scholarly journals The Van Microplate: A New Microcontinent at the Junction of Iran, Turkey, and Armenia

2021 ◽  
Vol 8 ◽  
Author(s):  
Hossein Azizi ◽  
Motohiro Tsuboi
Keyword(s):  
Active Continental Margin ◽  
Oceanic Lithosphere ◽  
Suture Zone ◽  
Arabian Plate ◽  
Magmatic Activity ◽  
The North ◽  
Eastern Turkey ◽  
Northwestern Iran ◽  
Two Phases ◽  
The Many

In northwestern Iran, magmatic activity occurred during three main intervals: The Cretaceous, Eocene, and Miocene-Quaternary. The first two phases of magmatic activity are more consistent with arc-type magmatism on an active continental margin; whereas the last phase, which has calc-alkaline and alkaline affinities, shows more similarity to postcollisional magmatism. Magmatic belts are mostly situated in the northern and eastern parts of the Oshnavieh–Salmas–Khoy ophiolite belt (OSK-Ophiolite) in northwestern Iran. The OSK-Ophiolite is known as the Neotethys, an ocean remnant in northwestern Iran, and extends to eastern Turkey and surrounds the Van area. This configuration shows that the Van microplate and surrounding ocean have played an important role in the evolution of magmatic activity in northwestern Iran, eastern Turkey, and the Caucasus since the Cretaceous. The Van microplate is situated among the Arabian plate to the south, northwestern Iran to the east, and Armenia to the north. The subduction of the northern branch of the Neotethys oceanic lithosphere beneath southern Eurasia has been critical in flare-up magmatism in the southern Caucasus since the Late Cretaceous. Considering the Van area as a new microplate makes understanding the geodynamic evolution of this area easier than in the many tectonic models that have been suggested before. When regarding the Van microplate, the main suture zone, which is known as the Bitlis–Zagros zone, should be changed to the Zagros–Khoy–Sevan–Akera suture zone, which extends to the eastern and northern Van microplate and western Iran.

scholarly journals Mineralogy, mineral chemistry and thermobarometry of post-mineralization dykes of the Sungun Cu–Mo porphyry deposit (Northwest Iran)

2020 ◽  
Vol 12 (1) ◽  
pp. 764-790
Author(s):  
Amin Allah Kamali ◽  
Mohsen Moayyed ◽  
Nasir Amel ◽  
Fadaeian Mohammad ◽  
Marco Brenna ◽  
...  
Keyword(s):  
Active Continental Margin ◽  
Mineral Chemistry ◽  
Quartz Diorite ◽  
Alkaline Magmatism ◽  
Porphyry Deposit ◽  
Average Percentage ◽  
The North ◽  
Northwestern Iran ◽  
Subduction System ◽  
Late Stages

AbstractThe Sungun copper–molybdenum porphyry deposit is located in the north of Varzaghan, northwestern Iran. The Sungun quartz-monzonite is the oldest mineralized intrusive body in the region and was emplaced during the Early Miocene. Eight categories of the late and unmineralized dykes, which include quartz diorite, gabbrodiorite, diorite, dacite, microdiorite and lamprophyre (LAM), intrude the ore deposit. The main mineral phases in the dykes include plagioclase, amphibole and biotite, with minor quartz and apatite and secondary chlorite, epidote, muscovite and sericite. The composition of plagioclase in the quartz diorite dykes (DK1a, DK1b and DK1c) varies from albite-oligoclase to andesine and oligoclase to andesine; in the diorite, it varies from andesine to labradorite; in the LAM, from albite to oligoclase; and in the microdiorite (MDI), it occurs as albite. Amphibole compositions are consistent with classification as hornblende or calcic amphibole. Based on their AlIV value (less than 1.5), amphibole compositions are consistent with an active continental margin affinity. The average percentage of pistacite (Ps) in epidotes formed from alteration of plagioclase and ferromagnesian minerals is 27–23% and 25–30%, respectively. Thermobarometric studies based on amphibole and biotite indicate approximate dyke crystallization temperature of 850–750℃, pressure of 231–336 MPa and high fO2 (>nickel-nickel-oxide buffer). The range of mineral compositions in the postmineralization dyke suite is consistent with a genetic relationship with the subduction of the Neotethys oceanic crust beneath the continental crust of the northwest part of the Central Iranian Structural Zone. Despite the change from calc-alkaline to alkaline magmatism, the dykes are likely related to the late stages of magmatic activity in the subduction system that also generated the porphyry deposit.

