are still poorly constrained. Here we present first detrital zircon ages (obtained by IA-SF-ICP-MS and SHRIMP) from Paleozoic and Mesozoic sandstones of the eastern Murzuq Basin, southern Libya, which unconformably overlie the Saharan Metacraton. Establishing the age and provenance of these sandstones has important implications for our understanding of the evolution of northern Gondwana during the Paleozoic, especially for reconstructions of paleo-source areas and transport paths. Detrital zircons from the sandstones show mainly early Paleozoic to Neoarchean ages with four main age populations, at 2750-2500 Ma (8%), 2200-1750 Ma (16%), 1060-920 Ma (18%), and 720-530 Ma (39%). About 13% of all concordant grains yield ages of 1600-1000 Ma. In addition, there are 9 zircon grains (0.7% of all concordant grains) with ages of 3600-2800 Ma. The presence of a high number of ca. 1 Ga zircons is enigmatic and their origin is controversial. Besides direct sourcing from ca. 1 Ga igneous rocks in eastern Chad and ca. 1 Ga igneous rocks along the southeastern margins of the Congo and Tanzania cratons, recycling of Neoproterozoic sediments containing ca. 1 Ga zircons is another alternative hypothesis to explain the presence of ca. 1 Ga zircons in the Paleozoic sedimentary sequence of central North Africa. The ubiquitous occurrence of ca. 1 Ga zircons in Paleozoic sediments of southern Libya provides insights into the correlation and paleotectonic arrangement of Gondwana-derived terranes, present, for example, in the eastern Mediterranean and in southwestern Europe. Current paleotectonic models of dextral terrane transport along the northern Gondwana margin during the early Paleozoic may need to be revised. (C) 2011 Elsevier B.V. All rights reserved.consortium of subscribing oil and gas companie
The political and economic context of Keynes’s 1933 Finlay lecture: transforming a business practitioner’s ways of knowing
No full textThis thesis is structured in the format of a three part Portfolio of Exploration to facilitate transformation in my ways of knowing to enhance an experienced business practitioner’s capabilities and effectiveness. A key factor in my ways of knowing, as opposed to what I know, is my exploration of context and assumptions. By interacting with my cultural, intellectual, economic, and social history, I seek to become critically aware of the biographical, historical, and cultural context of my beliefs and feelings about myself. This Portfolio is not exclusively for historians of economics or historians of ideas but also for those interested in becoming more aware of how these culturally assimilated frames of reference and bundles of assumptions that influence the way they perceive, think, decide, feel and interpret their experiences in order to operate more effectively in their professional and organisational lives. In the first part of my Portfolio, I outline and reflect upon my Portfolio’s overarching theory of adult development; the writings of Harvard’s Robert Kegan and Columbia University’s Jack Mezirow. The second part delves further into how meaning-making, the activity of how one organises and makes sense of the world and how meaning-making evolves to different levels of complexity. I explore how past experience and our interpretations of history influences our understandings since all perception is inevitably tinged with bias and entrenched ‘theory-laden’ assumptions. In my third part, I explore the 1933 inaugural University College Dublin Finlay Lecture delivered by economist John Maynard Keynes. My findings provide a new perspective and understanding of Keynes’s 1933 lecture by not solely reading or relying upon the text of the three contextualised essay versions of his lecture. The purpose and context of Keynes’s original longer lecture version was quite different to the three shorter essay versions published for the American, British
and German audiences
The Tumbarumba Basaltic Gem Field, New South Wales: in relation to sapphire-ruby deposits of eastern Australia
No full textSutherland, F. L., Graham, I. T., Pogson, R. E., Schwarz, D., Webb, G. B., Coenraads, Robert R., Fanning, C. M., Hollis, J. D., Allen, T. C. (2002): The Tumbarumba Basaltic Gem Field, New South Wales: In Relation to Sapphire-Ruby Deposits of Eastern Australia. Records of the Australian Museum 54 (2): 215-248, DOI: 10.3853/j.0067-1975.54.2002.1358, URL: https://journals.australian.museum/sutherland-et-al-2002-rec-aust-mus-542-215248
Transantarctic Mountains granitoid isotopic data
No full textThree sets of primary analytical data are provided as supplementary information to this research, posted as the following items:
A) zircon U-Pb results, including a narrative U-Pb age summary for each sample, describing zircon characteristics and age interpretations (PDF file format); Tables A1-A30, consisting of tabulated SHRIMP zircon U-Pb results for individual samples (CSV file format); and sample data sheets combining data Tables A1-A30 with graphical displays of Concordia diagrams and weighted-mean age plots for each sample (PDF file format).
