Towards the analysis of coral skeletal density-banding using deep learning

X-ray micro–computed tomography (µCT) is increasingly used to record the skeletal growth banding of corals. However, the wealth of data generated is time consuming to analyse for growth rates and colony age. Here we test an artificial intelligence (AI) approach to assist the expert identification of annual density boundaries in small colonies of massive Porites spanning decades. A convolutional neural network (CNN) was trained with µCT images combined with manually labelled ground truths to learn banding-related features. The CNN successfully predicted the position of density boundaries in independent images not used in training. Linear extension rates derived from CNN-based outputs and the traditional method were consistent. In the future, well-resolved 2D density boundaries from AI can be used to reconstruct density surfaces and enable studies focused on variations in rugosity and growth gradients across colony 3D space. We recommend the development of a community platform to share annotated images for AI.

Applied mineralogy of zirconium minerals: a case study of alkaline intrusion in SE-Brazil

Brazil has important zirconium resources when compared with other countries. However, most of the zirconium production in Brazil occurs as coproduct of the mining and processing of heavy mineral sands for the titanium minerals. This paper reports mineral and technological characterization studies associated with an alkaline intrusion in SE-Brazil. The data were obtained in a complex local rock known as “caldasite,” probably formed during hydrothermal alteration associated with post-magmatic events. The results obtained by multi-element analysis and X-ray diffraction analysis, petrography and scanning electronic microscopy indicated that zirconium concentration is about 66 wt%, having zircon and baddeleyite as most relevant minerals; gibbsite and anatase are found in minor proportions. The mineral assemblage developed a complex rock texture and structure associated with hydrothermal fluids percolation indicated by remobilization of zirconium in primary rocks. Caldasite presented concentric growth banding texture, revealed by zircon nucleation and baddeleyite microcrystalline interlaying. Results obtained indicate that caldasite has a high potential as zirconium resource due to concentration and mineral associations. Article Highlights This paper focused on the results of several techniques of mineralogical and technological characterization applied in an enriched-zirconium rock formed during hydrothermal alteration in alkaline intrusion in SE-Brazil. The results showed the rock is found in veins and has a mineral assemblage of zirconium, baddeleyite, gibbsite and anatase presented in a concentric growth banding texture. ZrO2 content is about 66% and preliminary results indicated the rock has a high potential for industry application.

Substrate growth dynamics and biomineralization of an Ediacaran encrusting poriferan

The ability to encrust in order to secure and maintain growth on a substrate is a key competitive innovation in benthic metazoans. Here we describe the substrate growth dynamics, mode of biomineralization and possible affinity of Namapoikia rietoogensis , a large (up to 1 m), robustly skeletal, and modular Ediacaran metazoan which encrusted the walls of synsedimentary fissures within microbial–metazoan reefs. Namapoikia formed laminar or domal morphologies with an internal structure of open tubules and transverse elements, and had a very plastic, non-deterministic growth form which could encrust both fully lithified surfaces as well as living microbial substrates, the latter via modified skeletal holdfasts. Namapoikia shows complex growth interactions and substrate competition with contemporary living microbialites and thrombolites, including the production of plate-like dissepiments in response to microbial overgrowth which served to elevate soft tissue above the microbial surface. Namapoikia could also recover from partial mortality due to microbial fouling. We infer initial skeletal growth to have propagated via the rapid formation of an organic scaffold via a basal pinacoderm prior to calcification. This is likely an ancient mode of biomineralization with similarities to the living calcified demosponge Vaceletia. Namapoikia also shows inferred skeletal growth banding which, combined with its large size, implies notable individual longevity. In sum, Namapoikia was a large, relatively long-lived Ediacaran clonal skeletal metazoan that propagated via an organic scaffold prior to calcification, enabling rapid, effective and dynamic substrate occupation and competition in cryptic reef settings. The open tubular internal structure, highly flexible, non-deterministic skeletal organization, and inferred style of biomineralization of Namapoikia places probable affinity within total-group poriferans.