Genetic interpretation of CSD for olivine through the dunite section of the Dovyren layered intrusion: linking with geochemistry and probable dynamics of the cumulate mush.

2020 ◽  
Author(s):  
Sergei Sobolev ◽  
Alexey Ariskin ◽  
Simone Tarquini ◽  
Ivan Pshenitsyn ◽  
Georgy Nikolaev ◽  
...  
Keyword(s):  
Parental Magma ◽  
Layered Intrusion ◽  
Coarse Grained ◽  
Main Body ◽  
Russian Science ◽  
Narrow Zone ◽  
Genetic Interpretation ◽  
Modal Layering ◽  
Lower Temperature ◽  
Log Linear

<p>The Yoko-Dovyren ultramafic-mafic intrusion (the northern Baikal region, Russia) has excellent outcropping as well as layering falls vertically. It`s age is 728 Ma. Length of the main body is 26 km. The modal layering of its central part (~3 km thick) includes a basal reversal (from chilled rocks to plagiolherzolites) followed with Pl-bearing to adcumulate dunite, troctolite and gabbroic sequence.</p><p>Over the past 20 years, several sections of the massif have been studied in detail. (Ariskin et al 2018) have determined two major types of parental magmas recorded in the FeO vs MgO trends for the Ol cumulates through the first 500 m of the cross-section. These two geochemically similar magmas are consistent with equilibrium olivine Fo88 and Fo86 in the range of temperatures from 1290°C to ~1200°C.</p><p>We present the results of quantification of CSD of olivine from the dunite succession, which argue for two types of olivine grain populations differing for the more primitive and relatively evolved magma.</p><p>The slope of the log-linear CSD function in the lower-temperature magmas has a less steep as compared to the higher temperature ones.  Both populations can be considered to represent intratelluric olivine crystallized at a pre-emplacement stage. At a stratigraphic level of 200 m from the lower contact, in some of the samples we observed changes in the CSD patterns, which evidence a coarsening of the populations within the Dovyren chamber. Starting from 350-400 m coarsening is noticeable everywhere, so that the CSD cease to be log-linear. In addition, in a narrow zone of 500-550 m dunite are found to display a pronounced bimodal (kinked) distribution of olivine. In a larger population, olivine has highest aspect ratio (up to 3-3.5) compared to other dunite samples. The origin of such dunite can be explained by the intrusion of hot portions of magma into the colder cumulus. In this case such elongated crystals may be due to the increased growth rate of the original olivine grains. The smaller population may be due to a new nucleation event after emplacement. CSD in cumulates above the «kinked dunites» demonstrate coarsening of olivine, with the most coarse-grained populations typical of highly contaminated dunite.</p><p>Thus, a rather narrow zone is distinguished in dunite, where we can observe primary intratelluric CSD, which is not substantially altered nither by peritectic reactions in the loose cumulus of the reversal sequence, where the temperature drops rapidly, nor by coarsening during long history of temperature oscillations close to the primary magmas condition above this zone.</p><p>This work support from the Russian Science Foundation (RSF, grant No. 16-17-10129)</p><p>Ariskin Alexey, Danyushevsky Leonid, Nikolaev Georgy, Kislov Evgeny, Fiorentini Marco, McNeill Andrew, Kostitsyn Yuri, Goemann Karsten, Feig Sandrin, and Malyshev Alexey. The dovyren intrusive complex (southern siberia, russia): Insights into dynamics of an open magma chamber with implications for parental magma origin, composition, and cu-ni-pge fertility. Lithos, 302:242–262, 2018.</p>

Hydrous mafic-ultramafic intrusives in a nascent arc (Massif du Sud, New Caledonia ophiolite).

2021 ◽  
Author(s):  
Arianna Secchiari ◽  
Alessandra Montanini ◽  
Dominique Cluzel ◽  
Elisa Ferrari
Keyword(s):  
Trace Element ◽  
Transition Zone ◽  
New Caledonia ◽  
Incompatible Trace Element ◽  
Coarse Grained ◽  
Main Body ◽  
Distinctive Features ◽  
First Occurrence ◽  
Ultramafic Cumulate ◽  
Compositional Variability

