Rheological study of methane gas hydrates in the presence of micron-sized sand particles

Natural gas hydrates,intricate crystalline structures formed by water molecules and small gas molecules,have emerged as a significant and globally impactful clean energy resource.However,their commercial exploitation faces challenges,particularly operational disruptions caused by sand-related blockages.Understanding the rheological properties of hydrate slurry,especially in the presence of micron-sized sand particles,is imperative for ensuring the flow assurance of subsea hydrate exploitation.This study extensively investigates the rheological properties of sand-containing hydrate slurries.The findings reveal that these slurries exhibit non-Newtonian fluid characteristics,including yield stress,thixotropy,and shear-thinning behavior.Solid-like elastic features are observed in sand-containing hydrate slurries before yielding,transitioning to viscous behavior after yielding.Even with a minimal amount of sand,both static yield stress and yield strain experience substantial changes,correlating with the increase in sand concentration.The research conclusively establishes the thixotropic nature of sand-hydrate slurries,where the viscosity decay rate is directly influenced by the shear rate.These insights aim to contribute comprehensively to the development of effective flow assurance strategies,ensuring the safe and stable operation of subsea hydrate exploitation.

Timming of Lithospheric Extension in Northeastern China:Evidence from the Late Mesozoic Nianzishan A-Type Granitoid Complex

New zircon U-Pb dates obtained by laser ablation inductively coupled plasma mass spectrometry（LA-ICP-MS）,whole-rock geochemical data and Sm-Nd and Rb-Sr isotopic data are presented for miarolitic alkaline granites,porphyritic syenite and rhyolites of the Nianzishan A-type granitoid complex（NAGC）in the Great Xing’an Range-Songliao Basin in Northeast（NE）China.New crystallization ages of 112.95±0.93 and 114.1±1.71 Ma for granite and 118.6±0.51 Ma for porphyritic syenite were determined by high-precision LA-ICP-MS.The εNd（t）of the rocks range from +1.85 to+2.06,with Nd model ages(TDM1)from 671 to 821 Ma,indicating that the NAGC originated from juvenile source rocks and exhibits geochemical characteristics of A1-and AA-type granite which formed in an extensional setting.We attribute the magmatism to regional extension and lithospheric thinning caused by the subduction of the western Pacific Plate about 120 to 100 Ma.

Research progress on ultra-precision machining technologies for soft-brittle crystal materials

Soft-brittle crystal materials are widely used in many fields, especially optics and microelectronics. However, these materials are difficult to machine through traditional machining methods because of their brittle, soft, and anisotropic nature. In this article, the characteristics and machining diff^culties of soft-brittle and crystals are presented. Moreover, the latest research progress of novel machining technologies and their applications for soft- brittle crystals are introduced by using some representative materials （e.g., potassium dihydrogen phosphate （KDP）, cadmium zinc telluride （CZT）） as examples. This article reviews the research progress of soft-brittle crystals processing.

Helium isotopic study on mantle degassing in the Altay orogenic zone,China

New helium isotopic data of ores and rocks from the Altay orogenic zone, Xinjiang,China are reported, which show that the pegmatites from No. 3 vein in the Keketuohai area have high 3He/4He ratios up to 1 .795 x 10-6 and 2.54 x 10-6. Such a result suggests that the metallogenic process of rare metal deposits in the Altay orogenic zone might be related to mantle degassing.