Intrusion, Extrusion and Metamorphism at Constructive Margins: Evidence from the Troodos Massif, Cyprus

Gass, I. G.; Smewing, J. D.

doi:10.1038/242026a0

Cited by 221 publications

(50 citation statements)

References 22 publications

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“…The ranges of Ti and V from the upper pillow lavas are restricted to ratios close to 10, suggesting that these rocks at least were formed in a high volatile environment such as an island arc or intra-arc basin. This conclusion is consistent with Pearce [7,8], Cameron et al [42], and Dick et al [56], but at odds with older interpretations [57,58].…”

Section: Application Of Ti/v Plots To Ophiolite Voicanicssupporting

confidence: 76%

Ti-V plots and the petrogenesis of modern and ophiolitic lavas

Shervais

1982

Earth and Planetary Science Letters

2,046

960

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Plots of Ti vs. V for many modern volcanic rock associations are diagnostic of tectonic setting and can be used to determine possible tectonic settings of ophiolites as well. The basis of this plot is the variation in the crystal/liquid partition coefficients for vanadium, which range with increasing oxygen fugacity from > 1 to << 1. Since the partition coefficients for Ti are almost always << 1, the depletion of V relative to Ti is a function of the fo2 of the magma and its source, the degree of partial melting, and subsequent fractional crystallization. Volcanic rocks from modern island arcs have Ti/V ratios of ~20, except for calc-alkaline volcanics which show the effects of magnetite fractionation. MORB and continental flood basalts have Ti/V ratios of about 20-50 and alkaline rocks have Ti/V generally >50. Back-arc basin basalts may have either arc-like or MORB-like Ti/V ratios, and sample suites from single back-arc basins may have Ti/V ratios ranging from 10 to 50. This range in Ti/V ratios in samples from a restricted geographical area may be diagnostic of the back-arc setting. The Ti/V plot is applied here to published data on ophiolites from a variety of postulated settings and in general supports the conclusions of previous investigators. Ophiolites from the western Mediterranean (Corsica, northern Apennines) and the "lower" Karmoy volcanics have Ti/V trends similar to MORB; the "upper" Karmo'y volcanics have alkaline Ti/V ratios. Lavas and tonalites in the Papuan ultramafic belt, the high-Mg andesites of Cape Vogel, and the upper pillow lavas at Troodos all have Ti/V ratios < 20, consistent with formation in an island arc setting. More specific evaluation of the tectonic setting of these and other ophiolites requires application of detailed geologic and petrologic data as well as geochemistry. The Ti/V discrimination diagram, however, is a potentially powerful adjunct to these techniques.

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Section: Application Of Ti/v Plots To Ophiolite Voicanicssupporting

confidence: 76%

Ti-V plots and the petrogenesis of modern and ophiolitic lavas

Shervais

1982

Earth and Planetary Science Letters

2,046

960

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“…[4,5,7,8]), but the discovery of glasses with compositions comparable to Cyprus lava whole rock compositions [6] has reduced the uncertainty associated with this question. Relative to their fresh precursors, the CY-1/ 1A lavas are enriched in K 2 O (up to 5 wt%) and depleted in Na 2 O (up to 1 wt%); depleted or enriched in CaO ( þ 6 wt%) (depending on carbonate content); and locally SiO 2 -depleted (up to 2 wt%) and MgO-enriched [26].…”

Section: Viscosity Of the Cy-1/1a Lavasmentioning

confidence: 99%

“…The dikes in the underlying sheeted dike complex are planar with no identi¢able pillow screens (dike abundance s 95%). The transition from Basal Group to sheeted dike complex is typically less than 100 m [4].…”

Section: Introductionmentioning

confidence: 99%

“…metamorphism of the Troodos lavas, Gass and Smewing [4] and Smewing et al [5] modi¢ed this early subdivision and de¢ned an axis sequence and an o¡-axis sequence (but not far enough o¡-axis for a sedimentary sequence to develop). The boundary between the two sequences was based on a relative lack of secondary mineralization in the younger, o¡-axis sequence.…”

Section: Introductionmentioning

confidence: 99%

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Melt viscosity, temperature and transport processes, Troodos ophiolite, Cyprus

Schouten

Kelemen

2002

Earth and Planetary Science Letters

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The lava section in the Troodos ophiolite, Cyprus, is chemically stratified and divided into a shallow lava sequence with low TiO 2 content and a deeper lava sequence with high TiO 2 content. We calculate the viscosity at magmatic temperature based on major element chemistry of lavas in Cyprus Crustal Study Project (CCSP) Holes CY-1 and 1A. We find that typical shallow low-Ti lavas have a magmatic viscosity that is two to three orders of magnitude lower than that of the deeper high-Ti lavas. This implies that, after eruption on-axis, Troodos low-Ti lavas would have been able to flow down the same slope faster and farther than high-Ti lavas. The calculated lava viscosity increases systematically from the lava^sediment interface to the bottom of the composite Hole CY-1/1A. This suggests that an efficient process of lava segregation by viscosity on the upper flanks of the paleo Troodos rise may have been responsible for the chemical stratification in the Troodos lava pile. Calculated magmatic temperature and molar Mg/ (Mg+Fe), or Mg#, decrease systematically down-section, while SiO 2 content increases. Correlation of Mg# in the lavas with Mg# in the underlying, lower crustal plutonic rocks sampled by CCSP Hole CY-4 shows that the shallow lavas came from a high-temperature, lower crustal magma reservoir which is now represented by high-Mg# pyroxenite cumulates, while the deeper lavas were erupted from a lower-temperature, mid-crustal reservoir which is now represented by gabbroic cumulates with lower Mg#. ß 2002 Published by Elsevier Science B.V.

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“…The Troodos lava complex has been divided into the Lower and Upper Pillow Lava suites (LPL and UPL) (e.g., Gass and Smewing 1973). The younger UPL are composed of basaltic andesites and basalts with common picritic lava¯ows and dykes (e.g., Schmincke et al 1983).…”

Section: Introductionmentioning

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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Intrusion, Extrusion and Metamorphism at Constructive Margins: Evidence from the Troodos Massif, Cyprus

Cited by 221 publications

References 22 publications

Ti-V plots and the petrogenesis of modern and ophiolitic lavas

Ti-V plots and the petrogenesis of modern and ophiolitic lavas

Melt viscosity, temperature and transport processes, 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

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