Resistivity logs of the Chinese Continental Scientific Drilling main hole: Implication for the crustal electrical structure of Dabie-Sulu Terrane, Central-Eastern China

Abstract

To understand the electrical structure of the Sulu (苏鲁) terrane, we analyzed the resistivity logs of the Chinese Continental Scientific Drilling main hole (CCSD-MH) and obtained the statistical characteristics of the resistivity log of ultrahigh-pressure (UHP) metamorphic rocks. To check the logs' quality, we compared the resistivity log data with the core test data. The two datasets show a good coherence. On the whole, the resistivity of the UHP metamorphic rocks from the CCSD-MH is very high (mostly higher than 1 000 Ω·m). From orthogneiss to paragneiss, amphibolite, retrograded eclogite, rutile eclogite, phengite eclogite, and ultramafic rock, the resistivity decreases gradually. The fracture zone, enrichment of metal minerals, and serpentinization of peridotite can probably cause the decrease of resistivity. Comparing the electrical structure of the crust of Dabie (大别) terrane and Sulu terrane, we can conclude that (1) the electrical structure of the crust of Dabie terrane and Sulu terrane shows a very big difference, (2) the high-resistivity zone of the north Sulu orogen extended to a very great depth (60 km), but the high-resistivity zone of Dabie orogen is over the depth of 25 km. KEY WORDS: resistivity log, CCSD-MH, UHP metamorphic rock, electrical structure, Dabie-Sulu terrane.