China
Africa
Explore chapters and articles related to this topic
Early Proterozoic Magmatism and Geodynamics — Evidence of a Fundamental Change in the Earth’s Evolution
Published in O.A. Bogatikov, R.F. Fursenko, G.V. Lazareva, E.A. Miloradovskaya, A. Ya, R.E. Sorkina, Magmatism and Geodynamics Terrestrial Magmatism Throughout the Earth’s History, 2020
Sm–Nd and Re–Os isotopic studies of mafic and ultramafic cumulates of the intrusions and associated dykes showed that it was formed by at least two magma types, referred to as U-type (ultramafic magma) and A-type (anorthositic magma). They differ in their major element, trace element, and precious metal abundance and isotopic composition and were derived from at least two distinct sources (Lambert et al., 1989, 1995). For U-type magma, the typical combination of low initial Os isotopic values with low initial Nd isotopic values (εNd<– 1), high 207Pb/204Pb for given 206Pb/204Pb (Wooden et al., 1990), and high (Ce/Yb)n ratios in the U-type cumulates and dykes is more consistent with the involvement of Re-poor but trace-element-enriched portions of the subcontinental lithospheric mantle in the petrogenesis of these magmas (Lambert et al.,1995). Following these investigators, the radiogenic initial Os isotopic composition of the J-M Reef and other portions of the elevated PGE concentrations suggest that A-type parental magmas incorporated Os from radiogenic early Archaean crust. Heterogeneous Nd and Os isotope data from the rocks below the J-M Reef suggest that the A-type magmas injected into the Stillwater magma chamber during crystallization of the U-type melts.
Diamond and carbon nanostructures for biomedical applications
Published in Functional Diamond, 2022
Yuxiang Xue, Xue Feng, Samuel C. Roberts, Xianfeng Chen
Natural diamonds are generally formed in subcontinental lithospheric mantle or even deeper where element carbon is deposited by oxidation-reduction reactions and recrystallised to diamond at extreme temperatures and pressures [15]. Through crustal movements over long time, diamond is brought to the surface by volcanic activity. However, natural diamond is scarce and expensive and cannot meet the demand of practical applications. The history of synthetic nanodiamond can be traced to 1950s [16]. In early researches, nanodiamonds were synthesised from controlled detonation by using carbon-containing explosives such as trinitrotoluene (TNT) and cyclotrimethylenetrinitramine (RDX) [17]. Since then, artificial nanodiamond has made a rapid development and progress. Figure 1 shows the images of nanodiamonds synthesised from carbon films after laser pulse [18]. Today, one could easily synthesis nanodiamond with different dimensions and shapes through detonation technique, high pressure, high temperature (HPHT) synthesis, chemical vapour deposition (CVD) and laser ablation (Table 1) [27–29].
The geochemistry and petrogenesis of Carnley Volcano, Auckland Islands, SW Pacific
Published in New Zealand Journal of Geology and Geophysics, 2018
John A. Gamble, Chris J. Adams, Paul A. Morris, Richard J. Wysoczanski, Monica Handler, Christian Timm
There is considerable geochemical and petrological evidence from the study of mantle xenoliths from S.E. Australia (Griffin et al. 1988; O’Reilly and Griffin 1988; Yaxley et al. 1991; McBride et al. 1996), southern Zealandia (McCoy-West et al. 2013, 2015, 2016; Scott et al. 2014; Liu et al. 2015; Scott, Brenna et al. 2016; Scott, Liu et al. 2016; Dalton et al. 2017) and Antarctica (Gamble and Kyle 1987; Handler et al. 2003; Martin et al. 2015; Panter et al. 2018) that the subcontinental lithospheric mantle is geochemically and mineralogically heterogeneous and has been variably metasomatised. Moreover, for Zealandia, Sm–Nd, Lu–Hf , U–Th–Pb and Re–Os model age calculations (Scott et al. 2014; Liu et al. 2015; McCoy-West et al. 2016; Scott, Brenna et al. 2016) have demonstrated depletion-enrichment events that extend from Palaeo-Proterozoic to late Phanerozoic times and have suggested mantle sources enriched by carbonatite as recently as 120∼100 Ma (Scott 2014, Scott et al. 2014; McCoy-West et al. 2016). Accordingly, for our modelling, we have selected Primitive Mantle (Sun and McDonough 1989, PM) for the convecting asthenospheric mantle source and depleted MORB mantle (Workman and Hart 2005, DMM) enriched by addition of 1% calci-carbonatite (Hoernle et al. 2002) for lithospheric mantle (DMM + 1%).
Mid-Devonian basaltic magmatism and associated sedimentation: the Ooloo Hill Formation, central-eastern South Australia
Published in Australian Journal of Earth Sciences, 2023
C. Wade, A. J. Reid, E. A. Jagodzinski, M. J. Sheard
The small volume and heterogeneous geochemical compositions of the Ooloo Hill Formation volcanic member suggest they formed by batch melting of isolated mantle reservoirs with little crustal residence time. Such melting is of inadequate volume to cause significant melting of the subcontinental lithospheric mantle. As a result, these magmas retain the asthenospheric signature of their source.