“Oman Exotics”—Oceanic carbonate build-ups associated with the early stages of continental rifting

Searle, Michael P.; Graham, Gordon Michael

doi:10.1130/0091-7613(1982)10<43:oecbaw>2.0.co;2

Cited by 125 publications

(47 citation statements)

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“…The Bisotoun and Radiolarite zones resulted from thinning of the Arabian Plate during Neotethys opening in PermianTriassic time (Searle and Graham, 1982;Kazmin et al, 1986;Fontaine et al, 1989). The Bisotoun zone (or Bisotoun platform) is composed of thick carbonate deposits at the northeastern rim of the Arabian Plate.…”

Section: Tectonic Settingmentioning

confidence: 99%

Spatial evolution of Zagros collision zone in Kurdistan, NW Iran: constraints on Arabia–Eurasia oblique convergence

Sadeghi

Yassaghi

2016

Solid Earth

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Abstract. Stratigraphy, detailed structural mapping and a crustal-scale cross section across the NW Zagros collision zone provide constraints on the spatial evolution of oblique convergence of the Arabian and Eurasian plates since the Late Cretaceous. The Zagros collision zone in NW Iran consists of the internal Sanandaj-Sirjan, Gaveh Rud and Ophiolite zones and the external Bisotoun, Radiolarite and High Zagros zones. The Main Zagros Thrust is the major structure of the Zagros suture zone. Two stages of oblique deformation are recognized in the external part of the NW Zagros in Iran. In the early stage, coexisting dextral strike-slip and reverse dominated domains in the Radiolarite zone developed in response to deformation partitioning due to oblique convergence. Dextral-reverse faults in the Bisotoun zone are also compatible with oblique convergence. In the late stage, deformation partitioning occurred during southeastward propagation of the Zagros orogeny towards its foreland resulting in synchronous development of orogen-parallel strikeslip and thrust faults. It is proposed that the first stage was related to Late Cretaceous oblique obduction, while the second stage resulted from Cenozoic collision. The Cenozoic orogen-parallel strike-slip component of Zagros oblique convergence is not confined to the Zagros suture zone (Main Recent Fault) but also occurred in the external part (MarekhilRavansar fault system). Thus, it is proposed that oblique convergence of Arabian and Eurasian plates in Zagros collision zone initiated with oblique obduction in the Late Cretaceous followed by oblique collision in the late Tertiary, consistent with global plate reconstructions.

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Section: Tectonic Settingmentioning

confidence: 99%

Spatial evolution of Zagros collision zone in Kurdistan, NW Iran: constraints on Arabia–Eurasia oblique convergence

Sadeghi

Yassaghi

2016

Solid Earth

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“…If the ophiolite formed by this`r idge-centered thrust'' model, then amphibolites of the metamorphic sole and volcanics of the ophiolite should have the same geochemical characteristics and form in the same tectonic setting (at a mid-ocean ridge spreading center). In Oman this is clearly not the case; abundant data show that amphibolites of the metamorphic sole are oceanic tholeiites, similar to Jurassic tholeiitic basalts in the Haybi melange, and are unrelated to rocks of the ophiolite [e.g., Alabaster et al, 1982;Lippard et al, 1986;Searle and Cox, 1999;Searle and Graham, 1982;. [60] Ridge collision/subduction ended the formation of normal ophiolitic crust (layered gabbros, ultramafic intrusives, calc-alkaline stocks and sills) because the young oceanic lithosphere was too buoyant to subduct, and the ophiolite entered a phase of intraoceanic thrusting along a shallow decollement ( Figure 7f).…”

Section: Stage 4: Deathmentioning

confidence: 99%

“…It has been suggested that Tethyan ophiolites like Oman formed in small, intracontinental ocean basins only a few hundred kilometers wide (``Red Sea model [Lippard et al, 1986;Robertson, 1986]). In the case of Oman this claim is difficult to understand in light of the fact that the Haybi melange contains late Permian to Triassic oceanic basalts and that sedimentary records show that rifting to form the passive margin of Oman began in the middle Permian and was complete by the early Triassic at the latest [Gealey, 1977;Glennie et al, 1974;Searle and Graham, 1982;Searle and Malpas, 1980]. If we assume a modest spreading rate of only 40 mm/ yr (20 mm/yr half rate) and 150 million years of spreading (early Triassic at 245 Ma to late Cretaceous at 95 Ma), then at least 6000 km of ocean basin must have existed!…”

Section: Stage 5: Resurrectionmentioning

confidence: 99%

“…It is a classic example of a Tethyan ophiolite that was obducted onto a passive continental margin and exposed by isostatic rebound of the continental margin beneath the ophiolite. Rifting of the northeastern margin of Gondwana to form the Neo-Tethys ocean began in the middle Permian and was completed by the early to mid Triassic (Figure 7a), as shown by the occurrence of Triassic seamounts of ocean island basalt with limestone carapaces in the Haybi melange [Robertson, 1986;Searle and Graham, 1982;. This NeoTethyan ocean basin persisted for at least 125 million years and was not completely consumed until the late Cretaceous [Glennie et al, 1974;Lippard et al, 1986;Searle and Cox, 1999;Yanai et al, 1990].…”

