GEOLOGICA CARPATHICA, 48, 1, BRATISLAVA, FEBRUARY 1997
ORIGIN OF LIFE ON EARTH: SELF-ORGANIZING
VESICLE-LIKE STRUCTURES IN CORDIERITE-ROCKS
FROM SOTO (ARGENTINA)
Institute of Mineralogy, Petrography and Geochemistry, University of Palermo, via Archirafi 36, 90123 Palermo, Italy
(Manuscript received October 5, 1995; accepted in revised form October 9, 1996)
At Orcoyana, in the Soto region (Argentina), two types of cordieritic rocks outcrop: a light variety and a
dark variety. Both of these contain, in very different quantities, very peculiar structures considered in literature as
porphyroblasts. In order to gain insight into their origin, a petrologic and geochemical study was carried out. In the
light of the new ordering principle, called ”order through fluctuation”, we applied the basic principles of self-organi-
zation dynamics to the Argentine structures. They appear to have ”self-organized” as colloidal dissipative structures
which formed in a self-organizing basic fluid. According to us, the origin of the Argentine structures involved a phase
separation process ensuing from spontaneous density fluctuations in critical conditions. As the phase separation pro-
ceeded the fluid comprised immiscible portions in a state of emulsion. When the segregated phase was very concen-
trated, the Argentine fluid exhibited three distinguishable phases. From a thermodynamic point of view, there was a
three-phase system, like a vesicle, with an interior, barrier and exterior.
Argentina, self-organization, cordierite-rocks, structural characters.
Self-organization is the dynamic principle underlying the
emergence of a rich world of forms manifest in various types
of structures, for example, biological, geochemical, and geo-
physical. It characterizes one of the two basic classes of
structures which may be distinguished in physical reality,
namely, the dissipative structures which are fundamentally
different from the equilibrium structures. Dissipative struc-
tures exhibit two different types of behaviour: near their
equilibrium, order is destroyed (as it is in isolated systems),
but far from equilibrium, order is maintained or emerges be-
yond instability thresholds (see e.g. Prigogine et al. 1972;
Nicolis & Prigogine 1977; Helleman 1980; Jantsch 1980;
Prigogine & Stengers 1984). As long as dissipative structures
exist, they produce entropy. However, this entropy does not
accumulate in the system but is part of a continuous energy
exchange with the environment. Entropy can also remain at
the same level or even decrease in the system. Structures of
this kind constitute the simplest case of spontaneous self-or-
ganization in open evolution (see e.g. Kauffman 1989; Ortol-
During research carried out on cordierite-rocks of the Soto
region (Argentina), very peculiar structures were discovered
(Gordillo 1974). The study of these structures and their host-
rock appears of considerable interest because it may provide
valuable petrogenetic information on self-organization dy-
namics which closely links together the animate and inani-
mate realms. By extrapolating from the most basic mecha-
nisms by which non-living organisms produce ”complexity”,
we seek to elucidate chemical mechanisms by which the
same fundamental processes could be achieved in living sys-
tems. In this paper petrologic, geochemical, and structural
features of the Soto rocks are presented. They show how
spontaneous organization worked into originating vesicle-
like structures in an Argentine basic colloidal fluid. Follow-
ing this a comparative analysis with membrane vesicles (pro-
tocells) is carried out.
The Soto region (Argentina) is part of the extensive Pre-
cambrian basement of the Sierra de Cordoba, which is com-
posed of high-grade gneisses, migmatites and intrusive gran-
ites. In this region, forming a roof over five small granite
hills, occur rocks containing cordierite in considerable and
unusual quantity (80–90 %). The country rock, El Pilón
granite, is a small pluton, outcropping over an area of ca. 16
, emplaced within quartz-biotite schists, some of which
remain as relicts in the granite and cordierite rocks. Because
of their beautiful blue colouring the Soto rocks have been in-
tensively quarried as ornamental stones. The principal out-
crops were found at Orcoyana in the quarries of Cerro Negro
and Tamain (65°00 W and 30°58 S, 800 m above sea level),
184 km NW of Cordoba City. The rock bodies show evident
signs of cataclasis and are more or less lenticular in shape.
