Recent high‐velocity rotary shear experiments results show that spherical nanoparticles can reduce fault friction dramatically during seismic slip. But questions like what are the roles of the nanoparticles in the whole slip are largely open problems. In this study, two types of nanoparticles were found in the Red River fault zone, including agglomerated nanoparticles in the ductile shear zone and spherical nanoparticles adjacent to the brittle faults. To ascertain the formation of these nanoparticles and explore the role of nanoparticles, the experiments under high temperature and pressure were conducted. The results of the experiments and of the previous studies suggest that the spherical nanoparticles can produce at the low temperature, which may lubricate the fault and significantly reduce the dynamic coefficient of friction. With the rise in temperature, the spherical nanoparticles are elongated or deformed to the agglomerated nanoparticles, which may no longer lubricate the fault, and lead the fault slip to slow down until it stops. Accordingly, this paper summarizes the role of these nanoparticles throughout the whole process of fault sliding.

The Bangong-Nujiang Suture Zone (BNSZ) in central Tibet hosts a series of dismembered Jurassic ophiolites that are widely considered as remnants of the vanished Meso-Tethys Ocean. In this study we present new compositional, isotopic, and geochronological data from anorthosites and gabbros of the Dongco and Lanong ophiolites in order to test several hypotheses about the nature of subduction in the Bangong-Nujiang Tethys Ocean (BNTO) during the Mesozoic era. Uranium–Pb dating of magmatic zircons separated from the Dongco anorthosites yielded an (average) age of 169.0 ± 3.7 Ma. Zircons separated from the Lanong anorthosites and gabbros yielded U–Pb ages of 166.8 ± 0.9 Ma and 167.3 ± 1.1 Ma, respectively. Zircons separated from the Dongco and Lanong anorthosites have positive ε_Hf(t) values (5.62–15.94 and 10.37–14.95, respectively). The Dongco anorthosites have moderate initial ⁸⁷Sr/⁸⁶Sr (0.703477–0.704144) and high ε_Nd(t) (+6.50 to +7.91). The Lanong anorthosites have high (⁸⁷Sr/⁸⁶Sr)_i (0.706058–0.712952) and ε_Nd(t) in the range of −1.56 to +2.02. Furthermore, the Lanong gabbros have high (⁸⁷Sr/⁸⁶Sr)_i (0.705826–0.706613) and ε_Nd(t) in the range of −0.79 to +4.20. Most gabbros from Dongco and a few gabbros from Lanong show normal mid-ocean ridge basalt (N-MORB)-like primitive mantle (PM)-normalized multi-element patterns. In contrast, most gabbros from Lanong show U-shaped chondrite-normalized rare earth element (REE) profiles. The investigated gabbros are characterized by wide ranges of δEu {(Eu)_N/[(Sm)_N*(Gd)_N]^1/2} values (0.83–2.53), indicating that some of them are cumulative rocks. The trace element contents of all anorthosite samples imply that their composition was controlled by cumulative processes. The geochemical and isotopic compositions of the non-cumulative gabbros from Dongco (δEu: 0.95–1.04) and Lanong (δEu: 0.83–1.03) indicate that their parental melts were derived from melting of heterogeneously depleted, juvenile mantle reservoirs. These rocks have arc-related affinities, indicating that their mantle sources were influenced by minor inputs of subducted lithospheric components. Our preferred hypothesis for the origin of the non-cumulative gabbros from Dongco is that they were formed in a transient back-arc basin (BAB) setting in the middle-western segment of the BNTO, whereas our preferred scenario about the origin of the non-cumulative gabbros from Lanong is that they were generated in a forearc setting in the middle part of the BNTO. We conclude that both geotectonic settings were developed in response to the northward subduction of the BNTO during the Middle Jurassic.

As a huge reservoir of economic metallic elements, oceanic polymetallic nodules have important strategic significance and are one of the main research objects in marine geology, especially their formation process and genetic mechanism. In this study, polymetallic nodules from the cobalt-rich crust exploration contract area in the Western Pacific Ocean were taken as the research object. Optical microscopy, scanning electron microscopy (SEM), X-ray diffraction (XRD), and energy dispersive spectroscopy (EDS) were used for observation and testing. The results indicate that many nanomineral particles, mainly composed of Fe and Mn, developed in polymetallic nodules from the western Pacific Ocean. The solid–liquid interface process of nanomineral particles plays an important role in the growth and evolution of nodules. We propose that the growth process of polymetallic nodules in the western Pacific Ocean can be divided into three stages. First, terrigenous detritus nucleates, and nanomineral particles composed of Fe, Mn, and other elements form, aggregate and attach to the core to form the initial shell. Second, a dense layer of the shell forms under stable conditions. In the third stage, the redox conditions of the nodules change, and the polymetallic nodules experience a variety of interface process modifications.

The Zhongjiannan Basin is located west of the South China Sea (SCS) and was affected by the left-lateral strike-slip of the Red River Fault (RRF), the West Edge Fault of the South China Sea (WEFSCS) and the continental rifting of the South China Sea in the early Cenozoic. The Zhongjiannan Basin formed in a strike-pull basin with an S‒N distribution. During the middle Miocene, the sea spreading of the SCS stopped, but the dynamic mechanism of the Zhongjiannan Basin, which controlled the sedimentary and the structural evolution after the late Miocene, remains unclear. In this paper, through the segment interpretation of the latest seismic section in the Zhongjiannan Basin, we conduct a comparative study of the sedimentary structure in the southern and northern Zhongjiannan Basin since the late Miocene. Combined with the regional tectonic dynamics analysis, we propose that the sedimentary and structural evolution of the Zhongjiannan Basin since the late Miocene was mainly controlled by residual magmatic activity in the Southwest Subbasin (SWSB) after expansion stopped, and the compressional structure stress field weakened gradually from south to north. The compressional tectonic stress field from north to south was formed in the northern basin under the dextral strike-slip movement of the RRF. The sedimentary and structural environment was relatively stable in the middle basin. Therefore, the sedimentary-structure evolution of the Zhongjiannan Basin since the late Miocene was controlled by the two different structural stress fields. The above knowledge not only has guiding significance for oil and gas exploration in the Zhongjiannan Basin but also provides a reference for studying the initiation time of dextral strike-slip along the Red River Fault Zone, as well as the junction position between the RRF and the WEFSCS.