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Olivine and pyroxene are two important classes of rock-forming minerals that have absorption bands in the visible/NIR that result from electronic crystal field transitions of Fe in octahedral coordination ().These absorptions are diagnostic of the minerals and their chemical composition (15, 16).Olivine [(Mg,Fe) 2 SiO 4] has a broad, complex absorption centered near …
The middle package is mostly composed of pyroxenite and feldspathic pyroxenite, but serpentinised olivine pyroxenite, feldspathic harzburgite and chromitite seams also sporadically occur. The upper unit comprises a sulphide-bearing and medium- to coarse-grained feldspathic pyroxenite (Fig. 6 ) with visible fine-grained interstitial sulphides.
DISCUSSION Pyroxenite–peridotite melt mixing The olivine compositions of the studied rocks strongly suggest that their primary melts were derived by melting of pyroxenite in agreement with the elevated wholerock FeOT/MnO of the southern Payenia basalts (Fig. 2) and their major element compositions in general (Søager & Holm, 2013).
[1] The contribution of olivine-poor lithologies (pyroxenite, eclogite, etc.) in the mantle to the composition of mantle-derived melts is a growing topic of discussion in light of results suggesting that some magmatic characteristics are not easily explained by melt derivation solely from peridotitic sources. To investigate this issue, we have examined the Hf and Os …
Both Zn/Fe and Mn/Zn have been shown to be very sensitive to the melting of an olivine-free and garnet-rich source (pyroxenite) as this process fractionates the Zn, Fe and Mn (Le Roux et al., 2011; Howarth and Harris, 2017) while fractionation between these elements during melting of an ol-opx assemblage (peridotite) is minimal.
Lavas with CaO contents that are lower than those defined by the red line are potentially partial melts of pyroxenite or high-degree partial melts of peridotite that experienced …
A pyroxenite containing 5% olivine. Essential minerals - these are minerals that are required within the classification of this rock:
The low-δ 18 O olivines show higher X px (weight fraction of pyroxenite-derived melt, related to Ni*FeO/MgO and Mn/Fe values of olivine 46; Supplementary Fig. 8), lower 100Ca/Fe, and Co/Fe than ...
Motivated by ref. 6, after correction to a Mg# of 0.89 (see Methods), there is a good correlation between NiO 89 and MnO 89 concentrations (in wt%) in primitive olivine phenocrysts in basalts 6,35 ...
Here we present new Ni data in olivine phenocrysts from the central Mexican Volcanic Belt (MVB), a Quaternary volcanic arc that is constructed on thick continental crust.
The silicic melts, reacting with DMM peridotite, would form pyroxenite by converting olivine to orthopyroxene (Herzberg 2011). Subsequent partial melting of this pyroxenite would …
U-Pb zircon dating by LA-ICP-MS and SHRIMP for one olivine pyroxenite yields complex age populations including Mesozoic ages of 97–158 Ma and 228 ± 8.7 Ma, Early Paleozoic ages of 418–427 Ma ...
It has a characteristic spotted appearance due to the presence of rounded or elongated pyroxene grains within the olivine matrix. Pyroxenite: Pyroxenite is a type of peridotite that is composed predominantly of pyroxene minerals, such as clinopyroxene or orthopyroxene, with minor amounts of other minerals. It is typically dark-colored and can ...
The contribution of olivine-poor lithologies (pyroxenite, eclogite, etc.) in the mantle to the composition of mantle-derived melts is a growing topic of discussion in light of results …
The Cr-pyroxenite group includes three websterites and one olivine clinopyroxenite (JSB06-36). They are bright green in hand sample and are texturally well equilibrated (Fig. 1a, b). The Cr-diopside websterites are dominantly composed of clinopyroxene (52–57%) and subordinate orthopyroxene (34–48%), and in some cases, rare spinel and …
According to the proposed model, carbonated melts/fluids released from the stagnant slab interacted with the lithospheric mantle, resulting in the transformation of the …
Olivine in ocean island basalts can provide unique insights into lithological heterogeneity (i.e., peridotite versus pyroxenite) in the mantle.
A resource for Mineralogy students. Actinolite; Albite; Alkali Feldspar; Almandine; Amazonite; Amphibole; Andalusite; Andesine
The best explanation is that the source of Xindian basalts is the Fe-rich source, such as pyroxenite. Summary. Olivine chemistry has the potential ability to identify the source lithology. Comparing with those peridotite melts, olivine phenocrysts of Xindian basalts bear higher Ni contents and Fe/Mn ratios, but lower Ca and Mn contents at a ...
1. Introduction. Olivine is a ubiquitous mineral in mafic-ultramafic rocks and serves as an excellent geochemical tracer (Sobolev et al., 2005, Sobolev et al., 2007; Foley et al., 2013; Wang et al., 2021).Being the first silicate mineral to crystallize from all primary mantle-derived melts, it provides insights on different magmatic processes in general and melting of mantle …
Olivine is the first mineral to crystallize in typical mantle-derived magmas, and can record important information regarding the primary melt composition prior to subsequent modification by crustal assimilation and/or fractional crystallization (Howarth and Harris, 2017).High Ni and low Ca-Mn contents of olivine phenocrysts have been interpreted to reflect …
One explanation for the skewed and multimodal distributions of olivine abundance in Archaean cratonic peridotites across the studied cratons is a two stage process, in which a baseline melt ...
Here, we test whether melting of peridotite alone can explain the observed trend in olivine compositions by combining new experimental data on the partitioning of Mn between …
Mantle olivines can be distinguished from volcanic olivines by lower concentrations of Ca (<700 ppm), Ti (<70 ppm), and often Cr. The melting of pyroxenites derived from …
The ultrabasic rocks, where not serpentinized, include peridotite, pyroxenite and dunite, commonly bearing small amounts of bytownite or anorthite (Hutchison and Dhonau, 1971). All are coarse-grained (1–3 mm). Olivine is commonly Fo 90.4, ortho-pyroxene Eng 82–90 Fs 0–8 Wo 1–10, clino-pyroxene En 69 Fs 3 Wo 28 (Omang, 1995). The ...
The mantle source is assumed to be composed of carbonated peridotite and pyroxenite, with peridotite containing 55% olivine, 13% orthopyroxene, 15% clinopyroxene 15% garnet and 2% calcite ...
The Howqua Olivine Pyroxenite and associated lavas occur in the Howqua River segment of the Cambrian Mount Wellington Greenstone Belt (Fig. 1). It forms a sill-like body approximately 50 m thick which extends, conformable with the stratigraphy within the greenstones (Fig. 2), over a strike distance of at least 4 km. ...
The trace element composition of olivine is a rapidly growing research area that has several applications of great potential. Mantle olivines can be distinguished from volcanic olivines by lower concentrations of Ca (<700 ppm), Ti (<70 ppm), and often Cr.The melting of pyroxenites derived from recycled ocean crust can be recognized in volcanic olivines by correlations of Mn, …
Hydrous slab components rich in Si, Na, and fluid mobile large-ion lithophile elements (LILE) transform mantle olivine to "reaction orthopyroxene." Along the ascent paths, and embedded into surrounding peridotite, secondary pyroxenite lithologies are created that are composed of "reaction orthopyroxene" next to mantle clinopyroxene and ...
In plagioclase-rich olivine pyroxenite at the top of the Lower Zone, chromite is locally replaced by hercynite. Marginal norite sill within the Lower Zone and its relationships with adjacent peridotite. Fine- to medium-grained norite in the interval of 1513.5–1517 m depth is composed predominantly of plagioclase (up to 70%) with subordinate ...
