, ii) W-Au granite-related 163 mineralization (IRGDs), and iii) Ba-Sb vein mineralization There is a consensus that the Pb-Zn-Ag 164 mineralization formed in epithermal conditions during a late Permian-Triassic magmatic-hydrothermal 165 event disconnected from an older W-Au mineralization Pb-Zn-Ag mineralization developed during the D3 left-lateral 167 wrench event that had a transtensional component. A low-temperature Ba-Sb mineralization in veins is 168 also present in the district, B3, B4, and within the Tighza fault quartz vein system, 2012.
, 172 For additional detailed geological data and descriptions concerning the geological setting, refer to 173, 2015.
, ) and temperatures up to 580°C, and associated with intrusion of calc-alkaline suite granitic 180 magma, (ii) a second stage responsible for the deposition of Au-As-Bi-Te, and (iii) a third stage that 181 includes base metal (Zn-Cu) mineralization. The three stages occurred during the emplacement- 182 cooling cycle of granitic intrusive activity. The pressure conditions associated with stages 2 and 3 are 183 close to the hydrostatic regime (ca. 550 bars) with temperature around 300°C. Stages 1 and 2 are 185 the emplacements of the granitic intrusions and the mineralized veins were controlled and coeval with 186 the D2 right-lateral transtensional deformation. The W-Au mineralization is spatially associated with 187 the main granitic intrusions (Figure 2), however, W-Au mineralization is also found far from the four 188 outcropping granitic stocks (Figure 2) This spatial relationship suggests that the mineralizing system 189 is not restricted only to the close vicinity of outcropping stocks and dykes. In addition, Cheilletz and 190 Isnard (1985) identified a hydrothermal metamorphic aureole, centered on the Mine/Mispickel/Kaolin 191 granitic stocks, that encompasses the W-Au occurrences (dashed contour in Figure 2) As the extent of 192 this metamorphic aureole is large relative to the outcrop extent of the granitic stocks and dykes, the 193 presence of a larger plutonic body, hidden at depth, was proposed. This hypothesis has been recently 194 re-proposed by, Because of this relationship to the 195 igneous intrusive bodies, igneous geochemistry, and the origin/nature of the associated fluids, a model 196 of Intrusion-Related Gold Deposits (IRGD) has been proposed for the Tighza W-Au mineralization, 2015.
, Subtle distinctions led) to classify this W-Au 198 mineralization as " porphyry-style " , a deposit group that includes and/or overlaps the IRGD definition 199 according to different authors and classifications, 0200.
, heat transfer in a porous medium was 399 coupled with Darcy law, and mass conservation is applied. The basic numerical scheme was tested and 400 validated by reproduction of different benchmark tests, Gerdes et al, 1998.
, Permeability was considered to be depth-dependent, and fluid density 402 and viscosity were considered to be temperature-dependent. All governing equations, physical laws, 403 boundary conditions, and initial thermal and fluid flow regimes are detailed in the Appendix, p.404, 2004.
, see their initial stage on Figure 15A) This EHE 499 developed within the W1 north vein close to the Mine granite which yields very homogenous Ar/Ar 500 ages on micas of around 286 Ma. Because the EHE and the major hydrothermal event leading to the 501 " Main " type W-Au deposition are both clearly related to magmatic activity, the presence of a 502 difference for the two mineralization types in the ages obtained using the same radiometric method is 503 consistent with the modeling results. The 3D hydrothermal models provide a possible answer for this 504 difference. Indeed, the numerical model we assumed a magmatic emplacement period lasting 3, 2015.
, At Tighza, this hypothesis is coherent with the 507 long-lasting 295-280 Ma magmatic-hydrothermal event responsible for the W-Au mineralization and 508 related (hidden) granite intrusion proposed by The application of R 2 AI in the 509 Tighza 3D model shows that the favorable physical conditions were detected during two periods 510 (Figure 8) The first period corresponds to a long-lived period of " Pre-Main " type mineralization 511 during which a shallow pluton (less than 8 km depth) is able to create PZM during the emplacement 512 period The second period corresponds 514 to a shorter-lived period of, Pre-Main " type mineralization might then correspond to the EHE observed in the W1 513 north vein system (292 Ma stage in Figure 15 of Marcoux et al. Main " type mineralization, gathering the stages I (W), II(Au-As-Bi-Te), 2006.
, To investigate this time-lag between these two periods of hydrothermal activities; during the 518 emplacement phase of intrusion and the initial cooling phase, the isotopic closure temperatures 519 muscovite and biotite were mapped in the 3D numerical model (Figure 10) The values of 350° and 520 450°C were used for the closure temperatures of muscovite and biotite, respectively (Spear 1993; Villa 521 1998) This temperature range is shown by grey regions in Figure 10. The mapping results show 522 clearly that the W1 structure, which hosts PZM during early pluton emplacement (Figure 8) is colder 523 than the Ar 40 /Ar 39 closure temperature of biotite at the time of the hottest phase (i.e. 10 Myrs; Figure 524 10) while the temperature in the granite core is still higher than the closure temperature range. The 525 same temperature range crosses the granite after 0.04 Myr of cooling (Figure 10). Thus, due to 526 advective heat transfer in permeable zones, a time-lag is observed between the emplacement of the 527 intrusives and related proximal high permeability zones (i.e. W1 structure) This result is in accordance 528 with theoretical models of Eldursi, which the presence of PZM before the hottest phase 529 of the pluton was demonstrated. 530 In the 3D hydrothermal modeling, this time-lag (ca. 2.8 Myrs) is shorter than the one observed 531 in the field, with the Tighza natural case showing a time-lag of around 5 Myrs, 2009.
, the time-lag (gap) 533 between Pre-Main " and " Main " types of mineralization increases because the intruded magma 534 creates warm conditions in which the fronts of closure temperature of muscovite and biotite need a 535 longer time to pass through the W1 vein and then the parent granite. Consequently, the time-lag 536 between the mineralization formed in W1 and the parent granite becomes longer. Although the 537 numerical modeling did not take the chemical and deformation contributions into account, the results 538 show that the time-lag between mineralization and the parent intrusion can be produced by favorable 539 physical conditions for mineralization before the cooling period (crystallization phase) This time-lag 551 proposed by, 532 From the modeling work, 2015.
, Lazaar General Manager of the CMT Mining Company, for free access to 561 the Tighza mine On the mine site, we are indebted to M. Ouchtouban, T. Montoy, H. Bounajma for 562 field, logistic assistance, and access to mining documents. We extend our sincere gratitude to M. Rossi 563 and an anonymous reviewer for their help to improve the first version of the manuscript, Special 564 thanks to David Quirt (AREVA Resources Canada Inc.) for his constructive remarks and final review 565 of the manuscript
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