Primitive Inselbogen- und ozeanische Laven von Hunter R�cken und der Hunter BruchZone: die Bedeutung der Zusammensetzung von Glas, Olivin und Spinell

Sigurdsson, IA; Kamenetsky, Vadim S.; Crawford, AJ; Eggins, Stephen; Zlobin, S. K.

doi:10.1007/bf01161564

Cited by 46 publications

(24 citation statements)

References 36 publications

(23 reference statements)

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“…According to Danyushevsky et al (1992), this re¯ects reequilibration of melt inclusions with their host olivine at lower temperatures, resulting in lower FeO contents of melt inclusions compared to the initially trapped compositions. Such`iron-loss' by melt inclusions in olivine is Sobolev et al (1993); western Paci®c boninites after Sobolev and Danyushevsky (1994), Sigurdsson et al (1993), and Danyushevsky, unpublished data; primitive island-arc tholeiites after Sigurdsson et al (1993), Monzier et al (1993), Allan (1994), and Danyushevsky, unpublished data; primitive mid-ocean ridge picrites and basalts (MORB) after Dmitriev et al (1991), Sobolev et al (1989), Kamenetsky (1996), and Danyushevsky and Kamenetsky, unpublished data; back-arc basin basalts (BABB) after Sigurdsson et al (1993), and Danyushevsky and Kamenetsky, unpublished data. Cr# = 100*[Cr/(Cr + A1)] and MORB from Vema fracture zone, Atlantic (Sobolev et al 1989).…”

Section: Resultsmentioning

confidence: 99%

Coexistence of two distinct mantle sources during formation of ophiolites: a case study of primitive pillow-lavas from the lowest part of the volcanic section of the Troodos Ophiolite, Cyprus

Portnyagin

Danyushevsky²,

Kamenetsky³

1997

Contributions to Mineralogy and Petrology

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We present a detailed mineralogical, petrological and melt inclusion study of unusually fresh, primitive olivine + clinopyroxene phyric Lower Pillow Lavas (LPL) found near Analiondas village in the northeastern part of the Troodos ophiolite (Cyprus). Olivine phenocrysts in these primitive LPL show a wide compositional range (Fo 82±92 ) and have higher CaO contents than those from the Upper Pillow Lavas (UPL). Cr-spinel inclusions in olivine are signi®cantly less Cr-rich (Cr/Cr + Al = 28±67 mol%) compared to those from the UPL (Cr# = 70±80). These features reect di erences in melt compositions between primitive LPL and the UPL, namely higher CaO and Al 2 O 3 and lower FeO* compared to the UPL at a given MgO. LPL parental melts (in equilibrium with Fo 92 ) had $10.5 wt% MgO and crystallization temperatures $1210°C, which are signi®cantly lower than those previously published for the UPL (14±15 wt% MgO and $1300°C for Fo 92 ). The fractionation path of LPL parental melts is also di erent from that of the UPL. It is characterized initially by olivine + clinopyroxene cotectic crystallization joined by plagioclase at $9 wt% MgO, whereas UPL parental melts experienced a substantial interval of olivine-only crystallization. Primitive LPL melts were formed from a mantle source which was more fertile than that of tholeiites from well-developed intra-oceanic arcs, but broadly similar in its fertility to that of MidOcean Ridge Basalt (MORB) and Back Arc Basin Basalts (BABB). The higher degrees of melting during formation of the LPL primary melts compared to average MORB were caused by the presence of subduction-related components (H 2 O). Our new data on the LPL coupled with existing data for the UPL support the existing idea that the LPL and UPL primary melts originated from distinct mantle sources, which cannot be related by progressive source depletion. Temperature di erences between these sources ($150°C), their position in the mantle ($10 kbar for the colder LPL source vs 15±18 kbar for the UPL source), and temporal succession of Troodos volcanism, all cannot be reconciled in the framework of existing models of mantle wedge processes, thermal structure and evolution, if a single mantle source is invoked. Possible tectonic settings for the origin of the Troodos ophiolite (forearc regions of intra-oceanic island arc, propagation of backarc spreading into arc lithosphere) are discussed.

