Spreading structure of the Troodos ophiolite, Cyprus: Some paleomagnetic constraints

Allerton, Simon; Vine, F. J.

doi:10.1130/0091-7613(1987)15<593:ssotto>2.0.co;2

Cited by 95 publications

(74 citation statements)

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“…In contrast, the structure within our field area is relatively simple with nearly vertical dykes and less than 100 m off-sets along dykeparallel faults [Boyle and Robertson, 1984;Eddy and Moores, 1987]. Fault block rotations generally less than 30° indicate that extension was accommodated mainly by extrusion and dyke intrusion [Allerton and Vine, 1987]. Thus the original seafloor topography was probably subdued and the lava-dyke boundary fairly laterally continuous.…”

Section: Alteration Patterns Versus Regional Structurementioning

confidence: 73%

“…Paleomagnetic [Allerton and Vine, 1987] and structural studies [Varga and Moores, 1985;Hurst et al, 1987] in western Troodos show that fault blocks were rotated, possibly along listric normal faults. Field relations suggest that tectonism postdated dyke injection [Schiffman and Smith, 1988] and that spreading was accommodated by alternating magmatic and amagmatic extension [Varga and Moores, 1985].…”

Section: Alteration Patterns Versus Regional Structurementioning

confidence: 99%

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Patterns and processes of alteration in the lavas and dykes of the Troodos Ophiolite, Cyprus

Gillis¹,

Robinson²

1990

J. Geophys. Res.

114

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Alteration panenu in the lavas and dykes of the Troodos Ophiolite, Cypnu, record a compte~ ~st~ of axial hydrochennal alteration, crustal aging, and.subsequent uplift ~d c;rnptac~ent of ~e ophiolite. ~1eld mappina shows that distribution of five alteration zooes, each ~ith duunct rruneralog•cal, gcochermcal, and hydroloaic characteristics, is influenced by igneous stratigraphy, st~cture~ a~d the nature a.nd thickness of the overlying aedimenu. Paragenetic aequences of ICCOlldary ~erals indicate .that alteration conditions changed proareasively as the crust cooled and moved o(f~Uls. Along spreading axes, low temperatures ~SO"C) were mainuined by the rapid flow of seawater m and out of the lavas, and .only minimal alteration took place. In contrast, lower water/rock ratios and hlgh~r te.mperarures (>200°C) m the dykes promoted extensive seawater·rock interaction. Althou~~ the sharp rue .m ~perarure between the two reJ.imes generally coincides with the lava-dyke transJUoo, late· stage mtrus1ons or hydrothermal upwellina zooes locally cause high·temperarure alteration to extend upward .into the lavas. As a segment of crust moved off·axis, temperatures remained tow in the lavas and proaress1vety decreased, ~rom. >250" 10 <80"C in the dykes. High permeability in the uppermost lavas led to the downward rruarauon of an oxidati~e alteration front whose thickness and spatial distribution was dependent upon the. rate and nature of sedimentation and, thus, the original seafloor morphology. Although field relations sho.w that alteration has a consistent vertical pattern in Troodos, the alteration zooes are not laterally oonunuous, and the stratigraphic depth of their boundaries varies considerably. IN1ROOUC110NEarly studies of the massive sulfide deposits [Constantinou and Govett, 1973) and alteration patterns within the Troodos ophiolite [Gass and Smewing, 1973) contributed greatly to the development of models for oceanic hydrothermal systems [SpooMr et al., 1977; C haprno.n and SpooMr, 1977] and subseafloor metamorphism [Coleman, 1977]. Subsequent discovery of high-temperature vents at mid-ocean ridges [e.g., Edmond et al., 1979), seamounts [MalaJwff et al., 1982], and back arc basins [Horbie et al., 1986] showed that hydrothermal circulation is a fundamental process in many oceanic environments.Mineralogical and chemical zonations within the Troodos massive sulfide ore deposits indicate that they formed from hydrothermal flu1ds whose compositions were remarkably similar to those venting on the seafloor today [Adamides, 1987;Herzig and Friedrich , 1987;Richards et al., 1989). Fluid compositions in Troodos were buffered by epidosites at conditions similar to those inferred for the root-zones of active systems at mid-ocean ridges [Bowers and Taylor, 1985;Richardson et al., 1987;Schiffman et al., 1987;Schiffman and Smith, 1988;Seyfried et al., 1988;Von Damm, 1988] . Because of these and other similarities, the upflow zones of the Troodos hydrothermal systems are thought to be ancient analogues of modem active systems [Oud...

