Fluidization processes based on experiments are reviewed to gain some useful insights and comparisons with those that occur in hydrothermal systems. Field and petrographic work, and microscope observation were carried out on samples from the Qiyugou Au-bearing breccia pipes from the East Qinling region, Henan Province. Evidence from macro- and micro-textures suggests that the style of breccias in the Qiyugou area can be grouped into three types： （1） jigsaw fit-stockwork texture, in which the interval between clasts is marked by fractures or filled with calcite or quartz veins; （2） larger breccias that are supported by smaller breccias, rock flour and alteration materials; in this type clasts moved over short distances, creating open spaces; （3） fluidized texture, where the clasts of different lithologies have rounded shapes. These observations are compared with those resulting from experiments on fluidization processes. The results of this comparison suggest that fluidization is an important geological process in the formation of the Qiyugou Au-bearing breccia pipes and gold mineralization. In addition, fluidization processes such as expansion, bubbling, slugging, channeling and spouting must have contributed to the formation of the pipes and were conducive to the development of gold mineralization. In the Qiyugou breccia pipes, gold mineralization occurs as disseminations, in stockwork veins, and open space infills. The ore zones form subparallel sheets that are nearly perpendicular to the walls of the pipes.
Based on the new data of isotopic ages and geochemical analyses, three types of Mesozoic granites have been identified for the Xiong＇ershan-Waifangshan region in western Henan Province： high-Ba-Sr I-type granite emplaced in the early stage （-160 Ma）, I-type granite in the middle stage （-130 Ma） and anorogenic A-type granite in the late stage （-115 Ma）. Geochemical characteristics of the high-Ba-Sr I-type granite suggest that it may have been generated from the thickened lower crust by partial melting with primary residues of amphibole and garnet. Gradual increase of negative Eu anomaly and Sr content variations reflect progressive shallowing of the source regions of these granites from the early to late stage. New ^40Ar/^39Ar plateau ages of the early-stage Wuzhangshan granite （156.0±1.1 Ma, amphibole） and middle-stage Heyu granite （131.8±0.7 Ma, biotite） are indistinguishable from their SHRIMP U-Pb ages previous published, indicating a rapid uplift and erosion in this region. The representative anorogenic A- type granite, Taishanmiao pluton, was emplaced at -115 Ma. The evolution of the granites in this region reveals a tectonic regime change from post-collisional to anorogenic between -160 Ma and -115 Ma. The genesis of the early- and middle-stage I-type granites could be linked to delamination of subducted lithosphere of the Qinling orogenic belt, while the late-stage A-type granites represent the onset of extension and the end of orogenic process. In fact, along the Qiniing -Dabie-Sulu belt, the Mesozoic granitoids in western Henan, Dabieshan and Jiaodong regions are comparable on the basis of these temporal evolutionary stages and their initial ^87Sr/^86Sr ratios, which may suggest a similar geodynamic process related to the collision between the North China and Yangtze cratous.
Magnetic susceptibility(MS)data were obtained from 11 sections of the Doushantuo(Edicaran)cap carbonate that directly overlies the Nantuo glacial diamictite in the southeastern margin of the Yangtze plat-form.The MS data revealed two regionally correlatable peaks at the bottom and top of the cap carbonate,sepa-rated by an interval of low values.The lower MS peak coincides with high percentage of insoluble siliciclastic residues that are compositionally identical to the matrix of the underlying diamictite,suggesting its origin con-trolled mainly by detrital components during the first phase of cap carbonate deposition at the end of the glacia-tion.The upper MS peak is associated with high clay content and iron sulfides,and can be interpreted as either derived from enhanced greenhouse weathering that could have brought more terrigenous components into the ocean,or the result of ocean anoxia at the late stage of cap carbonate deposition that could led to formation of abundant iron sulfides.The regionally consistent MS curves from the cap carbonates provided the first geo-physical record for the rapid climate change from icehouse to greenhouse conditions in the aftermath of the Neoproterozoic“snowball Earth”event.
Environmental magnetic measurements were carried out on the samples of street dust and topsoil,which were collected along the roadway in the urban and suburb of Beijing,including magnetic sus-ceptibility(χ),anhysteretic remanent magnetization(ARM),isothermal remanent magnetization(IRM)of all samples and temperature-dependence of magnetic susceptibilities and magnetic hysteresis pa-rameters of representative samples.Obvious differences exist between the samples of street dust and those of topsoil.Compared with topsoil samples,the concentration of magnetic particles and high-coercivity components in street dust samples are higher,and the magnetic grains are coarser.Both dust and topsoil samples are dominated by ferrimagnetic minerals,and iron particles are only detected in some dust samples.These results suggest that street dust samples reflect the characteris-tic of particles produced by industrial and traffic activities,and the magnetic property of topsoil sam-ples represents the characteristic of particles from both anthropogenic and natural sources.The dis-tribution of magnetic parameters is influenced by the environment where the samples are collected,like industry,traffic density and other road conditions.Hard isothermal remanent magnetization(HIRM)may be used as an indicator of particles produced by traffic activity.Dust storm samples collected on 17 and 18 April,2006 have different magnetic properties from street dust and natural particles,like loess and paleosol,which indicate that the dust storm might be mixed with anthropogenic particulates during transport and falling.
