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The Attic–Cycladic Crystalline Belt in the central Aegean region represents a major tectono‐stratigraphic unit of the Hellenides. The essential geological, magmatic and tectono‐metamorphic features are well documented. Unresolved questions concern the time of sediment accumulation and litho‐ and/or tectono‐stratigraphic relationships across the study area. In order to address this issue we have studied siliciclastic metasedimentary rocks from Andros Island, northern Cyclades. The sampling strategy aimed at covering the complete age range recorded by the Andros metamorphic succession. Detrital zircon U–Pb dating of nine samples indicates maximum depositional ages of c. 260 Ma for the topmost part of the metamorphic succession and of c. 160–140 Ma for rock sequences below a prominent serpentinite belt that is interpreted to outline a major tectonic contact. These age constraints are in accordance with interpretations suggesting that the metamorphic rocks of Andros represent different tectonic subunits (Makrotantalon Unit and Lower Unit) that are separated by a thrust fault. Modification of the internal structure of the Lower Unit by tectonic stacking can currently not be ascertained. The new data for the Lower Unit corroborate the importance of Late Jurassic–Early Cretaceous sediment accumulation for the larger study area. In contrast to some of the neighbouring islands, no evidence for transfer of Late Cretaceous (c. 80 Ma) material into the Andros sedimentary environment was found. The most striking feature of the zircon populations of the Lower Unit is a remarkable age cluster at 250–200 Ma that documents the importance of Triassic igneous sediment sources. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
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Ling Xiao-Xiao Huyskens Magdalena H. Li Qiu-Li Yin Qin-Zhu Werner Ronald Liu Yu Tang Guo-Qiang Yang Ya-Nan Li Xian-Hua 《Mineralogy and Petrology》2017,111(2):163-172
Mineralogy and Petrology - Well-characterized matrix-matched natural mineral references of known age are an important prerequisite for SIMS (secondary ion mass spectrometry) U–Th–Pb... 相似文献
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Scott Harlan Peter Jenniskens Michael E. Zolensky Qing‐Zhu Yin Kenneth L. Verosub Douglas J. Rowland Matthew Sanborn Magdalena Huyskens Emily R. Creager A. J. Timothy Jull 《Meteoritics & planetary science》2016,51(4):757-772
Meteorites have been found on the small Misfits Flat dry lakebed near Stagecoach, Nevada (119.382W, +39.348N). Since the first find on Sept. 22, 2013, a total of 58 stones of weathering stage W2/3 with a combined mass of 339 g have been collected in 19 visits to the area. This small (3.3 × 3.6 km) lakebed is now a newly designated dense collection area (DCA). Most meteorites were found in a small 350 × 180 m area along the north shore and most are fragments of several broken individual stones. Three of these fragments were classified as an LL4/5 of shock stage S2, now named Misfits Flat 001, one of which (stone MF33) fell 8.1 ± 1.3 ka ago based on the 14C terrestrial age, assuming it came from a 20–80 cm diameter meteoroid. In addition, a small darkly crusted meteorite MF34, now named Misfits Flat 002, was found 820 m WSW from the main mass. This meteorite is classified as an LL5 ordinary chondrite with shock stage S4/5. The meteorite is saturated in 14C at 63 dpm kg?1, suggesting it originated from the center of a 0.5 m diameter meteoroid, or deep inside a ~1.0 m meteoroid, less than 300 yr ago. Accounts exist of a fireball seen at 13:15 UT on March 2, 1895, that are consistent with the find location of Misfits Flat 002. 相似文献
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Peter Schmid-Beurmann Luisa Ottolini Frédéric Hatert Thorsten Geisler Magdalena Huyskens Volker Kahlenberg 《Mineralogy and Petrology》2013,107(4):501-515
The topotactic oxidation and delithiation reaction from triphylite, Li(Fe,Mn)PO4, leading to ferrisicklerite, Li<1(Fe3+,Mn2+)PO4, was investigated under hydrothermal conditions. A cuboid cut from a triphylite single-crystal (Palermo Mine, New Hampshire, USA) with the composition Li0.93(3)(Fe2+ 0.733(6),Fe3+ 0.015(1),Mn2+ 0.210(4),Mg0.063(2))1.021(8)P1.00(2)O4 in addition with ground bulk material were treated with KMnO4 and 30 % H2O2(aq) as oxidizing agent in a 0.1 N hydrochloric acid solution in the temperature range between 60 and 200 °C. At 120 °C a rim of 0.1 mm thickness of ferrisicklerite had formed around the core of unreacted triphylite. The sharp reaction boundary was clearly visible, due to the reddish brown absorption colors of ferrisicklerite, compared to colorless triphylite. Using single-crystal X-ray diffraction (XRD), secondary ion mass spectrometry (SIMS), electron probe micro-analysis (EPMA) and 57Fe-Mössbauer spectroscopy the product ferrisicklerite was characterized and its composition determined as Li0.30(7)(Fe2+ 0.049(1)Fe3+ 0.65(2)Mn2+ 0.218(5)Mg0.062(2))0.98(1)P1.01(3)O4, with unit cell parameters a?=?4.795(1), b?=?9.992(4), and c?=?5.886(2) Å. EPMA investigations across the reaction boundary showed no changes in the concentrations of Fe, Mn, Mg, and P. In contrast, SIMS measurements clearly proved the delithiated state of the ferrisicklerite product. Polarization microscopy revealed that the orientation of the ferrisicklerite rim was the same as that of the original triphylite single-crystal, confirming the strictly topotactic character of the reaction. 相似文献
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