Investigating the coupling between plume volcanism and massive iron formation deposition after the rise of oxygen
Abstract
Massive iron formations were the first recognized proxies for low surface oxygen concentrations, and so form critical archives of early Earth conditions. However, the record of iron formation deposition may be punctuated rather than uniform across the Precambrian. Furthermore, the historic link with oxygen is complicated by investigations that suggest that 1) iron deposition was sensitive to plume volcanism, and 2) primary precipitation of reduced phases is possible. These uncertainties are particularly striking when examining the resurgence in massive iron formations after the Great Oxidation Event (GOE) about 1.8 billion years ago. While previous work has documented a correspondence between magmatism and iron deposits, the direct mechanistic tie between plume magmatism and post-GOE iron formation has not been illustrated. A quantitative analysis of the ages and volumes of iron formations and magmatic rocks and predictions of iron input and outputs is necessary. Here we present results from new MATLAB modeling. First, we test the feasibility that a plume magmatic trigger is sufficient to initiate the 1.8 Ga iron deposition by investigating the range of fluxes from both plume and background inputs. Second, we explore the plume size needed to achieve globally ferruginous conditions. By fully exploring the model parameter space, including extreme values, we quantify sensitivity and capture the full range of system variability. Finally, we compare model outputs to a newly compiled database of ages, thicknesses and areas of 1.8 Ga iron formation and magmatism. This work investigates the necessity of plume magmatism in triggering post-GOE iron formation as well as testing what conditions were needed to achieve global ferruginous conditions ca. 1.8 Ga. Our results clarify feedbacks between the solid and fluid Earth and reveal the utility of iron formations for understanding the tempos and triggers of ancient redox and ocean chemistry.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2020
- Bibcode:
- 2020AGUFMPP0190001E
- Keywords:
-
- 0419 Biomineralization;
- BIOGEOSCIENCES;
- 0428 Carbon cycling;
- BIOGEOSCIENCES;
- 4912 Biogeochemical cycles;
- processes;
- and modeling;
- PALEOCEANOGRAPHY;
- 5225 Early environment of Earth;
- PLANETARY SCIENCES: ASTROBIOLOGY