Alpine-Himalayan Orogenic System Research Articles

A hydrous sub-arc mantle domain within the northeastern Neo-Tethyan ophiolites: Insights from cumulate hornblendites

Being a part of the large-scale Indus-Tsangpo suture zone ophiolites of the Alpine-Himalayan orogenic system, the Neo-Tethyan ophiolites of eastern Arunachal Himalaya, northeast India, are important in understanding the formation and evolution of the Neo-Tethyan lithosphere. This study focuses on the hornblendite dykes occurring within serpentinized peridotites of the Mayodia ophiolites in eastern Arunachal Himalaya, to ascertain the origin and evolution of such hydrous mineral cumulates within the ophiolite complex. Texturally and chemically, the hornblendites contain three types of amphiboles, Amp1 (pargasite), Amp2 (Mg-hornblende), and Amp3 (actinolite). The pargasites occur as large cm-sized phenocrysts and show cumulate textures while Mg-hornblende appears as both intercumulus grains between cumulus pargasites and surrounding partially resorbed clinopyroxene grains. Actinolite occurs along the breakdown zone of pargasite and is associated with other secondary minerals. The hornblendites are characterized by high MgO (~12–20 wt%) and low SiO2 (~42–44 wt%) with depleted light rare earth elements (REE) [(La/Sm)N = 0.29–0.52] and almost flat heavy REE [(Gd/Yb)N) = 0.89–1.11]. Moreover, the samples are characteristically depleted in high field strength elements (Nb, Ta, Ti, Hf) while being enriched in Pb. Geothermobarometric calculations yield high magmatic temperatures of ~950 and ~840 °C for pargasite and Mg-hornblende, respectively, and variable pressures with pargasite having the highest pressures (1.6–1.7 GPa) followed by Mg-hornblende (1.1–1.2 GPa) and finally actinolite (~0.55 GPa). Furthermore, fO2 calculations for the cumulus pargasites revealed highly oxidizing conditions (ΔNNO+2) and water content of parental melts (H2Omelt% = ~14.25 %). Parental melt calculations using whole-rock REE concentrations suggest formation from a hydrous sub-alkaline basaltic melt. Whole-rock initial SrNd isotopic ratios of the hornblendites reveal a primary signature for them, falling in the mantle array in proximity to the high-μ (HIMU) mantle reservoir. All these signatures point towards a magmatic arc affinity for these hornblendites. The host peridotite unit shows highly enriched REE concentrations (ƩREE = 18.13 ppm) with flat REE patterns compared to the other peridotites of the locality, which show depleted signatures. Olivine chemistry of the host peridotite unit depicts primary compositions falling in the mantle array. The olivine-liquid thermometer yields temperatures ~1000 °C, which are much lower than those of peridotites occurring in spreading centers (MOR or back-arc). These evidence suggest that the hornblendites and their host peridotite unit represent an island arc root complex, which further imply the hydrous nature of the Neo-Tethyan sub-arc mantle.

Iran Desert and Geology for Cultivation Potato

Geology is a branch of Earth science concerned with both the liquid and solid Earth, the rocks of which it is composed, and the processes by which they change over time. Geology can also include the study of the solid features of any terrestrial planet or natural satellite such as Mars. Iran and its neighbouring areas are considered as a complex puzzle, in which continental fragments of various origins were assembled and are now separated by discontinuous ophiolitic belts within the Alpine–Himalayan orogenic system At Kavir Iran central region on the volcanic-plutonic belt of central Iran. It is located in Rafsanjan (Kerman province). Igneous rocks in this area include volcanic rocks (andesite, Trachyandesite, basalt and dacite) and igneous rocks are calc-alkaline magma series. Sedimentary area is limestone, shale, conglomerate, sandstone. Filic and argillic alterations are most prevalent have. According to mineralogical studies, mineralization in this region includes iron oxide minerals, for example; Specularity And limonite, as well as secondary sulfide minerals such as borneite, colitis, digenite, and chalcocite, which are substitutes. Pyrite and chalcopyrite. Mineralization has occurred in the form of diffusion, veinlet, void filling and substitution. Potato is one of the most important legumes and constitutes a dominant portion of the global diet. Finally the effect of water stress. In this study, the potato savalan cultivar (StMYB) was the main factor (sandy, clayey soil, compost) and drought stress in four control levels and -0.3, -0.6, -1, and -1.5 MPa of soil water potential in three replicates form of a split plot. We show that in semnan desert the diversity in germplasm indicated that potato cultivars can be developed for production under certain degrees of drought and soil physical properties.

