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Geochemistry of the Alkaline Volcanic

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DOI: 10.1590/23174889201500020009 INVITED REVIEW Geochemistry of the alkaline volcanic- subvolcanic rocks of the Fernando de Noronha Archipelago, southern Atlantic Ocean Geoquímica das rochas vulcânicas-subvulcânicas alcalinas do Arquipélago de Fernando de Noronha, Oceano Atlântico Meridional Rosana Peporine Lopes1, Mabel Norma Costas Ulbrich2* ABSTRACT: The Fernando de Noronha Archipelago presents, on RESUMO: O Arquipélago de Fernando de Noronha mostra na sua its main island, a centrally-located stratigraphic unit, the Remédios ilha principal, na parte central, a Formação Remédios (idade em torno Formation (age around 8 – 12 Ma) constituted by basal pyroclastic de 8 – 12 Ma) constituída por rochas piroclásticas basais invadidas por rocks intruded by dikes, plugs and domes of varied igneous rocks, diques, plugs e domos de variadas rochas ígneas, capeadas por derrames capped by flows and pyroclastics of mafic to ultramafic rocks of e piroclásticas das rochas máficas a ultramáficas da Formação Quixaba the Quixaba Formation (age around 1 – 3 Ma), which is limited (idade de 1 a 3 Ma), separada da unidade inferior por uma superfície de from the underlying unit by an extensive irregular erosion surface. erosão extensa e irregular. Uma série predominante sódica de Remédios A predominant sodic Remédios series (basanites, tephrites, tephri- (basanitos, tefritos, tefrifonolitos, essexito, fonolitos) pode ser diferencia- phonolites, essexite, phonolites) can be separated from a moderately da da série moderadamente potássica (álcali basaltos, traquiandesitos, potassic Remédios sequence (alkali basalts, trachyandesites, tra- traquitos), pertencente à mesma unidade. Ambas as séries mostram ten- chytes), both alkaline series showing mostly continuous geochemi- dências geoquímicas geralmente contínuas em diagramas de variação de cal trends in variation diagrams for major as well as trace elements, elementos maiores e traços, indicando origem por cristalização fracionada indicating evolution by crystal fractionation (mainly, separation of (principalmente, separação de minerais máficos, incluindo apatitas e ti- mafic minerals, including apatites and titanites). There are textur- tanitas). São encontradas evidências mineralógicas e texturais apontando al and mineralogical evidences pointing to hybrid origin of some para origens hibridas em algumas rochas intermediárias (e.g., fenocristais intermediate rocks (e.g., resorbed pyroxene phenocrysts in basaltic reabsorbidos de piroxênio em traquiandesitos basálticos e alguns lampró- trachyandesites, and in some lamprophyres). The primitive Quixaba firos). As rochas primitivas do evento Quixaba, também alcalinas, são rocks are mostly melanephelinites and basanites, primitive under- mormente melanefelinitos fortemente insaturados e basanitos. A geologia saturated sodic types. Geology (erosion surface), stratigraphy (two (superfície de erosão), estratigrafia (dois eventos magmáticos distintos se- distinct units separated by a large time interval), petrography (varied parados por período prolongado), petrografia (evento Remédios petrogra- Remédios Formation, more uniform Quixaba unit) and geochemis- ficamente variado, o Quixaba mais uniforme) e geoquímica indicam try indicate that the islands represent the activity of a protracted vol- que as ilhas são o resultado de prolongado vulcanismo, alimentado por canic episode, fueled by intermittent melting of an enriched mantle, fundidos intermitentes de manto enriquecido, não relacionado com ati- not related to asthenospheric plume activity. vidade de pluma astenoférica. KEYWORDS: OIB; South Atlantic Ocean; Mafic to ultramafic PALAVRAS-CHAVES: OIB; Oceâno Atlántico meridional; rochas volcanic-subvolcanic rocks; Sodic and potassic series. vulcânicas-subvulcânicas máficas a ultramáficas; séries sódica e potássica. 1Pós-graduação, Instituto de Geociências, Universidade de São Paulo – USP, São Paulo (SP), Brazil. E-mail: [email protected] 2Instituto de Geociências,Universidade de São Paulo – USP, São Paulo(SP), Brazil. E-mail: [email protected] *Corresponding author Manuscript ID: 30305. Received: 04/12/2015. Approved: 05/18/2015. 