Tatsuo Nozaki

Japan Agency for Marine-Earth Science Technology | JAMSTEC · Submarine Resources Research Center

The historically productive copper-bearing Besshi-type sulphide deposits in the Japanese accretionary complex were formed as volcanogenic massive sulphide deposits on the deep-sea floor of the Panthalassa Ocean. Here we report that eleven typical Besshi-type deposits yielded Re-Os isochron ages around 150 Ma (148.4 ± 1.4 Ma from the composite isoch...

Seafloor massive sulphide deposits are potential resources for base and precious metals (Cu-Pb-Zn ± Ag ± Au), but difficulties in estimating precise reserves and assessing environmental impacts hinder exploration and commercial mining. Here, we report petrological and geochemical properties of sulphide chimneys less than 2 years old that formed whe...

Meteorite impacts have caused catastrophic perturbations to the global environment and mass extinctions throughout the Earth’s history. Here, we present petrographic and geochemical evidence of a possible impact ejecta layer, dating from about 11 Ma, in deep-sea clayey sediment in the Northwest Pacific. This clay layer has high platinum group eleme...

Seafloor hydrothermal deposits form when hydrothermal fluid mixes with ambient seawater, and constituent sulfide minerals are usually interpreted to precipitate abiogenically. Recent research drilling at Izena Hole and Iheya North Knoll in the middle Okinawa Trough (East China Sea), combined with secondary ion mass spectrometry determinations of δ3...

Seafloor massive sulphide (SMS) deposits, modern analogues of volcanogenic massive sulphide (VMS) deposits on land, represent future resources of base and precious metals. Studies of VMS deposits have proposed two emplacement mechanisms for SMS deposits: exhalative deposition on the seafloor and mineral and void space replacement beneath the seaflo...

Strata-bound ferromanganese (Fe–Mn) deposits (umbers) are thought to have formed by precipitation of Fe–Mn oxyhydroxides derived from seafloor hydrothermal activity at a mid-oceanic ridge. Fe–Mn oxyhydroxides effectively adsorb various elements (e.g., P, V, As, rare earth elements, and Os) dissolved in seawater. Of these elements, osmium (Os) is pa...

The Late Devonian, during which one of the “Big Five” Phanerozoic mass extinction events occurred, was one of the most important time intervals in Earth history. Nevertheless, the paucity of deep-sea records due to subduction has hampered elucidation of the pelagic environment during the Late Devonian in Panthalassa. However, ancient hydrothermal f...

Three-dimensional modeling of geoscientific data of limited amounts and strongly biased locations is difficult and impractical using almost any method. To obtain a correct spatial model from data under such constraints, this study systematically demonstrated the effectiveness of neural kriging (NK), which is based on a deep neural network (DNN) wit...

Better understanding metallogenesis in oceanic crust depends on costly sea-floor drilling projects in areas where metal-bearing deposits, such as sea-floor massive sulfide deposits, are currently forming. In 2018, International Ocean Discovery Program (IODP) Expedition 376 recovered drill cores from an active hydrothermal field at Brothers volcano,...

The hydrothermally active Brothers volcano on the Kermadec arc, New Zealand, hosts two geochemically distinct hydrothermal systems within a single caldera. At the NW Caldera, metal-sulfide–rich black smoker spires form on the caldera wall. In contrast, Fe-rich crusts and native sulfur-rich chimneys occur at the resurgent central Upper Cone. Previou...

We observed temperature variations over 10 months within a Kuroko ore (hydrothermal sulfide) cultivation apparatus installed atop a 50‐m‐deep borehole drilled in the Noho hydrothermal system in the mid‐Okinawa Trough, southwestern Japan, for monitoring of hydrothermal fluids and in situ mineral precipitation experiments. Temperature and pressure in...

Properly calibrated discrete dynode SEM ion-counting detectors and minimization of blank Os by an improved vial-cleaning method enables Os isotope analysis at the 1–15 pg level with high accuracy and precision.

Despite the widespread use of Re–Os isotopes in various geoscience fields, relatively little is known about the behavior of Re and Os during fluid-mediated hydrothermal alteration of igneous rocks in the (sub)seafloor, especially in an intraoceanic arc setting. Here, we provide a depth profile of Re–Os geochemistry at Site U1527, located on the NW...

We report geochemical and isotopic data for umber and related greenstone samples from the Aki umber deposit in the Northern Shimanto Belt, central Shikoku, southwest Japan. The greenstone underlying the umber deposit shows a geochemical signature typical for mid-ocean ridge basalts. Umber samples are characterized by notable enrichments in Fe, Mn,...

In this study, we performed a year-long in situ incubation experiment of a common ferrous sulfide (Fe-S) mineral, pyrite, at the oxidative deep seafloor in the hydrothermal vent field in the Izu-Bonin arc, Japan, and characterized its microbiological and biogeochemical properties to understand the microbial alteration processes of the pyrite, focus...