<p>The New Caledonia ophiolite hosts one of most complete sections of a nascent arc, representing an excellent natural laboratory for investigating the origin and the evolution of subduction systems. The sequence, originated during the onset of the Eocene subduction [1, 2], is composed of ultra-depleted forearc harzburgites [3] overlain by a dunite-dominated transition zone (500m thick), in turn overtopped by mafic-ultramafic cumulate lenses. The ultramafic rocks of the transition zone (mainly dunites and wehrlites) most likely resulted from melt-peridotite reactions involving primitive arc tholeiites and boninitic magmas [2]. By contrast, dunite-pyroxenite and gabbronorite cumulates derive from H<sub>2</sub>O-poor depleted melts transitional between boninites and arc-tholeiites [2, 4].</p><p>In this contribution, we report the first occurrence of amphibole-bearing ultramafic lithologies in the New Caledonia arc sequence. Our study deals with a petrological and geochemical characterisation of a 2.5km x 5km composite, roughly snowball-shaped, intrusive body, consisting of pyroxenite, dunite, wehrlite, hornblendite and associated mafic-ultramafic, locally sheared, dikes from the Plum area (Massif du Sud).  The pyroxenite component, which forms the core of the intrusion, consists of coarse-grained websterites, mainly composed of weakly oriented orthopyroxene (~ 30-75 vol.%) and clinopyroxene (~ 20-40 vol.%), with variable amounts of edenitic amphibole (~ 2-30 vol.%). The amphibole generally occurs as poikilitic crystals or develops as coronas on pyroxenes. Highly calcic plagioclase (An= 83-96 mol %) is scarce in the pyroxenite body (~ 2 vol. %), but more abundant in the associated dikes (~ 10-50 vol.%). Clinopyroxene shows variable Mg# (0.82-0.92) and low Al<sub>2</sub>O<sub>3 </sub>(0.99-2.00 wt%). Likewise, amphibole yields high Mg# (0.712-0.865). Estimated equilibrium temperatures based on conventional pyroxene thermometry range between 870-970°C, whereas amphibole-plagioclase pairs provide slightly lower values (800-910 °C).</p><p>Whole rocks have moderately high Mg# (71-82) and REE concentrations one to five times chondritic values. The websterites of the main body show LREE-depleted (La<sub>N</sub>/Nd<sub>N</sub> = 0.5-0.8), weakly concave downward patterns, with flat HREE segments (Lu<sub>N</sub>/Tm<sub>N</sub> = 1.1-1.3). The mafic-ultramafic dikes display similar patterns, bearing depleted to flat LREE segments (La<sub>N</sub>/Nd<sub>N</sub> = 0.6-1) and positive Eu anomalies. For all the investigated lithologies, extended trace element diagrams indicate enrichments for FME (i.e. Rb, Ba, U) and Th, coupled to Zr-Hf depletion. Strong Sr positive spikes are only observed for the crosscutting dikes, while the pyroxenite body yields Sr negative anomalies.</p><p>Geochemical modelling shows that the putative liquids in equilibrium with the websterites have intermediate Mg# (57–63) and incompatible trace element patterns sharing remarkable similarities with the New Caledonia CE-boninites [5]. However, they significantly differ from the equilibrium melts reported for the other intrusive rocks of the sequence [1, 4], suggesting greater compositional variability for the liquids ascending into the Moho transition zone and lower crust. Our results support the notion that petrological and geochemical heterogeneity of magmatic products may be distinctive features of subduction infancy.</p><p> </p><p>References</p><p>[1] Marchesi et al., Chem. Geol., 2009, 266, 171-186.</p><p>[2] Pirard et al., J. Petrol., 2013, 54, 1759–1792.</p><p>[3] Secchiari et al., Geosc. Front., 2020, 11(1), 37–55.</p><p>[4] Secchiari et al., Contrib. Mineral. Petrol., 2018, 173(8), 66.</p><p>[5] Cluzel et al., Lithos, 2016, 260, 429–442.</p>

scholarly journals The Kræmer Ø syenite, Kangerdlugssuaq: preliminary description of one of the voluminous oversaturated syenites of the East Greenland Tertiary

1991 ◽  
Vol 38 ◽  
pp. 145-151
Author(s):  
C. K. Brooks
Keyword(s):  
Main Part ◽  
Basaltic Magma ◽  
Coarse Grained ◽  
Skaergaard Intrusion ◽  
East Greenland ◽  
Partial Melt ◽  
Basaltic Melt ◽  
Basaltic Magmas ◽  
Modal Layering ◽  
Preliminary Description

Tue Kræmer Ø syenite, situated close to the Skaergaard intrusion, is typical of many oversturated syenites in the area. It consists of a maginal breccia with a sharp contact to the surrounding gneisses. This breccia, about 150 m wide is made up of basaltic clasts in a granitic matrix. It is associated with pegmatites, aplites and granophyres, all with a non-peralkaline characters. Tue main part of the syenite is a coarse-grained, massively jointed body with many large basic xenoliths and occasional modal layering. It is associated with peralkaline rhyolitic dikes and pegmatites. Anatexis of basement and crystal differentiation from a basaltic magma are thought to be unlikely processes to explain the origin of the syenites although the breccia matrix appears to be a simple partial melt of the gneisses. It is postulated thai such an anatectic melt, formed by heat transfer from basaltic magmas, becomes modified by diffusive interchange with the basaltic melt to generate the syenite in the way described for a nearby locality by Nielsen & Brooks (1988).

