Enrique Merino
Professor Emeritus
Geochemistry
Education
- Ph.D., l973, Geology and Geophysics, University of California at Berkeley
- Ingeniero de Minas, l967, School of Mining Engineering, Madrid
Research
After an early interest in water-rock equilibrium relations in sedimentary basins and in calculating the distribution of species dissolved in natural waters, I became interested in the dynamics of geochemical phenomena. It is through its reaction-transport dynamics, not through equilibrium, that a geochemical system may develop a characteristic spatial repetitive pattern. With collaborators, I studied stylolitization and metamorphic banding, intracrystalline oscillatory zoning of trace elements in calcite, orbicular zoning, the genesis of agate banding, the genesis of zebra veins in dolomites and in serpentinized ultrabasics, and the genesis of Banded Iron Formations – all cases of what I called in 1984 geochemical self-organization, and all produced by disequilibrium and feedback. Understanding and modeling each of those self-organizational patterns requires finding out which feedbacks take place in its genesis and incorporating them into the continuity equation. Petrography is essential, both to help construct the reaction-transport models and to check their spatial predictions.
Starting in 1990 I became interested in the geochemical dynamics, or chemical geodynamics, of larger scale phenomena, weathering and dolomitization, ore deposit genesis and metamorphism. Since these involve mineral replacement, understanding their dynamics required first understanding how replacement happens. Replacement of B by A is identified by its characteristic spatial properties – to preserve both volume and morphological details (as ghosts). These properties in turn require that A growth and B dissolution be strictly simultaneous and take place at mutually equal rates. The coupling factor that equalizes the rates turns out to be the growth-driven stress. The guest mineral, via the local stress it generates as it grows, pressure-dissolves the adjacent host mineral. The induced stress self-adjusts so as to always equalize the volumetric rates of guest mineral growth and host pressure-solution: this is why replacement preserves solid volume – the feature that petrographers have long reported. This discovery has led to insights into the dynamics of weathering (Merino et al, 1993), of bauxite (or terra rossa) formation (Merino & Banerjee, 2008), of metamorphic reactions such as the replacement of periclase by brucite in marbles, and of burial dolomitization (Merino and Canals 2011).
For example, we have discovered petrographically that the red clays known as terra rossa, or bauxite, form not residually or as a sediment as long held, but by replacement of the underlying limestone -- a surprise to geochemists and soils scientists -- and that the replacement, by releasing acid which generates additional dissolution porosity, may trigger the reactive-infiltration instability that "carves" the dissolution funnels and sinkholes of the karst limestone that contains the terra rossa itself -- a surprise to geomorphologists.The chemical dynamics imposed by the replacement ends up explaining why bauxite and karst are associated.
Understanding the physics of replacement helps unravel the old problem of burial dolomitization, a paradigm of metasomatism: the dolomite-for-calcite replacement, because it is self-accelerating via the Ca2+ pore fluid concentration, because it happens by pressure-solution, and because crystalline carbonates are strain-rate-softening, spontaneously passes -- continuously -- from replacive to displacive dolomite growth, and this is why characteristic sets of displacive, self-organized dolomitic zebra veins occur in burial dolostones the world over.
Publications
Merino E, Canals À (2011) Self-accelerating dolomite-for-calcite replacement: Self-organized dynamics of burial dolomitization and associated mineralization. Amer J Science, v.311, p.573-607; DOI 10.2475/07.2011.01 [pdf]
A. Banerjee, E. Merino (2011) Terra rossa genesis by replacement of limestone by kaolinite: Part III, Dynamic quantitative model. J. Geology, v.119, p. 259-274. [pdf]
J. G. Meert, F. Pruett, E. Merino (2009) An ‘inverse conglomerate’ paleomagnetic test and timing of in-situ terra rossa formation at Bloomington, Indiana. J. Geology 117, 126-138. [pdf]
Wang Yifeng; Xu Huifang; Merino E., & Konishi, Hiromi (2009) Generation of banded iron formations by internal dynamics and leaching of oceanic crust. Nature Geoscience, v. 2, p.781-784 plus Supplementary Info [pdf]
E. Merino, A. Banerjee (2008) Terra rossa genesis, implications for karst, and eolian dust: A geodynamic thread. J. Geology, v. 116, p. 62-75. [pdf]
Merino E., Canals À, and Fletcher R.C. (2006) Genesis of self-organized zebra textures in burial dolomites: Displacive veins, induced stress, and dolomitization. Geologica Acta; v 4, p.383-393 [pdf]
Merino E (2005) Very-high-temperature, closed-system origin of agates in basalts: New model, old and new evidence. In Kile D, Michalski T, & Modreski P, eds., A Symposium on Agate & Microcrystalline Quartz; Golden, Colorado, Sept 9-11 [pdf]
Zhang Y, Person M, and Merino E (2005) Hydrologic and geochemical controls on soluble benzene migration in sedimentary basins. Geofluids v. 5, p. 83-105. [pdf]
Fletcher R. and Merino E. (2001) Mineral growth in rocks: kinetic-rheological models of replacement, vein formation, and syntectonic crystallization Geochim Cosmochim Acta, v.65, pp. 3733-3748.[pdf]
Merino E. and Wang Yifeng (2001) Self-organization in rocks: Occurrences, observations, modeling, testing - with emphasis on agate genesis. In: H-J. Krug & J. H. Kruhl, eds., Non-Equilibrium Processes and Dissipative Structures in Geoscience, Self-Organization Yearbook, v.11, p.13-45; Berlin, Duncker and Humblot, 380 p.[pdf]
Merino E, Nahon D, and Wang Y (1999) Simultaneous replacement, redox, and self-organization in the weathering of Mn-rich shales at Moanda, Gabon. In Armannsson, H., ed., Geochemistry of the Earth's Surface, Balkema, Rotterdam, p. 393-395.