Higashi Aogashima Knoll Caldera (hereafter called HAKC) hydrothermal filed is a relatively new one discovered in 2015 by the research group of The University of Tokyo. There have been known three hydrothermal sites within the HAKC hydrothermal filed; (1) Central Cone Site, (2) Southeast Site and (3) East Site. Out of these three hydrothermal sites,...

Artificial hydrothermal vents, created by boreholes that discharge hydrothermal fluids and useful for observing secular changes in mineral precipitates and the chemical compositions of hydrothermal fluids, are periodically cleaned of scale deposits. Here, we report petrographic and geochemical features of hydrothermal scale with a concentric struct...

Seafloor hydrothermal deposits in the Okinawa Trough have been regarded as a modern analog of kuroko-type volcanogenic massive sulfide (VMS) deposits on land. VMS deposit is one of the primary producers of base metals (e.g. Cu, Pb, Zn) and precious metals (e.g. Au, Ag). However, owing to difficulties in accessing subseafloor samples/data without co...

The solid earth plays a major role in controlling Earth’s surface climate. Volcanic degassing of carbon dioxide (CO 2 ) and silicate chemical weathering are known to regulate the evolution of climate on a geologic timescale (> 10 ⁶ yr), but the relationship between the solid earth and the shorter (< 10 ⁵ yr) fluctuations of Quaternary glacial–inter...

The Carnian Pluvial Episode (CPE) was a global environmental change and biotic crisis that occurred during the Carnian (Late Triassic). The climate during the CPE was characterized by a short-lived period of extreme rainfall, and an extinction of marine taxa is known to have occurred during the latest Julian (i.e. early Carnian). Although these eve...

Recent geochemical data suggest the occurrence of an O2 overshoot during the mid-Paleoproterozoic (~2.3–2.0 Ga). This O2 overshoot appears to be consistent with carbon isotope records that suggest high burial rates of organic carbon during that period, the so-called Lomagundi Event. However, little is known about the changes in the ocean redox cond...

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Deep-sea sediments with total rare-earth elements and yttrium (ΣREY) concentrations exceeding 400 ppm, which are termed REY-rich mud, are widely distributed in the world oceans. Specifically, deep-sea sediments within the Japanese exclusive economic zone (EEZ) surrounding Minamitorishima Island in the western North Pacific have attracted significan...

The deep-sea clay that covers wide areas of the pelagic ocean bottom provides key information about open-ocean environments but lacks age-diagnostic calcareous or siliceous microfossils. The marine osmium isotope record has varied in response to environmental changes and can therefore be a useful stratigraphic marker. In this study, we used osmium...

Seafloor massive sulfide (SMS) deposits are typical of submarine mineral resources and generally rich in base metals (Cu, Pb, Zn); however, their distribution, configuration, and formation mechanism, especially sub-seafloor mineralization, remain poorly understood because of scant drilling and geophysical data. To address this problem, this study a...

During the cruise CK16-05 aboard the D/V Chikyu, we conducted natural gamma-ray logging with a through-the-bit logging system by using a memory-type geothermal exploration tool that has so-far been used only in terrestrial geothermal wells. This logging system was firstly tried during the cruise CK16-01 to reduce the cost and increase the efficienc...

Deep-sea sediments containing high concentrations of rare-earth elements and yttrium (REY), termed REY-rich mud, are widely distributed in the Pacific and Indian oceans. Mud layers with very high total REY (ΣREY) concentrations (>5000 ppm of ΣREY with ~1000 ppm of heavy rare-earth elements) have been discovered within the Japanese exclusive economi...

This study describes a method to quantify the chemical composition of deep30 sea hydrothermal deposits in situ using laser-induced breakdown spectroscopy (LIBS). Partial least squares (PLS) regression analysis is applied to spectra obtained using a long laser pulse with a duration of 150 ns. The number of measurements needed to address the spatial...

The increasing global demand for industrially critical metals has driven the development of deep-sea mineral resources. In the past, acoustic exploration has been utilised as an efficient technique for investigating deep-sea mineral resources. However, a practical method applicable to a wide distribution of resources has not yet been established. W...

Hitachiite, Pb5Bi2Te2S6, is a new mineral discovered in the Hitachi mine, located in the Ibaraki Prefecture of Japan. The mean of 21 electron microprobe analyses gave: Pb 52.01, Bi 23.06, Fe 0.69, Sb 0.17, Te 13.74, S 9.71, Se 0.54, total 100.04 wt.%. The empirical chemical formula based on 15 apfu is (Pb4.75Fe0.23)Σ4.98(Bi2.09Sb0.03)Σ2.12Te2.04(S5...

Pelagic cherts preserved in accretionary complexes represent former seafloor sediment that can retain geochemical evidence of paleoceanographic conditions that predate the oldest extant oceanic crust. The ratio of Os isotopes in seawater, in particular, is of wide interest as a source of insight into notable geologic events such as oceanic anoxic e...

