Neo-Tethyan Subduction Zone Research Articles

Characteristics of the amphibolites from Nigde metamorphics (Central Turkey), deduced from whole rock and mineral chemistry

Whole rock and mineral chemistry of amphibolites are presented for the lower (Gumusler Formation) and higher parts (Kaleboynu Formation) of the Nigde Massif with the aim to constrain protolith genesis and metamorphic P-T-conditions. The amphibolites, associated with a series of supracrustal metasediments, as thin layers and discontinuous pod/small lenses, are of igneous origin with composition of subalkaline and tholeiitic basalts. Based on immobile elements content and ratios, amphibolites from both formations are thought to have formed mostly by fractional crystallisation of pyroxene ± spinel, amphibole, plagioclase as well as apatite and titanite; coupled with minor crustal contamination. Contamination is particularly clear for the Gumusler Formation formed in a back-arc basin (Paleothetys) during magmatic ascent through the thickened Central Anatolian crust. The basic rocks could have been metamorphosed later at 7.5-3 ± 0.6 kb and 850-420°C, with the temperature gradient ranging from 35 to 122°C/km at different depths in the Neo-Tethyan subduction zone, and exhumed from depths of approximately 20 km via regional extension.

Transient, synobduction exhumation of Zagros blueschists inferred from P‐T, deformation, time, and kinematic constraints: Implications for Neotethyan wedge dynamics

We present the first P‐T, deformation time, and kinematic constraints on the only known blueschist facies rocks (BS) present in the Zagros (Hajiabad area). The BS were underplated below the Sanandaj‐Sirjan zone and crop out as kilometer‐scale bodies within extensive colored melange units marking discontinuously the Neotethyan suture zone. P‐T estimates point to high‐pressure/low‐temperature (HP‐LT) conditions around 11 kbar and 520–530°C for the majority of BS, along a ∼15°C km−1 gradient. Some exotic blocks in matrix serpentinite reached 17–18 kbar at ∼500°C. In situ laser probe 40Ar‐39Ar radiometric age constraints on phengite cluster between 85 and 95 Ma and suggest that (1) synconvergence exhumation of Zagros BS from 35–50 km to depths <15–20 km was accomplished before 80 Ma, (2) BS exhumation corresponded to a transient process with respect to the long‐lived subduction beneath Iran (∼150–35 Ma), and (3) age constraints for Zagros BS are 5–10 Myr older than for the nearby Oman HP‐LT rocks and broadly coincide with obduction processes in the region (circa 95–70 Ma). We propose that the mechanical coupling across the Neotethyan subduction zone (NSZ) beneath Iran was modified by the large‐scale plate rearrangement accompanying obduction, allowing for a short‐lived exhumation of Zagros BS. Exhumation ceased at the end of obduction, when subduction of the Arabian continental margin stopped. Kinematic calculations suggest that convergence velocities across the NSZ likely doubled (to ∼5–6 cm yr−1) during the period 118–85 Ma, so that BS exhumation may have been promoted by a combination of obduction movements and increased convergence velocities.

Insights from the Talysh of Azerbaijan into the Paleogene evolution of the South Caspian region

Research Article| November 01, 2005 Insights from the Talysh of Azerbaijan into the Paleogene evolution of the South Caspian region Stephen J. Vincent; Stephen J. Vincent 1CASP, Department of Earth Sciences, University of Cambridge, 181a Huntingdon Road, Cambridge CB3 0DH, UK Search for other works by this author on: GSW Google Scholar Mark B. Allen; Mark B. Allen 1CASP, Department of Earth Sciences, University of Cambridge, 181a Huntingdon Road, Cambridge CB3 0DH, UK Search for other works by this author on: GSW Google Scholar Arif D. Ismail-Zadeh; Arif D. Ismail-Zadeh 2Geology Institute of the Azerbaijan Academy of Sciences, 29A H. Javid Ave., Baku, Az1143, Azerbaijan Search for other works by this author on: GSW Google Scholar Rachel Flecker; Rachel Flecker 3CASP, Department of Earth Sciences, University of Cambridge, 181a Huntingdon Road, Cambridge CB3 0DH, UK Search for other works by this author on: GSW Google Scholar Kenneth A. Foland; Kenneth A. Foland 4Department of Geological Sciences, Ohio State University, Columbus, Ohio 43210, USA Search for other works by this author on: GSW Google Scholar Michael D. Simmons Michael D. Simmons 5CASP, Department of Earth Sciences, University of Cambridge, 181a Huntingdon Road, Cambridge CB3 0DH, UK Search for other works by this author on: GSW Google Scholar GSA Bulletin (2005) 117 (11-12): 1513–1533. https://doi.org/10.1130/B25690.1 Article history received: 27 Jul 2004 rev-recd: 15 Mar 2005 accepted: 24 Mar 2005 first online: 08 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Stephen J. Vincent, Mark B. Allen, Arif D. Ismail-Zadeh, Rachel Flecker, Kenneth A. Foland, Michael D. Simmons; Insights from the Talysh of Azerbaijan into the Paleogene evolution of the South Caspian region. GSA Bulletin 2005;; 117 (11-12): 1513–1533. doi: https://doi.org/10.1130/B25690.1 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract The age and mode of formation of the South Caspian Basin are disputed. An ∼10-km-thick, predominantly middle Eocene clastic and volcanic succession is exposed in the Talysh mountains of Azerbaijan at its western margin. Here, high-K alkali basalts pass laterally to the east and southeast into volcanogenic sandstone-dominated turbidity current and debris-flow deposits. These southeasterly directed depositional systems accumulated in water depths generally greater than 200 m and fed directly into the western South Caspian Basin. New Ar-Ar ages cluster around 39 Ma, with an upper, 1400-m-thick volcanic interval being deposited in 2.2 ± 0.2 m.y. We interpret that this rapid deposition and magmatism records a major back-arc extensional/transtensional event in the Talysh, north of the north-dipping Neotethyan subduction zone. This event is recognized across much of southwest Asia and may indicate a period of significant basin formation within the adjacent South Caspian Basin. A transition into Upper Eocene–Lower Oligocene strata, dominated by fine-grained turbidity current and hemipelagic sediments with slope instability features, is interpreted to mark the end of rifting and volcanism in the Talysh and the start of the Arabia-Eurasia collision. Overlying Oligocene coarse clastic rocks are interpreted as the erosional products of localized topography created by the further propagation of compressional deformation into the Talysh region. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Slow Senonian and fast Palaeocene–Early Eocene uplift of the granitoids in the Central Eastern Pontides, Turkey: apatite fission-track results

