Nature and Origin of Mineralizing Fluids in Hyperextensional Systems: The Case of Cretaceous Mg Metasomatism in the Pyrenees

<div>Conceptual cross-section of the North-Eastern Pyrenees region from Aptian to Turonian times with illustrations of (i) the fluid circulation model with two sources of primary brines. With respect to the hydrodynamics, the circulation of the two types of brines should have been temporally disconnected and (ii) the continuous interaction of these brines with the rocks leading to the formation of the whole magnesian metasomatic sequence (marbles → dolostones → talc; <svg height="11.6869pt" id="M29" style="vertical-align:-3.40333pt" version="1.1" viewbox="-0.0498162 -8.28357 90.6753 11.6869" width="90.6753pt" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink"><g transform="matrix(.013,0,0,-0.013,0,0)"><path d="M169 380V459C122 440 66 423 24 416V392C86 384 90 382 90 317V-135C90 -201 81 -207 17 -213V-240H253V-213C176 -207 169 -201 169 -125V6C182 -1 208 -11 238 -12C368 12 487 109 487 260C487 358 421 449 310 449C298 449 279 444 261 433L169 380ZM169 346C196 367 237 389 269 389C341 389 403 329 403 221C403 109 347 37 263 37C228 37 191 53 169 76V346Z"></path></g><g transform="matrix(.013,0,0,-0.013,6.929,0)"><path d="M380 106C343 72 306 56 265 56C195 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365 44 353 44 339C44 315 69 296 87 296C101 296 111 303 116 319C124 349 133 371 145 385C156 397 171 404 190 404C241 404 275 364 275 291V274C253 256 180 229 120 209C65 190 39 159 39 110C39 47 88 -12 159 -12C189 -12 237 25 277 52C282 35 288 21 301 8C312 -3 333 -12 348 -12L433 39ZM275 84C256 65 221 48 195 48C164 48 124 73 124 124C124 161 146 180 185 198C206 208 254 229 275 240V84Z"></path></g></svg> schists → <span class="nowrap"><svg height="9.65783pt" id="M30" style="vertical-align:-0.3499298pt" version="1.1" viewbox="-0.0498162 -9.3079 72.2243 9.65783" width="72.2243pt" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink"><g transform="matrix(.013,0,0,-0.013,0,0)"><path d="M390 111C344 68 312 56 269 56C212 56 118 102 118 241C118 346 175 401 241 401C277 401 312 388 342 360C350 352 355 349 361 349C372 349 394 371 394 392C394 403 391 411 378 422C362 436 329 449 288 449H287C250 449 190 432 138 392C71 341 37 274 37 197C37 90 112 -12 238 -12C297 -12 363 32 407 90L390 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514 133 568 201 568C274 568 318 519 318 435C318 349 255 267 193 193C144 135 87 78 32 23V0H405C417 45 427 89 440 131L412 140Z"></path></g></svg> represents the fact that the circulation of the brines derived from the seawater evaporation and derived from the serpentinization should have been temporally disconnected in the deposit.</div>

Geofluids

fig9

Figure 9

Figure 9: Nature and Origin of Mineralizing Fluids in Hyperextensional Systems: The Case of Cretaceous Mg Metasomatism in the Pyrenees 