Mineral Element Insiders and Outliers Play Crucial Roles in Biological Evolution

Abstract

The geosphere of primitive Earth was the source of life's essential building blocks, and the geochemical interactions among chemical elements can inform the origins of biological roles of each element. Minerals provide a record of the fundamental properties that each chemical element contributes to crustal composition, evolution, and subsequent biological utilization. In this study, we investigate correlations between the mineral species and bulk crustal composition of each chemical element. There are statistically significant correlations between the number of elements that each element forms minerals with (#-mineral-elements) and the log of the number of mineral species that each element occurs in, and between #-mineral-elements and the log of the number of mineral localities of that element. There is a lesser correlation between the log of the crustal percentage of each element and #-mineral-elements. In the crustal percentage vs. #-mineral-elements plot, positive outliers have either important biological roles (S, Cu) or toxic biological impacts (Pb, As), while negative outliers have no biological importance (Sc, Ga, Br, Yb). In particular, S is an important bridge element between organic (e.g., amino acids) and inorganic (metal cofactors) biological components. While C and N rarely form minerals together, the two elements commonly form minerals with H, which coincides with the role of H as an electron donor/carrier in biological nitrogen and carbon fixation. Both abundant crustal percentage vs. #-mineral-elements insiders (elements that follow the correlation) and less abundant outsiders (positive outliers from the correlation) have important biological functions as essential structural elements and catalytic cofactors.

Keywords: Earth crust; localities; metal cofactors; mineral elements; network analysis.

Figure 1

(A) Plot of the number of elements that each chemical element forms minerals with (#-mineral-elements) vs. the log of the number of minerals that each element occurs in the idealized chemical formula. (B) Plot of #-mineral-elements vs. the log of the number of mineral localities that each element occurs at. Essential biological elements (carbon, C; hydrogen, H; nitrogen, N; oxygen, O; phosphorus, P; sulfur, S) are labeled in green font and the abundant positive outlier non-biological element (gold, Au) is labeled in black font. A mineral locality is a location where a mineral occurs.

Figure 2

(A) Plot of the log of crustal percentage of each element (crustal abundance data compiled from Rudnick and Gao, 2003) vs. number of elements (#-mineral-elements). (B) Plot of the atomic number of each element vs. #-mineral-elements. Essential biological elements (carbon, C; hydrogen, H; nitrogen, N; oxygen, O; phosphorus, P; sulfur, S) are labeled in green font (the following essential biological elements were not included in the Rudnick and Gao (2003) study and subsequently not included in (A): carbon, C; hydrogen, H; nitrogen, N). Non-biological positive and negative outlier elements (arsenic, As; lead, Pb; Scandium, Sc; Gallium, Ga; ytterbium, Yb; bromine, Br; bismuth, Bi; uranium, U) are labeled in black font. Biological metals (iron, Fe; manganese, Mn; copper, Cu; zinc, Zn; nickel, Ni; molybdenum, Mo; cobalt, Co) are labeled in blue font.

Figure 3

(A) Bipartite mineral chemistry network of all S-containing minerals. The network contains element nodes and mineral nodes. Element nodes are represented by circles with chemical element symbols, mineral nodes are represented by smaller unlabeled colored circles. Element and mineral nodes are colored by Louvain network community [36]. (B) Same network as 3A, but with only minerals that contain S and Cu highlighted. (C) Same network as 3A, but with only minerals that contain S and Fe highlighted. (D) Same network as 3A, but with only minerals that contain S and C highlighted.

Figure 4

Combined bipartite mineral chemistry network of all Sc-containing minerals, Ga-containing minerals, Br-containing minerals, and Yb-containing minerals at (A) >1.7 billion years ago (Ga); (B) >0.6 Ga; (C) >0 Ga. Mineral nodes are colored by maximum known age.

Figure 5

Combined bipartite mineral chemistry network of all H-containing minerals, C-containing minerals, and N-containing minerals at (A) >3.5 billion years ago (Ga); (B) >2.3 Ga; (C) >0 Ga. Element and mineral nodes are colored by Louvain network community [36].