They vary in length from 40 to 60 m and in thickness from 5
to 10 m. The Argentine rocks are essentially of two kinds:
1) a light variety, which is more abundant in the Tamain
quarry and is composed entirely of coarse-grained pale grey-
ish blue cordierite with accessory quantities of biotite, quartz
and plagioclase, 2) a dark variety, prevailing in the quarry of
Cerro Negro, rich in biotite (15–38 %) with accessories of
quartz and plagioclase (Schreyer et al. 1979). In some out-
crops the green line in the rock is due to scarce chlorite de-
rived from the alteration of cordierite or biotite. The remain-
ing minor components of the cordieritic rocks are: silliman-
ite, muscovite, apatite, sporadic tourmaline and rarely epi-
dote of the piedmontite type. Under the microscope the
cordierite crystals are generally xenoblastic, though idioblas-
tic crystals do occur. Cordierite is generally pure, but in some
cases sillimanite, zircon, biotite and quartz occur as inclu-
sions. Its optic axial angle (2V
α) is 78
. Biotite approaches
1–2 mm in length and occurs as brown lamellae often having
fringed ends. In the Cerro Negro rocks biotite is deformed,
partially replaced by sillimanite, and in some cases chlori-
tized. Sillimanite occurs in prismatic or fibrous aggregates
along with cordierite and biotite; it rarely occurs inside
quartz crystals. Interstitial quartz and plagioclase are rare,
but they greatly increase in quantity in some neighbouring
minor outcrops (Gordillo 1974). According to Gordillo
(1974), the Argentine cordierite-rocks owe their origin to a
metasomatic process which involved the allochemical addi-
tion of Al-Mg-Fe-Mn as a basic front, derived from the gran-
ite, to the enveloping quartz-biotite schists. Subsequently,
Schreyer et al. (1979) suggested that the cordieritic rocks
from Soto originated by anatexis. According to these au-
thors, rocks initially rich in biotite and sillimanite melted by
biotite + sillimanite + quartz = cordierite + melt.
In particular, the cordierite and residual biotite remained as
a sort of restite because they were refractary relative to the
consequent melt which migrated away and was largely incor-
porated into the neighbouring granitic magma.
silicate colloidal particles can be either lyophilic or lyo-
phobic depending on whether the energy obtained by their
net interaction is higher or lower respectively, than the
sum of their attraction energy and the repulsion energy of
the silicate fluid. This net interaction is dependent on tem-
perature, electrolyte concentration, interparticle distance
and the size and shape of the particles making up the fluid
(for further information on silicate colloidal dispersions,
the reader is urged to see Elliston 1984; Lucido & Triolo
1989; and Lucido 1993a,b).
In order to gain insight into the origin of the above sphe-
roids, several Argentine rocks were sectioned. Fig. 1 shows
an incipient phase separation process producing light ”micel-
lar” (micelle is a colloid particle in suspension obtained by
the reversible association of a large number of amphiphilic
molecules under the effect of the solvent) acidic particles in
the Argentine basic fluid. The chemical and physical proper-
ties of this fluid are similar to those indicated for a mud flow.
In particular, the solid phases comprising the body of the ma-
terial are the same: essentially hydrated aluminosilicates, sil-
ica gels, and hydrous ferromagnesian minerals. The only dif-
ference could be the temperature which is largely dependent
on burial depth. The melt from which spheroid develop is of
necessity, therefore, a colloidal system of mixed hydrosili-
cates. The unique properties reside in the large surface to
volume ratio of the dispersed phase, such that the surface en-
ergy becomes an important component of the total energy of
the fluid. In this respect, in fact, the acidic particles form a
strong contrast to the black basic portion and indicate colloid
formation; in the most general terms they are coacervate-like
particles, and essentially are cordieritic in composition.