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Section: Resultsmentioning

confidence: 99%

Coexistence of two distinct mantle sources during formation of ophiolites: a case study of primitive pillow-lavas from the lowest part of the volcanic section of the Troodos Ophiolite, Cyprus

Portnyagin

Danyushevsky²,

Kamenetsky³

1997

Contributions to Mineralogy and Petrology

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“…The CaO content of the olivine is in the range of 0.53-0.38 wt. %, determined by LA and WDS analyses, much higher than those of typical subduction-related magmas (0.25-0.15 wt.%; Sigurdsson et al, 1993;Smith and Leeman, 2005). The overall high-CaO contents of the olivine could be explained by the crystallization from high-Ca (ankaramitic) magmas (Beattie, 1993).…”

Section: Petrography and Mineralogymentioning

confidence: 93%

High-K ankaramitic melt inclusions and lavas in the Upper Cretaceous Eastern Srednogorie continental arc, Bulgaria: Implications for the genesis of arc shoshonites

Marchev

Georgiev

Zajacz

et al. 2009

Lithos

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The Upper Cretaceous Yambol-Burgas region of the Eastern Srednogorie continental arc is characterized by unusually large volumes of mafic shoshonitic and ultra-K magmatism represented by high-Mg cumulitic rocks, and nepheline-normative ankaramites, absarokites and shoshonitic (high-alumina) basalts. The cumulitic rocks consist of phenocrysts of clinopyroxene and olivine ) with inclusions of spinel (Cr#75-78). Olivine high-Fo cores and clinopyroxene host glassy melt inclusions which have nephelinenormative compositions with ankaramitic CaO/Al 2 O 3 ratios (N 1), low SiO 2 (47.4-50.0 wt.%), high MgO (7.5-10.8 wt.%), high total alkalis and shoshonitic K 2 O/Na 2 O ratios (N1). Electron microprobe and LA-ICPMS analyses demonstrate that parental magma was a high-Ca primitive mantle melt. Melt inclusions from the less Fo 85 rim approach absarokite composition with CaO/Al 2 O 3 ratios b 1, lower MgO (5.2 wt.%), and higher total alkalis and K 2 O/Na 2 O ratio. The ankaramitic rocks are strongly porphyritic, composed of phenocrysts of altered olivine with spinel inclusions and large clinopyroxene. Their major and trace element compositions are similar to those of melt inclusions hosted in the high-Fo 91-90 cores and clinopyroxene of the cumulitic rock. The absarokites differ from the high-K ankaramites by slightly higher SiO 2 (50.6-52.7 wt.%), Al 2 O 3 and alkali-oxide contents, lower FeO and MgO and particularly low CaO/Al 2 O 3 (0.6-0.9) ratio. Compared to the absarokites, shoshonitic basalts have similar SiO 2 (50.2-52.8 wt.%) at lower MgO contents and CaO/Al 2 O 3 ratios (0.37-0.53). The presented extensive set of major and trace element data on melt inclusions and whole rocks, along with their main phenocryst compositions, is used to constrain the crystallization temperatures and pressures of the most primitive ankaramites. We suggest that ankaramite compositions are formed by melting of a garnet-free metasomatized mantle source rather than by melting of lower crustal cumulates. Numerical modelling demonstrates that the generation of absarokites and shoshonitic basalts is compatible with fractionation of olivine and clinopyroxene from ankaramitic magma. The high-Mg chemistry of cumulitic rocks is explained as the result of accumulation of these minerals.

