Expedition 352 methods

Abstract

Introduction 4 Sedimentology 8 Biostratigraphy 8 Fluid geochemistry 10 Petrology 16 Sediment and rock geochemistry 28 Structural geology 31 Physical properties 36 Paleomagnetism 38 Downhole logging 42 References

Magmatic Response to Subduction Initiation: Part 1. Fore‐arc Basalts of the Izu‐Bonin Arc From IODP Expedition 352

“…In Hole U1440B, located closest to the trench, basement consists of fore‐arc basalt, with ~145 m of lavas and hyaloclastites overlying an ~70‐m‐thick transition zone of lavas, hyaloclastites, and dikes, which in turn overlies a ~55‐m‐thick sheeted dike unit or sill complex at the base (Figure a; Reagan et al, ). Igneous rocks in Hole U1440B were divided into 15 chemostratigraphic units by the Expedition 352 science party (Reagan et al, ), based on chemical proxies determined by portable XRF analyses (Ryan et al, ), limited whole rock ICP‐OES analyses carried out at sea (Reagan et al, ), and on the physical attributes of the units inferred from core (Reagan et al, ). Below an uppermost unit of volcanic talus (Unit 1), and above the inferred sheeted complex of dolerite sills/dikes (Unit 15), the volcanic section comprises massive sheet flows, pillow lava, and hyaloclastites containing intermingled pillows or sheet flows (Figure a).…”

“…USGS (United States Geological Survey) and international standards were used to check our calibration curves throughout the analyses. In addition, we have access to data for 40 POOL samples, which were analyzed by ICP‐OES (inductively coupled plasma‐optical emission spetrometry) during the expedition and reanalyzed by XRF afterward (Reagan et al, ). POOL samples were chosen by the Expedition 352 Science Party to encompass the breadth of chemical variability in the recovered igneous material, with the goal of eventually yielding a self‐consistent database of major, trace, and isotopic data on the same homogenized powders.…”

Magmatic Response to Subduction Initiation, Part II: Boninites and Related Rocks of the Izu‐Bonin Arc From IODP Expedition 352

“…In addition to the personal samples described above, oxidized powders from 70 shipboard samples that were analyzed by inductively-coupled plasma -atomic emission spectrometry during the expedition were analyzed here by XRF only, using the same procedures. Carbonate correction was applied using the shipboard CO 2 analyses (Reagan et al, 2015f). Sample preparation is described in Reagan et al (2015f) and the data are presented in Table DS02 and the Pangaea data archive (Shervais et al, 2020).…”

Boninite and boninite-series volcanics in northern Zambales ophiolite: doubly vergent subduction initiation along Philippine Sea plate margins

“…Based on dredging and dive observations in the forearc trench slope, proto-arc basalts are found at deeper depths relative to boninites which occur upslope and subaerially at Chichijima (type locality) and Mukojima island groups (Ishizuka et al, 2011;Kanayama et al, 2012;Umino and Nakano, 2007). The hypothesis that protoarc basalt lies stratigraphically below boninite has been suggested by IODP Expedition 352 based on four sites drilled in the trench-side slope of the Bonin Ridge (Reagan et al, 2015(Reagan et al, , 2017. Both spontaneous and induced initiation have been replicated in numerical models of incipient subduction at the IBM.…”

“…Perez et al: Boninite and boninite-series volcanics in northern Zambales ophiolite Figure 1. (a) Distribution of subduction initiation rock suites in the Philippine Sea plate and spreading histories of associated marginal basins (Deschamps and Lallemand, 2002;Pearce et al, 1992;Reagan et al, 2017). (b) Regional geological map of the Zambales ophiolite after with whole-rock K-Ar and zircon U-Pb ages from Fuller et al (1989) and Encarnacion et al (1993).…”