The petrology of the Lugar Sill, SW Scotland

1987 ◽  
Vol 77 (4) ◽  
pp. 325-347 ◽  
Author(s):  
C. M. B. Henderson ◽  
F. G. F. Gibb
Keyword(s):  
Trace Elements ◽  
Magma Chamber ◽  
Major And Trace Elements ◽  
Central Unit ◽  
Residual Liquid ◽  
Multiple Injections ◽  
Incompatible Elements ◽  
Complete Section ◽  
Drill Cores

ABSTRACTA 49 m complete section through the 288 Ma Lugar Sill obtained from drill cores can be subdivided into nine units. The uppermost four units are teschenitic and are mirror images of the bottom four. A 35 m thick central unit consists of theralite passing down into kaersutite theralite and then picrite. Marginal chilling 'of the units indicates multiple intrusion from the outside inwards. Olivine in the central unit (Fo88–90) encloses Cr-rich spinels and increases in amount inwards to over 50%. Clinopyroxene, kaersutite and biotite show symmetrically increasing Fe/Mg from the centre of the sill outwards. Most major and trace elements vary symmetrically throughout the sill with those in the central unit reflecting mainly olivine distribution but incompatible elements exhibit upward enrichment. Remarkably, the most-evolved rocks in the sill are at its margins. The sill was formed by multiple injections of successively less-evolved teschenitic magmas followed by a larger pulse of theralitic liquid carrying abundant olivine phenocrysts. The amount of olivine in this final pulse increased during emplacement. Subsequent in-situ differentiation in the central unit, with upward enrichment in residual liquid and volatiles, gave rise to lugarites. The various magmas were produced in a lower-level magma chamber by differentiation of a mantle-derived, alkali-rich picritic magma.

scholarly journals Parental magma composition of the Main Zone of the Bushveld Complex: Evidence from in-situ LA-ICP-MS trace element analysis of silicate minerals in the cumulate rocks

2020 ◽  
Author(s):  
Shenghong Yang ◽  
Wolfgang D. Maier ◽  
Belinda Godel ◽  
Sarah-Jane Barnes ◽  
Eero Hanski ◽  
...  
Keyword(s):  
Trace Elements ◽  
Trace Element ◽  
Bushveld Complex ◽  
Trace Element Analysis ◽  
Parental Magma ◽  
Main Zone ◽  
Element Analysis ◽  
Silicate Minerals ◽  
Incompatible Elements

<p>In-situ trace element analysis of cumulus minerals may provide a clue to the parental magma from which the minerals crystallized. However, this is hampered by effects of the trapped liquid shift (TLS). In the Main Zone (MZ) of the Bushveld Complex, the Ti content in plagioclase grains shows a clear increase from core to rim, whereas most other elements (e.g., rare earth elements (REEs), Zr, Hf, Pb) do not. This is different from the prominent intra-grain variation of all trace elements in silicate minerals in mafic dikes and smaller intrusion, which have a faster cooling rate. We suggest that crystal fractionation of trapped liquid occurred in the MZ of Bushveld and the TLS may have modified the original composition of the cumulus minerals for most trace elements except Ti during slow cooling. Quantitative model calculations suggest that the influence of the TLS depends on the bulk partition coefficient of the element. The effect on highly incompatible elements is clearly more prominent ­­than on moderately incompatible and compatible elements because of different concentration gradients between cores and rims of cumulate minerals. This is supported by the following observations in the MZ of Bushveld: 1) positive correlation between Cr, Ni and Mg# of clinopyroxene and orthopyroxene, 2) negative correlation between moderately incompatible elements (e.g., Mn and Sc in clinopyroxene and orthopyroxene, Sr, Ba, Eu in plagioclase), but 3) poor correlation between highly incompatible elements and Mg# of clinopyroxene and orthopyroxene or An# of plagioclase. Modeling suggests that the extent of the TLS for a trace element is also dependent on the initial fraction of the primary trapped liquid, with strong TLS occurring if the primary trapped liquid fraction is high. This is supported by the positive correlation between highly incompatible trace element abundances in cumulus minerals and whole-rock Zr contents.</p><p>We have calculated the composition of the parental magma of the MZ of the Bushveld Complex. The compatible and moderately incompatible element contents of the calculated parental liquid are generally similar to those of the B3 marginal rocks, but different from the B1 and B2 marginal rocks. For the highly incompatible elements, we suggest that the use of the sample with the lowest whole-rock Zr content and the least degree of TLS is the best approach to obtain the parental magma composition. Based on calculation, we propose that a B3 type liquid is the most likely parental magma to the MZ of the Bushveld Complex.</p>

Geology and geochemistry of the molybdenite showings of the Ackley City batholith, southeast Newfoundland

1980 ◽  
Vol 17 (9) ◽  
pp. 1246-1258 ◽  
Author(s):  
J. B. Whalen
Keyword(s):  
Trace Elements ◽  
Vapour Phase ◽  
Major And Trace Elements ◽  
Composite Body ◽  
Precambrian Rocks ◽  
Geological Features ◽  
Tectonic Zones ◽  
Host Rocks ◽  
Residual Melt