Dating and forward modelling of the fission-track data of apatite samples from the Dereli–Şebinkarahisar region, south of Giresun in the Eastern Turkish Pontides, provides quantitative data on the regional tectonics resulting from the closure of neo-Thetys and the collision of Eurasia and Gondwana. The age vs. elevation profiles identified Senonian (80.7±3.2 to 62.4±2.5 Ma) slow uplift and denudation, interpreted as the result of the diapiric ascent of subduction-related plutons above the neo-Tethyan subduction zone beneath the Eurasian continent. This was followed by rapid differential uplift during the Palaeocene–Early Eocene (57.4±2.4 to 47.8±2.4 Ma), which juxtaposed granitoid units of different ages, compositions, and emplacement levels in the crust, and is thought to be related to the collision between the Pontide (Eurasian) and Anatolide (Gondwana) basements. The modelling results must be interpreted with caution, but appear to indicate a period of Mio-Pliocene (ca. 5 Ma) reheating related to volcanism associated with the westward escape of the Anatolian plate and uplift from the Pliocene (ca. 3.5 Ma) up to the present.

Exhumation of the west-central Alborz Mountains, Iran, Caspian subsidence, and collision-related tectonics

Crystallization and thermal histories of two plutons in the west-central Alborz (also Elburz, Elburs) Mountains, northern Iran, are combined with crosscutting relations and kinematic data from nearby faults to determine the Cenozoic tectonic evolution of this segment of the youthful Euro-Arabian collision zone. U/Pb, ^(40)Ar/^(39)Ar, and (U-Th)/He data were obtained from zircon, biotite, K-feldspar, and apatite. The Akapol pluton intruded at 56 ± 2 Ma, cooled to ∼150 °C by ca. 40 Ma, and stayed near that temperature until at least 25 Ma. The nearby Alam Kuh granite intruded at 6.8 ± 0.1 Ma and cooled rapidly to ∼70 °C by ca. 6 Ma. These results imply tectonic stability of the west-central Alborz from late Eocene to late Miocene time, consistent with Miocene sedimentation patterns in central Iran. Elevation-correlated (U- Th)/He ages from the Akapol suite indicate 0.7 km/m.y. exhumation between 6 and 4 Ma, and imply ∼10 km of Alborz uplift that was nearly synchronous with rapid south Caspian subsidence, suggesting a causal relation. Uplift, south Caspian subsidence and subsequent folding, reversal of Alborz strike-slip (from dextral to sinistral) and(?) eastward extrusion of central Iran, coarse Zagros molasse deposition, Dead Sea transform reorganization, Red Sea oceanic spreading, and(?) North and East Anatolian fault slip all apparently began ca. 5 ± 2 Ma, suggesting a widespread tectonic event that we infer was a response to buoyant Arabian lithosphere choking the Neo-Tethyan subduction zone.

Aptian-Albian palaeogeography of Neo-Tethyan domain

The Aptian-Albian interval (124.5-97.0 Ma) was a critical time both globally and for the Tethyan domain. In the Tethyan domain it was the time when a united Neo-Tethyan subduction zone became established between the future site of the Alps and Southeast Asia and greatly accelerated the rate of north-south convergence throughout the Tethyan region. A consequent widespread transgression on both Laurasian and Gondwanian margins deposited Orbitolina limestones and associated clastics on wide continental shelf areas. On the sea-floor of the Neo-Tethys ocean, organic-rich siliceous black shales, radiolarites, and turbidites with minor amounts of carbonates were deposited. Siliceous black shales accumulated under euxinic conditions of restricted small ocean basins of the Neo-Tethyan realm and along their margins. These areas received large amounts of organic debris from deltaic areas and coastal plains of the neighbouring continental shelves. Following the establishment of the north-dipping subduction zone, the Laurasian passive margin was largely converted to an active one, fringed by a large number of magmatic arcs that greatly influenced the sedimentation on the margin. Land areas and continental basins were widespread on this margin in northern Tibet, China and Indo-China. This was a consequence of the Late Triassic to Early Jurassic continental collissions and accompanied intracontinental convergence that lasted well into the Cretaceous. A detailed Aptian-Albian facies map and a crude palinspastic palaeogeographic map of the entire Tethyan realm are prepared in order to express the contrasts in sedimentation on Laurasian and gondwanian margins and to show the compatibility of the presented data with the most recent and reliable reconstructions of the major tectonic elements in Tethysides.