U-Pb zircon and K-Ar geochronology reveal the emplacement and cooling history of the Late Cretaceous Beypazarı granitoid, central Anatolia, Turkey

Helvacı, Cahit; Öztürk, Yeşim; Satır, Muharrem; Shang, C. K.

doi:10.1080/00206814.2014.921795

Cited by 14 publications

(18 citation statements)

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“…Out of 81 individual concordant zircon ages obtained, 76 were between 72 and 76 Ma, and none were older than 80 Ma. The new zircons ages overlap with those from Helvacı et al () over a narrow range. It is also geologically implausible that parts of the Beypazarı Granite, which is a medium‐sized, homogeneous pluton, cooled below 800–1,000 °C (the zircon closure temperature) at 92 Ma, and other parts 30 million years later at 62 Ma, as the data of Speciale et al () would imply.…”

Section: Campanian Beypazarı Granite : Paleo‐galatian Magmatic Arcsupporting

confidence: 62%

“…Geological map of the Ankara region modified from Turhan (). The isotopic ages, mostly zircon U–Pb, are from Keller et al (), Koçyiğit et al (), Köksal et al (), Delibaş et al (), and Helvacı et al ().…”

Section: Tectonic Setting and Stratigraphy Of The Ankara Regionmentioning

confidence: 99%

“…Helvacı et al () provided 75 ± 2‐Ma U–Pb zircon ages from four samples of the Beypazarı Granite, whereas ion microprobe U–Pb zircon dating in thin section produced a wide range of ages from 92 down to 62 Ma for the same pluton (Speciale et al, ). To solve this apparent anomaly, we have dated zircons from two samples of the Beypazarı Granite using laser ablation ICP‐MS technique.…”

Section: Campanian Beypazarı Granite : Paleo‐galatian Magmatic Arcmentioning

confidence: 99%

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Major Late Cretaceous Mass Flows in Central Turkey Recording the Disruption of the Mesozoic Continental Margin

2019

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The newly recognized Upper Cretaceous (~87 Ma) olistostrome belt in central Turkey west of Ankara extends for more than 112 km subparallel to the Izmir-Ankara suture with a width of 10 km. The Alacaatlı Olistostromes are stratigraphically underlain by a Triassic basement, and are up to 2 km thick. Over 80% of the blocks in the olistostromes consist of pelagic limestones, which reach up to 300 m in size; other blocks include basalt, chert, serpentinite, tuff, and sandstone. The limestone blocks are Jurassic and Cretaceous in age with micropaleontology documenting the presence of Callovian-Oxfordian, Tithonian, Berriasian, Aptian, Albian, Cenomanian, and Turonian stages. The flows are separated by intrabasinal sediments of shale, siltstone, and volcaniclastic sandstone with Albian (108-101 Ma) detrital zircons. The olistostromes show minor tectonic deformation, and are unconformably overlain by Santonian pelagic limestones. The deposition of the Alacaatlı Olistostromes was followed by arc magmatism, which started in the Campanian (~78 Ma) after a period of shortening and uplift, and the region became a fore-arc basin with deposition of shale and volcaniclastic sandstone with Campanian (78-72 Ma) detrital zircons. A number of peculiar features of these olistostromes including rapid uplift and erosion before the creation of a deep, short-lived (89-86 Ma) ephemeral basin, dominance of deep marine limestone blocks, and inception of arc magmatism approximately 9 Myr after their deposition indicate a major tectonic event involving the disruption of the continental margin prior to the onset of arc magmatism. This event is interpreted as a change from transform margin to subduction.

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Section: Campanian Beypazarı Granite : Paleo‐galatian Magmatic Arcsupporting

confidence: 62%

Section: Tectonic Setting and Stratigraphy Of The Ankara Regionmentioning

confidence: 99%

Section: Campanian Beypazarı Granite : Paleo‐galatian Magmatic Arcmentioning

confidence: 99%

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Major Late Cretaceous Mass Flows in Central Turkey Recording the Disruption of the Mesozoic Continental Margin

2019

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“…Okay 2008 and references therein). Andesitic dykes in the Strandja Massif (north-western Turkey) revealed ages of 78 Ma (Moore et al 1980), while granitoid intrusions in the Beypazarı region of the Sakarya Zone yielded ages of 72.5 ± 12.6 to 78.6 ± 4.7 Ma (Helvacı et al 2014). (Georgiev et al 2012).…”

mentioning

confidence: 95%

New structural and U–Pb zircon data from Anafi crystalline basement (Cyclades, Greece): constraints on the evolution of a Late Cretaceous magmatic arc in the Internal Hellenides

Martha

Dörr

Gerdes

et al. 2016

Int J Earth Sci (Geol Rundsch)

