A Study of Shock-Metamorphic Features of Feldspars from the Xiuyan Impact Crater

Abstract

Feldspar is the most abundant mineral in the Earth's crust and is widely distributed in rocks. It is also one of the most common minerals in meteorites. Shock-metamorphic features in feldspar are widely used to calibrate the temperature and pressure of shock events and can also provide clues for searching for impact craters on Earth. In this study, shocked alkali feldspars in the lithic breccia and suevite from Xiuyan Impact Crater were investigated using polarizing optical microscopes, Raman spectroscopy and electron microprobes to better constrain the shock history of this crater. For this study, feldspar grains occurring in gneiss clasts in the impact breccia and four shock stages were identified, e.g., weakly shocked feldspar, moderately shocked feldspar, strongly shocked feldspar, and whole rock melting. According to the shock classification system for alkali feldspar and felsic rocks, we estimated the shock pressure (SP) and post-shock temperature (PST) histories of these gneiss clasts. Weakly shocked feldspars display irregular fractures and undulatory extinction, and their shock stage is F-S2, which indicates that SP and PST are from~5 to~14 GPa and~100 • C, respectively. Moderately shocked feldspars show planar deformation features and are partially transformed into diaplectic glass, which indicates that the F-S5 shock stage of SP and PST is from~32 to~45 GPa and 300-900 • C. Strongly shocked feldspars that occur as vesicular glass indicate a shock stage of F-S6, and the SP and PST are 45-60 GPa and 900-1500 • C, respectively. The whole felsic rock melting occurs as mixed melt glass clast and belongs to the F-S7 stage, and SP and PST are >60 GPa and >1500 • C, respectively.The Xiuyan crater is a simple impact crater located in northeast China with a diameter of 1800 m, which was formed 50,000 years ago [17]. The basement rocks in the impact crater area are crystalline rocks composed of gneiss, granulite, and amphibolite, as well as minor basalt and marble. A drill hole at the center of the Xiuyan crater reveals that the crater contains a loosely consolidated impact breccia lens with a center thickness of about 188 m, which is underlain by 107-m-thick lacustrine sediments [17]. The upper part of the 153 m thick part of the impact breccia lens consists of gneiss, amphibolite, basalt, and marble fragments as well as a small amount of lithic breccia, whereas the lower 35 m thick part of the impact breccia lens is composed of gneiss, granulite and amphibolite fragments and small amount of melt-bearing breccia (suevite).So far, a variety of high-pressure minerals have been found in the suevite from the Xiuyan crater, such as coesite [14], reidite [18], TiO 2 -II [19], diamond [20], and maohokite [21]. This study focuses on the shock-metamorphic features of feldspar in impact breccias from the Xiuyan crater, and we try to reveal the shock histories of these feldspars.

Provenance of altered carbon phases and impact history of the Stac Fada Member, NW Scotland

“…Evidence for shock has also been identified within known impact craters in minerals such as gypsum (Brolly et al., 2017) and feldspar (Pickersgill et al., 2021; Xie et al., 2020). The latter can be used to estimate the temperature and pressure of shock events (Yin & Dai, 2020). As shown in this study, disordered carbon also has the potential to record pressure–temperature excursions associated with impact events and if properly calibrated, it could be a useful tool as a geothermometer (e.g., Beyssac et al., 2002; Kouketsu et al., 2014; Lahfid et al., 2010).…”

Nanotextures and formation process of coesite in silica glass from the Xiuyan impact crater

“…(2010a). The presence of vesicles in the alkali feldspar (albite and anorthoclase) glass (Yin and Dai 2020), but not in silica glass, further constrains that the postshock temperature exceeded the melting temperature of alkali feldspar of ~1100 °C (Keulen et al. [2015] and references therein), but did not reach the liquidus temperature of quartz (~1600 °C, Zhang et al.…”

Editorial for the Special Issue “Properties of Melt and Minerals at High Pressures and High Temperature”

“…The study of the corundum-bearing anatectic aluminous rocks exposed in the North Dabie orogen, Central China, with the micro-structural evidence of anatexis by dehydration melting of muscovite [33] serves as an ideal link between magmatic and metamorphic processes investigated in the study of shock metamorphic features of feldspar from the Xiuyan impact crater [34]. The partial melting of high-pressure (HP) and ultra-high-pressure (UHP) metamorphic rocks can profoundly influence the tectonothermal evolution of collisional orogens, the geochemical differentiation of the continental crust and the crust-mantle interaction dynamics within subduction zones [35][36][37][38].…”

“…The shock-metamorphic features can provide clues for the search for impact craters on Earth and can also enrich the understanding of the behavior of feldspar under high temperatures and high pressures. In the study of Yin et al [34], shocked alkali feldspars in the lithic breccia and suevite from Xiuyan Impact Crater were investigated using polarizing optical microscopes, Raman spectroscopy and electron microprobes to better constrain the shock history of this crater. The alkali feldspar had developed a variety of shock-metamorphic features, including irregular fractures, undulatory extinction, PDFs, diaplectic glass, and vesicular glass indicating an impressive shock history of the crater with shock pressure and post-shock temperature varying from 5 to >60 Gpa and T from~100 to >1500 • C (shock stage), respectively.…”