Stochastic joint modeling of hydrothermal alteration halos and associated geological structures applied to mining studies

Paul Marchal and Guillaume Caumon and Pauline Collon and Christophe Antoine and Patrick Ledru and Kelsey Mckee and Julien Mercadier. ( 2026 )
in: Mathematical Geosciences (https://doi.org/10.1007/s11004-026-10271-3)

Abstract

Hydrothermal mineral deposits are characterized by sub-concentric envelopes of alteration minerals surrounding the metallic profitable zone. These alteration halos are often used as exploration pathfinders, and their characterization can also be important for mine planning and geometallurgical purposes. This paper introduces a new approach to jointly model alteration halos and their geological controls. Indeed, the geometry of hydrothermally altered rocks is mainly controlled by geological features such as fault systems, or unconformities and smaller scale objects such as fracture networks. The proposed method defines a multicomponent structural skeleton as a support for modeling the boundaries of these halos. For this, an alteration potential field d(x) is computed from this structural skeleton is calculated to extract alteration levels as isovalues. As alteration patterns also depend on the petrophysical properties of the host rock, this alteration potential field can be adapted to account for heterogeneous rock material. This process is integrated into a marked point process framework: the skeleton components are simulated by a Metropolis-Hastings sampler, using a dedicated likelihood term to compute the consistency between the current model parameters and the observations. The application of the proposed methodology on a two-dimensional outcrop in Utah, analogous to mineralized hydrothermal sites, demonstrates the ability of the methodology to jointly infer plausible geometries of alteration halos and of the associated geological structures.

Download / Links

BibTeX Reference

@article{marchal:hal-05484538,
 abstract = {
Hydrothermal mineral deposits are characterized by sub-concentric envelopes of alteration minerals surrounding the metallic profitable zone. These alteration halos are often used as exploration pathfinders, and their characterization can also be important for mine planning and geometallurgical purposes. This paper introduces a new approach to jointly model alteration halos and their geological controls. Indeed, the geometry of hydrothermally altered rocks is mainly controlled by geological features such as fault systems, or unconformities and smaller scale objects such as fracture networks. The proposed method defines a multicomponent structural skeleton as a support for modeling the boundaries of these halos. For this, an alteration potential field d(x) is computed from this structural skeleton is calculated to extract alteration levels as isovalues. As alteration patterns also depend on the petrophysical properties of the host rock, this alteration potential field can be adapted to account for heterogeneous rock material. This process is integrated into a marked point process framework: the skeleton components are simulated by a Metropolis-Hastings sampler, using a dedicated likelihood term to compute the consistency between the current model parameters and the observations. The application of the proposed methodology on a two-dimensional outcrop in Utah, analogous to mineralized hydrothermal sites, demonstrates the ability of the methodology to jointly infer plausible geometries of alteration halos and of the associated geological structures.
},
 author = {Marchal, Paul and Caumon, Guillaume and Collon, Pauline and Antoine, Christophe and Ledru, Patrick and Mckee, Kelsey and Mercadier, Julien},
 doi = {10.1007/s11004-026-10271-3},
 hal_id = {hal-05484538},
 hal_version = {v1},
 journal = {{Mathematical Geosciences}},
 keywords = {Stochastic Modeling Hydrothermal Deposits Metropolis-Hastings Uncertainty quantification ; Stochastic Modeling ; Hydrothermal Deposits ; Metropolis-Hastings ; Uncertainty quantification},
 month = {April},
 pages = {https://doi.org/10.1007/s11004-026-10271-3},
 pdf = {https://hal.univ-lorraine.fr/hal-05484538v1/file/MG_template.pdf},
 publisher = {{Springer Verlag}},
 title = {{Stochastic joint modeling of hydrothermal alteration halos and associated geological structures applied to mining studies}},
 url = {https://hal.univ-lorraine.fr/hal-05484538},
 year = {2026}
}