Indenter tectonics in the Canadian Shield: A case study for Paleoproterozoic lower crust exhumation, orocline development, and lateral extrusion

There are lingering questions about how far back in geologic time plate tectonic processes began. In the Paleoproterozoic of eastern Laurentia, accretion of intra-oceanic juvenile terranes along the leading edge of the Superior craton apex (Ungava indenter) during the interval 1.87–1.83 Ga was followed by collision with the Churchill plate at ca. 1.83–1.79 Ga. Orthogonal shortening along the indenter led to early obduction of the juvenile terranes including the ca. 2.0 Ga Watts Group ophiolite, followed by out-of-sequence thrusting at ca. 1.83 Ga of granulite-facies crystalline basement of the Sugluk block (Churchill plate) along the Sugluk suture. Exhumation and erosion of the Sugluk block led to deposition of a foreland/delta fan sequence in the Hudson Bay re-entrant (Omarolluk and Loaf formations of the Belcher Group), with detritus sourced exclusively from the Sugluk block. Continued collision led to critical wedge development and orocline formation in the Hudson Bay re-entrant, forming a strongly arcuate fold-thrust belt. On the other (eastern) side of the indenter, material flow during crustal shortening was accommodated by lateral extrusion of microplates towards a then open ocean basin, in a manner similar to present-day extrusion of Indochina as a response to India – South China craton convergence. In the Churchill plate hinterland W-NW of the indenter, propagating strike-slip faults resulted in the far-field extrusion and oblique exhumation of Archean crustal slices of the Rae crustal block. The 1.83–1.79 Ga Superior-Churchill collision accommodated a minimum of 500 km of continent–continent convergence, with resulting style and mechanisms of orogenic growth and material flow similar to those observed in the Alpine-Himalayan orogenic system.

Zircon U-Pb-Hf isotopes, bulk-rock geochemistry and Sr-Nd-Pb isotopes from late Neoproterozoic basement in the Mahneshan area, NW Iran: Implications for Ediacaran active continental margin along the northern Gondwana and constraints on the late Oligocene crustal anatexis

The Mahneshan granite intrusions and granodiorite-gneiss bodies in northwest Iran are part of the Takab magmatic–metamorphic complex, which includes numerous Precambrian continental crust that are now embedded in the Alpine-Himalayan orogenic system. The Mahneshan magmatic assemblage comprises of late Ediacaran-Cambrian gneiss and granites (531–576 Ma) and late Oligocene biotite (25.41 ± 0.4 Ma) granite intrusion. The late Oligocene granite has intruded into the Neoproterozoic sequences in this area. The bulk-rock geochemistry shows that the Ediacaran-Cambrian granitoids and gneisses are calc-alkaline and preserve arc-related signatures. The zircon Hf and bulk rock Sr-Nd-Pb isotopic data suggest that the Ediacaran-Cambrian granitoid plutons were generated via partial melting of continental crust. The late Oligocene granite is formed by the anatexis of Neoproterozoic igneous rocks due to crustal thickening.The whole rock Sr-Nd and zircon Hf isotopic values, Mesoproterozoic Nd and Hf model ages and the existence of inherited zircons suggest the involvement of older crustal components in the genesis of the Mahneshan Ediacaran-Cambrian granitoids. The late Neoproterozoic rock units in the Takab area together with other Ediacaran-Cambrian magmatic segments in Iran were part of the Cadomian active continental margin that were situated along the northern Gondwana margin during the Neoproterozoic. The geochemical trace elements reported from the upper Neoproterozoic-Cambrian plutons along the Cadomian fragments in Iran toward Turkey and Iberia show that most of these granitoid melts were generated in pressures less than garnet stability field suggesting the continental arc thickness less than those reported from the Andes. Furthermore, the Hf and Nd model ages from the Ediacaran-Cambrian Mahneshan intrusions suggest the existence of hidden Paleoproterozoic-Mesoproterozoic rocks in the lower continental crust of Iran.

