Hidden melting signatures recorded in the Troodos ophiolite plutonic suite: evidence for widespread generation of depleted melts and intra-crustal melt aggregation

Coogan, L. A.; Banks, Graham J.; Gillis, K. M.; Macleod, Christopher; Pearce, Julian A.

doi:10.1007/s00410-002-0413-2

Cited by 22 publications

(6 citation statements)

References 62 publications

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“…Agar & Klitgord (1995) suggested that deformation is decoupled between the sheeted dyke complex and the plutonic complex based largely on the observation that dykes and faults in the plutonic complex dip west while they dip east in the sheeted dyke complex. However, Coogan et al (2002) show that many of the dykes intruding the plutonics are more depleted in incompatible trace elements than those in the sheeted dyke complex. This suggests that they may not have all been intruded as vertical parallel sheets at the same time, followed by differential rotation as required by Agar & Klitgord (1995).…”

Section: O D E L S F O R T H E S P R E a D I N G E V O L U T I O N mentioning

confidence: 87%

“…This would be somewhat surprising because the large amounts of water that must have been added to the Troodos mantle (Muenow et al 1990) should have led to increased melt production over that at mid‐ocean ridges and would either require a depleted mantle source and/or inefficient melt generation or extraction beneath the ophiolite (e.g. Martinez & Taylor 2002; Coogan et al 2002). Alternatively, if the basal layer is composed largely of ultramafic cumulates, this would indicate that substantially more melt was generated beneath the Troodos ophiolite than at a normal mid‐ocean ridge.Mass balance calculations, based on the composition of the lavas, dykes, mafic cumulates and ultramafic cumulates recovered by drilling in the Troodos ophiolite allow us to reconstruct the possible bulk crustal compositions in either end‐member scenario.…”

Section: Discussionmentioning

confidence: 99%

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Geophysical constraints on the crustal architecture of the Troodos ophiolite: results from the IANGASS project

Mackenzie¹,

Maguire²,

Coogan

et al. 2006

Geophysical Journal International

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S U M M A R YWe present results from modelling a combined 160 km seismic wide-angle reflection/refraction and gravity profile sited across the sheeted dykes, lavas and sediments of the northern part of the Troodos ophiolite, Cyprus. The P-wave seismic velocity and density model, including five separate layers, is defined to a depth of ∼10 km. This shows the ophiolite sequence dipping to the east beneath the central, well resolved, 85 km section of the line between Kambos in the west and Kelia in the east. The upper layer (average velocity 2.83 km s −1 ; density 2.21 g cm −3 ) is interpreted as consisting of sediments and the upper extrusive group. Beneath this, accepting that layer boundaries may be gradational beyond the experiment resolution, the layers are identified as the lower extrusive and basal groups (3.57 km s −1 ; 2.31 g cm −3 ), the sheeted dyke complex (SDC) (4.57 km s −1 ; 2.72 g cm −3 ), a gabbroic layer (6.31 km s −1 ; 2.92 g cm −3 ), and an ultramafic cumulate layer and/or serpentinized peridotite (7.00 km s −1 ; 3.00 g cm −3 ). While the thickness (∼6 km) of this layer beneath the proposed gabbroic layer is defined, positive identification of its composition is not possible, owing to the lack of discriminatory S-wave velocity information. The underlying material provides an unreversed velocity of 8.0 km s −1 beneath the western end of the profile. These modelled velocities and densities are compared with seismic models of oceanic crust and their implications for models of the tectonic evolution of the Troodos ophiolite are discussed.Several major faults are interpreted from the models, with throws of up to ∼500 m offsetting both the extrusive-SDC and the SDC-gabbroic layer boundaries. These are all downthrown to the west, there being no evidence from the data to suggest any major faults downthrown to the east. Our results therefore do not support existing tectonic models for a multiple graben structure within the ophiolite recording either the progress of an eastward stepping spreading centre or off-axis graben formation. Instead, assuming that the faults are downthrown towards the ridge axis, the data are consistent with a single spreading centre located to the west of the recording profile.

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Section: O D E L S F O R T H E S P R E a D I N G E V O L U T I O N mentioning

confidence: 87%

Section: Discussionmentioning

confidence: 99%

Geophysical constraints on the crustal architecture of the Troodos ophiolite: results from the IANGASS project

Mackenzie¹,

Maguire²,

Coogan

et al. 2006

Geophysical Journal International

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“…Proto-arc basement in Izu-Bonin-Mariana fore-arc (Bloomer & Hawkins 1983;Bloomer et al 1985;Parkinson & Pearce 1998) New Britain back-arc (Woodhead et al 1998); Parece Vela back-arc (Ohara et al 2003); Mariana back-arc (Ohara et al 2002); Chile Ridge (Klein & Karsten 1995) Selected examples and references Dariv (Makarychev et al 1986;Khain et al 2003;this paper); Khan Taishir (Zonenshain & Kuzmin 1978;Matsumoto & Tomurtogoo, 2003); Agardagh Tes-Chem (Phänder et al 2002); Trinity (Metcalf et al 2000); Papua (England & Davies 1973); Betts Cove (Church 1977(Church , 1979Church & Riccio 1977;Bédard et al 1998;Bédard 1999); Thetford Mines (Schroetter et al 2003); Troodos? (Coogan et al 2003).…”