Merino E. & Dewers T. (1998) Implications of replacement for reaction-transport modeling. J. Hydrology, v.209, p. 137-146. [pdf]
Nahon D. and Merino E. (1997) Pseudomorphic replacement in tropical weathering: Evidence, geochemical consequences, and kinetic-rheological origin. Amer. J. Science, v. 297, p. 393-417 [pdf]
Merino E., Girard J.-P., May M. T., & Ranganathan V. (1997) Diagenetic mineralogy, history, and dynamics of Mesozoic arkoses, Hartford rift basin, Connecticut. J. Sedim. Research 67, 212-224. [pdf]
Merino E, Wang Yifeng, and Deloule É (1995) Genesis of agates in flood basalts: Twisting of chalcedony fibers and trace-element geochemistry. Amer. J. Science 295, 1156-1176. [pdf]
Wang Y. and Merino E. (1995) Origin of fibrosity and banding in agates from flood basalts. Amer. J. Science 295, 49-77. [pdf]
Wang Yutian, Wang Yifeng, Merino E (1995) Dynamic weathering model: Constraints required by coupled dissolutn & pseudomorphic replacement Geochim. Cosmochim. Acta 59, 1559-1570.[pdf]
Wang Yifeng, Nahon D, and Merino E (1994) Dynamic model of the genesis of calcretes replacing silicate rocks in semi-arid regions. Geochim. Cosmochim. Acta 58, 5131-5145. [pdf]
Wang Y. and Merino E. (1993) Oscillatory magma crystallization by feedback between the concentrations of reactants and mineral growth rates. J. Petrology 34, 369-382.[pdf]
Merino E., Nahon D., and Wang Y. (1993) Kinetics and mass transfer of replacement: application to replacement of parent minerals & kaolinite by Al, Fe and Mn oxides during weathering. Amer. J. Science v. 293, p. 135-155. [pdf]
Merino E. (1992) Self-organization in stylolites. American Scientist 80, 466-473. [pdf]
Wang Y. and Merino E. (1992) Dynamic model of oscillatory trace element zoning in calcite: inhibition, double layen, and self-organization. Geochim. Cosmochim. Acta 56, 587-596. [pdf]
Merino E., Harvey C. & Murray H. (1989) Aqueous chemical control of the tetrahedral aluminum content of quartz, halloysite and other low-temperature aluminosilicates. Clays & Clay Minerals 37, 135-142.[pdf]
Ortoleva P., Merino E., Moore C., and Chadam J. (1987) Geochemical self organization, I. Feedbacks and quantitative modeling. Amer. J. Science 287, 979 1007.[pdf]
Ortoleva P., Chadam J.,Merino E., and Sen A. (1987) Geochemical self organization, II. The reactive infiltration instability in water rock systems. Amer. J. Science 287, 1008 1040.[pdf]
Ortoleva P, Auchmuty G, Chadam J, Hettmer J, Merino E, Moore CH, & Ripley E. (1986) Redox front propagation and banding modalities. Physica D, vol 19, p. 334-354. [pdf]
.Merino E. (l984) Survey of geochemical self-patterning phenomena. In Nicolis G and Baras F (eds), Chemical Instabilities: Applications in Chemistry, Geology, and Materials Science, NATO Adv. Sci. Series C, v. l20, p. 305-328, Reidel Publ. [pdf]
Merino E, Ortoleva P, & Strickholm P (1983) Generation of evenly spaced pressure solution seams during (late) diagenesis: a kinetic theory. Contrib. Mineral. Petrology, 82, 360 370.[pdf]
Ortoleva, P., Merino, E. and Strickholm, P. (l982) Kinetics of metamorphic layering in anisotropically stressed rocks. Amer. J. Science, v. 282, 6l7 643. [pdf]
Merino E (1979) Internal consistency of a water analysis & uncertainty of the calculated distribution of species. Geochim Cosmochim Acta 43, p. 1533-1542. [pdf]
Merino E. (l975) Diagenesis in Tertiary sandstones from Kettleman North Dome, California-I. Diagenetic mineralogy: J. Sed. Petrology 45, 320-336. [pdf]
Merino E. (l975) Diagenesis in Tertiary sandstones from Kettleman North Dome, California-II. Interstitial solutions: distribution of aqueous species at l00oC and chemical relation to the diagenetic mineralogy: Geochim. Cosmochim. Acta 39, l629-l645. [pdf]
Editorial Service
Associate editor, - J. Sedimentary Petrology 1986-1992
-Geochim. Cosmochim. Acta, 1992-2002