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“…Backarc basin magmas in this study are characterised by olivine + clinopyroxene ± plagioclase-phyric basalts from the eastern Manus spreading ridge, near PACMANUS hydrothermal field (Binns and Scott, 1993;Kamenetsky et al, 2001), the New Hebrides Troughs, separating the Vanuatu island arc from the active North Fiji basin (Maillet et al, 1995), and the Okinawa Trough formed by extension of continental lithosphere behind the Ryukyu arc -trench system (Shinjo et al, 1999). A variety of primitive arc lavas (olivinebearing arc tholeiites and boninites) are from well known ophiolitic complexes, such as New Caledonia (Cameron, 1989) and Troodos (Sobolev et al, 1993;Portnyagin et al, 1997), and from the Hunter RidgeHunter Fracture Zone, an aborted embyonic intraoceanic arc along the southern margin of the North Fiji Basin (Sigurdsson et al, 1993). As an example of intraplate oceanic magmatism, a picritic tholeiite from Mauna Loa, HI, was selected.…”

Section: Samples and Methodsmentioning

confidence: 99%

Fluid bubbles in melt inclusions and pillow-rim glasses: high-temperature precursors to hydrothermal fluids?

et al. 2002

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Hypotheses for the formation of many types of hydrothermal ore deposits often involve the direct contribution of magmarelated fluids (e.g., Cu -Mo -Au porphyries) or their superimposition on barren hydrothermal cells (e.g., volcanic-hosted massive sulfide deposits). However, the chemical and phase compositions of such fluids remain largely unknown. We report preliminary results of a comprehensive study of fluid bubbles trapped inside glassy melt inclusions in primitive olivine phenocrysts and pillow-rim glasses from basaltic magmas from different tectonic environments, including mid-ocean ridges (Macquarie Island, SW Pacific and Mid-Atlantic Ridge 43°N Fracture Zone), ocean islands (Hawaii) and a variety of modern and ancient backarc -island arc settings (eastern Manus Basin, Okinawa and Vanuatu Troughs, Troodos, New Caledonia and Hunter Ridge -Hunter Fracture Zone). Fluid bubbles from all localities, studied using electron microscopy with EDS and laser Raman spectroscopy, are composed of CO 2 -( ± H 2 O ± sulfur)-bearing vapor and contain significant amounts of amorphous (Na -K -Ca -Fe alumino-silicates and dissorded carbon) and crystalline phases. The crystals are represented mainly by carbonates (magnesite, calcite, ankerite, dolomite, siderite, nahcolite and rhodochrosite), sulfates (anhydrite, gypsum, barite and anglesite), and sulfides (pyrite, arsenopyrite, chalcopyrite and marcasite), though other minerals (brukite, apatite, halite, clinoenstatite, kalsilite, nepheline, amphibole and mica) may occur as well. We argue that chemical components (e.g., C, H, S, Cl, Si, Al, Na, K, Fe, Mn, Cr, Ca, Mg, Ba, Pb and Cu) that later formed precipitates in fluid bubbles were originally dissolved in the magmatic fluid, and were not supplied by host glasses or phenocrysts after entrapment. Magma-related fluid rich in dissolved metals and other non-volatile elements may be a potential precursor to ore-forming solutions. D

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Primitive Inselbogen- und ozeanische Laven von Hunter R�cken und der Hunter BruchZone: die Bedeutung der Zusammensetzung von Glas, Olivin und Spinell

Cited by 46 publications

References 36 publications

Coexistence of two distinct mantle sources during formation of ophiolites: a case study of primitive pillow-lavas from the lowest part of the volcanic section of the Troodos Ophiolite, Cyprus

Coexistence of two distinct mantle sources during formation of ophiolites: a case study of primitive pillow-lavas from the lowest part of the volcanic section of the Troodos Ophiolite, Cyprus

High-K ankaramitic melt inclusions and lavas in the Upper Cretaceous Eastern Srednogorie continental arc, Bulgaria: Implications for the genesis of arc shoshonites

Fluid bubbles in melt inclusions and pillow-rim glasses: high-temperature precursors to hydrothermal fluids?

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