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comprises from bottom to top: (a) Anafi Greenschist; (b) Anafi Amphibolite Group (orthoamphibolite with intercalations of metasedimentary rocks at the base); and (c) Chalepa Group (amphibolite facies metasediments with slices of serpentinite and granitoids). LA-ICP-MS and ID-TIMS 206 Pb/ 238 U zircon ages of granodiorite from the Chalepa Group reveal several similar zircon populations suggesting continuous emplacement of granitoids inside a magmatic arc from ca. 72.5 to 79 Ma. The minimum emplacement age of granodioritic magma, deduced from the 206 Pb/ 238 U median age of the youngest zircon population, is 72.6 +0.1/−0.2 Ma. Deformation (micro)fabrics of granodiorite result from low strain obtained at T > 600 °C. This along with the U-Pb ages and published K-Ar ages indicates intrusion of the plutonic rocks at deep structural levels followed by very slow cooling. Monzogranitic dykes cutting through granodiorite in north-eastern Anafi are undeformed and yielded a 206 Pb/ 238 U median age of 69.9 +0.7/−0.7 Ma. Based on the new and published data, the following implications for the tectonometamorphic evolution on Anafi can be made: (1) obduction and accretion of mantle slices (serpentinite) to the Asterousia-type rocks were prior to amphibolite facies metamorphism; (2) intrusion of granitoids during the middle to late Campanian within a magmatic-arc setting and coeval shift of the magmatic arc towards the south; (3) Maastrichtian intrusion of dykes; (4) Palaeocene greenschist facies metamorphism and coeval ductile top-to-the SE thrusting of the Anafi Amphibolite Group on top of the Anafi Greenschist; (5) post-Eocene brittle top-to-the SE thrusting of the Anafi Greenschist and the Anafi Amphibolite Group on top of flysch sediments; (6) clockwise rotation of the system and (Early) Oligocene brittle top-to-the SE thrusting of the Chalepa Group on top of all units mentioned above; and (7) ongoing clockwise rotation of the Aegean block during Abstract The Asterousia Crystalline Complex consists of Late Cretaceous amphibolite facies metamorphic rocks and associated granitoids, which can be found in exposures on Crete and the Cyclades (Greece). It is attributed to the Uppermost Unit and therefore to the Pelagonian domain of the Internal Hellenides. The tectonometamorphic evolution of this unit is still a matter of debate. We present new structural and petrological data of Asterousiatype rocks and greenschist facies metamorphic rocks from the island of Anafi in the southern Aegean Sea as well as U-Pb zircon ages of granitoids from Anafi. The crystalline sequence of Anafi rests on top of Eocene flysch and Electronic supplementary material The online version of this article (1 3 the Oligocene to Early Miocene and change in stress field (NE-SW compression).

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“…The Eocene plutonic belts in the Sakarya and Tavflanl› zones are shaded purple. The map was modified by Helvac› et al (2014Helvac› et al ( ) using fiengör (1984, Okay (1989) and Okay et al (1994Okay et al ( , 1996.…”

Section: Neogene Basins and Volcanism In Western Anatoliamentioning

confidence: 99%

Geological Features of Neogene Basins Hosting Borate Deposits: An Overview of Deposits and Future Forecast, Turkey

Helvacı¹

2015

Bulletin of the Mineral Research and Exploration

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The geometry, stratigraphy, tectonics and volcanic components of the borate bearing Neogene basins in western Anatolia offer some important insights into on the relationship between basin evolution, borate formation and mode of extension in western Anatolia. Some of the borate deposits in NE-SW trending basins developed along the ‹zmir-Bal›kesir Transfer Zone (‹BTZ) (e.g. Bigadiç, Sultançay›r and Kestelek basins), and other deposits in the NE-SW trending basins which occur on the northern side of the Menderes Core Complex (MCC) are the Selendi and Emet basins. The K›rka borate deposit occurs further to the east and is located in a completely different geological setting and volcanostratigraphic succession. Boron is widely distributed; including in soil and water, plants and animals. The element boron does not exist freely by itself in nature, but rather it occurs in combination with oxygen and other elements in salts, commonly known as borates. Approximately 280 boron-bearing minerals have been identified, the most common being sodium, calcium and magnesium salts. Four main continental metallogenic borate provinces are recognized at a global scale. They are located in Anatolia (Turkey), California (USA), Central Andes (South America) and Tibet (Central Asia). The origin of borate deposits is related to Cenozoic volcanism, thermal spring activity, closed basins and arid climate. Borax is the major commercial source of boron, with major supplies coming from Turkey, USA and Argentina. Colemanite is the main calcium borate and large scale production is restricted to Turkey. Datolite and szaibelyite are confined to Russia and Chinese sources. Four Main borax (tincal) deposits are present in Anatolia (K›rka), California (Boron), and two in the Andes (Tincalayu and Loma Blanca). K›rka, Boron and Loma Blanca have similarities with regard to their chemical and mineralogical composition of the borate minerals. Colemanite deposits with/without probertite and hydroboracite are present in west Anatolia, Death Valley, California, and Sijes (Argentina). Quaternary borates are present in salars (Andes) and playalakes and salt pans (USA-Tibet). Boron is a rare element in the Earth's crust, but extraordinary concentrations can be found in limited places. The formation of borate deposits can be classified as follows: a skarn group associated with intrusives and consisting of silicates and iron oxides; a magnesium oxide group hosted by marine evaporitic sediments; and a sodium-and calcium-borate hydrates group associated with playa-lake sediments and explosive volcanic activity. Some conditions are essential for the formation of economically viable borate deposits in playa-lake volcano-sedimentary sequences: formation of playa-lake environment; concentration of boron in the playa lake, sourced from andesitic to rhyolitic volcanics, direct ash fall into the basin, or hydrothermal solutions along graben faults; thermal springs near the area of volcanism; arid to semi-arid climatic conditions; and lake water with a pH of between 8.5 an...

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U-Pb zircon and K-Ar geochronology reveal the emplacement and cooling history of the Late Cretaceous Beypazarı granitoid, central Anatolia, Turkey

Cited by 14 publications

References 61 publications

Major Late Cretaceous Mass Flows in Central Turkey Recording the Disruption of the Mesozoic Continental Margin

Major Late Cretaceous Mass Flows in Central Turkey Recording the Disruption of the Mesozoic Continental Margin

New structural and U–Pb zircon data from Anafi crystalline basement (Cyclades, Greece): constraints on the evolution of a Late Cretaceous magmatic arc in the Internal Hellenides

Geological Features of Neogene Basins Hosting Borate Deposits: An Overview of Deposits and Future Forecast, Turkey

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