GIS-BASED ACCESSIBILITY ANALYSIS OF URBAN EMERGENCY SHELTERS: THE CASE OF ADANA CITY

Abstract. Accessibility analysis of urban emergency shelters can help support urban disaster prevention planning. Pre-disaster emergency evacuation zoning has become a significant topic on disaster prevention and mitigation research. In this study, we assessed the level of serviceability of urban emergency shelters within maximum capacity, usability, sufficiency and a certain walking time limit by employing spatial analysis techniques of GIS-Network Analyst. The methodology included the following aspects: the distribution analysis of emergency evacuation demands, the calculation of shelter space accessibility and the optimization of evacuation destinations. This methodology was applied to Adana, a city in Turkey, which is located within the Alpine-Himalayan orogenic system, the second major earthquake belt after the Pacific-Belt. It was found that the proposed methodology could be useful in aiding to understand the spatial distribution of urban emergency shelters more accurately and establish effective future urban disaster prevention planning. Additionally, this research provided a feasible way for supporting emergency management in terms of shelter construction, pre-disaster evacuation drills and rescue operations.

Detrital zircon and provenance analysis of Eocene–Oligocene strata in the South Sistan suture zone, southeast Iran: Implications for the tectonic setting

The north-south–trending Sistan suture zone in east Iran results from the Paleogene collision of the Central Iran block to the west with the Afghan block to the east. We aim to document the tectonic context of the Sistan sedimentary basin and provide critical constraints on the closure time of this part of the Tethys Ocean. We determine the provenance of Eocene–Oligocene deep-marine turbiditic sandstones, describe the sandstone framework, and report on a geochemical and provenance study including laser ablation–inductively coupled plasma–mass spectrometry U-Pb zircon ages and 415 Hf isotopic analyses of 3015 in situ detrital zircons. Sandstone framework compositions reveal a magmatic arc provenance as the main source of detritus. Heavy mineral assemblages and Cr-spinel indicate ultramafic rocks, likely ophiolites, as a subsidiary source. The two main detrital zircon U-Pb age groups are dominated by (1) Late Cretaceous grains with Hf isotopic compositions typical of oceanic crust and depleted mantle, suggesting an intraoceanic island arc provenance, and (2) Eocene grains with Hf isotopic compositions typical of continental crust and nondepleted mantle, suggesting a transitional continental magmatic arc provenance. This change in provenance is attributed to the Paleocene (65–55 Ma) collision between the Afghan plate and an intraoceanic island arc not considered in previous tectonic reconstructions of the Sistan segment of the Alpine-Himalayan orogenic system.

Geodynamic evolution of the Sanandaj-Sirjan Zone, Zagros Orogen, Iran

Abstract: The Sanandaj-Sirjan Zone is a metamorphic-magmatic belt, associated with the Zagros Orogen and part of the Alpine-Himalayan orogenic system in Iran. Stratigraphic, metamorphic, magmatic, and tectonic evidence presented here indicates that the Sanandaj-Sirjan Zone, the Central Iranian Microcontinent, and the North West Iranian Plate were a part of the Arabian plate until the Late Permian, when they separated during the opening of the Neotethys. Later subduction of the Neotethys oceanic crust beneath the Sanandaj-Sirjan Zone resulted in the complete closure of the Paleotethys Ocean in the Early Upper Triassic. The following extensional regime (related to slab roll-back) caused separation of the Sanandaj-Sirjan block, Central Iran Microcontinent, and North West Iranian Plate during the Upper Triassic to Lower Jurassic. The separation of these continental blocks caused sedimentation differences during that time. The North Tabriz and Nain-Baft Faults are probably the boundary between the Sanandaj-Sirjan Zone and Central Iran. The basin between the Sanandaj-Sirjan Zone and the Central Iranian block (the Iranian Microcontinent and North West Iranian Plate) closed in the Late Cretaceous. After that, these terranes experienced similar geological evolution, especially from the Oligocene to the Miocene.

