Study on the material source and enrichment mechanism of REE-rich phosphorite in Zhijin, Guizhou.

Rare earth element (REE)-rich phosphorite in the Guizhou region mainly exists in the Doushantuo Formation and Gezhongwu Formation in early Cambrian strata, which are some of the important strata containing phosphorite resources in China. The early Cambrian Zhijin phosphorite in Guizhou Province, China, has high rare earth element and yttrium (REY) contents of up to 2500 ppm, with heavy REY (HREY) contents accounting for ~ 30% of the total REY contents. However, the specific controlling source and environment of phosphorite (especially the REEs in Zhijin phosphorite) are still unsolved. Through field geological investigations; mineralogical, geochemical, Sr-Nd isotope analyses; and tectonic characteristics, the material source, sedimentary environment and seawater dynamics of REEs in phosphorite are studied. It is considered that the REEs enriched in the Zhijin phosphorite are mainly affected by precipitation from hydrothermal fluid. Moreover, from the late Ediacaran to the early Cambrian, the depositional environment from the bottom to the top of the water tended to be hypoxic, and the activity of hot water fluid tended to be strong. The change in redox conditions is closely related to the rise and fall of sea level. Combined with the tectonic background, these results show that the weakly oxidized environment may be an important factor controlling the enrichment of REEs. The enrichment of REEs may be closely related to volcanic hydrothermal activity, later diagenesis and seawater dynamics.

A Testing Method for Shipborne Atomic Gravimeter Based on the Modulated Coriolis Effect.

Shipborne atomic gravimeter (SAG) is an instrument that can directly measure absolute gravity in dynamic environments. As a new type of gravity sensor, a standard method for evaluating its detailed performance has not been proposed and the detailed performance of SAG was rarely reported. In this paper, a system of dynamic gravity measurement, which was integrated with a home-made atomic gravimeter, is demonstrated, and a novel and simple method for testing the performance of SAG on the lake based on the modulated Coriolis effect is put forward. Firstly, in the state of ship mooring, a tilt modulation of the gravity sensor has been realized to make sure the Raman wave vector is parallel to the gravity axis. Moreover, a comparison between the measurement result of CG-5 and SAG has also been carried out to evaluate the accuracy of the SAG. Then, the Coriolis effect modulating experiment is carried out with various routes on lake to test its performance in dynamic environments. In the ship mooring state, the accuracy has been demonstrated to be 0.643 mGal. The internal consistency reliabilities are evaluated to be 0.8 mGal and 1.2 mGal under the conditions of straight line and circle navigation, respectively.

Research on aeromagnetic data error analysis and processing of multi-rotor UAV based on variational mode decomposition algorithm.

Aeromagnetic survey of multi-rotor UAV is widely used in small and medium-sized mineral resources survey, engineering investigation, non-explosive detection and other fields due to its advantages of high safety, low cost and convenient operation. The original data of UAV aeromagnetic survey includes interference from external environment, interference from UAV platform and interference from airborne electromagnetic equipment. The interference is mainly shown as striping anomaly along the direction of the survey line in the aeromagnetic anomaly map, which affects the accuracy of aeromagnetic compensation and information detection of geological anomaly body, thus affecting the accuracy of interpretation of geological anomaly body. In this paper, the algorithm of Variational Modal Decomposition (VMD) is introduced to filter and preprocess the aeromagnetic data to obtain high quality aeromagnetic data. At the same time, the source and characteristics of the errors are predicted according to the interference size and spectrum characteristics of the Modal function errors, which provides a reference for the optimization of aeromagnetic system.