Pseudo-Karst Silicification Related to Late Ni Reworking in New Caledonia

Cathelineau, ‪Michel; Boiron, Marie-Christine; Grimaud, Jean‐Louis; Favier, Sylvain; Teitler, Yoram; Golfier, Fabrice

doi:10.3390/min13040518

Cited by 3 publications

(2 citation statements)

References 59 publications

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“…These phyllosilicates are ultimately dissolved into goethite to form the oxide horizon. While precipitation of quartz have been reported in such geochemical systems, recent studies have highlighted the impact of evaporation to reach the saturation with respect to quartz (Cathelineau et al, 2023). Furthermore, preliminary studies regarding its precipitation in fully saturated media have highlighted its absence in the system (Myagkiy et al, 2017).…”

Section: Conceptual Models Of Weathering In Fractured Mediamentioning

confidence: 99%

Reactive Transport Modeling in Porous Fractured Media: Application to Weathering Processes

Favier,

Teitler,

Golfier

et al. 2024

Water Resources Research

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Complex permeability distribution is frequently encountered in weathered rocks with inherited heterogeneities, such as networks of discontinuities that impact fluid flow and water‐rock interactions. Reactive transport modeling is a powerful tool for analyzing fractured media's chemical weathering dynamics. In this study, two different ways to model the fracture‐matrix interaction were explored. A 1D dual‐porosity simulation of reactive transport is designed to study the global impact of fractures on the weathering progression front, compared with a Single Porosity (S.P.) (unfractured) reference model. Then a 2D discrete model using a Discrete Fracture Matrix (DFM) representation is built to highlight the importance of medium geometry and fracture connectivity on weathering. The relevance of such models was evaluated in the case of weathering processes affecting ultramafic units in New Caledonia. Comparing the average behavior of the dual and S.P. models reveals a similar trend in both global mineralogical evolutions. Yet differences occur when confronting the weathering rates. By extending the weathering over a greater depth, the fractures favor a smoother transition between the saprolite horizon and the oxide ore. Furthermore, a partition of the newly formed phyllosilicates occurs in fractures and matrix: Ni‐phyllosilicates preferentially precipitate in fractures, while Mg‐phyllosilicates remain trapped within the matrix due to differences in residence time and liquid‐to‐solid ratio. The DFM modeling highlights the effect of the connectivity of a complex fracture network on the dissolution‐precipitation processes. Depending on the permeability and geometry, fluid flow is modified, favoring the formation of weathering heterogeneities typically observed on the field.

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Section: Conceptual Models Of Weathering In Fractured Mediamentioning

confidence: 99%

Reactive Transport Modeling in Porous Fractured Media: Application to Weathering Processes

Favier,

Teitler,

Golfier

et al. 2024

Water Resources Research

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“…On the contrary, profile 83, from the center of the plateau, presents fragmented microcrystalline quartz vein infillings and displays evidence of reworking along the profile. This would be a result of complex, not well-understood episodes of precipitation of silica-forming crusts, the collapse of part of the profile, and further replenishment downwards produced by active tectonics during the Pliocene [31,69].…”

Section: Mineral Variations and Weathering Process Across The Laterit...mentioning

confidence: 99%

Geochemistry and Mineralogy of the Clay-Type Ni-Laterite Deposit of San Felipe (Camagüey, Cuba)

Tauler,

Galí,

Villanova-de-Benavent

et al. 2023

Minerals

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The Ni-laterite deposit at the San Felipe plateau, located 30 km northwest of Camagüey, in central Cuba, is the best example of a clay-type deposit in the Caribbean region. San Felipe resulted from the weathering of mantle peridotites of the Cretaceous Camagüey ophiolites. In this study, a geochemical and mineralogical characterization of two profiles (83 and 84) from the San Felipe deposit has been performed by XRF, ICP-MS, quantitative XRPD, oriented aggregate mount XRD, SEM, FE-SEM, and EMPA. Core 83, with a length of 23 m and drilled in the central part of the plateau, presents a notable concentration of cryptocrystalline quartz fragments and a rather poor content of NiO, averaging 0.87 wt.%. Core 84, which is 12 m long and drilled at the border of the plateau, lacks silica fragments and presents a higher NiO content, averaging 1.79 wt.%. The smectite structural formulae reveal that they evolve from trioctahedral to dioctahedral towards the top of the laterite profiles. Quantitative XRD analyses indicate that smectite is a dominant Ni-bearing phase, accompanied by serpentine and minor chlorite. Serpentine, as smectite, is enriched in the less soluble elements Fe3+, Al, and Ni towards the top of the profiles. Core 83 seems to have been affected by collapses and replenishments, whereas core 84 may have remained undisturbed.

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Peridotite Weathering and Ni Redistribution in New Caledonian Laterite Profiles: Influence of Climate, Hydrology, and Structure

Cathelineau,

Teitler,

Grimaud

et al. 2024

Minerals

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The peridotite massifs of New Caledonia are characterised by complex hydrodynamics influenced by intense inherited fracturing, uplift, and erosion. Following the formation of the erosion surfaces and alteration processes, these processes drive chemical redistribution during weathering; particularly lateritisation and saprolitisation. Magnesium, silica, and trace elements such as nickel and cobalt—released as the dissolution front advances—are redistributed through the system. New observations and interpretations reveal how lateritic paleo-land surfaces evolved, and their temporal relationship with alteration processes since the Oligocene. Considering the geometry of discontinuity networks ranging from micro-fractures to faults, the transfers occur in dual-permeability environments. Olivine dissolution rates are heterogeneously due to differential solution renewal caused by erosion and valley deepening. Differential mass transfer occurs between mobile regions of highly transmissive faults, while immobile areas correspond to the rock matrix and the secondary fracture network. The progression of alteration fronts controls the formation of boulders and the distribution of nickel across multiple scales. In the saprolite, nickel reprecipitates mostly in talc-like phases, as well as minor nontronite and goethite with partial diffusion in inherited serpentine. The current nickel distribution results from a complex interplay of climatic, hydrological and structural factors integrated into a model across different scales and times.

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Pseudo-Karst Silicification Related to Late Ni Reworking in New Caledonia

Cited by 3 publications

References 59 publications

Reactive Transport Modeling in Porous Fractured Media: Application to Weathering Processes

Reactive Transport Modeling in Porous Fractured Media: Application to Weathering Processes

Geochemistry and Mineralogy of the Clay-Type Ni-Laterite Deposit of San Felipe (Camagüey, Cuba)

Peridotite Weathering and Ni Redistribution in New Caledonian Laterite Profiles: Influence of Climate, Hydrology, and Structure

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