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Manganese nodules are a potential source of critical metals such as Cu, Ni, and Co and are widely distributed on the abyssal plains of the global oceans. A polymetallic nodule metallogenic belt with a heterogeneous and spatially clustered nodule distribution was recently discovered in NW Pacific inter-seamount basin (NPIB) areas. However, the geological processes that regulate the nodule occurrence in that region are unresolved. Here, we report on the characteristics of a high-density field of manganese nodules in the abyssal plain north of Suda Seamount. Ship-borne multibeam bathymetric data reveal a typical seamount sector-collapse topography characterized by radial lineaments of debris channels and ridges formed by rapid debris-avalanche flow. Backscatter data linked with underwater observation indicate that manganese nodules are more concentrated (50%–80% areal coverage) along the main body of the debris apron compared to adjacent neighboring areas (

Seamount phosphates are increasingly regarded as potential resources for rare earth elements (REE) and plus yttrium (REY). Carbonate fluorapatite (CFA) formed within seamount ferromanganese (Fe Mn) crusts is the most common seamount phosphate mineral. However, reports on the mineralogy and geochemistry of CFA are few and thus its origin and acquisition of trace elements are not well understood. In this study, we analyzed the major and trace elements of CFA in Fe Mn crusts collected from Western and Central Pacific seamounts to investigate the genesis of trace elements in the CFA. This is the first study to use in situ analytical techniques such as electron microprobe analyzer (EPMA) and laser ablation-inductively coupled plasma mass spectrometry (LA-ICP-MS) to analyze seamount CFA. We found that the CFA hosts abundant minor and trace elements and propose that ionic substitutions are responsible for the high contents of SO3, SiO2, REY, Sr, Na, Fe, and Mn in the CFA veins found in the Fe Mn crusts, i.e., SiO32− and SO42− substitute for PO42−, while REE3+, Y3+, Na+, Fe2+, and Mn2+ substitute for Ca2+. REE3+ substitutions for Ca2+ in the CFA are charge-compensated by Na+ substitution for Ca2+. Fourier transform infrared spectroscopy (FTIR) analysis shows that CO32– mainly substitutes for PO42− in the CFA crystal structure, and there is a minor substitution of PO42− by CO3F3−. Ocean water is the major source of the P and REY, which when precipitated as seamount CFA is characterized by high ∑REE (345 to 6016 ppm) and heavy-REE (HREE) enrichments. Monazite grains dispersed in the seamount CFA contribute trace amount of REY. These results shed light on the composition and element mobility of seamount CFA with economic potential, which also provides valuable insights into global ocean chemical cycling (e.g. REE).

Mineral formation in the modern oceans can take place over millions of years as a result precipitation from ambient ocean water, or orders of magnitude more rapidly from hydrothermal activity related to magmatic and tectonic processes. Here, we review associations between transform faults and related fracture zones and marine minerals. We define marine transform faults as strike-slip or oblique faults that accommodate lateral offsets along plate boundaries or shifting crustal blocks, and fracture zones as relicts of transform faulting extending beyond mid-ocean ridge offsets. We consider specifically the modern ocean and exclude regions where the transform or fracture has clearly not generated the mineral deposit, such as the Clarion-Clipperton fracture zone manganese nodule field. As a result, the summarized deposits are mainly hydrothermal in origin. Oceanic transform faulting has rarely been considered of interest for the mineralization and formation of ore deposits; however, there are locations in the modern oceans where transform faults and fracture zones are spatially related to mineral deposits. These occurrences suggest that transform faulting and fracture zones may be linked to mineralization at (A) intersections with other tectonic features, (B) where transform faults begin to resemble rifts through intra-transform crustal thinning, spreading, and the formation of pull-apart basins, and (C) as a result of serpentinization reactions due to exposure of deep-seated rocks by fracturing and faulting.