Compositional signatures of SSZ-type peridotites from the northern Vourinos ultra-depleted upper mantle suite, NW Greece

The northern Vourinos massif, located in the Dinarides-Hellenides mountain belt in the Balkan Peninsula, forms a section of the so-called Neotethyan ophiolitic belt in the Alpine-Himalayan orogenic system. It is comprised mainly of a well-preserved mantle sequence, dominated by voluminous massive harzburgite with variable clinopyroxene and olivine modal abundances, accompanied by subordinate coarse- and fine-grained dunite. The harzburgite rock varieties are characterized by high Cr# [Cr/(Cr+Al)] values in Cr-spinel (0.47–0.74), elevated Mg# [Mg/(Mg+Fe2+)] in olivine (0.90–0.93), low Al2O3 content in clinopyroxene (≤1.82wt.%) and low average bulk-rock concentrations of CaO (0.52wt.%) and Al2O3 (0.40wt.%), which are indicative of their refractory nature. In addition, dunite-type rocks display even more depleted compositions, containing Cr-spinel and olivine with higher Cr# (0.76–0.84) and Mg# (0.91–0.94), respectively. They also display extremely low average abundances of CaO (0.13wt.%) and Al2O3 (0.15wt.%). The vast majority of the studied peridotites are also strongly depleted in REE. Simple batch and fractional melting models are not sufficient to explain their ultra-depleted composition. Whole-rock trace element abundances of the northern Vourinos mantle rocks can be modeled by up to 22–31% closed-system non-modal dynamic melting of an assumed primitive mantle (PM) source having spinel lherzolite composition. The highly depleted compositional signatures of the investigated peridotites indicate that they have experienced hydrous melting in the fore-arc mantle region above a SSZ. This intense melting event was responsible for the release of arc-related melts from the mantle. These melts reacted with the studied peridotites causing incongruent melting of pyroxenes followed by considerable olivine and Cr-spinel addition in terms of cryptic metasomatism. This later metasomatic episode has obscured any geochemical fingerprints indicative of an early mantle melting event in a MOR setting. The lack of any MOR-type peridotites in the northern Vourinos depleted mantle suite is quite uncommon for SSZ-type Neotethyan ophiolites.

インドネシア非火山性外弧のオフィライト―世界最若オフィオライトの産状と岩石学的多様性―

The western Pacific region, where the Eurasia, Australia, and Pacific plates currently interact, has been recognized as an important site for constraining the origins and emplacement of ophiolites (particularly for island-arc or supra-subduction zone types), because the spatial distribution of oceanic micro-plates and numerous ophiolitic rocks along their convergent margins infers possible genetic linkages among them. Mafic-ultramafic rocks distributed in the Timor-Tanimbar island chain, eastern Indonesia may be a good example of the on-going emplacement of the marginal basin lithosphere on the continental margin in the arc-continent collision zone, and are recognized as a possible modern analogue for Mesozoic Tethyan-type ophiolites (e.g. Troodos and Oman) in the Alpine-Himalayan orogenic system. Geological occurrence suggests that the buoyant subduction of the Australian continent uplifted fragments of newly formed mantle-crust section, which extends to neighboring pre-emplaced forearc marginal basins. However, from petrological and geochemical points of view, young pillowed basalt, dolerite, and gabbroic cumulate commonly possess island-arc signatures, whereas structurally underlying peridotites are mostly fertile (lherzolitic) in composition. This suggests that the crustal section is not linked to the underlying mantle by a genetic melt-and-residua relationship, as inferred from the lack of complete succession and the presence of abundant crosscutting structures. This inconsistency leads to the emergence of two contrasting models accounting for the unusual occurrence of a fertile mantle in the forearc setting of the Timor-Tanimbar region: (1) thrust-stacked fragments of the subcontinental mantle originally exhumed in the rifting stage of Australia; (2) depth-related heterogeneities in the lithospheric part of the mantle wedge. We note that the current debates on the origins of fertile lherzolites found throughout the Tethyan sutures and western Pacific regions can be settled through a better understanding of Timor-Tanimbar peridotite masses by age-dating studies employing several radiogenic isotope systematics.