The Ackley City batholith of southeast Newfoundland is an oval-shaped granitoid of approximately 5400 km2 which intruded Ordovician and Precambrian rocks of the Gander and Avalon tectonic zones, respectively, about 345 Ma ago. It is a composite body, consisting mainly of K-feldspar megacrystic granite and alaskite. Spatially related to the southeast contact of the alaskite are younger aplites and pegmatites within which are six separate molybdenite showings. The showings vary in their type of host rocks and in features of mineralization and alteration, but can all be classed as being of aplite–pegmatite type.This notably felsic (SiO2 > 71.8%) pluton has alkaline affinities and features indicative of derivation from an igneous source (I-type). Some major and trace elements exhibit considerable variations. These variations and other geological features indicate that aplites and pegmatites formed by in situ fractional crystallization of the alaskite at shallow depths (1.8 to 3.7 km) to produce a roof-zone complex. Mo is localized in these rocks, which formed from the final residual melt and coexisting vapour phase, and is considered to be closely genetically related to them.

The petrology and geochemistry of the Creag Dubh composite sill, Whiting Bay, Arran, Scotland

1977 ◽  
Vol 114 (1) ◽  
pp. 1-8 ◽  
Author(s):  
N. W. Rogers ◽  
I. L. Gibson
Keyword(s):  
Trace Elements ◽  
Magma Chamber ◽  
Major And Trace Elements ◽  
Rock Types ◽  
Petrology And Geochemistry

SummaryAnalysis of 17 samples for both major and trace elements reveals that, unlike most other Tertiary composite intrusions, the Creag Dubh sheet possesses silicic margins and a doleritic centre. The two rock types grade together rapidly without chilling at the upper and lower internal contacts. However, there is evidence for mixing of the two magma types prior to or during emplacement with the production of limited amounts of intermediate hybrids. The central dolerite appears to be later than the marginal felsites which in places back-vein the dolerite. The sequence of intrusion is tentatively related to the upward draining of a strongly zoned magma chamber.

scholarly journals Geochemistry of garnet megacrysts from the Mir kimberlite pipe (Yakutia) and the nature of prothokimberlite melt

2019 ◽  
Vol 486 (5) ◽  
pp. 583-587
Author(s):  
A. M. Agashev
Keyword(s):  
Trace Elements ◽  
Rare Earth ◽  
Rare Earth Elements ◽  
Negative Correlation ◽  
Kimberlite Pipe ◽  
Major And Trace Elements ◽  
Major Elements ◽  
Incompatible Elements ◽  
Composition Study ◽  
Melt Composition

The paper presents the results of major and trace elements composition study of garnet megacrysts from Mir kimberlite pipe. On the major elements composition those garnets classified as low Cr and high Ti pyropes. Concentrations of TiO2 show a negative correlation with MgO и Cr2O3 contents in megacrysts composition. Fractional crystallization modeling indicates that the most appropriate melt to reproduce the garnet trace elements signatures is the melt of picritic composition. Composition of garnets crystallized from kimberlite melt do not correspond to observed natural garnets composition. Kimberlites contain less of Ti, Zr, Y and heavy REE (rare earth elements) but more of very incompatible elements such as light REE, Th, U, Nb, Ba then the model melt composition that necessary for garnet crystallization.

scholarly journals In Situ Chalcophile and Siderophile Element Behavior in Sulfides from Moroccan Middle Atlas Spinel Peridotite Xenoliths during Metasomatism and Weathering

Minerals ◽  
2019 ◽  
Vol 9 (5) ◽  
pp. 276 ◽  
Author(s):  
Katrin J. Westner ◽  
Christoph Beier ◽  
Reiner Klemd ◽  
Inga Osbahr ◽  
Nadine Brooks
Keyword(s):  
Trace Elements ◽  
Solid Solutions ◽  
Inductively Coupled Plasma ◽  
Major And Trace Elements ◽  
Spinel Peridotite ◽  
Inductively Coupled ◽  
Plasma Mass Spectrometry ◽  
Middle Atlas ◽  
Mantle Processes

In situ chalcophile and siderophile major and trace elements were analyzed in sulfides from eight Moroccan Middle Atlas lherzolite xenoliths using electron microprobe and laser ablation inductively coupled plasma mass spectrometry. The sulfides occur enclosed in primary silicates, interstitial in the peridotite matrix, and associated with glass-bearing melt pockets. Monosulfide solid solutions are enriched in these xenoliths relative to pentlandite and intermediate solid solutions. Regardless of the textural occurrence, sulfide platinum-group element (PGE) patterns are distinguished into residual ([Pd/Ir]N < 1 and [Pt/Pd]N > 1 or [Pt/Pd]N < 1), melt-like ([Pd/Ir]N > 1), and unfractionated patterns. The coexistence of both residual and melt-like PGE signatures on a cm scale in a single sample implies that sulfides may record initial depletion and subsequent re-enrichment more effectively than constituent silicates do. Chalcophile and siderophile trace elements other than the PGEs are fractionated between the precipitated sulfide phases, but do not vary systematically with the PGE signatures, suggesting that the PGEs are comparatively sensitive to melting and depletion. In addition, Fe-rich hydroxides generated by sulfide breakdown due to atmospheric weathering display PGE systematics almost identical to their precursor sulfides, implying that they may be reliable tracers of mantle processes even after extensive weathering.

