Multilateral development banks (MDBs) are international institutions that provide financial assistance for the development of their member states. Decision-making of MDBs is undertaken by the representatives of shareholders by voting. This article uses the absolute Banzhaf power index to measure the voting power of the shareholders of subregional MDBs, which have a voting system with a layered structure of different stock classifications. Differences in the voting power of shareholders holding different classifications of stocks are analyzed. The article also aims to explore the influence of the special voting system in the protection of the voting power in developing countries in the subregional MDBs of Latin America and the Caribbean. This protection benefits the democracy and independence of countries in the region.
The Fe 2 O 3 CaOTiO 2 BaSO 4 system is established through miniature sintering experiments to reveal the mechanism of BaSO 4 and vanadium‐titanium magnetite (VTM) with the help of X‐ray diffraction, scanning electron microscope and energy dispersive spectroscopy, and thermogravimetry. The results show that in the absence of BaSO 4 , the phase of the sinter consists of CaFe 2 O 4 , TiO 2 , Fe 2 O 3 , CaTiO 3 , and CaFe 2 O 5 . When the content of BaSO 4 is 1% and 2%, CaTiO 3 decreases and the number of needle‐like CF increases. Some Ba 2+ solidly dissolve into CF and CaTiO 3 to form trace BaFe 12 O 19 and BaTi 2 O 5 . When the content of BaSO 4 increases to 4%, the CaSO 4 phase appears, the formation of C 2 F is accelerated, and the content of CF and CaTiO 3 continues to decline. The needle‐like calcium ferrate gradually transforms into columnar and lamellar. As the BaSO 4 content continues to increase to 6% and 8%, although the trend of each phase is similar to that at 4%, it is almost entirely composed of columnar calcium ferrite, barium ferrite, and incomplete tetragonal and rhombic Fe 2 O 3 . The results of the study provide a theoretical basis for the utilization of VTM and barium‐containing iron ores in practical production.
Triassic granitic magmatism is widespread in the Eastern Kunlun Orogenic Belt (EKOB), northern Tibetan Plateau. Some of the granitoids are characterized by high Sr and low Y contents, and consequently high Sr/Y ratios. These high Sr/Y-ratio granitoids are often interpreted as adakitic rocks, originating from the thickened continental lower crust. However, studies have shown that granitoids with high Sr/Y ratios may have formed via other geological processes. This paper reports U–Pb ages, geochemical and Sr–Nd–Hf isotopic data for newly discovered granodiorite porphyries in the Kunlun River area of the Eastern Kunlun Orogenic Belt, and discusses whether the EKOB experienced crustal thickening during the Triassic. The granodiorite porphyries crystallized at 205 Ma. They have some adakitic characteristics with SiO 2 = 66.96–69.68 wt.%, Sr/Y ratios = 31–43, La/Yb = 26.9–57.9, Y = 8.47–11.3, Yb = 0.75–1.30, and MgO = 0.44–0.99 wt.%. However, the relatively flat heavy rare earth element patterns indicate that garnet was not the main residue in the magma source. In addition, combined with Nd–Hf isotopic data, these results indicate that the timing of the original generation of the crustal sources of the granodiorites should be Mesoproterozoic, with the involvement of older (Paleoproterozoic) components. The granodiorite porphyries were emplaced in a post-collisional environment after the northward subduction of Paleo-Tethyan oceanic lithosphere, and without thickening of the continental crust.
The deep strata in the Ordos Basin exhibit characteristics of high temperature and high stress. Conventional methods for assessing drillability (normal temperature and pressure) fail to accurately understand the drilling resistance characteristics of deep rocks in this region, leading to improper guidance for selecting formation drilling tools and prolonging drilling cycles. This study employs physical experiments and numerical simulations to conduct drillability tests on core samples taken from the region under high-temperature and high-pressure conditions, simultaneously simulating the rock breaking process under different temperature and pressure conditions. The study investigates the variation patterns of rock drillability grade values and von Mises stress values during rock breaking under single-factor and multi-factor analyses of temperature and pressure conditions. Combining these variation patterns, an optimization analysis of the back rake angle of PDC drill bits used in drillability experiments is conducted to guide the selection of drill bits on site. The results indicate that the variation patterns of von Mises values from finite element simulations are consistent with the drillability grade values under high-temperature and high-pressure conditions. Under single-factor conditions, von Mises stress and drillability grade values generally increase with rising temperature before decreasing, while they increase with increasing confining pressure. Under multi-factor conditions, confining pressure is the primary influencing factor within the range of 0 to 50 MPa, while the influence of temperature becomes prominent between 180 °C to 200 °C, with a weakening effect of confining pressure. Model application: Selecting a back rake angle of 30° for PDC drill bits yields optimal rock-breaking results. The research findings hold significant implications for understanding the low rock-breaking efficiency of deep strata, optimizing drill bit parameters, and enhancing drilling efficiency.
Abstract Global basaltic rocks show large variations in nickel (Ni) isotopic compositions relative to peridotites. The origin of this difference remains unknown. We analyzed Ni isotopic compositions of mineral separates from seven Beiyan peridotite xenoliths and 16 nephelinites from eastern China. Spinel is isotopically heavier, and clinopyroxene is systemically lighter than coexisting olivine and orthopyroxene. An ionic model predicts that olivine, orthopyroxene, and spinel are in Ni isotopic equilibrium, whereas clinopyroxene of metasomatic origin is out of equilibrium. The nephelinites have higher Fe 3+ /ΣFe but lower δ 60/58 Ni values than the peridotites. Mantle silicate melting likely leads to enrichment of heavy Ni isotopes in melts, and, importantly, it cannot explain the negative correlation between δ 60/58 Ni and Fe 3+ /ΣFe of the nephelinites. Therefore, the light Ni isotopic signature requires the involvement of a low‐ δ 60/58 Ni component. Sulfide is a minor Ni‐rich component in the mantle and is isotopically lighter than the silicates. The relative proportion of Ni from sulfides vs. that from silicates varies in mantle‐derived magmas, depending on the sulfur content at sulfide saturation and melting degree. Thus, low‐degree melts with high abundance of dissolved sulfides can be variably enriched in light Ni isotopes. We propose that enhanced sulfide dissolution at high oxygen fugacity is a key reason for light Ni isotopic compositions in the nephelinites. This sulfide dissolution model may also be responsible for producing the Ni isotopic variation in global mafic lithologies. When the highly oxidized, low‐degree melts react with the peridotitic region, they can impart light Ni isotopic signatures to mantle rocks.
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