Clearly visible are primary plate-like particles (platelets),
subspherical flocs and clusters of flocs. Organic structures of
this type have been suggested as being significant in biogen-
esis (e.g. Oparin 1924; Haldane 1929; Bernal 1954). Fig. 2
exhibits an emulsion-like structure. This textural relationship
indicates liquid immiscibility between the acidic and basic
portions. Liquid immiscibility occurs when the positive en-
thalpy of mixing outweighs the entropy of mixing term so
that the free energy of mixing is positive (Ryerson & Hess
1978). In practice, each element distributes itself between the
two liquids in such a way as to achieve a minimum energy
state. This implies that the structural characteristics of basic
melts more readily permit stable coordination of cations by
oxygen (Watson 1976). Therefore, the elements normally
forming framework structures are concentrated in the acidic
portions, whereas the less polymerizing ones are partitioned
into the basic portions (Hess 1971). The dimensions of these
portions suggest that the unmixing phenomenon is not relat-
ed to an early stage of evolution. The immiscible lighter por-
tions scattered in the black basic fraction of Fig. 2 have a
quartz-feldspathic composition. Fig. 3 shows a well-devel-
oped spotted texture. Fe-Mg rich basic spots (or spherules)
are dispersed in a clearer Al-Si rich phase. The spotted tex-
ture is inverted if compared with the texture showed in
Fig. 1. The latter shows light acidic particles scattered in the
basic matrix, whereas the spotted texture has basic spots dis-
persed in the acidic fraction. Card-house texture is incipient
all around the basic spots. Further textural evidence of the
In many outcrops the cordierite occurs as unusual subsphe-
roidal or oviform shapes. Most of these shapes range from 4
to 6 cm, but in some places they reach approximately 20 cm
in their greatest dimension (see Fig. 6d as an example).
These spheroids are often rimmed by aggregates of biotite.
The smaller spheroids are monocrystalline, the larger ones
are polycrystalline aggregates in a groundmass rich in quartz
and feldspar (Schreyer et al. 1979). In the literature (Gordillo
1974; Schreyer et al. 1979) these structures are considered to
be porphyroblasts. However, the following evidence sharply
contradicts this view: a) the rock does not have the typical
banded structure of a gneiss; b) the rock does not possess the
characteristic fabric of a hornfels, c) cordierite is coarse
grained (its grains generally measure from 2 to 10 mm) and
becomes only rounded by granulation; d) interstitial quartz
generally shows the effects of strain, whereas cordierite is
rarely affected; e) the fact that spheroids were soft and capa-
ble of being deformed (Figs. 5c and 6d) strongly suggest col-
loidal conditions of formation. In this respect, the study of
colloidal fluids as precursors of rocks has became more and
more important in any petrogenetic process, whatever the na-
ture of the fluid may be, magma, partial melt, or aqueous so-
lution (Lucido 1993a). Today, the term colloid is indistinctly
applied to all systems formed by entities having high specific
surfaces independently of the dispersed substance (see e.g.
Hiemenz 1986; Hunter 1987; Lyklema 1993). In particular,
ORIGIN OF LIFE ON EARTH 5
process forming colloidal aggregates in the Argentine basic
fluid is shown in Fig. 4. This figure exhibits blobs conceptu-
ally similar to ”reverse” micelles. They consist of a cordierit-
ic non-polar lyophobic portion (straight chain) attached to a
basic lyophilic polar portion. These reverse colloidal phases
originated when high concentrations of cordieritic material
was reached, because the basic polar portion is characterized
by the tendency to associate with itself rather than to remain
in close proximity to the cordieritic chain. Sometimes, in
both Cerro Negro and Tamain quarries, the dark basic and
the light cordieritic rock outcrop in continuity. Fig. 5 shows
the transition between the dark variety and the light variety.
More specifically, at the outcrop scale, Fig. 5 illustrates the
evolution (from bottom to top) of the phase separation pro-
cess which led to the formation of the subspheroidal struc-
tures. In particular, Fig. 5a exhibits incipient subspheroidal
structures. Fig. 5b represents a nucleation process all around
the basic spots: spheroids at different stages of growth are
evident. Finally, Fig. 5c shows well-developed oviform
structures always having a basic nucleus inside. From all the
above-reported data and from the geochemical and petrologi-
cal research that we have carried out (Lucido 1981, 1983a,
Phase separation in the Argentine basic fluid. ”Micellar”
cordieritic particles: platelets, flocs and clusters of flocs. Width of
figure is 10 cm.
Emulsion-like texture from an Argentine rock-sample. Ba-
sic and acidic immiscible portions showing lobate margins. Width
of figure is 60 cm.
Detail of Argentine rock exhibiting ”reverse or inverted
micelles”-type blobs. Note the radial organization of the light
cordieritic chains all around the basic polar portion. Width of fig-
ure is 13 cm.