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Section: Alteration Patterns Versus Regional Structurementioning

confidence: 73%

Section: Alteration Patterns Versus Regional Structurementioning

confidence: 99%

Patterns and processes of alteration in the lavas and dykes of the Troodos Ophiolite, Cyprus

Gillis¹,

Robinson²

1990

J. Geophys. Res.

114

View full text Add to dashboard Cite

show abstract

“…Paleomagnetic studies of the upper crust and overlying sedimentary sequence [e.g., Morris et al, 2006] showed that the entire ophiolite had rotated by nearly 90°anti-clockwise during the emplacement (late Cretaceous to early Eocene), leading to an expected remanent magnetization direction of 273°/38°(a 95 = 6.5°). Any deviation of remanent magnetization from this direction reflects pre-emplacement accretion-related rotations [e.g., Allerton and Vine, 1987;Bonhommet et al, 1988;Ebert et al, 2010;MacLeod et al, 1990]. Although the gabbros studied here lack independent structural information, remanence directions together with the assumed N-S trend of rotation axis (parallels the Solea axis) are sufficient to correct for tectonic rotations.…”

Section: Discussionmentioning

confidence: 99%

Direct evidence for dynamic magma supply fossilized in the lower oceanic crust of the Troodos ophiolite

Granot

Abelson

Ron

et al. 2011

Geophys. Res. Lett.

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Temporal and spatial variabilities of mantle upwelling and melt supply in mid‐ocean ridges (MORs) have long been documented. Such variabilities span a range of scales and have a profound effect on the structure as well as the composition of the oceanic crust. Previous seismic and gravity studies have suggested that the lower oceanic crust plays a major role in accommodating these changes in melt supply. Here we report the first direct evidence for a sharp transition from coherent sub‐horizontal to near vertical magma flows frozen in the lower oceanic crust of the Troodos ophiolite at the segment edge near a fossil ridge‐transform intersection. We constrain the preferred petrofabric lineation directions at 13 gabbroic sites using anisotropy of magnetic susceptibility (AMS) verified by electron backscatter diffraction. Pre‐emplacement accretion‐related rotations were corrected using magnetic remanence directions. We identify two provinces of nearly uniform susceptibility directions (principal axes) and attribute them to two magmatic episodes. A more focused mantle upwelling and melting episode near the segment midpoint may have resulted in lower crustal lateral magma flows along the fossil segment‐edge, whereas uniform mantle upwelling and melt supply along the entire axis may have resulted in vertical magma flows at the segment‐edge. Overall, our data verify the vital role of the lower oceanic crust in accommodating changes in mantle upwelling and melt supply beneath MORs.

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“…The sidescan and multibeam sonar data, supplemented with field observations from ophiolites (parts of oceanic crust that have been uplifted above sea level), have also allowed us to develop ideas on how the volcanic crust develops from individual volcanic eruptions [49][50][51][52].…”

Section: (A) Mid-ocean Ridgesmentioning

confidence: 99%

Aspects of marine geoscience: a review and thoughts on potential for observing active processes and progress through collaboration between the ocean sciences

Mitchell

2012

Phil. Trans. R. Soc. A.

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Much progress has been made in the UK in characterizing the internal structures of major physiographic features in the oceans and in developing understanding of the geological processes that have created or shaped them. UK researchers have authored articles of high impact in all areas described here. In contrast to terrestrial geoscience, however, there have been few instrumented observations made of active processes by UK scientists. This is an area that could be developed over the next decades in the UK. Research on active processes has the potential ability to engage the wider public: Some active processes present significant geo-hazards to populations and offshore infrastructure that require monitoring and there could be commercial applications of technological developments needed for science. Some of the suggestions could involve studies in shallow coastal waters where ship costs are much reduced, addressing tighter funding constraints over the near term. The possibilities of measuring aspects of volcanic eruptions, flowing lava, turbidity currents and mass movements (landslides) are discussed. A further area of potential development is in greater collaboration between the ocean sciences. For example, it is well known in terrestrial geomorphology that biological agents are important in modulating erosion and the transport of sediments, ultimately affecting the shape of the Earth's surface in various ways. The analogous effect of biology on large-scale geomorphology in the oceans is also known but remains poorly quantified. Physical oceanographic models are becoming increasingly accurate and could be used to study further the patterns of erosion, particle transport and deposition in the oceans. Marine geological and geophysical data could in turn be useful for further verification of such models. Adapting them to conditions of past oceans could address the shorter-period movements, such as due to internal waves and tides, which have been barely addressed in palaeoceanography.

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Spreading structure of the Troodos ophiolite, Cyprus: Some paleomagnetic constraints

Cited by 95 publications

References 0 publications

Patterns and processes of alteration in the lavas and dykes of the Troodos Ophiolite, Cyprus

Patterns and processes of alteration in the lavas and dykes of the Troodos Ophiolite, Cyprus

Direct evidence for dynamic magma supply fossilized in the lower oceanic crust of the Troodos ophiolite

Aspects of marine geoscience: a review and thoughts on potential for observing active processes and progress through collaboration between the ocean sciences

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