Thematic Articles

Complex systems display diversification in type, patterning, and behavior over time through varied selective mechanisms. Such systems are observed in numerous natural and cultural contexts, including nucleosynthesis, minerals, prebiotic organic synthesis, languages, material culture, and cellular life. These systems possess such qualitatively similar characteristics as diversification into new environments (radiation), episodic periods of innovation (punctuation), and loss of types (extinction). Comparisons among these varied systems thus point to general principles of complexification.

The ability of organisms to synthesize skeletons and functional biomin- Too stucure to one of the mot remartable agents in the timeline of mineral evolution. The relatively abrupt rise of such forms in the fossil record marks the beginning of a new type of chemistry whereby biology develops a playbook of mineralization processes whose strategies scientists are only beginning to decipher. The first outlines of an impressive picture are emerging, in which the blochemical machinery and sequence of instructions that pass forward to subsequent generations are being defined. Yet, skeletons are anything but static in the transfer. The fossil record shows the dynamic responses of skeletal structures to shifts in environmental conditions over acolook time.

Before the Great Oxidation Event (GOE), at ~2.4 Ga, the mineralogical record of the near-surface continental environment indicates a low partial pressure of oxygen during weathering, which restricted many elements to a low oxidation state and limited the number of possible minerals formed from these elements. Calculations show that local pulses in the production of O2 by photosynthesis could mobilize some metals (e.g. Mo and Re, but not U), but this O2 would be completely consumed. After the GOE, many elements could occur in one or more oxidized forms in minerals in the near-surface environment. This development resulted in an explosive growth in the diversification of minerals.

The oldest vestiges of crust and marine environments occur only in a few remote areas on Earth today. These rocks are Hadean–Eoarchean in age (~4.5 to 3.6 billion years old) and represent the only available archive of the mineral environments in which life originated. A mineral inventory of the oldest rocks would thus help to constrain the likeliest minerals involved in the origin of life. Such a survey is important from the perspective of mineral evolution, as the emergence of life and subsequent global changes caused by organisms were responsible for more than half the 4400 known minerals on the modern Earth.

The approximately 250 mineral species found in meteorites record the earliest stages of the birth of our solar system. Refractory minerals that formed during the violent deaths of other stars and during condensation of our own solar nebula mixed with a wide range of silicates, sulfi des, and metals to form the most primitive chondritic meteorites. Subsequent aqueous alteration, thermal metamorphism, and shock metamorphism further diversified the minerals found in meteorites. Asteroidal melting at first increased and then dramatically decreased mineralogical diversity, before a new phase of igneous differentiation that presaged the processes that would occur in terrestrial planets.

The basic building blocks of all minerals are the approximately 290 stable or long-lived isotopes of 84 elements. Yet, when the universe began and nuclear reactions ceased after about 15 minutes, the only elements present were hydrogen, helium, and traces of lithium. After the groundbreaking work by Cameron and Burbidge and coworkers in the 1950s, it is now understood that all the other elements are made in stars in an ongoing cycle of nucleosynthesis. Stars form, create new elements via nuclear reactions, and finally disperse the new elements into space via winds and explosions, forming the seeds for new stars.

Mineral evolution, which frames mineralogy in a historical context, is based on the premise that the geosphere and biosphere have coevolved through a sequence of deterministic and stochastic events. Three eras of mineral evolution—planetary accretion, crust and mantle reworking, and biologically mediated mineralogy—each saw dramatic changes in the diversity and distribution of Earth’s near-surface minerals. An important implication of this model is that different terrestrial planets and moons achieve different stages of mineral evolution, depending on the geological, petrological, and biological evolution of the body.