Detail of Argentine rock showing reverse colloidal phases
forming spotted texture. Evident basic spots (or spherules) are
scattered in the light acidic portion. These spots are the future nu-
clei of the Argentine spheroids. Width of figure is 12 cm.
1990, 1993a,b; Lucido & Triolo 1983, 1984, 1989; Lucido et
al. 1994), the following genetic model appears explain all
features of the Argentine structures.
The genetic model
Phase separation and critical fluctuations
Under certain circumstances an immiscible new fluid
phase originates in the Argentine cooling basic melt (Fig. 1).
This new liquid phase has a more sialic composition than the
neighbouring basic melt. As the cooling fluid reaches the
critical consolution temperature (Tc), immiscible portions of
cordieritic composition in a state of dispersion form (see
Fig. 2). This results from density fluctuations in the basic
fluid at this temperature. The fluctuations involving high sur-
face charge ions (e.g. Fe, Mg, Ca, Mn, Ti, P) will be more ef-
fectively dampened than the others, resulting in a tendency
of the fluid to split into two portions, one enriched in high
charge ions and the other enriched in low charge ions (e.g.
Si, Al, Na, K). As the phase separation proceeds the fluid
will behave more like a fluid with short range correlations
(see Lucido & Triolo 1983, 1984). The effect of decreasing
the temperature is also to decrease the fluctuations that char-
acterize the critical behaviour. These space and time depen-
dent fluctuations are small for temperatures far above the
critical, T >> Tc, and grow in size near Tc.
In the unstable regime of phase separation, the linear theo-
ry of spinodal decomposition holds initially. The ultimate
limit of metastability is reached when the nucleation barrier
is no longer small,
F* is the nucleation Helmhotz
free energy barrier) is in the order unity (Binder 1984). At
this stage one can observe a smearing of the transition be-
tween nucleation and spinodal decomposition in this finite
regime (Lucido et al. 1994). This smearing is small in the
mean-field critical regime, but it becomes large when ap-
proaching unity, at the crossover region to the non-mean-
field critical regime. For a time smaller than the crossover
time (t < t
), very weak fluctuations will grow, but the
wavelength does not change i.e., the fluctuations ”compacti-
fy” (Heermann & Klein 1983) but do not coarsen. For t > t
one enters a basically nonlinear regime where the inhomoge-
neous structure coarsens. Under these conditions, a closely
related new phase appears in the melt, that is similar in den-
sity to a liquid. The densities of the liquids are different and
the interfacial free surface energy is high. However, decrease
in the magnitude of the interfacial free surface energy as the
result of cooling and/or coalescence of the differentiated par-
ticles is not negligible. As a consequence, we find spots of
dark (Fe-Mg rich) phase dispersed in a clearer phase richer in
elements forming framework structures, particularly Al and
Si (see e.g. Fig. 3).
Three different stages showing the evolution in time (from bot-
tom to top) of the formation process of the Argentine structures. a —
(initial stage) — immiscibility at a late stage of its evolution. Note that
in the right upper part of the photograph there is a first well-developed
subspheroidal structure. b — (intermediate stage) — cordieritic materi-
al nucleating all around the basic spots. c — (final stage) — well devel-
oped subspheroidal or oviform structures. Note that spheroids were soft
and capable of being deformed. Width of figure is 60 cm.
Colloid formation near the metastable state
If temperature and pressure are sufficiently high, any fluid
consists of a single liquid phase, that is, the small condensed
species which form the liquid contain a small number of at-
ORIGIN OF LIFE ON EARTH 7
oms. On cooling, however, when a given portion of fluid
contains a few hundred atoms or more, and the structural or-
der of atoms in the species has a longer range than is normal
in liquid, it must be regarded as a separate immiscible phase
and the system will be colloidal. In this manner, the forma-
tion of a colloidal system leads to inhomogeneities in the
chemical composition. In particular, during the dispersion of
the Argentine cordieritic material C in the basic fluid B, su-
persaturation conditions are created in which molecular and
ionic units combine to form assemblies similar to micelles.
Fig. 1 shows three types of ”micellar” cordieritic particles:
a) platelets, namely, primary plate-like dispersed particles,
b) subspherical particles or flocs, and c) clusters of flocs.