Marine ferromanganese (Fe-Mn) nodules and crusts are archives of past environmental conditions and potential mineral resources. Over the last 30 years, many have been discovered in the northern South China Sea (SCS). To determine the origin of the Fe-Mn deposits, a comprehensive laboratory analysis of physical properties, mineralogy and geochemistry was conducted on newly collected Fe-Mn nodule/crust samples. The results revealed that there are three types of Fe-Mn deposits: (1) Fe-rich nodules containing essentially goethite occur on the northeastern slope of the SCS, with high Fe, low Mn (Mn/Fe = 0.03) and low trace metals and rare earth elements concentrations; (2) Smooth Fe-Mn nodules and crusts composed of asbolane, todorokite and CFA occur along the northwestern marginal of the SCS that have similar Fe and Mn contents (Mn/Fe = 1.21), moderate trace metal enrichments, and a positive Ce anomaly; (3) Fe-Mn nodules and crusts composed of asbolane, todorokite and birnessite that occur in the central basin of the SCS have higher Mn and lower Fe contents (Mn/Fe = 1.45). This depositional pattern was associated with major changes in oceanographic conditions and tectonic regimes. The northeastern slope deposits occur in a contourite depositional system, are strongly enriched in Fe relative to Mn (average 38.7% and 0.96%, respectively), formed from the combination of hydrogenetic and diagenetic processes. We propose a new genetic model for Fe-Mn nodules, which formed through the oxidation of pyrite and pyrite-barite concretions that formed by rapid early diagenetic growth (average 3320 mm/Myr) on continental margins above the carbonate compensation depth, and dominated by hydrocarbon seep structures and strong erosive action of bottom currents along the northeastern slope. In contrast, the introduction of vigorous deep-water flow from the North Pacific promoted the slow growth (4–7 mm/Myr) of hydrogenetic Fe-Mn nodules and crusts along the northwestern margin. Finally, hydrogenetic growth of Fe-Mn nodules and crusts in the central basin may have been enhanced by volcanic processes. Our data provide new insights into the genesis and province characteristics of the Fe-Mn nodules and crusts of the northern SCS., CAS Key Laboratory of Marginal Sea Geology, Chinese Academy of Sciences, China, University of Chinese Academy of Sciences, China, Servicio de Cartografía Geológica Marina, Instituto Geológico y Minero de España, España, U.S. Geological Survey, Estados Unidos

Ferromanganese crusts and nodules may provide a future resource for a large variety of metals, including many that are essential for emerging high- and green-technology applications. A brief review of nodules and crusts provides a setting for a discussion on the latest (past 10 years) research related to the geochemistry of sequestration of metals from seawater. Special attention is given to cobalt, nickel, titanium, rare earth elements and yttrium, bismuth, platinum, tungsten, tantalum, hafnium, tellurium, molybdenum, niobium, zirconium, and lithium. Sequestration from seawater by sorption, surface oxidation, substitution, and precipitation of discrete phases is discussed. Mechanisms of metal enrichment reflect modes of formation of the crusts and nodules, such as hydrogenetic (from seawater), diagenetic (from porewaters), and mixed diagenetic–hydrogenetic processes.

We present bulk chemical and mineralogical compositions, as well as petrographic and outcrop descriptions, of rocks collected from three measured outcrop sections of the Rex Chert Member of the Phosphoria Formation in southeast Idaho. The three measured sec- tions were chosen from 10 outcrops of Rex Chert that were described in the field. The Rex Chert overlies the Meade Peak Phosphatic Shale Member of the Phosphoria Formation, the source of phosphate ore in the region. Rex Chert removed as overburden constitutes part of the material transferred to waste-rock piles during phosphate mining. It is also used to surface roads in the mining district. It has been proposed that the chert be used to cap and isolate waste piles, thereby inhibiting the leaching of potentially toxic elements into the environment. The rock samples studied here are from individual chert beds representative of each stratigraphic section sampled. The Cherty Shale Member of the Phosphoria Formation that overlies the Rex Chert in measured section 1 and the upper Meade Peak and the transition zone to the Rex Chert in section 7 were also described and sampled. The cherts are predominantly spiculite composed of granular and mosaic quartz, and sponge spicules, with various but minor amounts of other fossils and detrital grains. The Cherty Shale Member and transition rocks between the Meade Peak and Rex Chert are siliceous siltstones and argillaceous cherts with ghosts of sponge spicules and somewhat more detrital grains than the chert. The dominant mineral is quartz. Carbonate beds are rare in each section and are composed predominantly of calcite and dolomite in addition to quartz. Feldspar, mica, clay minerals, calcite, dolomite, and carbonate fluorapatite are minor to trace minerals in the chert. The concentration of SiO2 in the chert averages 94.6 wt.%. Organic-carbon content is generally very low, but can be as much as 1.8% in Cherty Shale Member samples and as much as 3.3% in samples from the transition between the Meade Peak and Rex Chert. Likewise, phosphate (P2O5) is generally low in the chert, but can be as much as 3.1% in individual chert beds. Selenium concentrations in Rex Chert and Cherty Shale Member samples vary from

