High Affinity Of Ti Research Articles

Platinum-group element geochemistry of the Panjal Traps: constraints on mantle melting and implications for mineral exploration

Abstract Forty-two volcanic rocks of the Panjal Traps were analysed for platinum-group elements (PGEs) to investigate the magma genesis, high-temperature behaviour and exploration potential of these elements. The PGE data exhibit substantial variability and show no systematic relation to their low- or high-Ti affinity. Instead, the basalts can be subdivided into a PGE-undepleted group (group 1) that has ΣPGE >10 ppb and Cu/Pd <30 000, and a PGE-depleted group, which consists of a subgroup showing limited (group 2A) or substantial depletion in Ir-series PGEs relative to Ni (group 2B). The group 1 samples indicate an S-undersaturated history, whereas the group 2 samples might have different origins in terms of S-saturation. Fractionation of a tiny amount of sulfide melts (0.075–0.1%) from a representative group 1 sample accounts for the chalcophile element patterns observed in the group 2B samples. The relatively high Cu/Pd, unfractionated Ni/Ir and low PGE abundances observed in the group 2A samples cannot be explained by equilibration of an immiscible sulfide melt alone, and probably require decomposition of residual sulfides into sulfide melt and a monosulfide solid solution in the mantle restite. Our results question the notion that the coexistence of PGE-undepleted and -depleted magmas is prospective in the exploration of magmatic Ni–Cu–(PGE) sulfide mineralization.

Joining of Silicon Nitride to Metal (Mo and Ti) Using a Cu-Foil Interlayer

This work focuses on various aspects of diffusion bonding silicon nitride to Mo and Ti using a Cu-foil interlayer. Si3N4/Cu/Ti/Cu/Si3N4 and Si3N4/Cu/Mo/Cu/Si3N4 combinations have been diffusion joined at temperatures ranging from 950 to 1150 °C using different holding times in Ar. The results show that Si3N4 could not be bonded to Mo at temperature lower than 1100 °C even for holding times of 60 minutes, however, successful joining is achieved at 1150 °C. On the other hand, successful joining is accomplished at 1050 and 1100 °C for a Si3N4/Cu/Ti/Cu/Si3N4 sample. In the Si3N4/Cu/Ti system, joining occurs by the formation of a reactive interface with several reaction products on the metal side of the joint. All the silicon nitride samples have joined to titanium with no several interfacial cracking and porosity at the interface. The results corresponding to the Si3N4/Cu/Mo system show that a higher temperature is required to join the materials compared with the Si3N4/Cu/Ti system, since the formation of liquid produced by the interaction of Cu with Ti and Si promotes bonding and the high affinity of Ti for Si results in rapid interface formation.

Titanium(IV) targets phosphoesters on nucleotides: implications for the mechanism of action of the anticancer drug titanocene dichloride.

Abstract Reactions between the anticancer drug titanocene dichloride (Cp2TiCl2) and various nucleotides and their constituents in aqueous solution or N,N-dimethylformamide (DMF) have been investigated by 1H and 31P NMR spectroscopy and in the solid state by IR spectroscopy. In aqueous solution over the pH* (pH meter reading in D2O) range 2.3-6.5, CMP forms one new species with Ti(IV) bound only to the phosphate group. In acidic media at pH*<4.6, three species containing titanocene bound to the phosphate group of dGMP, AMP, dTMP and UMP are formed rapidly. The bases also appear to influence titanocene binding. Only one of these Ti(IV)-bound species can be detected in the pH* range of 4.6-6.5 in each case. The order of reactivity towards Cp2TiCl2(aq) at pH* ca. 3 is GMP>TMP approximately AMP > CMP. At pH* > 7.0, hydrolysis of Cp2TiCl2 predominated and little reaction with the nucleotides was observed. Binding of deoxyribose 5'-phosphate and 4-nitrophenyl phosphate to Cp2TiCl2(aq) via their phosphate groups was detected by 31P NMR spectroscopy, but no reaction between Cp2TiCl2(aq) and deoxyguanosine, 9-ethylguanine or deoxy-D-ribose was observed in aqueous solution. The nucleoside phosphodiesters 3',5'-cyclic GMP and 2',3'-cyclic CMP did not react with Cp2TiCl2(aq) in aqueous solution; however, in the less polar solvent DMF, 3',5'-cyclic GMP coordination to [Cp2Ti]2+ via its phosphodiester group was readily observed. Binding of titanocene to the phosphodiester group of the dinucleotide GpC was also observed in DMF by 31P NMR. The nucleoside triphosphates ATP and GTP reacted more extensively with Cp2TiCl2(aq) than their monophosphates; complexes with bound phosphate groups were formed in acidic media and to a lesser extent at neutral pH. Cleavage of phosphate bonds in ATP (and GTP) by Cp2TiCl2(aq) to form inorganic phosphate, AMP (or GMP) and ADP (or GDP) was observed in aqueous solutions. In addition, titanocene binding to ATP was not inhibited by Mg(II), but the ternary complex titanocene-ATP-Mg appeared to form. These reactions contrast markedly with those of the drug cisplatin, which binds predominantly to the base nitrogen atoms of nucleotides and only weakly to the phosphate groups. The high affinity of Ti(IV) for phosphate groups may be important for its biological activity.

TECTONO-MAGMATIC SETTING OF THE JURASSIC OPHIOLITES FROM THE SOUTH APUSENI MOUNTAINS (ROMANIA): PETROLOGICAL AND GEOCHEMICAL EVIDENCE

In the South Apuseni Mountains (Romania), Jurassic ophiolites can be found in association with Upper Jurassic - Lower Cretaceous island-arc magmatic suites, within a narrow belt which marks the boundary between the Eurasian and Apulian Palaeozoic continental margins. These ophiolites are highly dismembered, and sections of the lowermost crust and upper mantle are not present. New data on the field occurrence, petrology, and geochemistry of the plutonic, subvolcanic, and volcanic ophiolitic units are presented. The plutonic rocks consist of both layered and isotropic gabbros, as well as subordinate Fe-gabbros, and quartz-diorites. Ultramafic cumulates are very scarce, and include plagioclase-dunites and plagioclase-wehrlites. The subvolcanic section is represented by typical sheeted dyke complexes, cropping out in several localities and including basalts and basaltic andesites. The volcanic section includes pillowed and massive lava flows, as well as subordinate volcanic breccias, all displaying high-Ti magmatic affinity. The geochemical characteristics of these volcanic rocks are very similar to those of basalts generated at Mid-Ocean Ridge (MORBs), as well as those of the high-Ti ophiolitic complexes of the Dinaride and Hellenide orogenic belts. The constituent minerals of the intrusives are olivine, plagioclase, clinopyroxene (rarely orthopyroxene), Cr-spinel, and Fe- Ti-oxides. The subvolcanic and volcanic rocks contain plagioclase, clinopyroxene, and Fe-Ti oxides. The clinopyroxene chemistry also confirms the high-Ti affinity.