It has been long observed that the amalgamation of supercontinents, including Rodinia, is coeval with peaks of U-Pb ages of global detrital zircons. However, our new compilation of global geochemical, mineralogical, and ore geologic records shows that the assembly of Rodinia stands out from others, in terms of whole-rock trace element geochemistry, as well as records of mineralogy and ore deposits. During the assembly of Rodinia, Nb, Y, and Zr concentrations were enriched in igneous rocks, with prolific formation of zircon and minerals bearing Th, Nb or Y, and REE-bearing ore deposits. At the same time, many types of ore deposits are relatively poorly represented in Rodinin terranes, including deposits of orogenic gold, porphyry copper, and volcanic hosted massive sulfide deposits, with a corresponding paucity of many minerals (e.g., minerals bearing Au, Sb, Ni) associated with these deposits. We interpret these records as indicating the prevalence of 'non-arc' magmatism and a relative lack of subduction-related arc magma preserved in the surviving pieces of the Rodinia supercontinent, distinct from other episodes of supercontinent assembly. We further attribute the prevalence of 'non-arc' magmatism to enhanced asthenosphere-lithosphere interactions in the Mesoproterozoic, and speculate that the lack of 'arc-collisional' magma may be related to enhanced erosion of Rodinia orogenic belts.

Several lines of evidence point to low rates of net primary production (NPP) in Archean oceans. However, whether Archean NPP was limited by electron donors or nutrients, particularly phosphorus (P), and how these factors might have changed over a billion years of recorded Archean history, remains contentious. One major challenge is to understand quantitatively the biogeochemical cycling of P on the early Earth. In Part I of this series (Hao et al., 2020), we estimated the weathering flux of P to the oceans as a function of temporally increasing continental emergence and elevation through Archean time. In Part II, we conduct thermodynamic and kinetic simulations to understand key processes of P cycling within the Archean ocean, including seafloor weathering, recycling of organic P, the solubility and precipitation of secondary phosphate minerals, and the burial diagenesis of P precipitates. Our calculations suggest low solubilities of apatite minerals in Archean seawater, primarily due to nearly neutral pH and high levels of Ca. This low solubility, in turn, implies a negligible contribution of apatite dissolution to P bioavailability in Archean seawater.

YI welcome the "Comment" from Hatert et al. (2021) related to the proposal for an "Evolutionary system of mineralogy" (Hazen 2019) and thank them for their historically informed, conceptually nuanced, and consistently constructive contribution. They offer corrections related to two facets of my paper that seemed unfairly to criticize aspects of the International Mineralogical Association's Commission on New Minerals, Nomenclature and Classification (IMA-CNMNC) protocols for classifying minerals.

The crystal structure of the unique nickel porphyrin mineral abelsonite, NiC31H32N4, has been solved using direct methods with 2195 independent reflections to a final R-1 = 0.0406. Abelsonite crystallizes in the triclinic space group P (1) over bar, with Z = 1 and unit-cell parameters a = 8.4416(5) angstrom, b = 10.8919(7) angstrom, c = 7.2749(4) angstrom, alpha = 90.465(2)degrees, beta = 113.158(2)degrees, and gamma = 78.080(2)degrees at the measurement condition of 100 K, in very good agreement with previous unit-cell parameters reported from powder diffraction. The structure consists of nearly planar, covalently bonded porphyrin molecules stacked approximately parallel to (1 (1) over bar1), and held together by weak intermolecular Van der Waals forces. The molecules within a layer are slightly tilted such that molecular planes do not overlap, and an up-turned ethyl group on one molecule sits adjacent to a down-turned ethyl group on a neighboring molecule of the same layer. Layers are stacked along a vector normal to (1 (1) over bar1) such that an aromatic ring at one corner of the molecule lies directly above the opposite aromatic ring of the molecule below. Although a single molecule does not quite possess (1) over bar symmetry, matching ethyl groups at roughly opposite ends of the molecule enable orientational disorder, in which molecules can randomly adopt one of two different orientations while still stacking in the same manner. The aggregate of these two random orientations produces an overall symmetry of P (1) over bar.

Resolving how Earth surface redox conditions evolved through the Proterozoic Eon is fundamental to understanding how biogeochemical cycles have changed through time. The redox sensitivity of cerium relative to other rare earth elements and its uptake in carbonate minerals make the Ce anomaly (Ce/Ce*) a particularly useful proxy for capturing redox conditions in the local marine environment. Here, we report Ce/Ce* data in marine carbonate rocks through 3.5 billion years of Earth's history, focusing in particular on the mid-Proterozoic Eon (i.e., 1.8 - 0.8 Ga). To better understand the role of atmospheric oxygenation, we use Ce/Ce* data to estimate the partial pressure of atmospheric oxygen (pO(2)) through this time. Our thermodynamics-based modeling supports a major rise in atmospheric oxygen level in the aftermath of the Great Oxidation Event (similar to 2.4 Ga), followed by invariant pO(2) of about 1% of present atmospheric level through most of the Proterozoic Eon (2.4 to 0.65 Ga).

Ecological observations and paleontological data show that communities of organisms recur in space and time. Various observations suggest that communities largely disappear in extinction events and appear during radiations. This hypothesis, however, has not been tested on a large scale due to a lack of methods for analyzing fossil data, identifying communities, and quantifying their turnover. We demonstrate an approach for quantifying turnover of communities over the Phanerozoic Eon. Using network analysis of fossil occurrence data, we provide the first estimates of appearance and disappearance rates for marine animal paleocommunities in the 100 stages of the Phanerozoic record. Our analysis of 124,605 fossil collections (representing 25,749 living and extinct marine animal genera) shows that paleo-community disappearance and appearance rates are generally highest in mass extinctions and recovery intervals, respectively, with rates three times greater than background levels. Although taxonomic change is, in general, a fair predictor of ecologic reorganization, the variance is high, and ecologic and taxonomic changes were episodically decoupled at times in the past. Extinction rate, therefore, is an imperfect proxy for ecologic change. The paleo-community turnover rates suggest that efforts to assess the ecological consequences of the present-day biodiversity crisis should focus on the selectivity of extinctions and changes in the prevalence of biological interactions.

Saturn's moon Enceladus has a potentially habitable subsurface water ocean that contains canonical building blocks of life (organic and inorganic carbon, ammonia, possibly hydrogen sulfide) and chemical energy (disequilibria for methanogenesis). However, its habitability could be strongly affected by the unknown availability of phosphorus (P). Here, we perform thermodynamic and kinetic modeling that simulates P geochemistry based on recent insights into the geochemistry of the ocean-seafloor system on Enceladus. We find that aqueous P should predominantly exist as orthophosphate (e.g., HPO42-), and total dissolved inorganic P could reach 10-7 to 10-2 mol/kg H2O, generally increasing with lower pH and higher dissolved CO2, but also depending upon dissolved ammonia and silica. Levels are much higher than <10-10 mol/kg H2O from previous estimates and close to or higher than 10-6 mol/kg H2O in modern Earth seawater. The high P concentration is primarily ascribed to a high (bi)carbonate concentration, which decreases the concentrations of multivalent cations via carbonate mineral formation, allowing phosphate to accumulate. Kinetic modeling of phosphate mineral dissolution suggests that geologically rapid release of P from seafloor weathering of a chondritic rocky core could supply millimoles of total dissolved P per kilogram of H2O within 105 y, much less than the likely age of Enceladus's ocean (108 to 109 y). These results provide further evidence of habitable ocean conditions and show that any oceanic life would not be inhibited by low P availability.