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P-T-X evolution of paleo- hydrothermal systems related to granites and active geothermal systems : the data from fluid inclusion studies M. Cathelineau and M.C. Boiron Thanks to coll. with CNR-IGG , G. Gianelli, G. Ruggieri, M. Puxeddu


  1. P-T-X evolution of paleo- hydrothermal systems related to granites and active geothermal systems : the data from fluid inclusion studies M. Cathelineau and M.C. Boiron Thanks to coll. with CNR-IGG , G. Gianelli, G. Ruggieri, M. Puxeddu Works on Larderello geothermal system from 1986 to 2007 and Alpi Apuane (Ch. Montomoli, Pisa Univ.) and coll. with O. Vanderhaeghe, J. Vallance, A.S. André on paleo-hydrothermal systems

  2. ������������������������� ����������������������� Meteoric fluids Crust Crustal fluids Mantle fluids mantle ���� ����������������

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  5. �������������������������������� ��������������������������� ������������������ ��������/�������/��������������/� �������� Optical microscopy, IR, UV microthermometry PTX Water-gas-salt system * Raman : gas, Cl ) ��,.���- LIBS : cations, trace elts % Na 3 I (u.a) )' ° ° �/0�� EOS ° ° 8 ( Li Ca Liquid-Vapour modelling Li *' ° ° /.� 6 Si ° ° ' 4 Mg ('' (+' %'' %+' )'' )+' *'' ��, ° ° �- 2 ° ° 740 660 580 ������������������������� λ λ (nm) λ λ

  6. �������������������� "���2 ��������2�5������2��������2 �!�2��$ % 2��4 % 2 ���������������������������(' �1 ��������������� ��������������������������������2������������������������������������� ������ ���������#��������/�����#���������2 �����������������������3����2� ������4������� ��2���2������2�����������������2�!�����3�������2�

  7. Development of accretion prism Low geothermal gradient Relief formation Meteoric fluids Meteoric fluids crust Crustal fluids mantle Mantle fluids Thermal evolution of the continental crust in subduction zones

  8. Meteoric fluids Crustal fluids Transition from crustal thickening to crustal thinning formation of metamorphic core complexes, horts and grabens, crustal cooling during thinning

  9. Meteoric fluids Crustal fluids Mantle fluids and heat Partial melting High geothermal gradients Gravitational collapse

  10. Continental convergence Thickening, and accretion Incipient melting Increase of temperature due to radioactive decay Partial melting Formation of an anatectic layer Pervasive melt migration Network of granitic veins Sense of melt migration (sills/ dykes feeding larger Intrusions) Exhumation / crystallization of the partially molten crust Orogenic collapse Extension of the upper Vanderhaeghe, 2001 crust

  11. magma Shallow brittle to ductile transition Divergent collapse (Vanderhaeghe and Teyssier, 2001) synchronous with late exhumation gravitanional collapse of the overthickened crust may be divergent or convergent with or without (brittle) extension of the upper crust Normal faulting Ductile thinning of the lower crust >> nearly isothermal decompression, followed by rapid cooling

  12. Gravitational collapse accompanied by shallow intrusion of leucogranites >> nature of the fluids involved in the local heat transfer, and cooling ??

  13. Fluid typology in past geothermal systems related to granites Northern Portugal

  14. Anticlinal de Valongo (D1v) Synforme de Bragança (D3v) Anticlinal de Marao (D1v) Antiforme de Miranda Complexe granitique Batholite de Villa Bassin de Morais do Douro (D3v) de Minho-Beira Real-Moncorvo WSW ENE km 10 0 -10 Complexe Allochtone Aut ochtone Hercynian granites Granites hercynien Allochtone supérieur Ordovicien moyen à Dévonien supérieur Ophiolite Quartzites Chevauchements majeurs Allochtone inférieur Complexe grauwackeux Chevauchements secondaires Paraautochtone Complexe gneissique Précambrien Northern Portugal (Miranda do Douro-Porto cross-section; after Ribeiro et al., 90) Fig. : Profil géologique Miranda do Douro (ENE) - Porto (WSW) (d’après Ribeiro et al., 1990, modifié)

