Comments on “the troodos ophiolitic complex was probably formed in an island arc”, by A. Miyashiro and subsequent correspondence by A. Hynes and A. Miyashiro

Gass, I. G.; Neary, C. R.; Plant, Jane A.; Robertson, Alastair H.F.; Simonian, K. O.; Smewing, J. D.; Spooner, E. T. C.; Wilson, Ronald

doi:10.1016/0012-821x(75)90202-2

Cited by 44 publications

(4 citation statements)

References 13 publications

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“…With the exception of four small areas, there is genertrue mid-oceanic spreading center is a subject of dispute [e.g., ally a regional tilt of the dikes toward the west. (The three Miyashiro, 1973;Hynes, 1975;Gass et al, 1975;Moores, 1975; small areas which show eastward tilts possibly may reflect Pearce, 1975], Robertson and Woodcock [1979] have argued antithetic fault blocks or subsequent deformation of the ½omconvincingly that the regional stratigraphic relations on Cy-plex. One block which shows a northward tilt is adjacent to prus and in surrounding regions point toward an origin in a the transform fault.)…”

Section: Troodos Complex This Assumption May Not Be Strictly Valid Fomentioning

confidence: 99%

Tectonic rotations in extensional regimes and their paleomagnetic consequences for oceanic basalts

Verosub¹,

Moores²

1981

J. Geophys. Res.

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Paleomagnetic samples of many Deep‐Sea Drilling Project (DSDP) basalts have shallower inclinations than would be inferred from the paleolatitude at which the basalts were extruded at mid‐ocean ridges. Rather than arising from peculiarities of the geomagnetic field, the anomalous magnetic directions may result from tectonic rotations along the listric normal faults which often characterize extensional tectonic regimes. Several lines of evidence support this conclusion: observations of the Basin and Range Province, an extensional tectonic regime occurring in continental crust; observations of the Troodos complex, Cyprus, an oceanic extensional tectonic regime now exposed on land; and analysis of possible fault patterns associated with the magma chambers postulated to occur at some mid‐oceanic ridges. The tectonic rotations resulting from movement along the listric normal faults occur about a horizontal axis generally perpendicular to the extension direction and typically amount to 30° to 50°, although rotations as large as 70° to 90° are not uncommon. The paleomagnetic consequences of these rotations can be calculated for DSDP basalts if the original strike and latitude of a ridge are known. At four DSDP sites for which adequate data are available, namely sites 319, 332, 410, and 417, rotations ranging from 50° to 70° are required to explain the paleomagnetic results. If the original strike and location of the ridge are not known, as is the case for most of the older parts of the Pacific Ocean, the paleomagnetic data and the inferred rotation determine a relationship between possible ridge strikes and locations. This information, combined with a similar but independent relationship derived from the marine magnetic anomalies, puts severe constraints on the original strike and location of the ridge.

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Section: Troodos Complex This Assumption May Not Be Strictly Valid Fomentioning

confidence: 99%

Tectonic rotations in extensional regimes and their paleomagnetic consequences for oceanic basalts

Verosub¹,

Moores²

1981

J. Geophys. Res.

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“…In particular, the presence of glassy volcanic rocks containing unusually high MgO (>10 wt%) with intermediate (i.e., andesitic) silica (~55 wt% SiO 2 ) is unlike the basalts and their derivative melts typical of mid-ocean ridges. However, for many geologists, the occurrence on Troodos of a prominent sheeted dike complex represented concurrent magmatism and extension, and the absence of stratovolcanoes with aprons of volcaniclastic debris typical of island arcs seemed incompatible with a convergent margin origin (e.g., Gass et al, 1975).…”

