HiPerBorea aims to enable quantitative and predictive modeling of the thermo-hydrological evolution of cold environments covered by permafrost (25% of lands of northern hemisphere) under climate change. Permafrost thaw is associated with major feed-backs on greenhouse gases cycles (e.g.: thawing of previously frozen organic carbon pools). Its dynamics is a key factor for climatic evolution. The involved physics are highly coupled and non-linear, and simulating them at the scale of long-term monitored watersheds requires the development of spatially distributed and process oriented high performance computing tools. The fields of applications are numerous, from the hydro-bio-geochemistry of cold areas to engineering applications such as infrastructure stability in cold environments or site scale cryo-barriers in polluted industrial areas. The approach that we aim to apply in order to reach this goal is to develop an OpenFOAM® framework for parallel computing modeling of thermo-hydrodynamics of cold continental surfaces. The team of the project already recently produced a validated and high performance simulation tool for coupled thermo-hydrological transfers in the ground with freeze/thaw of the pore water, the so-called permaFoam solver (Orgogozo et al., 2019), with a good scalability tested on tier-2 and tier-1 supercomputers up to 4000 cores, and enabling to deal with large problems such as a 1.2 billion cells mesh problems (Orgogozo et al., 2015). In this project we would like to further develop the high performance computing capabilities of permaFoam and to apply them to perform highly challenging, watershed scale, centennial simulations of thermo-hydrologic transfers in long term environmental monitoring stations of arctic and sub-arctic regions. The goal is to give a proof of concept of the benefit that can be expected from the use of modern high performance computing techniques for cold regions sciences and engineering. In order to relevantly use this computational power, the permaFoam solver will be further developed to cope with all the determinant processes for water catchment hydrology and hydrogeology in boreal areas. As such it will: 1) integrates in a numerically efficient way the main external processes that control permafrost hydrology, such as bryophytic layer (i.e. moss and lichen cover) dynamics, solar radiation penetration and snow cover thermal insulation; 2) be validated for watershed scale modeling according to the current international standards, and parameterized based on field data sets from sites of long term monitoring of permafrost (eu-interact.org, IRN CAR WET SIB); 3) be used to perform 3D, watershed scale modeling of arctic and sub-arctic permafrost dynamics in response to climate change, thanks to its good parallel performances, which will be optimised for current supercomputers along the project (from the Tier-2 regional meso-centre to the Tier-0 PRACE european computing infrastructures). HiPerBorea will proceed in three main steps: 1) developing, testing and validating the needed numerical tool, 2) applying this tool to the already numerically studied Kulingdakan experimental watershed (Orgogozo et al., 2019) in order to establish an efficient, consolidated methodology for 3D watershed scale, centennial cryohydrologic modeling and finally 3) simulating the responses of four reference long term monitoring boreal catchments to various IPCC scenarios of climate change (CMIP5 projections). Technically speaking the goal is to test the limit size of the applications that can be dealt with the present performances of permaFoam (ability to deal with billion cells mesh, with up to 4000 cores on Tier-1 supercomputers), and to go beyond these limits along the project – towards 10 billions cells mesh, and tens of thousands of used cores on Tier-0 supercomputers.

The supply of raw materials to European countries is becoming under increasing pressure. France makes no exception to this situation which stimulates national initiatives in the field of mineral exploration. The mineral potential of granitic rocks is now being re-evaluated, and new types of granite-related mineralizations, such as granitic pegmatites, are being considered as exploration targets. Pegmatites form a significant proportion of Variscan terranes. They consist of complex internally zoned small to medium size (< 0.1-1 km3) bodies with marked variations in texture as well as in grain size, and are characterized by the occurrence of unusually large crystals. Granitic pegmatites are among the most fractionated igneous rocks on Earth. They concentrate a wide range of critical elements (Be, Cs, Li, Nb, Sb, Sn, Ta, W). Besides being potential sources of these elements, granitic pegmatites also produce quartz, feldspars and mica phases of interest for the mineral and ceramic industries. Since the renewal of mineral exploration must be accompanied by an update of the scientific knowledge, an integrated research programme coordinated at the French national scale is proposed on Variscan granitic pegmatites. The program can be viewed as a comprehensive test of the anatectic origin of pegmatites. It provides a re-evaluation of the classical model of granite derivation and constitutes a possibly new paradigm for these potential mineral resources. It comprises three main parts and includes fundamental conceptual aspects and others more practical allowing exploration operations to be optimized and pegmatite bodies to be targeted. (A) Classical models of pegmatite formation assume their derivation from less fractionated magmas represented in the field by granitic plutons. However, many examples of pegmatites show neither spatial nor genetic relations with granites, leading to the alternative model of pegmatitic melts being generated by crustal melting. In this new model, pegmatite emplacement would be determined by the ascension of pegmatitic batches from their source. It is proposed to test this new model on selected examples of pegmatite fields from Limousin, Galicia, Catalogna and Montagne Noire. In parallel, spatial analysis techniques will be applied on the same pegmatite fields to quantify the distribution of the pegmatite bodies. Finally, a numerical approach will be implemented to better constrain the physical processes associated with the ascent of pegmatite melts. (B) The genesis of pegmatites by low degree partial melting of crustal sources will be tested experimentally. Granitic to pegmatitic melts will be generated under variable P-T conditions, for different protoliths (including enriched lithologies) and under different fluid regimes. The resulting glasses and residual phases will be analyzed for major and trace elements (Li and critical elements). In addition, an isotopic characterization approach will be implemented to constrain the origin of pegmatites from the above districts. It will be based on the coupled use of 18O/16O and 7Li/6Li which allows the influence of the source and of magmatic differentiation to be deciphered. Finally, studies of crystallization kinetics will be carried out to constrain timescales of pegmatite consolidation. (C) the differentiation and internal evolution of rare-element pegmatites involves poorly known mechanisms such as melt immiscibility and boundary layer processes. These aspects will be studied experimentally in presence of HFSE metals (Nb-Ta-Ti) to assess their partitioning between immiscible melts and their concentration in boundary layer melts. In parallel, crystallization experiments from pegmatitic melts doped with rare metals will be performed to measure the partition coefficients of the various metals between HFSE minerals and to calibrate thermobarometers.