307 Brazilian Journal of Geology, 45(2): 307-333, June 2015 Geochemistry of volcanic rocks of Fernando de Noronha INTRODUCTION Quixaba Formation. Almeida also separated the basanitic rocks outcropping at the São José peninsula, containing Within-plate oceanic islands are made up mostly o fa mantle xenoliths, from the Quixaba rocks and defined them series of diverse alkaline volcanic and subvolcanic rocks of as the youngest São José Formation. a basaltic ancestry, collectively called oceanic island basalts The next contribution to the FN geology was provided (OIB), clearly separated from the occurrences related to by Cordani (1970), who published K-Ar geochronological midoceanic ridge basalts (MORB), which belong to the data for the various rock types (K-Ar methodology; cf. also tholeiitic series. The name OIB, however, covers a wide Cordani et al. 2004). More recent and more precise 40Ar/39Ar range of petrographic and chemical variations, as displayed results can be found in Perlingeiro et al. (2013). in the literature on these rocks. The archipelago was visited sporadically by geologists Specifically in the Atlantic Ocean, many OIB islands who added geochemical and isotopic data (Gunn & Watkins are known and have been extensively studied, such as the 1976; Stormer & Whitney 1978; Schwab & Bloch 1985; Canarias Islands (Hoernle & Schmincke 1993; Araña et al. Cornen 1986; Gerlach et al. 1987; Weaver 1990). 1994; Gurenko et al. 2006), the Cabo Verde Archipelago More recently, geologists from the University of São (Furnes & Stillman 1987; Dyhr & Holm 2010; Ancochea Paulo presented contributions on FN (two Master’s thesis, et al. 2012) and the islands of Trindade and Martin Vaz one doctorate thesis: Maríngolo 1995; Lopes 1997, 2002), (Almeida 1961; Marques et al. 1999; Siebel et al. 2000). and several abstracts and publications on the subject (Ulbrich The Fernando de Noronha (FN) Archipelago is situated & Ruberti 1992; Ulbrich 1993; Ulbrich et al. 1994, 2004; in the southern Atlantic Ocean, at longitudes 32o 28’ to Maríngolo & Ulbrich 1997; Lopes & Ulbrich 1997, 1998; 32o 24’W and parallels 3o 52’ to 3o 50’ south. It outcrops at Ulbrich & Lopes 2000a, 2000b).A summary paper on the about 345 km from the nearest coastline (the Brazilian state lithogeochemistry and mineral chemistry of the Quixaba of Rio Grande do Norte), and belongs administratively to Formation was published in a Brazilian journal (Lopes & the state of Pernambuco, Brazil. It covers 18.4 km2, consti- Ulbrich 2006), and a more recent one on the mineral chem- tuted by one large island (16.9 km2), with a main NE-SW istry of these rocks (Lopes et al. 2014). A recent study on FN trending course, and many smaller islands (along both the was presented at Queensland as a Ph.D. thesis, dealing with occidental outlines of the main island, as well as a string geochronologic and petrogenetic aspects (Perlingeiro 2012). of them extending to the NE: Cuscuz, São José, Rasa, Sela Field work consisted mainly in the recognition and sam- Gineta, do Meio, Rata). pling of the several rock types identified by Almeida, add- The archipelago belongs to a vast volcanic edifice posi- ing more detailed information on the presence of dikes and tioned along the Fernando de Noronha ridge that rests on their structural disposition. The whole district is now mostly the ocean floor at a depth of around 4,000 m, stretching a natural reserve (Parque Nacional Marinho or Parnamar, some 75 km along an E-W trending fracture zone (Almeida the National Marine Park), subjected to oversight by the 1955, 2012; Bryan et al. 1972), which is supposed to have Brazilian Environmental Agency (Instituto Brasileiro de Meio channeled to the surface mantle-derived magmas. The old- Ambiente – IBAMA). IBAMA granted permission for col- est registered volcanism along this fracture zone is found lecting samples even in areas of total protection under their on its alleged continuation on the continental margin, jurisdiction. A total of about 109 hand specimens were col- at Ceará state, there presenting locally alkaline magma- lected in several field trips (1989, 1997, 1999). tism, dated 40 Ma ago, interpreted by some authors to be the result of the activity of a plume (appropriately called the Fernando de Noronha plume) impacting the westward STRATIGRAPHIC UNITS moving Southamerican plate. This plume is supposedly AND GEOLOGIC OCCURRENCES also the heat source responsible for the eruption of the Fernando de Noronha volcanic rocks (Fodor et al. 1998, Almeida (1955) mapped two units in the Archipelago, 2002; Almeida 2012). the older Remédios Formation, exposed as a centrally located The geologic units in FN were mapped by Fernando de erosion window, constituted mainly by accumulations of pyro- Almeida, who presented a classic publication on the geol- clastic material intruded by several dike systems and various ogy, petrography, stratigraphy and geomorphology of the plugs and domes, and the subhorizontal flows of the younger islands (Almeida 1955; see Fig. 1). Almeida defined two Quixaba Formation, bordering the Remédios Formation on main mapping units, the products of two volcanic events, both sides (to the NE and to the SW; Fig. 1). The pyroclas- the older Remédios Formation, separated by an erosion tic beds in the Remédios Formation are deeply altered and surface from the overlying, petrographically more uniform converted to soil