Section: Introductionmentioning

confidence: 99%

How to Create New Subduction Zones: A Global Perspective

Arculus¹,

Gurnis²,

Ishizuka³

et al. 2019

Oceanog

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“…Ophiolites have long been recognized as remnants of oceanic lithosphere, but the site and circumstances of their origins have been the subject of much controversy. Early studies focused on ophiolites as an analogue for oceanic crust formed at midocean-ridge spreading centers (e.g., Moores et al, 1968;Moores, 1969;Dewey and Bird, 1971;Gass et al, 1975;Moores, 1975;Moore and Liou, 1979;Smewing, 1981). Later work proposed that most ophiolites, including the classic occurrences in Cyprus and Oman, formed above subduction zones in an environment related to island-arc volcanism (e.g., Miyashiro, 1973;Pearce, 1975Pearce, , 1980Alabaster et al, 1982;Shervais, 1982;Shervais and Kimbrough, 1985).…”

Section: Introductionmentioning

confidence: 99%

Tonalites, trondhjemites, and diorites of the Elder Creek ophiolite, California: Low-pressure slab melting and reaction with the mantle wedge

Shervais¹

2008

Special Paper 438: Ophiolites, Arcs, and Batholiths: A Tribute to Cliff Hopson

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The Elder Creek ophiolite, which crops out along the South, Middle, and North Forks of Elder Creek, is the largest exposure of mid-Jurassic Coast Range ophiolite in the northern Coast Ranges of California. The Elder Creek ophiolite contains almost all of the components of a classic ophiolite (mantle tectonites, cumulate ultramafi cs and gabbro, dike complex, volcanics), although most of the volcanic section has been removed by erosion and redeposited in the overlying Crowfoot Point breccia. It differs from classic ophiolite stratigraphy in that it has substantial volumes (25%-30% of the complex) of felsic plutonic rocks intimately associated with the other lithologies. The felsic lithologies include hornblende diorite, quartz-diorite, tonalite, and trondhjemite, which crop out in four distinct associations: (1) as rare, small pods within the sheeted dike complex, (2) as the felsic matrix of igneous breccias (agmatites), (3) 1-25-m-thick dikes that crosscut cumulate or isotropic gabbro, and (4) sill-like plutons up to 500 m thick and 3 km long that intrude the upper part of the plutonic section. Typical phase assemblages include quartz, plagioclase, hornblende, and pyroxene, in a hypidiomorphic texture. The Elder Creek tonalite-trondhjemite-diorite (TTD) suite spans a wide range in composition: 54%-75% SiO 2 , 3.3%-14.3% FeO*, and 2.7%-6.4% MgO; all are low in K 2 O (<0.7%). The large sill-like plutons are generally higher in silica (average 69% SiO 2) than the dikes, pods, and agmatite matrix (average 60% SiO 2). Mg#'s range from 65 to 17, with Cr up to 227 ppm at 58% silica. High-Mg diorites with 4%-7% MgO at 53%-58% SiO 2 are common in the dike suite, but relatively high MgO, Mg#, and Cr values are found in the large plutons as well. The major-and trace-element characteristics are consistent with partial melting of subducted, amphibolite-facies oceanic crust at relatively low pressures (5-10 kbar) outside the garnet stability fi eld. Melting of subducted oceanic crust at these pressures can only occur during the collision and subduction of an active spreading center. Subsequent reaction of these melts with the overlying mantle wedge has increased their refractory element concentrations. The occurrence of zircons with inherited Pb isotope characteristics implies the involvement of subducted sediments containing an ancient zircon component. Formation of the Elder Creek TTD suite was a transient event associated with ridge collision-subduction. This is consistent with previous models for the Coast Range ophiolite and other suprasubduction-zone ophiolites; it is not consistent with an ocean-ridge spreading-center origin.

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Comments on “the troodos ophiolitic complex was probably formed in an island arc”, by A. Miyashiro and subsequent correspondence by A. Hynes and A. Miyashiro

Cited by 44 publications

References 13 publications

Tectonic rotations in extensional regimes and their paleomagnetic consequences for oceanic basalts

Tectonic rotations in extensional regimes and their paleomagnetic consequences for oceanic basalts

How to Create New Subduction Zones: A Global Perspective

Tonalites, trondhjemites, and diorites of the Elder Creek ophiolite, California: Low-pressure slab melting and reaction with the mantle wedge

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