Ophiolite

In Fig. 1.85 iron contents of epidote from two different geologic environments, island arc and oceanic ridge or ophiolite, are summarized. It can be seen in Fig. 1.85 that the iron content of epidote from ridge basalt and ophiolite is generally lower than... 

Cowan, J.E. and Cann, J. (1988) Supercritical two-phase separation of hydrothermal fluids in the Troodos ophiolite. Nature, 333, 259-261. 

Zaccarini, F. Garuti, G. 2008. Mineralogy and chemical composition of VMS deposits of northern Apennine ophiolites, Italy evidence for the influence of country rock type on ore composition. Mineralogy and Petrology, 84, 61-83. 

Khan S.D., Khalid Mahmood, K, Casey, J.F. 2006. Mapping of Muslim Bagh ophiolite complex (Pakistan) using new remote sensing, and field data. Journal of Asian Earth Sciences, 30, 333-343. 

The geology of Cyprus is dominated by four distinct terranes - the Troodos Ophiolite Complex composed of mafic and ultramafic rocks, the Circum-Troodos Sedimentary Sequence containing calcarenites, siltstones and carbonates, the Mamonia Complex composed of igneous, sedimentary and metamorphic rocks and the Kyrenia Terrain containing a series of allochthonous massive and recrystallised limestones dolomites and marbles. These terranes generate highly varied landscapes (Fig 1). 

Fig 1. View from edge of Messaoria Plain at Tseri towards dissected palaeo-fan surfaces in middle ground and the Troodos Ophiolite Complex mountains in the background. 

Layne GD (2003) Advantages of secondary ion mass spectrometry (SIMS) for stable isotope microanalysis of the trace light elements. EOS Trans, Am Geophys Union 84 F1635 Lundstrom CC, Chaussidon M, Kelemen P (2001) A Li isotope profile in a dunite to Iherzolite transed within the Trinity Ophiolite evidence for isotopic fractionation by diffusion. EOS Trans, Am Geophys Union 82 991... 

Seafloor spreading eventually pushes oceanic crust into subduction zones where the hydrothermal sediments and rock are recycled back into the mantle. A small fraction of these deposits is uplifted, or obducted, onto land. These rescued deposits are termed ophiolites. Because of their metal enrichments, they serve as major ore bodies and have been mined for various precious metals, such as copper, for thousands of years. 

Ophiolites Ancient pieces of oceanic crust that have been thrust up onto the continents as a result of geologic uplift. 

Fig. 1. Primitive mantle (PM) normalized whole rock PGE profiles for stratiform chromitites from the Stillwater Complex and for podiform chromitites from the mantle section of Thetford Mines Ophiolite (TMO). Note the similarity between IPGE contents of chromitites from these different tectonic settings. D.L.= detection limit.

We analyzed chromites from 1) podiform chromitite deposits from the mantle section of the Thetford Mines Ophiolite (TMO), southern Quebec Appalachians (Canada) 2) stratiform chromitite seams found within the Stillwater Complex, Montana (USA). In addition, we also analyzed chromite in lavas from different tectonic settings in order to 1) verify whether the IPGE solubility in chromite could be related to geological setting and... 

Page, P. 2006. Petrogenese de I ophiolite de Thetford Mines, Quebec, Canada, avec un accent particulier sur les roches du manteau et les chromitites. Ph.D. thesis, Institut National de la Recherche Scientifique, Quebec, PQ, Canada, 282 p. 

Palladium, platinum, rhodium, ruthenium and iridium in chromite-rich rocks form the Semail ophiolite, Oman. Canadian Mineralogist, 20, 537-548. 

The Tyrone Plutonic Group comprises a basic igneous association of layered, isotropic and pegmatitic gabbros, doleritic sheeted dykes and rare basaltic pillow lavas first recognized as ophiolitic by Hutton etal. (1985). 

Though limited, the geochemistry presented herein serves to show the broad compositional differences (Fig. 2a) between the ophiolitic, normal-type MORB (Fig. 2b) and the volcanic arc-related granitoids (Fig. 2c). Current geochemical research, targeted towards the location of potential VMS mineralization, will expand and improve this area of investigation. 

A U-Pb zircon age of 480 1 Ma from layered gabbros at Scalp (Fig 1b - SC) provides the only direct age for the ophiolitic Tyrone Plutonic Group so far. This age date negates the need for the obduction of contemporaneous ophiolite and an active volcanic arc and simplifies the tectonomagmatic evolution. 

The difference in age between the ophiolitic Tyrone Plutonic Group (c. 480 Ma) and Tyrone Volcanic Group (c. 473 -464 Ma) allows time for northwards directed obduction (c. 475 Ma) of the Tyrone Plutonic Group related to southwards directed subduction (Fig. 4c), followed by the establishment of northwards directed subduction and the development of the Tyrone Volcanic Group arc (Fig. 4d). 

A U-Pb zircon age of 480 1 Ma provides the first direct isotopic age for the ophiolitic Tyrone Plutonic Group. 

Northern New Brunswick - A Synthesis. Economic Geology Monograph, 11, 245-301. Hutton, D.H.W., Aftalion, M., Halliday, A. N. 1985. An Ordovician ophiolite in County Tyrone, Ireland. Nature, 315, 210-212. VandenBerg, a. H. M. Cooper, R. A. 1992. The Ordovician Graptolite Sequence of Australasia. Alcheringa, 16, 33-85. 

Langton, J. P. 1993. Stratigraphy, structure, and geochemistry of the ophiolitic inlier. Northern New Brunswick. Unpublished MSc thesis. Queen s University. 

Lundstrom CC, Chaussidon M, Hsui AT, Keleman P, Zimmermann M (2005) Observations of Li isotope variations in the Trinity ophiolite evidence for isotope fractionation by diffusion during mantle melting, Geochim Cosmochim Acta 69 735-751 Luz B, Barkan E (2000) Assessment of oceanic productivity with the triple-isotope composition of dissolved oxygen. Science 288 2028-2031... 

Ozawa, K. and Shimizu, N., 1995. Open-system melting in the upper mantle Constraints from the Hayachine-Miyamori ophiolite, northeastern Japan. J. Geophys. Res., 100 22315-22335. 

The Ligurian complex tectonically superimposed on the Tuscan units, consisting of middle to late Jurassic ophiolites and radiolarites plus Cretaceous to Eocene pelagic limestones and flysch sequences. 

Principi G (1994) Stratigraphy and evolution of the Northern Apennine accretion wedge with particular regard to the ophiolitic sequences a review. Boll Geofis TeorAppl 36 243-269... 

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