Fig. 3: Texture and mineralogy of typical pyrite-marcasite rosettes (PMRs). | Communications Earth & Environment

Fig. 3: Texture and mineralogy of typical pyrite-marcasite rosettes (PMRs).

From: Evidence for high-frequency oxygenation of Ediacaran shelf seafloor during early evolution of complex life

Fig. 3

a A PMR composed of a relatively large pyrite (Py) nucleus and a cortex composed of intergrown quartz (Qtz) and radiating marcasite (Mrc) blades. b, c Close-up of the PMR nucleus showing irregular shape (b) and poikilitic internal texture (c) as a result of corrosion. d–g A PMR consisting of a small, irregular pyrite nucleus (circled in d), a cortex of intergrown quartz (Qtz) and radiating marcasite (Mrc) blades, and a pyrite rim (Py). f Raman image of the PMR showing the distribution of apatite (Ap), quartz, pyrite, marcasite and barite (Brt). g Raman image showing the presence of organic matter (OM) in the quartz of the cortex and in the surrounding apatite. Note the intergrowth of quartz and marcasite (f) and ubiquitous presence of organic matter in quartz and apatite (g). h Raman spectra of various phases. a, e Transmitted light image, crossed polars; b, c backscattered electron image; d reflected light image.

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