Closure of India–Asia collision margin along the Shyok Suture Zone in the eastern Karakoram: new geochemical and zircon U–Pb geochronological observations

2020 ◽  
Vol 157 (9) ◽  
pp. 1451-1472 ◽  
Author(s):  
Shailendra Pundir ◽  
Vikas Adlakha ◽  
Santosh Kumar ◽  
Saurabh Singhal
Keyword(s):  
Fractional Crystallization ◽  
Late Cretaceous ◽  
Inductively Coupled Plasma ◽  
Active Continental Margin ◽  
Oceanic Lithosphere ◽  
Suture Zone ◽  
Geochemical Evolution ◽  
Geochronological Data ◽  
Inductively Coupled ◽  
Geochemical Analyses

AbstractNew whole-rock geochemical analyses along with laser ablation multi-collector inductively coupled plasma mass spectrometry U–Pb zircon ages of the granite–rhyolite from the Karakoram Batholith, exposed along the Shyok Valley, NW India, have been performed to understand the timing and geochemical evolution of these magmatic bodies and their implications for the geodynamic evolution of the Karakoram Batholith. New geochronological data on granites and rhyolites along with previously published geochronological data indicate that the Karakoram Batholith evolved during Albian time (~110–100 Ma) owing to the subduction of Tethys oceanic lithosphere along the Shyok Suture Zone. This region witnessed a period of no magmatism during ~99–85 Ma. Following this, the Kohistan–Ladakh arc and Karakoram Batholith evolved as a single entity in Late Cretaceous and early Palaeogene times. Late Cretaceous (~85 Ma) rhyolite intrusions within the Karakoram Batholith show calc-alkaline subduction-related signatures with a highly peraluminous nature (molar A/CNK = 1.42–1.81). These intrusions may have resulted from c. ~13.8 % to ~34.5 % assimilation of pre-existing granites accompanied by fractional crystallization during the ascent of the magma. The contamination of mantle wedge-derived melts with crust of the active continental margin of the Karakoram most likely enhanced the high peraluminous nature of the rhyolite magma, as has been constrained by assimilation fractional crystallization modelling. Two granite samples from the contact of the Shyok Metamorphic Complex and Karakoram Batholith indicate that the post-collisional Miocene magmatism was not only confined along the Karakoram Fault zone but also extends ~30 km beyond the Shyok–Muglib strand.

Migration of post-collisional volcanism in northwestern Iran at plate tectonic velocities

2020 ◽  
Author(s):  
Axel Schmitt ◽  
Jalil Ghalamghash ◽  
Razieh Chaharlang ◽  
Jamshid Hassanzadeh ◽  
Seyed Mousavi
Keyword(s):  
Age Distribution ◽  
Sampling Bias ◽  
Oceanic Lithosphere ◽  
Suture Zone ◽  
Published Data ◽  
Age Difference ◽  
Plate Tectonic ◽  
Volcanic Stratigraphy ◽  
Magmatic Arc ◽  
Northwestern Iran

<p>Post-collisional magmatism of Neogene-Quaternary age is manifested in a long but disjointed belt of volcanoes broadly paralleling the Arabia-Eurasia suture zone. Volcanic compositions in this belt share geochemical characteristics with subduction-related magmas, yet they postdate subduction and formed in the wake of continental collision. Potential mechanisms for melt generation in the absence of subduction include slab break-off, lithospheric mantle delamination, or incorporation of fusible crustal rocks or sediment into the mantle through subduction or collision, leading to volcanism seemingly randomly distributed in time and space. In northwestern Iran, the two largest post-collisional volcanic centers are Sahand and Sabalan stratocones, which are located at distances of 150 and 300 km on a line perpendicular to the strike of the suture zone, where they overlie rocks of the Eocene-Oligocene Urumieh-Dokhtar magmatic arc. Here, we present U-Pb zircon ages for intermediate lavas and pyroclastic rocks from Sabalan volcano which complement published data for the Sahand and Sabalan systems [1, 2]. In both sample suites, inherited zircon from the basement is scarce and restricted to Cretaceous and Eocene-Oligocene ages for Sahand, and Archean, late Proterozoic and Oligocene-Miocene ages for Sabalan. Individual samples display coherent young populations that likely crystallized shortly before eruption. In addition, many samples show evidence of antecrystic zircon, indicating a long-lived subvolcanic reservoir where older intrusive rocks became recycled. Because of this recycling, the overall zircon age distribution of each volcano better represents the duration of magmatic activity than a compilation of eruption ages would. Based on the oldest antecrystic zircon ages, the onset of magmatism is constrained to ca. 10 Ma for Sahand, and ca. 5 Ma for Sabalan. This age difference shows a progression in the onset of magmatism that is consistent with plate tectonic velocities of ~30 mm/a. This rate and the northeastward direction of the volcanic migration also matches the reconstructed convergence of the Neotethyan oceanic lithosphere towards Eurasia. Apparent pulses in zircon production for both, Sahand and Sabalan, as well as a tailing off in the frequency of older ages are likely due to sampling bias of the volcanic stratigraphy, where younger eruptive products may have destroyed or obscured older units. Regardless of this bias, U-Pb and U-Th disequilibrium zircon ages from both volcanoes consistently indicate late Pleistocene eruptions as young as <173 ka and <110 ka for Sahand and Sabalan, respectively. The systematic younging of the onset of volcanism for these two volumetric dominant volcanic centers in northwestern Iran suggests that passage of a detached oceanic slab following closure of the Neotethys is a viable mechanism for post-collisional magmatism in the region.</p><p>[1] Ghalamghash, J., Schmitt, A. K., & Chaharlang, R. (2019), Lithos, 344, 265-279.</p><p>[2] Ghalamghash, J., Mousavi, S. Z., Hassanzadeh, J., & Schmitt, A. K. (2016), J Volc Geotherm Res, 327, 192-207.</p>