Section: Proto-arc and Supra-subduction Ophiolitesmentioning

confidence: 99%

“…The Troodos Ophiolite has many characteristics, including crystallization sequences, that fit with a proto-arc origin, but this ophiolite is not associated with volcaniclastic or igneous rocks with an arc affinity (e.g. Coogan et al 2003). In contrast, evidence for an arc environment of origin is much weaker in some of the classic ophiolites that have been proposed to have originated in supra-subduction zone environments (e.g.…”

Section: Proto-arc and Supra-subduction Ophiolitesmentioning

confidence: 99%

Late Neoproterozoic proto-arc ocean crust in the Dariv Range, Western Mongolia: a supra-subduction zone end-member ophiolite

Dijkstra

Brouwer

Cunningham

et al. 2006

JGS

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An unusual late Neoproterozoic (c. 572 Ma) ophiolite is exposed in the Dariv Range (western Mongolia), which contains intermediate to acidic lavas and sheeted dykes, and an igneous layered complex consisting of gabbro-norites, websterites, orthopyroxenites and dunites underlain by serpentinized mantle harzburgites. Based on the compositions of the crustal units and the crystallization sequences in the mafic and ultramafic cumulates we conclude that the entire oceanic crust, including the cumulates, was made from arc magmas with boninitic characteristics. The Dariv rocks bear a strong resemblance to rocks recovered from the modern Izu-Bonin-Mariana fore-arc, a fragment of proto-arc oceanic basement, and we propose that the Dariv Ophiolite originated in a similar tectonic setting. A metamorphic complex consisting of amphibolite-to granulite-facies metasedimentary and meta-igneous rocks was thrust over the ophiolite. This metamorphic complex probably represents a Cambrian arc. Thrusting started before 514.7 AE 7.6 Ma as constrained by new sensitive high-resolution ion microprobe U-Pb zircon analyses from a syn-to post-tectonic diorite. The Dariv Ophiolite is a type-example of a proto-arc ophiolite, a special class of supra-subduction zone ophiolites.

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“…The solid products of magmatic processes beneath active ridges are hidden from view so much of the petrologic information regarding growth of oceanic crust comes from ophiolites and gabbros exposed in tectonic windows and detachment zones [ Nicolas , 1989; Bédard , 1993; Boudier et al , 1996; Macleod et al , 1996; Natland and Dick , 1996, 2002; Coogan et al , 2000; Macleod and Yaouancq , 2000; Koga et al , 2001; Coogan et al , 2002a, 2002b, 2003a, 2003b; Karson et al , 2002; Dick et al , 2002]. These studies support the view that the crustal magma system facilitates chemical refining of ascending melts and metasomatism of the partially solid crust, processes that have been collectively called syntexis [ Bédard and Hébert , 1996; Bédard et al , 2000].…”

Section: Introductionmentioning

confidence: 99%

Magmatic processes in developing oceanic crust revealed in a cumulate xenolith collected at the East Pacific Rise, 9°50′N

Ridley

Perfit

Smith

et al. 2006

Geochem Geophys Geosyst

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[1] The petrology and geochemistry of a xenolith, a fragment of a melt-bearing cumulate, within a recently erupted mid-ocean ridge (MOR) lava flow provide information on petrogenetic processes occurring within the newly forming oceanic crust beneath the northern East Pacific Rise (NEPR). The xenolith reveals important petrologic information about MOR magmatic systems concerning (1) melt distribution in a crystal-dominated mush; (2) melt-crystal reactions within the mush; (3) the chemistry of melts that have contributed to the cumulate lithology; and (4) the chemistry of axial melts that enter the axial magma system. The xenolith was enclosed within a moderately primitive, normal mid-ocean ridge basalt (NMORB) erupted in 1991 within the neovolcanic zone of the NEPR, at approximately 9°50 0 N. The sample is a matrix-dominated, cumulate olivine anorthosite, composed of anorthite (An 94-90 ) and bytownite (An 89-70 ), intergranular olivine (Fo 86±0.3 ), minor sulfide and spinel, and intergranular glass. Marginal corrosion of plagioclase, and possibly olivine, and internal remelting of plagioclase indicate syntexis. It is surmised that the pore volume was eviscerated several times with moderately primitive basaltic melts and reduced by intergranular crystallization of forsteritic olivine. The presence of anorthite as a cumulate phase in the xenolith and the observation of anorthite xenocrysts in NMORB lavas, and as a cumulate phase in ophiolite gabbros, indicate that Ca-rich melts that are not a part of the NMORB lineage play an important role in the construction of the oceanic crust.

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Hidden melting signatures recorded in the Troodos ophiolite plutonic suite: evidence for widespread generation of depleted melts and intra-crustal melt aggregation

Cited by 22 publications

References 62 publications

Geophysical constraints on the crustal architecture of the Troodos ophiolite: results from the IANGASS project

Geophysical constraints on the crustal architecture of the Troodos ophiolite: results from the IANGASS project

Late Neoproterozoic proto-arc ocean crust in the Dariv Range, Western Mongolia: a supra-subduction zone end-member ophiolite

Magmatic processes in developing oceanic crust revealed in a cumulate xenolith collected at the East Pacific Rise, 9°50′N

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