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 Interests
After an early interest in water-rock equilibrium relations in sedimentary basins and in calculating the distribution of species dissolved in natural waters (1974-1980), I became interested in the dynamics of geochemical phenomena. It is through its reaction-transport dynamics that a geochemical system develops a characteristic spatial pattern, a zoning, a texture. I studied stylolitization and metamorphic banding, intracrystalline oscillatory zoning of trace elements in calcite, orbicular zoning, and the genesis of agate banding and fibrosity, 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, which explicitly contains time and in particular space. Petrography is essential, both to help construct the reaction-transport models and to check their spatial predictions. (Models of the "reaction-path" type cannot predict where in the system will minerals form or how transport interacts with reaction(s), an inability stemming from the fact that the equilibrium condition, on which pathcalc models are based, is blind to space.)
A new feedback quantitatively modeled by mathematicians in the 80s - the reactive-infiltration instability - was based on my idea whereby CO2 evolved during petroleum maturation acidifies the aqueous pore fluid and spontaneously destabilizes the advancing planar dissolution front into preferential permeability "fingers" - through which the oil migrates. This feedback was later applied by others to the injection of magma into the crust. In current work, I have discovered which reaction triggers the reactive-infiltration instability perhaps responsible for "carving" the karst-sink morphology typical of many limestones and some basalts. Another new feedback we found (1993) helped explain how calcium carbonate crystals may spontaneously acquire oscillatory zoning of trace elements as they grow. And still another (1995) accounts for the systematically fibrous habit of quartz in agates: the self-accelerating growth of quartz destabilizes the advancing planar crystallization front into tiny fingers, each of which is a quartz fiber.
Starting in 1990 I became interested in the dynamics of weathering and dolomitization. Since both of these involve mineral replacement, understanding their dynamics required first understanding how replacement happens (1993-2001), which required connecting the old empirical concept of force of crystallization, renamed induced stress, to first principles of kinetics and rheology (1997, 2001). It turns out that the replacing mineral, via the local stress it generates as it grows, pressure-dissolves the host mineral. The induced stress self-adjusts so as to always equalize the volumetric rates of guest mineral growth and host-mineral pressure-solution: this is why all replacements are volume-for-volume -- a feature that petrographers have long reported. This fundamental discovery has led to a string of serendipitous insights. For example, we have discovered recently that the red clays known as terra rossa form by replacing the underlying limestone - a surprise to geochemists and soils scientists - and that the replacement, by producing acid which generates additional 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 new understanding of replacement physics also helps unravel the old problem of burial dolomitization, a paradigm of metasomatism at a moving reaction front: the dolomite-for-calcite replacement, because it is self-accelerating via the Ca++ pore fluid concentration, because it happens by pressure-solution, and because crystalline carbonates are strain-rate-softening, spontaneously passes 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. (Still another new feedback, one involving the induced stress, accounts for the striking equidistance between the veins.) None of these forward models and predictions - predictions all confirmed by observations - could have been imagined without the new view of replacement via pressure solution.
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