Seafloor hydrothermal sulfides, which are expected to be a future resource for metals, could be a potential source for metal contamination in the seawater around mining sites. In this chapter, we illustrate the potential for metal leaching of both non-oxidized (non-exposed to atmosphere; before and during exploitation) and oxidized (exposed to atmo...

Ancient hydrothermal metalliferous sediments (umber) have recently attracted attention as a new rare-earth element resource. We conducted chemical leaching experiments on three different umber ores to optimize the hydrometallurgical extraction process, especially regarding the grinding process. The three umber ore samples, which were collected from...

The Pb isotope compositions of galena in hydrothermal deposits obtained by drillings from two hydrothermal fields in the middle Okinawa Trough were studied. One of the study fields was the Iheya North field located on a volcanic complex and the other was the Izena field located in the sediment-filled caldera structure. LA-MC-ICP-MS was applied to d...

Through the 4.6 Gyr of Earth’s history, ore deposit has been formed via close linkage with the evolution of this planet. Ore deposit is an abnormally enriched material of targeted elements and its enrichment mechanism macroscopically controlled by “Geology” and microscopically controlled by “Geochemistry.” “Front line of economic geology” is the fi...

Basement rocks of the Japanese islands consist mainly of accretionary complexes younger than ca. 400 Ma. Various types of stratiform and/or massive ore deposits that formed on a paleo-seafloor are hosted within the Japanese accretionary complexes. In the present study, we review recent progress on metallogenetic research and outline unsolved proble...

Abstract We observed the initial release rate of metals from four fresh (i.e., without long time exposure to the atmosphere) hydrothermal sulfide cores into artificial seawater. The sulfide samples were collected by seafloor drilling from the Okinawa Trough by D/V Chikyu, powdered under inert gas, and immediately subjected to onboard metal-leaching...

The Proterozoic Bryah and Yerrida basins of Western Australia contain important base and precious metal deposits. Here we present microtextural data, trace element and S isotope analyses of massive sulphide mineralisation hosted in Palaeoproterozoic subvolcanic rocks (dolerite) recently discovered at Red Bore. The small-scale high-grade mineralisat...

The commercial use of metals such as copper, lead, and zinc has markedly increased in recent years, resulting in increased interest in deep-sea mining of seafloor hydrothermal sulfide deposits. However, the full extent of the impact of deep-sea mining at hydrothermal field deposits on the environment remains unclear. In addition to impacting the de...

Scandium is a critical element in state-of-the-art, green technologies. However, it is also extremely expensive due to its scarcity. Recently, some deep-sea sediments that contain significant amounts of rare-earth elements that are indispensable to modern industries have been discovered in the western North Pacific Ocean, and the concentration of S...

We performed X-ray adsorption fine structure (XAFS) analyses of Y, Ce, Fe, and P for rare earth elements and yttrium-rich muds (REY-rich muds) from the two regions of the Pacific Ocean: the eastern South Pacific and the central North Pacific. Yttrium K-edge XAFS revealed that calcium phosphate (apatite) is the common host of REY even in the hydroth...

Potential risks of supply shortages for critical metals including rare-earth elements and yttrium (REY) have spurred great interest in commercial mining of deep-sea mineral resources. Deep-sea mud containing over 5,000 ppm total REY content was discovered in the western North Pacific Ocean near Minamitorishima Island, Japan, in 2013. This REY-rich...

This study investigates methods to analyze Laser-induced breakdown spectroscopy (LIBS) signals generated from water immersed deep-sea hydrothermal deposits irradiated by a long pulse (>100 ns) that are analyzed using Artificial Neural Networks (ANNs). ANNs require large amounts of training data to be effective. For this reason, we propose methods t...

Conclusions: The Darreh-Rasoul Fe-Pb deposit in the southeast of Malayer and the northwestern part of Malayer-Esfahan metallogenic belt formed in the lower Cretaceous Clastic-Carbonate sequence in the extentional back-arc setting. Based on field geology, texture and structure and ore facies, two stratiform horizons can be distinguished in this depo...

Submarine hydrothermal deposits are one of the promising seafloor mineral resources, because they can store a large amount of metallic minerals as sulfides. The present study focuses on the electrical properties of active modern submarine hydrothermal deposits, in order to provide constraints on the interpretation of electrical structures obtained...

Whale carcasses (whale falls) deposited on the deep seafloor are associated with a distinctive biotic community. A fossil whale bone recovered from São Paulo Ridge, South Atlantic Ocean, during cruise YK13–04 Leg 1 of R/V Yokosuka was covered by a ferromanganese (Fe–Mn) crust approximately 9 mm thick. Here, we report an age constraint for this foss...

We report detailed lithological and chemical characteristics of deep-sea sediments, including rare-earth elements and yttrium-rich mud (REY-rich mud), in the Japanese Exclusive Economic Zone (EEZ) around Minamitorishima Island. Three research cruises obtained fourteen sediment cores collected by piston coring. Based on the visual descriptions and g...