The Sariçiçek Howardite Fall in Turkey: Source Crater of HED Meteorites on Vesta and İmpact Risk of Vestoids

The Sariçiçek howardite meteorite shower consisting of 343 documented stones occurred on 2 September 2015 in Turkey and is the first documented howardite fall. Cosmogenic isotopes show that Sariçiçek experienced a complex cosmic ray exposure history, exposed during ~12–14 Ma in a regolith near the surface of a parent asteroid, and that an ~1 m sized meteoroid was launched by an impact 22 ± 2 Ma ago to Earth (as did one third of all HED meteorites). SIMS dating of zircon and baddeleyite yielded 4550.4 ± 2.5 Ma and 4553 ± 8.8 Ma crystallization ages for the basaltic magma clasts. The apatite U-Pb age of 4525 ± 17 Ma, K-Ar age of ~3.9 Ga, and the U,Th-He ages of 1.8 ± 0.7 and 2.6 ± 0.3 Ga are interpreted to represent thermal metamorphic and impact-related resetting ages, respectively. Petrographic, geochemical and O-, Cr- and Tiisotopic studies confirm that Sariçiçek belongs to the normal clan of HED meteorites. Petrographic observations and analysis of organic material indicate a small portion of carbonaceous chondrite material in the Sariçiçek regolith and organic contamination of the meteorite after a few days on soil. Video observations of the fall show an atmospheric entry at 17.3 ± 0.8 kms-1 from NW, fragmentations at 37, 33, 31 and 27 km altitude, and provide a pre-atmospheric orbit that is the first dynamical link between the normal HED meteorite clan and the inner Main Belt. Spectral data indicate the similarity of Sariçiçek with the Vesta asteroid family (V-class) spectra, a group of asteroids stretching to delivery resonances, which includes (4) Vesta. Dynamical modeling of meteoroid delivery to Earth shows that the complete disruption of a ~1 km sized Vesta family asteroid or a ~10 km sized impact crater on Vesta is required to provide sufficient meteoroids ≤4 m in size to account for the influx of meteorites from this HED clan. The 16.7 km diameter Antonia impact crater on Vesta was formed on terrain of the same age as given by the 4He retention age of Sariçiçek. Lunar scaling for crater production to crater counts of its ejecta blanket show it was formed ~22 Ma ago

The Saricicek howardite fall in Turkey: Source crater of HED meteorites on Vesta and impact risk of Vestoids