B) Table B1, consisting of tabulated SHRIMP zircon O-isotope results for individual samples (CSV file format).
C) Table C1, consisting of tabulated LA-MC-ICPMS zircon Hf-isotope results for individual samples (CSV file format).We obtained new U-Pb ages and O-Hf isotopic compositions in zircons from nearly 40 samples of Ross Orogen granitoids covering a large section of the modern Transantarctic Mountains in Antarctica. New age and isotopic analysis of zircons from this large suite of Ross Orogen granitoids spanning >2,000 km along the orogen provide a wealth of new geochronologic, tracer, and inheritance information, enabling us to investigate the pace of magmatism, along-strike temporal and geochemical trends, sources of melts, and tectonic mode of convergence during magmatism. Data provided to the Data Repository include primary individual sample results of in situ analysis of zircon. Age and isotopic signatures were obtained by in situ analysis of the same zircon domains to first define ages by the U-Pb method, followed by O- and Hf-isotope analysis. U-Pb and O-isotope analysis were done by sensitive high-resolution ion microprobe (SHRIMP) at Australian National University, and precise Hf-isotope analysis was done using a laser ablation system coupled to a multi-collector inductively coupled plasma mass spectrometer (LA-MC-ICPMS) at Washington State University. Summary tabulations of the sample data are included with a manuscript. Also included is a narrative summary of zircon U-Pb age results for each sample, describing zircon characteristics and age interpretations.National Science FoundationGoodge, John W.; Fanning, C. Mark; Fisher, Chris M.; Vervoort, Jeff D.. (2022). Transantarctic Mountains granitoid isotopic data. Retrieved from the University Digital Conservancy, https://doi.org/10.13020/stzs-xd13
Sapphires, zircons and SHRIMP: the Sutherland connection
No full textVolume: 134Start Page: 105End Page: 10
The Chaitenia accretionary orogen of northwest Patagonia: new U-Pb SHRIMP ages of the Foreland Domain
No full textThe Andean basement of NW Patagonia between 39º and 43º S contains remnants of Devonian plutonic, volcanic and metamorphic rocks. While some of them were clearly emplaced in continental crust at the easternmost edge of North Patagonian Massif, in the west of the North Patagonian Cordillera and the coastal region, the igneous rocks were developed in an oceanic environment. Thus, a Foreland Devonian Domain (FDD) and a Pacifi c Devonian Domain (PDD) are distinguished on either side of the modern Andean Cordillera (Fig. 1). While the Devonian granites of the Foreland Domain can be unambiguously ascribed to subduction in a continental margin (see references in Rapela et al. 2021), the more scattered outcrops of pillow lavas, alkaline trachyte-rhyolite and primitive granites of the PDD required more detailed studies to determine their petrogenesis and tectonic signifi cance. Initial studies suggested that they represented the mixed products of an oceanic island arc that later became accreted to the continent as an allochthonous terrane (the Chaitenia terrane of Hervé et al. 2016). However, whole-rock geochemistry shows that the pillow lavas are dominated by back-arc basalts and that metasandstones interbedded with the pillow lavas contain detrital zircons with U-Pb ages, Hf and O isotope compositions comparable to those of the Foreland Domain granites, i.e., they are of contemporary continental provenance. Thus, they are more likely to represent a Devonian parautochthonous terrane, formed after continental rifting and was laterally accreted during closure of a back-arc basin in an orogen that also encompasses the fore-arc (Rapela et al. 2021), and which we now refer to as the Chaitenia Accretionary Orogen (CAO). Five stages have been recognized in its evolution: (i) a continental arc stage that involved the San Martín arc (c. 405-395 Ma, Emsian); (ii) a forearc rift-ridge transition stage (c. 395-390 Ma, Emsian-Eifelian); (iii) a marginal basin stage that involves the starting of an oceanic arc, the Chaitenia arc (c. 380-390 Ma, Eifelian-Givetian); (iv) a double arc stage (365-380 Ma, Giovetian-Frasnian) and (v) closing of the Chaitenia marginal basin (c. 360-340 Ma, Fammenian-Visean).Fil: Rapela, Carlos Washington. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigaciones Geológicas. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Centro de Investigaciones Geológicas; ArgentinaFil: Hervé, Francisco. Universidad Andrés Bello; ChileFil: Pankhurst, Robert. British Geological Survey; Reino UnidoFil: Calderón, Mauricio. Universidad Andrés Bello; ChileFil: Fanning, Christopher Mark. Australian National University; AustraliaFil: Quezada, Paulo. Universidade Tecnologia Federal Do Parana.; BrasilXXI Congreso Geológico ArgentinoPuerto MadrynArgentinaAsociación Geológica Argentin