Section: Case History 2: Semail Ophiolite Omanmentioning

confidence: 99%

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Birth, death, and resurrection: The life cycle of suprasubduction zone ophiolites

Shervais

2001

Geochem Geophys Geosyst

461

275

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[1] Abstract: Suprasubduction zone (SSZ) ophiolites display a consistent sequence of events during their formation and evolution that suggests that they form in response to processes that are common to all such ophiolites. This sequence includes the following: (1) birth, which entails the formation of the ophiolite above a nascent or reconfigured subduction zone; this stage is typically characterized by the eruption of arc tholeiite lavas and the formation of layered gabbros and sheeted dike complex; (2) youth, during which is continued melting of refractory asthenosphere (depleted during birth) occurs in response to fluid flux from the subducting slab, with extensional deformation of the older plutonic suite, eruption of refractory lavas, and the intrusion of wehrlite-pyroxenite; (3) maturity, with the onset of semistable arc volcanism, typically calc-alkaline, as the subduction zone matures and stabilizes, and the intrusion of quartz diorite and eruption of silicic lavas; and (4) death, which is the sudden demise of active spreading and ophiolite-related volcanism, which in many cases is linked to collision with an active spreading center and the onset of shallow underthrusting of the buoyant spreading axis; expressed as dikes and lavas with oceanic basalt compositions that crosscut or overlie rocks of the older suites; (5) resurrection, with emplacement by obduction onto a passive margin or accretionary uplift with continued subduction. The early stages (1± 3) may be diachronous, and each stage may overlap in both time and space. The existence of this consistent progression implies that ophiolite formation is not a stochastic event but is a natural consequence of the SSZ tectonic setting.

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“…Jebel Akdar is one of the regional tectonic windows opening through the oceanic allochthon of the Hawasina volcano-sedimentary nappe complex and the overlying Semail ophiolite (Poupeau et al 1998). The Hawasina Nappes are remnants of the distal part of the south Neotethyan continental margin, whereas the Arabian Platform corresponds to its shallow-water (neritic) proximal part (Searle and Graham 1982;Béchennec et al 1988). The lowgrade greenschist-facies Late Proterozoic rocks in the Jebel Akhdar dome are unconformably overlain by weakly metamorphosed middle Permian to Cenomanian carbonates.…”

Section: Geological Settingmentioning

confidence: 99%

Influence of climate and dolomite composition on dedolomitization: insights from a multi-proxy study in the central Oman Mountains

Vandeginste

John

2012

Journal of Sedimentary Research

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Dedolomitization is an important diagenetic process that can yield information on the history of paleo-fluids in a given aquifer or outcrop, and by extension it offers a window into past hydrologic conditions. Dedolomitization is also relevant economically as it can alter the porosity and permeability of carbonates, thus affecting reservoir quality. Despite considerable research, the process of dedolomitization is still not entirely understood. Here, new findings from the central Oman Mountains highlight the importance of dolomite chemistry and fluctuating climate on dedolomitization. Petrographic, mineralogical, and geochemical data from both altered and pristine dolomite hosted in Jurassic carbonate rocks from the Sahtan Group and outcropping at Wadi Mistal in the Jebel Akhdar tectonic window reveal two dolomite bodies with different characteristics, stratabound and fault-related dolostone. The (ferroan) dolomite crystals are larger in the fault-related dolostone, whereas the (non-ferroan) dolomite crystals are smaller in the stratabound dolostone. Petrography reveals a complex suite of alteration textures, including pristine dolomite, recrystallized dolomite, and calcitized dolomite (dedolomite). Iron oxides are present pervasively in the altered rocks, and different alteration textures co-occur in the same sample. Relative to unaltered dolomite in this outcrop, the recrystallized dolomite is characterized by similar positive carbon isotope values but less negative oxygen isotope values, and the calcitized dolomite is characterized by even less negative oxygen isotope values and more negative carbon isotope values. Based on field data and petrography, two phases of alteration are evident, an earlier dedolomitization event affecting the stratabound dolomite only, and a more pervasive Pleistocene-Holocene alteration phase associated with surface weathering that affected both the fault-related dolomite and to a lesser extent the stratabound dolomite. Stable isotope results further suggest that the more recent subaerial weathering phase happened under two alternating climate regimes: dedolomitization was triggered by meteoric fluids that interacted with soil-related carbon during humid climatic period(s), whereas recrystallization of ferroan fault-related dolomite happened during more arid climatic period(s) with less developed soils and lower fluid-rock interaction. These results suggest that weathering of ferroan fault-related dolomite can lead to formation of goethite and recrystallized, non-stoichiometric dolomite (with a reset stable oxygen isotope signature), and sometimes to dedolomitization.

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“Oman Exotics”—Oceanic carbonate build-ups associated with the early stages of continental rifting

Cited by 125 publications

References 0 publications

Spatial evolution of Zagros collision zone in Kurdistan, NW Iran: constraints on Arabia–Eurasia oblique convergence

Spatial evolution of Zagros collision zone in Kurdistan, NW Iran: constraints on Arabia–Eurasia oblique convergence

Birth, death, and resurrection: The life cycle of suprasubduction zone ophiolites

Influence of climate and dolomite composition on dedolomitization: insights from a multi-proxy study in the central Oman Mountains

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