Abstract Ophiolite assemblages record structural, magmatic, and metamorphic processes that preceded their entrapment in orogenic belts by continental plate collisions. Ophiolite genetic models appealing to ‘oceanic’ or ‘suprasubduction’ provenance are still unable to reconcile several basic problems, including: (1) the association of boninites with oceanic ridge-type structural settings; (2) the diachronous ‘patch-like’ distribution of ophiolites in orogenic belts; (3) disparate ages between and within their mantle and crustal sections; (4) the lack of evidence for ‘obduction’ at modern passive margins. In contrast, the proposal that ophiolite genesis is exclusive to intra-oceanic forearc settings is compelling, given their uniquely shared structural, lithological, and stratigraphic attributes. Forearcs are interpreted to record discrete stages of subduction ‘rollback’ cycles, examples of which begin with subduction nucleation and the formation of boninitic ‘proto-arcs’, followed by arc splitting and concomitant retreat of the evolving arc-forearc complex. Forearc assemblages are likely to resist subduction to become entrapped in orogens, in contrast to denser, recently formed back-arc basin lithosphere, which is reconsumed by subduction following collision of the retreating forearc. As a model for Neo-Tethyan ophiolite genesis, this is predicated on the notion that rollback cycles are driven by ductile asthenosphere mobilized prior to and during collisions of Gondwana fragments with accreting Eurasia. It is also consistent with the apparent correlation of ophiolite ages with collisional events and their conjugate plate kinematic adjustments. Here, we use the slab rollback model as a template for interpreting the structural, magmatic, and metamorphic characteristics of well-studied Tethyan ophiolites, in Albania (Mirdita), Cyprus (Troodos), and Oman (Semail).

Abstract SE Asian carbonate formations have been reviewed with the aim of understanding the influence of tectonics on their development and reservoir potential through the Cenozoic. Regional tectonics, via plate movements, extensional basin formation, and uplift, was the dominant control on the location of carbonate deposits. These processes controlled the movement of shallow marine areas into the tropics, together with their emergence and disappearance. Although ∼ 70% of the 250 shallow marine carbonate formations in SE Asia were initiated as attached features, 90% of economic hydrocarbon discoveries are in carbonate strata developed over antecedent topography, of which more than 75% were isolated platforms. Faulted highs influenced the siting of nearly two thirds of carbonates developed over antecedent topography. Around a third of carbonate units formed in intra- and interarc areas; however, economic reservoirs are mainly in backarc and rift-margin settings (∼ 40% each). Carbonate edifices show evidence of syntectonic sedimentation through: (1) fault-margin collapse and resedimentation, (2) fault segmentation of platforms, (3) tilted strata and differential generation of accommodation space, and (4) modification of internal sequence character and facies distribution. The demise of many platforms, particularly those forming economic reservoirs, was influenced by tectonic subsidence, often in combination with eustatic sea-level rise and environmental perturbations. Fractures, if open or widened by dissolution, enhance reservoir quality. However, fracturing may also result in compartmentalization of reservoirs through formation of fault gouge, or fault leakage via compromised seal integrity. This study will help in reservoir prediction in complex tectonic regions as the petroleum industry focuses on further exploration and development of economically important carbonate reservoirs.