The interaction between platelets may result in three differ-
ent modes of particle associations: 1) edge-to-edge, 2) edge-
to-face, and 3) face-to-face. The edge-to-face and edge-to-
edge associations lead to three-dimensional voluminous
card-house textures that generate flocs (see Lucido & Triolo
1989). Otherwise, the thicker and larger particles which re-
sult from face-to-face associations are tactoids.
As long as the temperature of the fluid remains near the
critical consolution temperature, the colloidal dispersion is
metastable. A metastable state is characterized by an affinity
which is not zero, but has a zero velocity of reaction (De
Donder & Van Risselberghe 1936). Metastable states may
thus persist over great lengths of time. Moreover, during liq-
uid immiscibility, surfaces of a C cordieritic particle may be
solvated to form C-B interfaces (see stage 2 of Fig. 8). So, if
is the free energy of association of C molecules and
is the free energy of association of B molecules,
will be the free energy of sorption of molecules C onto the
surfaces of B with the formation of an interface C-B. In the
metastable dispersion, C will be a lyophobic colloid and
(Lucido & Triolo 1989). That is, the
lyophobic colloid C has a characteristic property, a true inter-
face with a defined surface tension, which exists between the
disperse particles and the dispersing medium. As we shall
see in the next section, the formation of this interface is the
clue to account for the self-organization of the Argentine
Self-organization of Argentine structures
During phase separation, cordieritic platelets gradually
emerge in the cooling Argentine fluid (Fig. 1). When the flu-
id reaches the critical temperature, basic spots (or spherules)
in a bidispersed metastable state are obtained. In particular, a
migration of cordieritic platelets from fluid to basic spots
comes about (Figs. 2 and 3). Cooling damps the thermic mo-
tion of the fluid and generates in it ordered structures. In this
regard, Fig. 4 shows structures conceptually similar to ”re-
verse or inverted micelles”. As a matter of fact, cordieritic
particles are specifically absorbed by an acidic – basic inter-
face. Considering the chemical properties of the two liquid
portions, it is inferred that the particle charges have the same
sign but the potentials of the individual particles are differ-
ent. In such a case, the magnitude of the repulsion energy is
determined by the particles with the lower potentials (Yariv
Four different stages showing the formation of a single Argen-
tine spheroid. a — photograph showing the initial stage: single basic
spot or spherule having nothing or very little cordieritic material
around it; width of figure is 3.5 cm. b — the increased accretion
around the entire basic spot forms a cordieritic corona (block-house
structure); width of figure is 4.5 cm. c — the further accretion of
cordieritic material around a basic spot forming well-developed
spheroid; width of figure is 12.5 cm. d — photograph showing the fi-
nal stage: a big cordieritic spheroid showing a biotitic basic nucleus
inside and a thin border having the same composition on the outside.
Note light phases within the nucleus; width of figure is 19 cm.
& Cross 1979), that is, by the cordieritic liquid particles. Fur-
thermore, the higher potential of the basic polar group can
change the radius but not the strength of the interacting force
(e.g. Sonntag & Strenge 1972). Thus, since the cordieritic
material is nonpolar, bonds between cordieritic and basic
components are weak and the interaction energy occurring at
the interface is low. In this manner, subject to available ener-
gy flows on or near the Earth’s surface, matter organizes it-
self toward those states we regard as central to life.
It is obvious that on the surface of a basic spot (see
Fig. 6a) all sites are equally susceptible to sorption, and
therefore the maximum possible value of the number of par-
ticles absorbed per unit of area corresponds to the state when
the entire surface is occupied by the absorbed particles, and
is determined by the surface area occupied by the sorbed par-
ticles. In the case of particles having a highly elongated
shape, as for example the cordieritic chains, the area they oc-
cupy on the basic spot surface depends on their position,
whether they are horizontal or vertical, the latter orientation
giving a greater density of absorbed particles (Lucido & Tri-
olo 1989). As a consequence, the maximum possible num-
ber of particles absorbed per unit area is not constant, but
increases with concentration. In a first stage, card-house
texture is formed around the basic spot. Successively, as
sorption on the basic surface increases, block-house texture
is formed (Fig. 6b). As the mean separation of cordieritic
sorbed particles further increases, dense packing is attained,
resulting in interaction between neighbouring sorbed parti-
cles (Fig. 6c). This interaction brings about the closure of the
cordieritic layer into a vesicle-like structure. There is a de-
crease of Gibbs free energy accompanying the formation of
this structure; more specifically, it represents a local free-en-
ergy minimum. In other words, this interaction results in a
greater tendency for cordieritic particles to be sorbed onto
the basic spot surfaces. In fact, the surface-absorbed particles
are compacted in continuous layers (coronas) in which lyo-
phobic bonding occurs. Subsequently, these layers coarsen
and form thick layers of finite extent all around the basic
spot. In practice, the basic spots act as nucleation centers.