First U-Pb SHRIMP age for the Pilmatué Member (Agrio Formation) of the Neuquén Basin, Argentina: Implications for the Hauterivian lower boundary
No full textAmmonite-based biostratigraphic schemes for the Lower Cretaceous are fairly well refined across the world, from the standard zonation in the West Mediterranean province to the Boreal and Austral provinces in the northern and southern hemispheres, respectively. However, the lack of radioisotopic ages associated to the fossil-rich, Lower Cretaceous marine successions has hindered the accurate establishment of the numerical ages for the lower boundaries of its several stages (from Berriasian to Albian). Geochronological dating by U-Pb SHRIMP of a tuff layer that occurs within beds belonging to the Holcoptychites neuquensis Zone in the Pilmatué Member of the Agrio Formation in the Austral province (Neuquén Basin, Argentina) has resulted in an absolute age of 130.0 ± 0.6 Ma (2 sigma internal errors only) or 130.0 ± 0.8 Ma (including calibration and decay constant uncertainties). This age is interpreted to represent the time of eruption and thus the timing of the pyroclastic deposit. The H. neuquensis Zone is the equivalent of the A. radiatus Zone in the West Mediterranean province. Therefore, the obtained age is the first numerical data that could help constrain the Hauterivian lower boundary. Indeed, there is reasonable agreement with the latest proposed lower boundary of the Hauterivian at ~132.9 Ma. On the other hand, the duration recently established for this stage would be hard to reconcile with the stratigraphic record of the entire Hauterivian in the study region (northeastern Neuquén Basin). Therefore, the results of this contribution could also help to assess the extent of the Hauterivian and associated stages.Fil: Schwarz, Ernesto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigaciones Geológicas. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Centro de Investigaciones Geológicas; ArgentinaFil: Spalletti, Luis Antonio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigaciones Geológicas. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Centro de Investigaciones Geológicas; ArgentinaFil: Veiga, Gonzalo Diego. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigaciones Geológicas. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Centro de Investigaciones Geológicas; ArgentinaFil: Fanning, C. Mark. Australian National University; Australi
Origin of Late Triassic Granitoids of the Coastal Cordillera of Southern Central Chile (34°–37°S): Multi‐Isotopic Evidence of Slab Tearing Effects on Pre‐Andean Magmagenesis
No full textThe Coastal Cordillera of Central Chile (34°–37°S) holds a series of Late Triassic granitoids classically interpreted as early Andean subduction-related magmatism based on their arc-like geochemical signature. Here, we present geochemical, isotopic, and geochronological data and a tomotectonic analysis that challenge this idea indicating a local interruption of the normal subduction process likely associated with a slab-tearing event. Our results suggest that the source of the magmas is related to melting of asthenospheric mantle and crustal rocks of a metasedimentary Paleozoic complex. We suggest that partial melting of these sources was triggered by a slab tear-related asthenosphere upwelling producing high-silica S/I- and S-Type granites of the Constitución and Hualpén areas, and anorogenic A-Type granitoids in Cobquecura area. Also, partial melting of a metasomatized asthenospheric mantle plus continental crust that experienced previous high-temperature hydrothermal alteration would have generated high-silica magmas with low δ18O, high Pb, CHUR-like 87Sr/86Sr, and 143Nd/144Nd ratios that originated La Estrella Granite. Our results offer an alternative explanation for the existence of subtle magmatic arc-like geochemical signatures in the study area and support a segmentation of the active margin during the Late Triassic. The widespread upper-plate magmatic record of slab-tearing, spanning the Coastal Cordillera of Central Chile to the intraplate Neuquén basin in Argentina, and the lower mantle record of a slab gap, detected in ours and previous tomotectonic analyses, make the Late Triassic slab-tearing event in southwestern Pangea the most robustly constrained pre-Cenozoic slab tear process so far.Fil: Rossel, Pablo. Universidad Andrés Bello; ChileFil: Gianni, Guido Martin. Universidad Nacional de San Juan; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Juan; ArgentinaFil: Reinoso, Valeria. Universidad Andrés Bello; ChileFil: Fanning, C. Mark. The Australian National University; AustraliaFil: Ducea, Mihai N.. University of Arizona; Estados UnidosFil: Muñoz, Tamara. Universidad Andrés Bello; ChileFil: Salvat, Daniela. Universidad Andrés Bello; Chil
- …