Geology and thermochronology of Tertiary Cordilleran-style metamorphic core complexes in the Saghand region of central Iran

An ~100-km-long north-south belt of metamorphic core complexes is localized along the boundary between the Yazd and Tabas tectonic blocks of the central Iranian micro-continent, between the towns of Saghand and Posht-e-Badam. Amphibolite facies mylonitic gneisses are structurally overlain by east-tilted supracrustal rocks including thick (>1 km), steeply dipping, nonmarine siliciclastic and volcanic strata. Near the detachment (the Neybaz-Chatak fault), the gneisses are generally overprinted by chlorite brecciation. Crosscutting relationships along with U-Pb zircon and ^(40)Ar/^(39)Ar age data indicate that migmatization, mylonitic deformation, volcanism, and sedimentation all occurred in the middle Eocene, between ca. 49 and 41 Ma. The westernmost portion of the Tabas block immediately east of the complexes is an east-tilted crustal section of Neoproterozoic–Cambrian crystalline rocks and metasedi-mentary strata >10 km thick. The ^(40)Ar/^(39)Ar biotite ages of 150–160 Ma from structurally deep parts of the section contrast with ages of 218–295 Ma from shallower parts, and suggest Late Jurassic tilting of the crustal section. These results define three events: (1) a Late Jurassic period of upper crustal cooling of the western Tabas block that corresponds to regional Jurassic–Cretaceous tectonism and erosion recorded by a strong angular unconformity below mid-Cretaceous strata throughout central Iran; (2) profound, approximately east-west middle Eocene crustal extension, plutonism, and volcanism (ca. 44–40 Ma); and (3) ~2–3 km of early Miocene (ca. 20 Ma) erosional exhumation of both core complex and Tabas block assemblages at uppermost crustal levels, resulting from significant north-south shortening. The discovery of these and other complexes within the mid-Tertiary magmatic arcs of Iran demonstrates that Cordilleran-style core complexes are an important tectonic element in all major segments of the Alpine-Himalayan orogenic system.

Gold in Turkey—a missing link in Tethyan metallogeny

The gold metallogeny of Turkey constitutes a sector of the Tethyan Eurasian Metallogenic Belt (TEMB) within the Alpine–Himalayan orogenic system that formed from Jurassic–Cretaceous to the present. This orogenic system produced many different types of deposits related to subduction, collision, post-collision and rifting processes. Gold deposits, as well as other mineral deposits of Turkey, are mainly concentrated in Late Mesozoic and Tertiary rocks. Evaluation of the gold metallogeny of Turkey is based on a GIS database compilation of known gold deposits and prospects. Currently available data show that Turkey has a gold endowment, including reserves and resources, of approximately 31.5 M oz [979 tonnes] in 51 deposits, 21 of which contain more than 0.2 M oz gold. The other 30 deposits contain a total of approximately 1 M oz [31 tonnes] gold resources. Two recent discoveries, Kisladag and Copler, currently contain total resources of 17.6 M oz Au [549 tonnes], more than 50% of the total Turkish gold endowment. Turkey possesses a wide spectrum of gold deposits related to Mesozoic and Cenozoic volcanoplutonic arcs. However, porphyry gold (copper), epithermal gold (including both high- and low-sulfidation styles), and gold-rich volcanic-associated massive sulfide (including both Kuroko- and Cyprus-types) are the most economically important to date. Orogenic gold, including listwanite-hosted, placer gold and skarn-hosted gold are relatively less important or abundant deposit types. Other potential gold systems for exploration include Carlin-type gold, detachment-fault-related gold, iron oxide–copper–gold, and gold in carbonate-replacement and manganese deposits.

The Saghand Region, Central Iran: U-Pb geochronology, petrogenesis and implications for Gondwana Tectonics

