Petrological and Chemical Evolution of the Northeastern Troodos Extrusive Series, Cyprus

Bednarz, Ulrich; Schmincke, Hans‐Ulrich

doi:10.1093/petrology/35.2.489

Cited by 43 publications

(30 citation statements)

References 58 publications

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“…In contrast, mid-crustal gabbroic rocks sampled from 700 to 1700 m depth in the CY-4 hole have clinopyroxenes with Mg#'s from 0.65 to 0.825 and TiO 2 greater than 0.32 wt%, consistent with crystallization from more evolved liquids with Mg#'s from 0.3 to 0.52 and TiO 2 greater than 0.85 wt%, such as the lavas in the lower part of the CY-1A core. Such a correlation has previously been suggested by several investigators [13,42,44,45] on the basis of Mg# and TiO 2 contents in clinopyroxene in the CY-4 drill core, in comparison with whole rock and clinopyroxene phenocryst compositions in the lavas (Fig. 5J) …”

Section: Depth Of Magma Reservoirs In the Crustsupporting

confidence: 80%

“…This is also re£ected in the direct comparison of clinopyroxene compositions. Hachured boxes show a range of composition of clinopyroxene phenocrysts in lower lavas (augites in HTS of [13]) and upper lavas (clinopyroxene in LTS but not Lo-LTS of [13]). Only upper lavas have clinopyroxene phenocrysts with Mg# as high and TiO 2 contents as low as clinopyroxene in plutonic rocks at greater than 1700 m in Hole CY-4.…”

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

confidence: 99%

“…However, the thickness of the low-Ti lavas in Holes CY-1/1A is not typical of the area. Bednarz and Schmincke [13] estimate that one third of the volcanic pile and V15% of the dike section are composed of lowTi lithologies. This implies the average volume of low-Ti lavas per dike event was three times larger than the average volume of high-Ti lavas per dike event.…”

Section: Down-section Variation In Viscositymentioning

confidence: 99%

“…For example, in Holes CY-2/2A, the low-Ti suite is 6 100 m whereas it is s 400 m in Hole CY-1/1A. Moreover, low-Ti lavas comprise on average one third of the volcanic sequence [13] whereas in the Akaki area it comprises two thirds.…”

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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Section: Depth Of Magma Reservoirs In the Crustsupporting

confidence: 80%

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

confidence: 99%

Section: Down-section Variation In Viscositymentioning

confidence: 99%

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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“…However, recent studies have revealed that the lowest parts of the LPL, representing the earliest recognized Troodos volcanic episode, are composed of relatively low-Ti lavas more primitive than later LPL (Bednarz et al 1991;Sobolev et al 1993;Bednarz and Schmincke 1994). Andesites and dacites are interpreted to be directly related to those more primitive LPL by open-system fractional crystallization (Bednarz and Schmincke 1994).…”

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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