scholarly journals Ore-Bearing Magmatic Systems with Complex Sn–Au–Ag Mineralization in the North-Eastern Verkhoyansk–Kolyma Orogenic Belt, Russia

Minerals ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 266
Author(s):  
Vera A. Trunilina ◽  
Andrei V. Prokopiev
Keyword(s):  
Active Continental Margin ◽  
Orogenic Belt ◽  
Crustal Extension ◽  
Margin Setting ◽  
The North ◽  
Magmatic Rocks ◽  
Isotopic Methods ◽  
North Eastern ◽  
Magmatic Stage ◽  
Mineral Compositions

This paper reports the results of a study of magmatic rocks with Sn–W–Au–Ag mineralization from the Kuranakh, Elikchan, and Istekh ore fields in the Northern batholith belt of the north-eastern Verkhoyansk–Kolyma orogenic belt in Eastern Russia. Using petrographic, mineralogical, geochemical, and isotopic methods, we determined the mineral compositions, petrochemistry, and geochemistry of magmatic rocks, the P–T conditions of their generation and crystallization, and their geodynamic affinity. The studied magmatic rocks have common geochemical characteristics that likely reflect the influence of fluids supplied from a long-lived, deep-seated mantle source. The ore fields are characterized by Sn–W–Au–Ag–Pb polygenetic mineralization. The magmatic and metallogenic evolution comprised five stages for the formation of magmatic rocks and ores. During the first stage (Berriasian–Barremian), arc-related magmatic rocks formed in an active continental margin setting and were associated with Au–Ag mineralization. The second, third, and fourth stages (Aptian–Campanian) took place in a crustal extension and rift setting, and were accompanied by Au–Ag and Sn–W mineralization. During the fifth (post-magmatic) stage, Sn–Ag–Sb and Pb–Ag mineralization occurred.

A review of the tectonics of the northern Middle East region

1984 ◽  
Vol 121 (6) ◽  
pp. 577-587 ◽  
Author(s):  
P. E. R. Lovelock
Keyword(s):  
Late Cretaceous ◽  
Kinematic Model ◽  
Continental Collision ◽  
Dead Sea ◽  
Plate Motion ◽  
Arabian Plate ◽  
Southern Boundary ◽  
The North ◽  
The Dead ◽  
Two Stages

AbstractThe structure of the northern part of the Arabian platform is reviewed in the light of hitherto unpublished exploration data and the presently accepted kinematic model of plate motion in the region. The Palmyra and Sinjar zones share a common history of development involving two stages of rifting, one in the Triassic–Jurassic and the other during late Cretaceous to early Tertiary times. Deformation of the Palmyra zone during the Mio-Pliocene is attributed to north–south compression on the eastern block of the Dead Sea transcurrent system which occurred after continental collision in the north in southeast Turkey. The asymmetry of the Palmyra zone is believed to result from northward underthrusting along the southern boundary facilitated by the presence of shallow Triassic evaporites. An important NW-SE cross-plate shear zone has been identified, which can be traced for 600 km and which controls the course of the River Euphrates over long distances in Syria and Iraq. Transcurrent motion along this zone resulted in the formation of narrow grabens during the late Cretaceous which were compressed during the Mio-Pliocene. To a large extent, present day structures in the region result from compressional reactivation of old lineaments within the Arabian plate by the transcurrent motion of the Dead Sea fault zone and subsequent continental collision.