They are the loci around which, antagonistically, the segre-
gated phases place themselves. Field-relationships indicate
that the growth (acidic accretion) of a single spheroid with
time is in accord with the general evolution of the rocks from
basic to acidic (see Fig. 5). Evidently, as single spheroids
grow the light variety of the outcropping rock increases. In
some cases, the accretion towards the basic spots occurs at a
lower rate. In this event, to obtain the same amount of mate-
rial against the dark spots, a longer accretion period may be
necessary. Thus, depending on circumstances, accretion may
occur more or less quickly, generating in time, different-tex-
tured zones. They are due to variation in the rates of growth
and nucleation during the evolution of the fluid. These tex-
tural variations represent modifications in the distribution of
kinetic energy and therefore suggest a fluctuation of the fluid
cooling conditions. Finally, with time, we may even expect
to see a well defined biotitic border (see Fig. 6d) separating
the neighbouring matrix from the thick cordieritic layer. At
this stage of the process (ripening) the vesicle-like structure
is completed. The interior fluid, at first, reflects closely the
composition of the environment at the time of spheroid clo-
sure. There are, in fact, two basic fluid phases, the inner and
outer, separated by the cordieritic layer.
Summing up, the above structure provides in one sweep
for: (1) the partition of the world into interior and exterior,
and (2) a three-phase system enabling transborder couplings.
This three-phase system consists of a polar interior (corre-
sponding to a in Fig. 8), a nonpolar intermediate zone (corre-
sponding to b in Fig. 8) and a polar exterior (corresponding
to c in Fig. 8) — the environment. We think that this abrupt
transition may have led also to the directed chemistry or vec-
torial chemistry necessary for the origin of life.
Comparison with membrane vesicles
The Morowitz model
Very recently, Morowitz (1992) presented a radically new
model of the origin of life on Earth 4 billion years ago. He
Micellar colloidal structures. A — A biomolecular leaflet
of amphiphiles, or bilayer; the black dots represent lyophilic polar
heads and wavy lines represent lyophobic tails. B — Bilayer vesi-
cle (after Yariv & Cross 1979).
Schematic illustration of the formation of a single spher-
oid. 1 — Origin of a basic spot in the Argentine fluid; 2 — for-
mation of a reverse micelle-like structure, after separation of
cordieritic particles; 3 — card-house structure around the basic
spot; 4 — block-house structure around the basic spot; 5 — con-
tinuous layer origin around the basic spot; 6 — layer thickening;
— origin of a thin exterior border.
ORIGIN OF LIFE ON EARTH 9
postulated that core metabolic processes have not changed
with time. We can thus use a study of modern biochemistry
to advance our knowledge about the chemical processes of
the earliest prokaryotes
. According to Morowitz (1992),
events of a purely statistical order from disorder occurred in
the primitive chemical domain giving rise to identifiable,
distinguishable, and persistent structures. These structures
must by their very nature have been nonequilibrium entities
and likely far from equilibrium on some time scale. All non-
equilibrium structures are subject to thermal decay, hence the
necessity of processing matter and energy to preserve a pat-
tern following the second law of thermodynamics. Persis-
tence of a far-from-equilibrium entity can occur only by a re-
prieve from the degradation wrought by random thermal
motion. Persistence of a pattern can occur by replication, and
as long as the pattern gives rise on average to more than one
similar pattern, that pattern will exponentially increase.
However, once matter and energy become necessary for per-
sistence, the entities are in competition for molecules and en-
ergy source from the environment. The systemic forces lead-
ing to speciation exist as long as there is any memory at all,
memory being implied in the notion of persistence. The syn-
thesis requires a flow of energy from a source, and this ener-
gy eventually leaves the system.
