Integrated geophysical exploration of the north east Troodos Ophiolite, Cyprus.
thesisposted on 19.11.2015, 09:04 by Nicholas John Cooper
Troodos Ophiolite is a remnant of Tethyan oceanic crust of Cretaceous age with well-preserved but complex extensional tectonics along its northern flank. Recent geological studies have provided improved models for the formation and extension environment of Troodos and its associated mineralisation. A geophysical program of seismic refraction, electromagnetic (MT-TEM) and potential field exploration has evaluated and developed aspects of these models. Analysis of aeromagnetic, satellite, and regional geophysical datasets suggests that the Solea and younger Larnaca ridge structures are comprised of NNW-NW oriented half graben cut by near-orthogonal transcurrent features. The known mineralisation was controlled by the extensional faulting. Although partially obscured by sediments, the Larnaca structure exhibits clearer regional anomalies and its western flank was the focus of the seismic refraction and MT-TEM surveys. Four refraction lines were recorded parallel and perpendicular to the proposed Larnaca axis. The 2D velocity structure of the oceanic Layer 2 and upper Layer 3 equivalent units was modelled to depths of 2.5-3.0 km, and revealed NW trending, normally faulted half graben dissected by reactivated ENE faulting with minor transform displacement. The compartmentalized "chequer board" tectonics are down faulted at the ophiolite-sediment contact, and the sediments thin towards the Larnaca axis. An apparent moho reflection occurred at 6.0 - 7.0 km. The MT-TEM and potential field data confirmed and constrained the Larnaca extensional model. Detailed TEM reconnaissance studies on a 3.31 km2 grid at Mathiatis-Sha modelled the Layer 2 resistivity structure to depths of 300 m, and refined the relationship between faulting and mineralisation for northern Troodos. Rigourous testing of the TEM method has established it as a powerful mineral exploration tool in the ophiolitic environment. The integrated model correlates with modern and ancient analogues and provides a framework for tectonic studies within an intermittent spreading regime.