Utility of trace elements in apatite for discrimination and correlation of Quaternary ignimbrites and co-ignimbrite ashes, Japan

Identification of the source caldera for the Middle Miocene ash‐flow tuffs in the Kii Peninsula based on apatite trace‐element composition

“…From the view point of apatite trace-element content, the Muro Ashflow Tuff also exhibited variation among basal, lower main and middle-upper main parts (Figure 5a). A similar trend has been reported for the late Quaternary Aso-3, Aso-4, Yabakei and Imaichi pyroclastic flow deposits (Takashima et al, 2017), all of which exhibit stratigraphic variation with respect to the occurrence and composition of apatite within the multiple-eruption episode. Takashima Identifying the source caldera for these ash-flow tuffs in the Inner Zone has been controversial.…”

“…Indeed, the identical trace-element compositions in the apatite in the ash-flow tuffs from the Kumano-North and Kumano calderas (Figure 4b, c) could imply that multiple eruptions may have occurred. Additionally, since apatite crystals are relatively resistant to subsequent alteration, such as welding or diagenesis (Kuwabara et al, 2019;Takashima et al, 2017Takashima et al, , 2020, they preserve the trace-element properties at the time of magma eruption. Therefore, the trace-element properties in apatite are well suited for clarifying the origin of the igneous and volcaniclastic rocks in the MFVK, which have similar chemical compositions in terms of bulk major and trace elements; however, it has been proposed that most of these rocks underwent subsequent alteration, partly by the dense welding (Shinjoe et al, 2007(Shinjoe et al, , 2010.…”

“…For the electron probe microanalysis, 20 apatite crystals per sample were analyzed for major and trace elements at the Material Solutions Center, Tohoku University, using a wavelength dispersive, field-emission electron probe microanalyzer (JEOL JXA-8530 F, JEOL Ltd., Tokyo, Japan). The apatite analyses followed the method described in Takashima et al (2017) and used an acceleration voltage of 15 kV with a beam current of 20 nA. All analyses were conducted with a defocused electron beam (10 μm) and the peak and background counting times were 30 and 15 s per element, respectively.…”

“…Recently, tephrochronology based on trace-element compositions of apatite has been widely applied to the analysis of altered volcaniclastic sediments. Apatite is highly resistant to burial diagenesis, welding and weathering processes (Churchman & Lowe, 2012;Morton & Hallsworth, 2007;Takashima et al, 2017), and its trace-element composition is known to change with crystallization in response to various magmatic conditions (Miles et al, 2014;Prowatke & Klemme, 2006). By utilizing such characteristics, several studies on the apatite trace-element compositions of tephras and ash-flow tuffs have been successful in identifying source calderas and in correlating tephra deposits (Kuwabara et al, 2019;Sell & Samson, 2011a, 2011bTakashima et al, 2017Takashima et al, , 2020.…”

Machine Learning Applied to K-Bentonite Geochemistry for Identification and Correlation: The Ordovician Hagan K-Bentonite Complex Case Study

“…The geochemistry of igneous apatite is complex, and in response to various magmatic conditions during crystallization (e.g., oxygen fugacity, temperature, crystallization rate, chemical composition), its trace-element composition can acquire a characteristic geochemical fingerprint [1,2]. Because of this, the geochemistry of apatite is a powerful tool for testing tectonostratigraphic hypotheses and for the high-resolution correlation of pyroclastics produced by large volcanic eruptions, as demonstrated by its successful use in many investigations of tephras ranging in age from the Paleozoic to the recent Cenozoic [3][4][5][6].…”