Morowitz (1992) developed a model in which cells origi-
nate first, proteins follow, and genes evolve last. He pro-
posed that the first step toward the origin of life was the
spontaneous condensation of amphiphilic bilayers (Fig. 7).
The bilayers are not linear structures but are sheets which
easily may fold to form a closed vesicle, or protocell. Be-
cause the vesicle emerges with such unique properties, it is
important to reiterate that it is a spontaneously forming struc-
ture representing local minimum free energy. Following vesi-
cle formation two phases are present in the system, the inner
and the outer, separated by the amphiphilic bilayer. Since the
lyophobic portion of the bilayer has a very low solubility for
polar compounds, the inner and outer phases can maintain
different chemical compositions. Moreover, a bilayer has a
very high electrical capacitance so that a small charge sepa-
ration can lead to substantial transbilayer voltages. Another
property of the vesicle is that it forms surfaces and opens the
possibility of heterogeneous phase catalysis. Again, vesicle
allows for pH differences, and oxidation-reduction differenc-
es between the two phases. The above differences open up
the possibility of electrochemical and protonchemical reac-
tions. Life on Earth as we know it must have been associated
with liquid water (Lucido 1982, 1983b, 1989a) since its be-
ginning. Nonaqueous life forms have been suggested, but the
principle of continuity and the evidence from petrology and
geochemistry (Lucido 1989a,b, 1990) demand that biogene-
sis be considered as a series of events occurring in a watery
milieu. Water is an essential metabolite as well as a solvent;
it is also the source of protons in membrane protonchemistry.
As before mentioned, the vesicle forms a local free-energy
minimum for certain classes of amphiphilic molecules in an
The interior solution, at first, reflects closely the composi-
tion of the environment at the time of vesicle closure. Fol-
lowing this, vesicles can grow by the insertion of slightly
water-soluble amphiphiles into the existing membrane. At
this stage cellular life began, and also the origin of species
started. This model fulfills the principle of continuity and has
the distinct advantage of being testable. It is also supported
by evidence from biology, biochemistry and biophysics.
Comparing the rock-structures occurring in the Argentine
outcrops with membrane-vesicles, it is possible to distin-
guish the following important analogies.
1 — Membrane-vesicles and Argentine structures are a
simple case of spontaneous self-organization.
2 — Phase separation phenomena are in both cases respon-
sible for the origin of the primary particles from the environ-
3 — In both cases, from a physico-chemical point of view,
the genetic environment was a colloidal one.
4 — In both, order is processed from disorder, a character-
istics of the transition from a homogeneous chemical domain
to a heterogeneous one.
5 — The lyophobic or lyophilic character of matter is in
both cases absolutely central to its structure and function.
6 — The formation of the Argentine structures and mem-
brane-vesicles involved an abrupt transition forming a three-
phase system: interior, barrier, and exterior (see a, b and c in
7 — As a result, in both cases, increased amounts of parti-
cles are segregated, and these cause the growth of the indi-
vidual structures, by addition to the existing layers.
On the basis of the above-mentioned analogies and consid-
ering the foregoing results the following is proposed.
a — The Argentine spheroidal or oviform structures are
b — The Argentine structures and membrane-vesicles are
formed by means of a unique mechanism.
c — The sequence of the events which in time led to the
formation of a single spheroid is: 1) basic spot origin 2) re-
verse micelle-like 3) card-house structure 4) block-house
structure 5) continuous layer origin 6) layer thickening 7) ex-
terior border origin. This sequence is schematically indicat-
ed on Fig. 8.
d — In agreement with Morowitz (1992), our genetic mod-
el defines the characteristics of the simplest distinct au-
totrophic system that might have developed prebiotically.
The author would like to express his
sincere appreciation to Prof. J. V. Gonzales Segura and Prof.
N. A. Hillar Puxeddu of the Cordoba University (Argentina),
Mr. Nunzio Di Matteo and Mr. Benito Pennisi of the A.R.L.
co-operative society, Sicilristoro (Palermo), for their interest,
kindness and assistance in providing him with rock-speci-
mens. The writer is also extremely grateful to the two anony-
mous referees. This work has been supported by M.U.R.S.T.
(Ministero dell’Università della Ricerca Scientifica e Tec-
nologica) and by C.N.R. (Consiglio Nazionale delle
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