The Phosphoria Formation has been the subject of intensive study for nearly 100 years. Most work during the first half of the twentieth century on the Phosphoria Formation fell under three US Geological Survey (USGS) programs. The first program, from 1909 to 1916, was concerned with mapping the extent of phosphate rock within the western United States, the so-called Western Phosphate Field. Many of the basic features concern- ing the distribution, structure, and composition of the Phosphoria were determined during that time. The work of Blackwelder was especially critical in delineating geochemical con- ditions of the depositional basin, the Phosphoria sea. An important process in the formation of the Phosphoria Formation, coastal upwelling, was not understood in those earlier works. A detailed understanding of the processes involved in coastal upwelling was first developed by Kazakov in the late 1930s and those processes were later applied to the Phosphoria Formation in the late 1940s by McKelvey and co-workers. The second USGS program began in 1941 and involved detailed sampling and analyses of Phosphoria rocks to deline- ate vanadium-rich zones, which were discovered during the earlier USGS program. This sampling and analysis program also identified zinc- and uranium-rich strata within the Phosphoria Formation. The discovery of uranium, along with an increasing demand for phosphate, led to the third large USGS program headed by McKelvey, which began in 1947. From 1947 to 1952, hundreds of stratigraphic sections were measured, described, and sam- pled from 200 locations in Montana, Wyoming, Idaho, and Utah. From this work, a com- prehensive genetic model was developed for the sedimentary and oceanographic conditions that promoted phosphorite deposition. Delineation of regional facies changes, thickness changes, and chemical and petrologic changes also provided criteria for regional correla- tions of rock units. The cyclic nature of deposition of Phosphoria Formation strata was emphasized. Succeeding studies in the 1960s and 1970s established the characteristics of regional and local depositional environments and paleogeographic and paleoclimatic con- ditions of the Phosphoria sea and surrounding areas. The Phosphoria Formation was placed into a more restrictive Middle Permian time frame than had been used by previous workers. From the 1980s to the present, investigations focused on the details of phosphogenesis and the use of sequence stratigraphy to understand the role that sea level played in the evolution of the Phosphoria sea and in the cyclic deposition of the Phosphoria sequence.

This chapter describes the geology and hydrology of Cook Islands that are a part of Polynesia. The Cook Islands are located in the central South Pacific between the Society Islands to the east and the Tonga and Samoa Islands to the west. The Islands consist of 15 islands divided into a northern group of six islands and a southern group of nine islands. The population of the Cook Islands has been steadily declining because of dual citizenship with New Zealand and the consequent migration of many to that country. The two groups have distinct climates and oceanographic settings, tectonic origins, geomorphologies, hydrologic resources, and geologic histories. The southern group of islands form two linear volcanic chains; crustal loading and flexure associated with Quaternary volcanism on Rarotonga uplifted the makatea islands. In contrast, most islands of the northern group are located on the tectonically stable Manihiki Plateau, which was formed from an outpouring of lava at a triple junction during the Early Cretaceous.

In order to determine the depositional environments of orogenic belt cherts, we compared chert sequences that we studied in Costa Rica, California, and Alaska with cherts recovered by the Deep Sea Drilling Project during Legs 62 and 69. Leg 62 recovered cores in open-ocean environments on Hess Rise and the Mid-Pacific Mountains, and Leg 69 recovered deposits from the south flank of the Costa Rica Rift. Comparisons of lithologic associations, sedimentary structures, chemistry, sedimentation rates, and modes of formation clearly show that chert sequences occurring in orogenic belts are not analogous to cherts that have been drilled in open-ocean environments. the orogenic belt chert sections we studied apparently formed in tectonically produced basins near continental margins. No known cherts of any age drilled in the Pacific Ocean basin resemble the ribbon cherts observed on land. Cherts from the deep sea occur mainly as nodules or lenses in, or above, limestone and chalk, and compose a small percentage of the overall sedimentary sequences. Typical deep-sea open-ocean cherts such as those from Legs 62 and 69, formed by replacement of calcareous or clayey sediments, whereas, bedded ribbon cherts in orogenic belt sequences, such as those from Costa Rica, California, and Alaska, formed by diagenetic recrystallization of alternating contrasting sediment types, such as siliceous ooze and hemipelagic clay, tuff, or sandstone. Many of the chert beds were laid down by turbidity currents. the cherts we studied in orogenic belts are in depositional continuity with greenstone as well as graywacke turbidites. Sections rarely, if at all, have limestones associated with them.