Distribution of Culicoides molestus (Skuse) (Diptera : Ceratopogonidae) in Man-made Canals in South-eastern Queensland

1979 ◽  
Vol 30 (5) ◽  
pp. 653 ◽  
Author(s):  
DS Kettle ◽  
EJ Reye ◽  
PB Edwards
Keyword(s):  
Specific Gravity ◽  
High Water ◽  
Soil Samples ◽  
Main Body ◽  
South Eastern ◽  
Narrow Zone ◽  
Mean High Water ◽  
Tidal Water ◽  
Tide Level ◽  
Water Springs

In soil samples flooded for 18 h C. molestus larvae were scarce in the top 0.5 cm, most dense in 0.5-1.5 cm and most numerous in 1.5-8.5 cm depth. They were recovered from mean high water springs to mean tide level but were concentrated (87.6%) in a narrow zone above mean tide level and including mean high water neaps. There was no evidence that their distribution was influenced by remoteness from the main body of tidal water. Higher density fluids than normal, e.g. syrup, specific gravity > 1.3, were required to extract larvae of C. molestus.

P-T-fluid conditions of mineral equilibria in garnet-biotite crustal xenoliths from the Yubileinaya and Sytykanskaya kimberlite pipes, Yakutian kimberlite province.

2021 ◽  
Author(s):  
Natalia Seliutina ◽  
Oleg Safonov ◽  
Vasiliy Yapaskurt ◽  
Dmitry Varlamov ◽  
Igor Sharygin ◽  
...  
Keyword(s):  
Water Activity ◽  
Siberian Craton ◽  
Database Systems ◽  
Potassium Feldspar ◽  
Coarse Grained ◽  
Chemical Compositions ◽  
Exchange Reactions ◽  
Russian Science ◽  
Isotopic Evidence ◽  
Crustal Xenoliths

<p>This study provides the results of research of the garnet-biotite crustal xenoliths from the Yubileinaya (372±4.8 Ma) and Sytykanskaya (363±13 Ma) kimberlite pipes of the Alakit-Markhinsky field (Siberian craton). Isotopic evidence on zircons from similar crustal xenoliths (Grt+Bt+Pl+Kfs+Qtz±Scp) showed Archean Hf model ages (TDM = 3.13-2.5 Ga) and thus indicated that most of the lower and middle crust beneath the Markha terrane was produced in the Archean time (Shatsky et al., 2016).</p><p>The xenoliths are represented by the assemblage Grt+Bt+Pl+Kfs±Opx. Quartz is present only as rare inclusions in garnets. The rocks are coarse-grained, slightly foliated with garnets porphyroblasts of up to 5 cm in size. A spectacular feature of the rocks is an abundance of K-feldspar. Garnet grains are almost compositionally homogeneous, although they show a rimward decrease of the Mg and Ca contents indicating exchange reactions during cooling. Biotites are characterized by high F increasing from 1.5 wt.% in cores up to 2.2 wt.% in rims, as well as TiO<sub>2</sub> up to 7.8 wt.%, which is typical for high-grade rocks. Orthopyroxene (up to 5.5 wt. % Al<sub>2</sub>O<sub>3</sub>) relics are preserved both as inclusions in garnet and as individual grains in the rock matrix. Plagioclase occurs both as separate grains and as lamellae in potassium feldspar.</p><p>The bulk chemical compositions correspond to a metagraywacke. The REE spectra in these rocks are rather flat with slight enrichment in LREE. All the studied rocks are characterized by a distinct negative Eu anomaly (Eu/Eu* = 0.31-0.45).</p><p>Calculations using the PERPLEX software version 6.7.6 (Connolly, 2005) for Mg and Ca in Grt, Mg in Bt, and Ca in Pl indicated temperatures 630-730°C and pressures 5.8-7.2 kbar for the rocks. However, equilibria involving Al<sub>2</sub>O<sub>3</sub> in orthopyroxene corresponds to temperatures of 750-800<sup>o</sup>С at a similar pressure. It indicates that metamorphism of the garnet-biotite rocks reached higher temperatures, but they were actively modified later during cooling and insignificant decompression (by about 1 kbar). Calculations using the TWQ software version 2.3 (Berman, 2007) indicate consistent temperatures 610-680°C for the garnet-orthopyroxene and 640-690<sup>o</sup>C for garnet-biotite Mg-Fe exchange equilibria. Calculations using the Grs+2Prp+Kfs+H<sub>2</sub>O=Phl+3En+3An equilibrium demonstrated water activity below 0.1. Such low water activity could indicate an influence of highly concentrated alkaline Cl-F-bearing brines. This assumption is confirmed by extensive development of potassium feldspar, absence of quartz in the matrix, and elevated Cl contents of biotite, 0.1-0.3 wt. % at high #Mg (>0.7) and F content.</p><p><em>The study is supported by the Russian Science Foundation project 18-17-00206.</em></p><p><strong> </strong><strong>References </strong></p><p>Berman, R. G. (2007). winTWQ (version 2.3): a software package for performing internally-consistent thermobarometric calculations. Geological survey of Canada, open file, 5462, 41.</p><p>Connolly, T. M., & Begg, C. E. (2005). Database systems: a practical approach to design, implementation, and management. Pearson Education.</p><p>Shatsky, V. S., Malkovets, V. G., Belousova, E. A., ... & O’Reilly, S. Y. (2016). Tectonothermal evolution of the continental crust beneath the Yakutian diamondiferous province (Siberian craton): U–Pb and Hf isotopic evidence on zircons from crustal xenoliths of kimberlite pipes. Precambrian Research, 282, 1-20.</p>

