Petrographic Analysis and Tectonic Implications of the Plutons in the Gilead 7.5 Quadrangle: Connections to the Piscataquis Volcanic Arc and Sebago Batholith

The bedrock geology of the Gilead 7.5’ Quadrangle was mapped for a more updated version using digital field mapping methods. This research was funded by the Billings Fund and the Maine Geological Society. Previous studies of this region is the current bedrock map by Moench, Hatch, and Lyons (1983). This study focuses on the plutonic history using thin section, estimated modes of QAP diagrams, and geochemical data from X-ray Fluorescence. The two igneous intrusions in this area of study are the Quartz Diorite Suite and the two-mica granites that are found as sills and plutons. The Quartz Diorite Suite is characterized as foliated synkinematic rocks and are closely related to the New Hampshire Plutonic Series (NHPS) associated with the Piscataquis Volcanic Arc. Data from the study show the close correlations with the Winnesepaukee Tonalite from a previous study conducted on the NHPS by Dorais (2003). The two-mica granites are homogeneous in nature with an abundance of pegmatites and are believed to be an extension of the Sebago Batholith that are Carboniferous to Permian in age. For the two-mica granites, the geochemical data did not correlate as well with Tomascak et al. (1996) data but did have a general trend. Based on the data, the hypothesis surrounding the plutons and tectonic history is explained through two or possibly three tectonic events, the Acadian, Neoacadian, and Alleghanian Orogeny. These finding as well as the new changes in the metasedimentary units have significant implications for regional Appalachian tectonics, and validate the importance of creating a new map

Arithmetic PCA for Encrypted Data

Reducing the size of large dimensional data is a critical task in machine learning (ML) that often involves using principal component analysis (PCA). In privacy-preserving ML, data confidentiality is of utmost importance, and reducing data size is a crucial way to cut overall costs. This work focuses on minimizing the number of normalization processes in the PCA algorithm, which is a costly procedure in encrypted PCA. By modifying Krasulina\u27s algorithm, non-polynomial operations were eliminated, except for a single delayed normalization at the end. Our PCA algorithm demonstrated similar performance to conventional PCA algorithms in face recognition applications. We also implemented it using the CKKS (Cheon-Kim-Kim-Song) homomorphic encryption scheme and obtained the first 6 principal components of a 128$\times$128 real matrix in 7.85 minutes using 8 threads

Bedrock geology of the Gilead quadrangle, Maine

Maine Geological Survey, Open-File Map 18-12.https://digitalmaine.com/mgs_maps/3068/thumbnail.jp

Bedrock geology of the Gilead quadrangle, Maine

Maine Geological Survey, Open-File Map 18-12.https://digitalmaine.com/mgs_maps/3068/thumbnail.jp

Bedrock Geology of the Gilead Quadrangle, Maine

Maine Geological Survey, Open-File Map 18-12

Initial results from the Oman Drilling Project Multi-Borehole Observatory: Petrogenesis and ongoing alteration of mantle peridotite in the weathering horizon

International audienceThe Oman Drilling Project “Multi-Borehole Observatory” (MBO) samples an area of active weathering of tectonically exposed peridotite. This article reviews the geology of the MBO region, summarizes recent research, and provides new data constraining ongoing alteration. Host rocks are partially to completely serpentinized, residual mantle harzburgites, and replacive. Dunites show evidence for “reactive fractionation,” in which cooling, crystallizing magmas reacted with older residues of melting. Harzburgites and dunites are 65%–100% hydrated. Ferric to total iron ratios vary from 50% to 90%. In Hole BA1B, alteration extent decreases with depth. Gradients in water and core composition are correlated. Serpentine veins are intergrown with, and cut, carbonate veins with measurable 14C. Ongoing hydration is accompanied by SiO2 addition. Sulfur enrichment in Hole BA1B may result from oxidative leaching of sulfur from the upper 30 m, coupled with sulfate reduction and sulfide precipitation at 30–150 m. Oxygen fugacity deep in Holes BA3A, NSHQ14, and BA2A is fixed by the reaction 2H2O = 2H2 + O2 combined with oxidation of ferrous iron in serpentine, brucite, and olivine. fO2 deep in Holes BA1A, BA1D, and BA4A is 3–4 log units above the H2O-H2 limit, controlled by equilibria involving serpentine and brucite. Variations in alteration are correlated with texture, with reduced, low SiO2 assemblages in mesh cores recording very low water/rock ratios, juxtaposed with adjacent veins recording much higher ratios. The proportion of reduced mesh cores versus oxidized veins increases with depth, and the difference in fO2 recorded in cores and veins decreases with depth