On the Attributes of Mineral Paragenetic Modes

Abstract

The mineral kingdom has experienced dramatic increases in diversity and complexity through billions of years of planetary evolution as a consequence of a sequence of physical, chemical, and biological processes. Each new formational environment, or “mineral paragenetic mode,” has its own characteristic attributes, including the stage of mineral evolution and geological age, ranges of T, P, duration of formation events, and other environmental influences on mineral formation. Furthermore, the minerals associated with each paragenetic mode have a wide range of average properties, including hardness, density, and chemical and structural complexity. A survey of attributes of 57 mineral paragenetic modes representing the full range of mineral-forming processes reveals systematic trends, including: (1) minerals documented from older paragenetic processes are systematically harder on average than those from more recent processes; (2) minerals from paragenetic modes formed at lower T (notably <500 K) display greater average structural complexity than those formed at high T (especially >1000 K); and (3) minerals from paragenetic modes that display greater average chemical complexity are systematically less dense than those from modes with lesser average chemical complexity. In addition, minerals formed in anhydrous environments and/or by abiotic processes are, on average, significantly denser and harder than those formed in hydrous environments and/or by biotic processes.

The Average Symmetry Index of Minerals Co-Varies with Their Hydrogen Content, Rarity, and Paragenetic Mode

“…Additionally, we examined correlations between the average mineral symmetry index and the maximum and minimum pressure and temperature conditions associated with each of the 57 paragenetic modes. For each paragenetic mode, Hazen et al [33] estimated minimum and maximum PT values at which minerals from that subset are likely to form. These values, which were used to clump minerals according to their PT formation conditions, are presented in Figure 3 alongside their respective best-fit lines.…”

“…Furthermore, Figure 2C shows that a higher percentage of hydrous minerals in a paragenetic mode brings down not only the mean symmetry index but also the variance of the symmetry index, suggesting a stabilizing or moderating effect of hydrogen incorporation on lower symmetry crystal structure modifications. [33]. The fits for all the plots have been weighted proportional to the number of minerals in each group of paragenetic modes.…”

“…Because the Dolivo-Dobrovol'sky approach was based on the multiplicity of a holohedral point group of a crystal system, it could also be easily adapted and used for other point groups and space groups. Therefore, we here expand applications of this approach to several co-evolving mineral attributes, including rarity, hydrogen content, and other averaged attributes of paragenetic modes [33]. In the effort to develop a more accurate metric of symmetry through time, in this paper, we did not only use the maximum multiplicities of holohedral classes of each crystal system but rather the maximum multiplicities of all 32 point groups.…”

Molecular assembly indices of mineral heteropolyanions: some abiotic molecules are as complex as large biomolecules

“…The estimated molecular assembly indices of these proposed Titan organic minerals range from 5 to 10. If such abiotic compounds do exist on Titan, then, by analogy with the multi-stage congruent evolution of minerals on Earth [ 46 , 47 ], local pockets of much greater abiotic molecular complexity are likely to persist, as well.…”

“…An important conclusion of prior studies is that planets and moons, given sufficient time and chemical processing, display remarkable degrees of mineral evolution, which include striking increases in the average diversity and complexity of minerals [ 33 , 34 , 46 , 47 ]. On Earth, the earliest minerals formed by high-temperature condensation display an average complexity per unit cell of approximately 83 bits, with no minerals incorporating molecule-like subunits with MA indices >6.…”