Review article: Reclaiming the rebellion: 1798 in 1998

1999 ◽  
Vol 31 (123) ◽  
pp. 395-410
Author(s):  
Ian McBride
Keyword(s):  
New York ◽  
Rural Communities ◽  
Review Article ◽  
Physical Force ◽  
Celtic Tiger ◽  
Men And Women ◽  
International Dimension ◽  
Good Friday ◽  
The North ◽  
The Many

Few Irish men and women can have escaped the mighty wave of anniversary fever which broke over the island in the spring of 1998. As if atoning for the failed rebellion itself, the bicentenary of 1798 was neither ill-coordinated nor localised, but a genuinely national phenomenon produced by years of planning and organisation. Emissaries were dispatched from Dublin and Belfast to remote rural communities, and the resonant names of Bartlett, Whelan, Keogh and Graham were heard throughout the land; indeed, the commemoration possessed an international dimension which stretched to Boston, New York, Toronto, Liverpool, London and Glasgow. In bicentenary Wexford — complete with ’98 Heritage Trail and ’98 Village — the values of democracy and pluralism were triumphantly proclaimed. When the time came, the north did not hesitate, but participated enthusiastically. Even the French arrived on cue, this time on bicycle. Just as the 1898 centenary, which contributed to the revitalisation of physical-force nationalism, has now become an established subject in its own right, future historians will surely scrutinise this mother of all anniversaries for evidence concerning the national pulse in the era of the Celtic Tiger and the Good Friday Agreement. In the meantime a survey of some of the many essay collections and monographs published during the bicentenary will permit us to hazard a few generalisations about the current direction of what might now be termed ‘Ninety-Eight Studies’.

scholarly journals Diocesan Licensing and Medical Practitioners in South-West England, 1660–1780

2004 ◽  
Vol 48 (1) ◽  
pp. 49-68 ◽  
Author(s):  
Ian Mortimer
Keyword(s):  
Early Modern ◽  
Specific Context ◽  
Medical Practitioners ◽  
Medical Expertise ◽  
North West ◽  
The North ◽  
Decentralized Trade ◽  
South West ◽  
The Many ◽  
South West England

The licensing of provincial surgeons and physicians in the post-Restoration period has proved an awkward subject for medical historians. It has divided writers between those who regard the possession of a local licence as a mark of professionalism or proficiency, those who see the existence of diocesan licences as a mark of an essentially unregulated and decentralized trade, and those who discount the distinction of licensing in assessing medical expertise availability in a given region. Such a diversity of interpretations has meant that the very descriptors by which practitioners were known to their contemporaries (and are referred to by historians) have become fragmented and difficult to use without a specific context. As David Harley has pointed out in his study of licensed physicians in the north-west of England, “historians often define eighteenth-century physicians as men with medical degrees, thus ignoring … the many licensed physicians throughout the country”. One could similarly draw attention to the inadequacy of the word “surgeon” to cover licensed and unlicensed practitioners, barber-surgeons, Company members in towns, self-taught practitioners using surgical manuals, and procedural specialists whose work came under the umbrella of surgery, such as bonesetters, midwives and phlebotomists. Although such fragmentation of meaning reflects a diversity of practices carried on under the same occupational descriptors in early modern England, the result is an imprecise historical literature in which the importance of licensing, and especially local licensing, is either ignored as a delimiter or viewed as an inaccurate gauge of medical proficiency.

Overburden geochemical signature of the Lac des Iles platinum group element deposit, northwestern Ontario, Canada

2007 ◽  
Vol 44 (8) ◽  
pp. 1151-1168 ◽  
Author(s):  
Peter J Barnett
Keyword(s):  
Mineral Exploration ◽  
Shallow Groundwater ◽  
Soil System ◽  
Near Surface ◽  
Rock Fragments ◽  
The North ◽  
Northwestern Ontario ◽  
Airborne Contamination ◽  
The Many ◽  
Lac Des Iles

Many previously published studies of the behaviour of Pt and Pd in till and soils have been done in areas of complex stratigraphy or very thin overburden cover, making the interpretation of soil results difficult because of the many variables associated with these settings. At the Lac des Iles mine site in northwestern Ontario, there are excellent exposures of the overburden in a series of exploration trenches. Glacial dispersal trains can be observed in till (C horizon) geochemistry (e.g., Ni, Cr, Cu, and Co). Regional geochemical dispersal trains of elements, such as Ni, Cr, Mg, and Co associated with the North Lac des Iles intrusion, can be detected for about 4 km beyond the western margin of the Mine Block intrusion. Entire dispersal trains range from 5 to 7 km in length and about 1 to 2 km in width. The dispersal of North Lac des Iles intrusion rock fragments tends to mask the response of the Mine Block intrusion. Dispersal trains of Pt and Pd are not well defined and tend to be very short, <1 km in length, due to the initial low concentrations of these elements in C-horizon till samples from the Lac Des Iles area. An exception to this is the Pd dispersal train originating from the high-grade zone that is up to 3 km long. Pd, Pt, Ni, and Cu appear to be moving both within and out of the soil system downslope into surface and shallow groundwater. It is suggested that these elements, to varying degrees, are moving in solution. Airborne contamination from mine operations of the humus has adversely affected the ability to determine the effectiveness of humus sampling for mineral exploration at Lac des Iles. The airborne contamination likely influences the geochemical results from surface water, shallow groundwater, and near-surface organic bog samples, particularly for the elements Pd and Pt.

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