  15. Northern Portugal

  16. Valongo anticline N130 ° E fault D3 shear zone Mineralised zone W E (N130 ° E) Au N30-60 ° E faults Syn to post D3 granite Post D3 granite Aplite

  17. Castromil Aqueous carbonic fluids Th ( ° ° C) ° ° 400 Aqueous fluids in 350 metamorphic rocks N115-140 N115- 300 140 ° ° E N90 ° ° Primary 250 Unoriented samples N30-60 N5 200 Primary (H2O-Vol) Primary Unoriented samples 150 (H2O-Vol) N30-60 ° ° E ° ° N90 ° ° E ° ° 100 0 2 4 6 8 10 12 14 16 Salinity (% wt % eq. NaCl)

  18. Castromil 300 Aplite intrusion P (MPa) 10 km lithostatic P 250 Reequilibrated 400 fluid inclusions (metamorphic fluids) 405 7 km lithostatic P 200 366 150 365 Greisen 4 km lithostatic P stage 357 100 331 Q3 gold stage 4 km Q1/Q2 Fe-S-As 50 stage hydrostatic P 335 284 312 0 150 450 100 200 250 300 350 400 500 T ( ° ° C) ° °

  19. Aqueous-carbonic fluids ! 400-450 ° ° C ° ° � Geopressured Local unmixing � pseudo-metamorphic fluids Blackschists � H 2 O- CO 2 CH 4 -N 2 � δ 18 O =9-12‰ δ δ δ >450 ° ° C ° ° 0.0015<Br/Cl<0.005 � � Recharge fluids: Meteoric waters � Resident aqueous fluids � 1-3 eq.wt% NaCl δ 18 O = -1/+4‰ δ δ δ 0.0003<Br/Cl<0.001 + 120-150 ° ° C ° ° Mixing zone Au-ore deposit 180-250 ° ° C ° ° Residual hot δ 18 O = 0/+6‰ δ δ δ aqueous fluids 250-300 ° ° C ° ° 1-3 eq.wt% NaCl

  20. Late intrusion in French Massif Central : Intense microfracturing and fluid percolation N 116 Granite γ 1 - coarse ASA96-4 grained ASA96-3 Granite γ2 - RAZES ASA96-7 Lac ASA96-6 . de F.RN20 St Pardoux Granite γ3 − fine grained faults 114 e i m samples é o N . F Large hydrothermal 113 pipes 138 140 FANAY PENY 132 112 MARGNAC 500 m 805 522 519 520 521 524

  21. ASA96-3 Aqueous inclusions N N Vw and Lw 1 N N=56 N=20 Aqueous inclusions All data . Lw 2 , low salinity . . . . . . . . . . N . . ° ° N N=9 ° N=27 ° Aqueous - carbonic ° 2 phases Lc-w 2 Aqueous-carbonic + 3 phases Lc-w 1 Aqueous inclusion Lw 2 , low salinity

  22. 300 (a) (b) 320 Ma 325 Ma 250 90 ° C/Km 200 (Litho) (c) Lc-w1 P (MPa) 150 Litho.P Lc-w2 Lw2 m 100 K / C 0 9 ° ) o r d y H ( Hydro.P 50 V/L 0 100 200 300 400 500 600 700 T ( ° ° C) 305 Ma ° °

  23. P Metamorphic peak conditons Progressive exhumation Decompression and abnormal heat flows Effects of quick penetration Local abnormal heat flows of cold meteoric waters ° C/km 25 ° ° ° T

  24. 6��������5������������� ��������������������� ������ ������������������� "#�������#����� $���������� %� �!��������� ��� ���� &��� ������!�� '� ��������� �������� ����������������������������� ���������

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