Lateral chemical heterogeneity in the Palaeocene upper mantle beneath the Scottish Hebrides

1980 ◽  
Vol 297 (1431) ◽  
pp. 229-244 ◽  
Keyword(s):  
Trace Elements ◽  
North Atlantic ◽  
Upper Mantle ◽  
Major Element ◽  
Major And Trace Elements ◽  
The North ◽  
Incompatible Elements ◽  
Major Element Chemistry ◽  
Pass Through ◽  
Incompatible Trace Elements

The early major products of Tertiary volcanicity in both Skye and Mull are transitional basic lavas, similar in their major-element chemistry to world-wide alkali basalt series. In contrast, their contents of incompatible trace elements bear more resemblance to those of olivine tholeiites. The Mull basalts have similar ranges of silica saturation, Mg/(Mg+Fe), Y and Yb, but lower overall abundance ranges of strongly incompatible elements than the Skye basalts. The variation of incompatible elements in the Mull and Skye lavas is consistent with a model of a mantle source from which a small amount of melt (no more than 1 % ?) had been extracted, with the pre-Tertiary upper-mantle fusion beneath Mull slightly greater than beneath Skye. Chemical and tectonic considerations suggest that this mantle was neither residual from the formation of the Archaean Lewisian complex, nor emplaced as a result of tension associated with the Gainozoic rifting of the North Atlantic. Data on major and trace elements for a mafic alkalic dyke of the Permian swarms that pass through western Scotland show that these have the requisite geochemical characteristics to have caused this depletion. Such dykes are more abundant in the region of Mull than Skye.

In situ analysis of major and trace elements of anhydrous minerals by LA-ICP-MS without applying an internal standard

2008 ◽  
Vol 257 (1-2) ◽  
pp. 34-43 ◽  
Author(s):  
Yongsheng Liu ◽  
Zhaochu Hu ◽  
Shan Gao ◽  
Detlef Günther ◽  
Juan Xu ◽  
...  
Keyword(s):  
Trace Elements ◽  
Internal Standard ◽  
Major And Trace Elements ◽  
In Situ Analysis ◽  
Icp Ms

scholarly journals MK-1 Orthopyroxene—A New Potential Reference Material for In-Situ Microanalysis

Minerals ◽  
2021 ◽  
Vol 11 (12) ◽  
pp. 1321
Author(s):  
Lihui Jia ◽  
Qian Mao ◽  
Bin Su ◽  
Shitou Wu ◽  
Liangliang Huang ◽  
...  
Keyword(s):  
Trace Elements ◽  
Reference Material ◽  
Analytical Techniques ◽  
Major And Trace Elements ◽  
Major Elements ◽  
Metamorphic Belt ◽  
Ultramafic Intrusion ◽  
Binocular Microscope ◽  
Good Agreement

Orthopyroxene, an important phase in mantle-derived rocks, has become a powerful tool to unravel mantle nature and magma processes. However, the applications have been hindered by the lag in the development of analytical techniques, such as shortage of reference materials. Orthopyroxene grains derived from an ultramafic intrusion at the Mogok metamorphic belt (Myanmar) were evaluated for the potential use of orthopyroxene as a reference material for in-situ microanalysis. Approximately 20 g of 0.5–3 mm pure orthopyroxene grains were separated under binocular microscope and analyzed using EPMA, LA-ICPMS, and bulk analytical methods (XRD, XRF, and solution-ICPMS) for major and trace elements at four institutions. Eleven core-to-rim profiles carried out using EPMA and twelve core-to-rim profiles determined using LA-ICPMS suggest that MK-1 orthopyroxene grains are sufficiently homogeneous, with RSD < ±2% (1σ) for major elements (Mg, Si, and Fe) and RSD < ±10% (1σ) for trace elements (Na, Al, Ca, Ti, Cr, Co, Zn, Ni, Mn, Sc, and V). In addition, the composition of MK-1 orthopyroxene was also measured by XRF and solution-ICPMS measurements in two different laboratories, to compare with the results measured using EPMA and LA-ICPMS. The results indicated a good agreement with RSE < ±2% (1σ) for major elements and RSE < ±5% (1σ) for most trace elements, except for Na (±9.73%) and Ti (±6.80%). In an overall assessment of these data, MK-1 orthopyroxene can be considered as a reference material for in-situ microanalysis, which would provide solid trace elements data for a better understanding of mantle source and magmatic evolution.

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