Abstract
The application of thermal methods, such as Rock−Eval 6 pyrolysis or differential thermal analysis, provides complex information about sediment and rock properties, including thermal behaviour, degree of maturity, alteration of organic matter, and high temperature combustion synthesis mineral products. In this study, thermal methods included experiments on the thermokinetics of modern deep-sea sediments of the Northeast Pacific Basin. For experimental the procedure, twelve samples of siliceous clayey silts collected from the Clarion−Clipperton Fracture Zone (CCFZ), Interoceanmetal claim area, were analysed. CCFZ is highly prospective as a giant marine polymetallic deposit which contains several economically valuable metals, such as Ni, Cu, or Co. Hydrocarbon potential, thermal maturity, and roasting products were investigated. Mineralogical characteristics of thermal products were investigated. The obtained results of thermal experiments were compared with sedimentological, mineralogical, and geochemical data of bulk sediments. The total enthalpy ΔHTot. and activation energy Ea were proposed as a new lithogeochemical proxies of oxygen depletion during oxic−suboxic diagenesis. The distinctive increase in positive enthalpy (or heat transmission) was observed with the burial depth, where pelagic sediments showed strong oxygen depletion and consumed more energy during phase transformations.
Highlights
The Miocene−Quaternary pelagic sediments covering abyssal basins of the equatorial Pacific have been widely studied in recent years, being host to economically valuable polymetallic nodules and sensitive, diverse deep-sea life [1,2,3,4,5]
Quaternary pelagic sediments from the Clarion–Clipperton Fracture Zone reveal fair hydrocarbon potential, related to the burial diagenesis of bio-siliceous organic matter, and its further degradation occurring in oxic–suboxic conditions
Due to the intensive matrix effects, the occurrence of organic oxygen compounds, and catalytic influences of dispersed metals, the Tmax and Vr0 parameters estimated during Rock–Eval pyrolysis are not applicable for determining the thermal maturity of modern pelagic sediments
Summary
The Miocene−Quaternary pelagic sediments covering abyssal basins of the equatorial Pacific have been widely studied in recent years, being host to economically valuable polymetallic nodules and sensitive, diverse deep-sea life [1,2,3,4,5]. Deep-sea basins are usually identified with increased biogenic accumulation, and a potential source of hydrocarbons released due to the decomposition of organic matter [6,7,8]. Both polymetallic nodules and pelagic sediments contain low amounts of organic carbon, being uniformly distributed on the seafloor [9,10,11]. Minerals 2020, 10, 901 factors are counted as the most important for polymetallic nodule formation and distribution on the seafloor [5,9,12].
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