Search Results (3)

Volcanism is an important geological evolutionary process on the Moon. The study of lunar volcanic features is of great significance and value to understanding the geological evolution of the Moon better. Lunar domes are one of the essential volcanic features of the Moon. However, the existing lunar dome detection methods are still traditional manual or semiautomatic identification approaches that require extensive prior knowledge and have a complex identification process. Therefore, this paper proposes an automatic detection method based on improved YOLOv7 for lunar dome detection. First, a new lunar dome dataset was created by digital elevation model (DEM) data, and the effective squeeze and excitation (ESE) attention mechanism module was added to the backbone and neck sections to reduce information loss in the feature map and enhance network expressiveness. Then, a new SPPCSPC-RFE module was proposed by adding the receptive field enhancement (RFE) module into the neck section, which can adapt to dome feature maps of different shapes and sizes. Finally, the bounding box regression loss function complete IOU (CIOU) was replaced by wise IOU (WIOU). The WIOU loss function improved the model’s performance for the dome detection effect. Furthermore, this study combined several data enhancement strategies to improve the robustness of the network. To evaluate the performance of the proposed model, we conducted several experiments using the dome dataset developed in this study. The experimental results indicate that the improved method outperforms related methods with a mean average precision (mAP@0.5) value of 88.7%, precision (P) value of 85.6%, and recall (R) value of 86.4%. This study provides an effective solution for lunar dome detection. Full article

Quarrying for aggregate material at Hornsby in New South Wales (Australia) exposed a >100 m-deep cross-section of the volcanic neck of a Jurassic diatreme, which extruded through the Sydney Basin deposits. The cross-section reveals volcanic features at many scales. Globally, there are very few instances of such excellent 3D exposure. It is arguable that this exposure alone makes it a geosite of international value. However, evaluation of the Hornsby Diatreme using a geoheritage toolkit shows that it meets various geoheritage conservation criteria, being a reference site, and an historically and culturally important site, as well as hosting important archival material. It has significant features at various scales: at the macroscale, where dish beds are visible on all quarry walls, preserving the structure formed during volcanic accretion and later caldera collapse; at the mesoscale, where breccia and surge layers are visible, providing insight into how magma interacted with various host rock types; and at the microscale, where lapilli, chilled margins on host rock blocks, and carbon-rich xenoliths are visible in hand specimens. As such, the Hornsby Quarry hosts a world-class array of volcanic features and preserves an important period of volcanic and post-volcanic history within the Sydney Basin, fostering geoeducation and geotourism. Full article

Significant volumes of rhyolites and granites of the Pliocene-Pleistocene age are exposed in the collision zone of the Greater Caucasus, Russia. The volcanic history of the region includes ignimbrites and lavas associated with the Chegem caldera (2.9 Ma) and Elbrus volcano (1.98 and 0.7 Ma) and rhyolitic necks and granites in Tyrnyauz (1.98 Ma). They are characterized by a similar bulk and mineral composition and close ratios of incompatible elements, which indicates their related origin. The 1.98 Ma Elbrus ignimbrites, compared to the 2.9 Ma Chegem ignimbrites, have elevated concentrations of both compatible (Cr, Sr, Ca, Ni) and incompatible elements (Cs, Rb, U). We argue that the Elbrus ignimbrites were produced from magma geochemically similar to Chegem rhyolites through fractionation crystallization coupled with the assimilation of crustal material. The 1.98 Ma Eldjuta granites of Tyrnyauz and early ignimbrites of the Elbrus region (1.98 Ma) are temporally coeval, similar mineralogically, and have comparable major and trace element composition, which indicates that the Elbrus ignimbrites probably erupted from the area of modern Tyrnyauz; the Eldjurta granite could represent a plutonic reservoir that fed this eruption. Late ignimbrites of Elbrus (0.7 Ma) and subsequent lavas demonstrate progressively more mafic mineral assemblage and bulk rock composition in comparison with rhyolites. This indicates their origin in response to the mixing of rhyolites with magmas of a more basic composition at the late stage of magma system development. The composition of these basic magmas may be close to the basaltic trachyandesite, the flows exposed along the periphery of the Elbrus volcano. All studied young volcanic rocks of the Greater Caucasus are characterized by depletion in HSFE and enrichment in LILE, Li, and Pb, which emphasizes the close relationship of young silicic magmatism with magmas of suprasubduction geochemical affinity. An important geochemical feature is the enrichment of U up to 8 ppm and Th up to 35 ppm. The trace element composition of the rocks indicates that the original rhyolitic magma of Chegem ignimbrites caldera was formed at >80%–90% fractionation of calc-alkaline arc basalts with increased alkalinity. This observation, in addition to published data for isotopic composition (O-Hf-Sr) of the same units, shows that the crustal isotopic signatures of silicic volcanics may arise due to the subduction-induced fertilization of peridotites producing parental basaltic magmas before a delamination episode reactivated the melting of the former mantle and the lower crust. Full article