The Saricicek howardite meteorite shower consisting of 343 documented stones occurred on September 2, 2015 in Turkey and is the first documented howardite fall. Cosmogenic isotopes show that Saricicek experienced a complex cosmic-ray exposure history, exposed during 12-14Ma in a regolith near the surface of a parent asteroid, and that an 1m sized meteoroid was launched by an impact 22 +/- 2Ma ago to Earth (as did one-third of all HED meteorites). SIMS dating of zircon and baddeleyite yielded 4550.4 +/- 2.5Ma and 4553 +/- 8.8Ma crystallization ages for the basaltic magma clasts. The apatite U-Pb age of 4525 +/- 17Ma, K-Ar age of 3.9Ga, and the U,Th-He ages of 1.8 +/- 0.7 and 2.6 +/- 0.3Ga are interpreted to represent thermal metamorphic and impact-related resetting ages, respectively. Petrographic; geochemical; and O-, Cr-, and Ti-isotopic studies confirm that Saricicek belongs to the normal clan of HED meteorites. Petrographic observations and analysis of organic material indicate a small portion of carbonaceous chondrite material in the Saricicek regolith and organic contamination of the meteorite after a few days on soil. Video observations of the fall show an atmospheric entry at 17.3 +/- 0.8kms(-1) from NW; fragmentations at 37, 33, 31, and 27km altitude; and provide a pre-atmospheric orbit that is the first dynamical link between the normal HED meteorite clan and the inner Main Belt. Spectral data indicate the similarity of Saricicek with the Vesta asteroid family (V-class) spectra, a group of asteroids stretching to delivery resonances, which includes (4) Vesta. Dynamical modeling of meteoroid delivery to Earth shows that the complete disruption of a 1km sized Vesta family asteroid or a 10km sized impact crater on Vesta is required to provide sufficient meteoroids 4m in size to account for the influx of meteorites from this HED clan. The 16.7km diameter Antionia impact crater on Vesta was formed on terrain of the same age as given by the He-4 retention age of Saricicek. Lunar scaling for crater production to crater counts of its ejecta blanket show it was formed 22Ma ago.Istanbul UniversityIstanbul University [40339, 58261]; Scientific and Technological Research Council of TurkeyTurkiye Bilimsel ve Teknolojik Arastirma Kurumu (TUBITAK) [MFAG/113F035]; Swiss National Science foundationSwiss National Science Foundation (SNSF)European Commission [PZ00P2_154874]; Swiss National Science foundation (NCCR PlanetS)Swiss National Science Foundation (SNSF); Ministry of Science and Higher Education of the Russian Federation [3.1959.2017/4.6]; Act 211 of the Government of the Russian Federation [02.A03.21.0006]; National Natural Science Foundation of ChinaNational Natural Science Foundation of China (NSFC) [41403055]; Simons Foundation [302497]; Academy of FinlandAcademy of FinlandEuropean Commission [299543]; NASA Cosmochemistry ProgramNational Aeronautics & Space Administration (NASA) [NNX14AM62G]; NASA Emerging Worlds Program [NNX16AD34G]; NASA NEOO program [NNX14-AR92G]We thank N. Ergun and family in the village of Saricicek for donating the meteorites studied here and collecting meteorite fall coordinates. We thank E. Atalan and S. Ozdemir at Bingol University, and E. Necip Yardim and M. Cicek at Mus Alparslan University, for facilitating our research at the campuses, and S. Pamuk at the Bingol police headquarters. We thank A. and T. Ozduman, police officers in Bingol, for assisting with the field study. For technical assistance, we further acknowledge support from M. Fehr, Y.-J. Lai, and L. Hoffland (NASA Ames Research Center); David Mittlefehldt (NASA JSC); K. Wimmer (Ries Crater Museum); J. Sanchez (Planetary Science Institute); A. Neesemann (Free University Berlin); S. Atanasova-Vladimirova and I. Piroeva (Institute of Physical Chemistry, BAS); and B. Georgieva and V. Strijkova (Institute of Optical Materials and Technologies, BAS). This work was supported by Istanbul University (Project No. 40339 and 58261), the Scientific and Technological Research Council of Turkey (MFAG/113F035), the Swiss National Science foundation (PZ00P2_154874 and NCCR PlanetS), the Ministry of Science and Higher Education of the Russian Federation (Project # 3.1959.2017/4.6), Act 211 of the Government of the Russian Federation, contract No 02.A03.21.0006, the National Natural Science Foundation of China (41403055), the Simons Foundation (302497), the Academy of Finland (299543), the NASA Cosmochemistry Program (NNX14AM62G), the NASA Emerging Worlds Program (NNX16AD34G), and the NASA NEOO program (NNX14-AR92G).WOS:0004680269000012-s2.0-8506395701

A New Natural Secondary Reference Material for Garnet U-Pb Dating by TIMS and LA-ICP-MS

Gem quality andradite-rich garnet (IUC-1), obtained from the Miocene trachyte dome near Ankara city (Turkey), has been identified as a potential natural secondary reference material for U-Pb dating. In this study, U-Pb dating was performed in five different laboratories using isotope dilution TIMS and laser ablation ICP-MS to determine the homogeneity of euhedral garnet crystals. The U-Pb ID-TIMS data for IUC-1 yielded 207Pb/235U and 206Pb/238U ages of 20.9 0.4 and 20.6 0.8 Ma respectively, and these values are consistent with U-Pb LA-ICP-MS analyses, in which different garnet crystals yielded ages of 20.8 0.1, 20.7 0.1, 20.7 0.2 and 20.2 0.1 Ma. An andradite (IUC-2) from the Serc eoren wollastonite skarn (Turkey) can be used as a secondary reference material provided detailed imaging of the € crystals is undertaken. ID-TIMS data yielded 207Pb/235U and 206Pb/238U ages of 20.4 0.4 and 20.9 1.0 Ma respectively, and yielded U-Pb ages on different grains of 20.5 0.1, 20.7 1.0, 20.8 1.7 and 20.9 1.6 Ma. The assigned weighted mean age of IUC-1 (20.4 0.5 Ma, 2s) is proposed as a 2023 reference value. IUC-1 garnet is expected to contribute significantly to rapidly developing garnet geochronology in the near future