The Saghand area of East-Central Iran exposes rocks that comprise the substratum of the Central Iranian continental terrane, as part of the larger Alpine-Himalayan orogenic system. Our new U-Pb ages and geochemical data from the magmatic, metamorphic and siliciclastic rocks of the Saghand area unravel three main episodes of orogenic activity in the latest Neoproterozoic-Early Cambrian, the Late Triassic, and the Eocene. Geologic events in the oldest episode include in chronological order, low- to medium-grade metamorphism, calc-alkaline plutonism, rhyolitic to andesitic volcanism, and widespread trondhjemite emplacement, from 547 Ma to 525 Ma. The Late Triassic event (approximately 220-213 Ma) is characterized by the emplacement of granite-tonalite plutons. The extensive, high-grade metamorphic rocks, migmatites and post-kinematic intrusions of Eocene age (47-44 Ma) occur in a distinct domain, in the western part of the Saghand area. These rocks previously were thought to represent the Precambrian basement of the Central Iranian Terrane. The terminal Neoproterozoic-Early Cambrian orogeny in central Iran was related to a broad-scale magmatic arc that developed along the Proto-Tethyan margin of the Gondwanaland supercontinent. The fragmented remains of that margin occur as displaced terranes, including the Central Iranian Terrane, now embedded within the Alpine-Himalayan orogenic system. The newly recognized Late Triassic intrusions of the Saghand area are indicative of a tectonomagmatic episode of possible collisional nature, in accord with the previously identified Early Kimmerian (Cimmerian) event in the region. The extensive Eocene metamorphic and magmatic activities correspond to the early Alpine Orogeny, which resulted from the convergence between Arabian and Eurasian plates, and the Cenozoic closure of the Tethys oceanic tract(s) by subduction.

Ophiolites in earth history: introduction

Ophiolites record significant evidence for tectonic and magmatic processes from rift-drift through accrefionary and collisional stages of continental margin evolution in various tectonic settings. Structural, petrological and geochemical features of ophiolites and associated rock units provide essential information on mantle flow field effects, including plume activities, collision-induced aesthenospheric extrusion, crustal growth via magmatism and tectonic accretion in subductionaccretion cycles, changes in the structure and composition of the crust and mantle reservoirs through time, and evolution of global geochemical cycles and seawater compositions. Ophiolite studies over the years have played a major role in better understanding of mid-ocean ridge and subduction zone processes, mantle dynanlics and heterogeneity, magma chamber processes, fluid flow mechanisms and fluid-rock interactions in oceanic lithosphere, the evolution of deep biosphere, the role of plate tectonics and plume tectonics in crustal evolution during the Precambrian and the Phanerozoic, and mechanisms of continental growth in accretionary and coltisional mountain belts. Through multi-disciplinary investigations and comparative studies of ophiolites and modern oceanic crust and using advanced instrumentation and computational facilities, the international ophiolite community has gathered a wealth of new data and syntheses from ophiolites around the world during the last 10 years. The purpose of this book is to present the most recent data, observations and ideas on different aspects of 'ophiolite science' through case studies and to document the mode and nature of igneous, metamorphic, tectonic, sedimentological and/or biological processes associated with the evolution of oceanic crust in different tectonic settings in Earth's history. It comprises 32 papers collected in six sections on temporal relations anaongst ophiolite genesis, mantle plume events and orogeny in Earth history; Tethyan ophiolites in the AlpineHimalayan orogenic system; magmatic, metamorphic and tectonic processes in ophiolite genesis; hydrothermal and biogenic alteration of oceanic crust; mechanisms of ophiolite emplacement; and regional occurrences of ophiolites and their geodynamic implications.

Active tectonics of the Black Sea with GPS

The Black Sea occurs within the Anatolian sector of the Alpine-Himalayan orogenic system. In this region northward moving African and Arabian plates collide with Eurasian plate. From this collision the Anatolian block moves westward with a rotation pole located approximately north of Sinai peninsula. Tectonic styles and rates in the circum Black Sea and along the Crimea have been poorly known. A GPS project was initiated in 1995 with the collaboration between Istanbul Technical University, MIT and Joint Institute of Physics of the Earth (Moscow). To carry out the project, two GPS campaigns were performed. Data have been analysed by the well-known GPS processing program, GAMIT which is a comprehensive GPS analysis package, and GLOBK, a Kalman filter. This paper presents the important outputs from the two GPS campaigns and gives suggestions for the future investigations in the region. The important outcome of the project is that the N-S motions along mostly in the Eastern margin of the Black Sea are in a few mm/year, such as SINO, a southern coast site, with a rate of 1.4 ± 1.7 mm/year in NW direction, and GELE, a northern coast site, with a rate of 2.2 ± 2.8 mm/year in SE direction, while the velocities in the Anatolian region are approximately 10–20 ± 3–5 mm/year.