Basalts Dredged from the Northeastern Pacific Ocean
Volcanic rocks dredged from seamounts, fault ridges, and other major geological features of the northeast Pacific Ocean include a wide variety of basalts. Most of these are vesicular, porphyritic types with near analogues in the Hawaiian and other oceanic islands. In addition, aluminous basalts and diabasic theoleiites impoverished in potassium also occur. There is no simple correlation of composition, degree of oxidation, vesiculation, or hydration of these basalts with texture, or depth of dredge site. Most samples appear to have been extruded at much shallower depths than those now pertaining at the dredge site. The distribution of these basalts suggests that the andesite line coincides with or lies on the continent side of the foot of the continental slope.
Spilite und der basaltische Vulkanismus
Unter dem Sammelliamen ,,Spilite" werden basische Gesteilie verschiedeller Geliese zusammeligefaBt, die chemisch als ,,verw~sserte" Basalte mit meist tiberdurehsehnittlichen Na20mad CO~-Gehalten aufzufassen sin& Ihr Milieralbestand ist durch das Vorherrschen voli Albit und Chlorit gekennzeiehnet; wichtige Nebenbestalidteile sind Carbonate, Epidot lind Fe-Oxide. Bei der Mehrzahl der Spilite (insbesolidere der typiseben Spilit-Keratophyr-Assoziationen) dtirfte es sich um tieftemperierte Bildungen aus einem wasserreieheli Magma handeln. Ein aliderer Tell repdisentiert wahrscheinlich ,,Metabasalte" vom Gr/insteintyp sowie autometamorphe Bilduligen. Eine Spilitisierung slibmarin gef6rderter Basalte dutch H20und Na-Aufnahme aus dem Meerwasser wird dnreh Beobachtlingen an Basalten tier heutigei~ TiefseebSden wenig gesttitzt.
Analysis of the stress wave effect during coal breakage by a high-pressure abrasive air jet
In view of the defects of borehole collapse, inhibition of gas desorption and migration of gas existing in hydraulic fracturing and other hydraulic permeability–increasing measures for soft coal seams with low-permeability technology is proposed for coal breakage by a high-pressure abrasive gas jet for relieving pressure and increasing permeability. The comparative analysis of gas jet flow field structure between convergent nozzle and Laval nozzle has been given by numerical simulation. For Laval nozzle, the expansion wave and compression wave alternate and move forward steadily in gas jet and vanish when potential core length reaches maximum. So, the Laval nozzle can form more stable flow filed structure of gas jet and avoid shock wave in gas jet. Furthermore, a high-speed camera is adopted to analyze the jet structure and verify the conclusion of numerical simulation. Based on thermodynamic theory, this article calculates and analyzes the critical local sound velocity and pressure generated from the stress wave during the process of coal breakage by the gas jet. Furthermore, experimental coal breakage by a high-pressure abrasive gas jet is carried out. The high-pressure abrasive gas jet impacts the coal body as a quasi-static load and a dynamic load and forms corrosion pits on the surface of the coal body. Penetrating cracks are formed within the coal in the pattern of the loaded stress wave which leads to coal breakage. The effects of porosity and permeability on the propagation of the stress wave in coal are analyzed by establishing the dispersion equation for the spread of the stress wave in coal. The results show that porosity has a significant effect on wave velocity and that the attenuation of the stress wave is intensified with an increase in porosity. Moreover, the stress wave attenuation is more obvious at high frequency. The effect of permeability on the wave velocity is not significant at low frequencies. In contrast, at high frequency and relatively low permeability, the wave velocity increases with the permeability, and the attenuation of the wave velocity initially increases and then decreases. When the permeability is greater than 10−11 m2, the wave velocity is not affected by the permeability. However, the stress wave is not attenuated.