Lu Xiancai

Discovery of low-mature hydrocarbon in manganese nodules and ooze from the Central Pacific deep sea floor

Extracts from manganese nodules and ooze from the Central Pacific deep sea floor were analyzed using the chromatogram-mass spectrum, and it was found that most of the biomarker molecules are of the low-mature type (some have characteristics of mature): the ratio of “A”/C is high between 11.4%–19.75%; CPI is 1.22–1.23; C31-22S/ (22S+22R) hopane is 0.59–0.60, Tm/Ts is 0.99–1.99; βa moretane/(aβ+βa) hopane is 0.12 – 0.14; C29 sterane 20S/(20S+20R) is 0.35 – 0.41; ββ/(ββ+αα) is 0.38 – 0.45; arene TA(I)/TA(I+II) is 0.16–0.21; methyl-phenanthrene index (MPI1) is 0.35–0.67. According to the geological settings of the sampling area and its organic geochemical characteristics, it is considered that the hydrothermal activities on the ocean floor facilitate the decomposition of organic matter in the sediment, which leads to the generation and migration of hydrocarbon into manganese nodules and ooze. This discovery is important for understanding the mechanisms of hydrocarbon generation in the ocean floor and for expanding the potential of oil and gas exploration in the ocean.

Observation of ultra-microtexture of fault rocks in shearing-sliding zones∗

Abstract Based on scanning electronic microscopic observation of three fault rocks in ductile-brittle shearing-sliding zones (including one palimpsest mylonite sampled from deep bore cores of Cajon Pass, California, two flowing-structured carbargillites sampled from Shaancan Well 1 located in north Shaanxi, and Well NH located in Huanghai, respectively), micron- and nanometer-scaled ultra-fine grinding grain texture of fault rocks is discovered in this study. And the geological significance of grinding grain texture is discussed in terms of its particulate organization, rheology of particulate slipping, laminar petrography and micro dynamics including dynamotherman metamorphism, fluid transferring, particulate autorotation, and so on. In addition, the remaining problems to be solved and broad prospects in this new study field are also discussed. ∗Supported by Natural Science Foundation of China (Grant Nos. 40372092, 40373024, 40172067, and 40172034) and the State Key Laboratory of Geology and Exploitation...

Adsorption Behaviour of Tween80 on Graphite

Techniques including thermogravimetry (TG), Fourier-transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) were applied to characterize the adsorption behaviour of Tween80 on graphite. TG is a suitable method for determining the amount of Tween80 adsorbed since it is not restricted by the large amount of solvent adsorbed in this disperse system. The results indicate that TG may provide an alternative method for measuring the amount adsorbed in some disperse systems in which there are significant differences between the thermal behaviours of the adsorbate, adsorbent and solvent. The adsorption isotherms of Tween80 were of the Langmuir type, with the adsorbed amount attaining a maximum value at temperatures between 30°C and 50°C. XPS and FT-IR measurements were used to provide detailed information about the functional group shift. In addition, AFM images indicated that the adsorption of Tween80 has a considerable influence on the topography of graphite, with the adsorbate being adsorbed preferentially on the step defect sites at the edge of the graphite crystal.

Simulating experiment on the hydrothermal superimposing metallogenesis of the Dongguashan strata-bound copper deposit

Series of sedimentary hydrothermal-diplogenetic copper deposits have been found scattering in the region along the middle-lower reaches of the Yangtze River, and their metallogenetic mechanism is still in hot debate. In order to reveal the ore-forming kinetics of sedimentary process and hydrothermal superimposition, and evaluate the role of sedimentary pyrite in the enrichment and precipitation of copper, a set of simulating experiments on the reaction between pyrite and CuCl2 solution were conducted. According to the physicochemical characteristics of the ore-forming fluid of the Dongguashan copper deposit, Anhui Province, 100 MPa was selected as the experimental pressure, and the experimental temperatures were set at 450, 350, 250 and 150°C, respectively. The reactions between pyrite grains isolated from the Shimenkou strata-bound pyrite deposit and the solution with 0.2 mol/L CuCl2 and 1.0 mol/L NaCl were experimentally simulated. Then, variations in surface topography and surface chemistry of the experimental pyrite grains were documented using scanning electronic microscopy (SEM), atomic force microscopy (AFM), Auger electron spectrometry (AES) and X-ray photoelectron spectroscopy (XPS), and the solution and newly formed minerals were analyzed using inductively coupled plasma (ICP-AES) and X-ray diffraction (XRD) techniques. Desulphurization of pyrite surface was observed and new copper minerals were detected. It is proposed that pyrite can act as a geochemical barrier for the enrichment and precipitation of copper from the solution under the experimental conditions. Furthermore, the ore-forming mechanism of sedimentary hydrothermal-diplogenetic copper deposits was discussed.

Oxidation and Mineralization of Mn2+ Ions Mediated by Pseudomonas putida: Insights from an Experimental Study

The formation of manganese oxides in nature is commonly mediated by microorganisms. In this study, the mineralization of biogenic manganese oxidation mediated by Pseudomanas putida has been experimentally investigated by employing various characterization techniques, including SEM, FESEM, TEM, XRD, and STXM-NEXAFS. The results indicate that Mn2+ ions can be oxidized into Mn (IV) minerals (birnessite and pyrolusite) and Mn(III) minerals (hausmannite and feitknechtite), successively. The primary products (birnessite and pyrolusite) further transformed into hausmannite and feitknechtite under Mn2+ ion-enriched conditions. However, birnessite and pyrolusite are the end-products of the continuous microbial oxidation processes. These biogenic Mn oxides are poorly crystallized, which provides them with a high potential for usage in environmental restoration of contaminated soils and waters contaminated with heavy metals. The approaches employed in this study will also enrich genesis research of biological oxidation of Mn(II) species in nature.