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    Miner Petrol (2010) 98:91–110 DOI 10.1007/s00710-009-0055-4 ORIGINAL PAPER Iron isotope compositions of carbonatites record melt generation, crystallization, and late-stage volatile-transport processes Clark M. Johnson & Keith Bell & Brian L. Beard & Aaron I. Shultis Received: 6 January 2009 /Accepted: 1 May 2009 /Published online: 30 May 2009 # Springer-Verlag 2009 Abstract Carbonatites define the largest range in Fe iso- fluid-rock or fluid-magma interactions comes from the tope compositions yet measured for igneous rocks, record- common occurrence of Fe isotope disequilibrium among ing significant isotopic fractionations between carbonate, carbonate, oxide, silicate, and sulfide minerals in the oxide, and silicate minerals during generation in the mantle majority of the carbonatites studied. The common occurrence and subsequent differentiation. In contrast to the relatively of Fe isotope disequilibrium among minerals in carbonatites restricted range in δ56Fe values for mantle-derived basaltic may also indicate mixing of phenocyrsts from distinct magmas (δ56Fe=0.0±0.1‰), calcite from carbonatites have magmas. Expulsion of Fe3+-rich brines into metasomatic δ56Fe values between −1.0 and +0.8‰, similar to the range aureols that surround carbonatite complexes are expected to defined by whole-rock samples of carbonatites. Based on produce high-δ56Fe fenites, but this has yet to be tested. expected carbonate-silicate fractionation factors at igneous or mantle temperatures, carbonatite magmas that have modestly negative δ56Fe values of ~ −0.3‰ or lower can Introduction be explained by equilibrium with a silicate mantle. More negative δ56Fe values were probably produced by differen- Stable and radiogenic isotope studies of carbonatites have tiation processes, including crystal fractionation and liquid been used to monitor the secular evolution of the sub- immiscibility.
  • The Alkaline Volcanic Rocks of Craters of the Moon National Monument, Idaho and the Columbia Hills of Gusev Crater, Mars Details

    The Alkaline Volcanic Rocks of Craters of the Moon National Monument, Idaho and the Columbia Hills of Gusev Crater, Mars Details

    The alkaline volcanic rocks of Craters of the Moon National Monument, Idaho and the Columbia Hills of Gusev Crater, Mars Details Meeting 2016 Fall Meeting Section Planetary Sciences Session Terrestrial Analogs for Planetary Processes: Oceans, Volcanoes, Impacts, and Dunes I Identifier P31E-01 Authors Haberle, C W*, Mars Space Flight Facility, Arizona State University, Tempe, AZ, United States Hughes, S S, Idaho State University, Idaho Falls, ID, United States Kobs-Nawotniak, S E, Department of Geosciences, Idaho State University, Idaho Falls, ID, United States Christensen, P R, Arizona State University, Tempe, AZ, United States Index Sediment transport [4558] Terms Atmospheres [5405] Titan [6281] Venus [6295] Abstract Idaho's Eastern Snake River Plain (ESRP) is host to extensive expressions of basaltic volcanism dominated by non evolved olivine tholeiites (NEOT) with localized occurrences of evolved lavas. Craters of the Moon National Monument (COTM) is a polygenetic lava field comprised of more than 60 lava flows emplaced during 8 eruptive periods spanning the last 15 kyrs. The most recent eruptive period (period A; 2500-2000 yr B.P.) produced flows with total alkali vs. silica classifications spanning basalt to trachyte. Coeval with the emplacement of the COTM period A volcanic pile was the emplacement of the Wapi and Kings Bowl NEOT 70 km SSE of COTM along the Great Rift. Previous investigations have determined a genetic link between these two compositionally distinct volcanic centers where COTM compositions can be generated from NEOT melts through complex ascent paths and variable degrees of fractionation and assimilation of lower-middle crustal materials. The Mars Exploration Rover, Spirit, conducted a robotic investigation of Gusev crater from 2004-2010.