scholarly journals Adsorption of Fibrinogen on Silica Surfaces—The Effect of Attached Nanoparticles

Biomolecules ◽  
2020 ◽  
Vol 10 (3) ◽  
pp. 413 ◽  
Author(s):  
Kristin Hyltegren ◽  
Mats Hulander ◽  
Martin Andersson ◽  
Marie Skepö
Keyword(s):  
Crystal Structure ◽  
The Body ◽  
Surface Proteins ◽  
Coarse Grained ◽  
Main Body ◽  
Protein Film ◽  
Silica Surfaces ◽  
Coarse Grained Model ◽  
Nanostructured Silica ◽  
Fibrinogen Molecule

When a biomaterial is inserted into the body, proteins rapidly adsorb onto its surface, creating a conditioning protein film that functions as a link between the implant and adhering cells. Depending on the nano-roughness of the surface, proteins will adsorb in different amounts, with different conformations and orientations, possibly affecting the subsequent attachment of cells to the surface. Thus, modifications of the surface nanotopography of an implant may prevent biomaterial-associated infections. Fibrinogen is of particular importance since it contains adhesion epitopes that are recognized by both eukaryotic and prokaryotic cells, and can therefore influence the adhesion of bacteria. The aim of this study was to model adsorption of fibrinogen to smooth or nanostructured silica surfaces in an attempt to further understand how surface nanotopography may affect the orientation of the adsorbed fibrinogen molecule. We used a coarse-grained model, where the main body of fibrinogen (visible in the crystal structure) was modeled as rigid and the flexible α C-chains (not visible in the crystal structure) were modeled as completely disordered. We found that the elongated fibrinogen molecule preferably adsorbs in such a way that it protrudes further into solution on a nanostructured surface compared to a flat one. This implicates that the orientation on the flat surface increases its bio-availability.

Quantitative Model for Clusters of String-like Cooperative Motion in a Coarse-Grained Glass-Forming Polymer Melt

2014 ◽  
Vol 1622 ◽  
pp. 95-111 ◽  
Author(s):  
Beatriz A Pazmiño Betancourt ◽  
Jack F. Douglas ◽  
Francis W. Starr
Keyword(s):  
Configurational Entropy ◽  
Polymer Melt ◽  
Quantitative Model ◽  
Coarse Grained ◽  
Residual Entropy ◽  
Arrhenius Behavior ◽  
String Length ◽  
Glass Forming ◽  
Free Parameters ◽  
Lower Temperature

ABSTRACTWe apply a living polymerization theory to describe cooperative string-like particle rearrangement clusters observed in simulations of a coarse-grained polymer melt. The theory quantitatively describes the interrelation between the average string length L, configurational entropy Sconf, and the order parameter for string assembly Φ without free parameters. Combining this theory with the Adam-Gibbs (AG) model allows us to predict the relaxation time τ in a lower temperature T range than accessible by current simulations. In particular, the combined theories suggest a return to Arrhenius behavior near Tg and a low T residual entropy, thus avoiding a Kauzmann ‘entropy crisis’.

scholarly journals Geoquímica das Rochas Máficas Toleíticas da Suíte Pós-Colisional Paulo Lopes, Neoproterozóico do Sul do Brasil

2005 ◽  
Vol 32 (2) ◽  
pp. 69 ◽  
Author(s):  
LUANA MOREIRA FLORISBAL ◽  
LAURO NARDI ◽  
MARIA DE FÁTIMA BITENCOURT ◽  
LEANDRO MENEZES BETIOLLO
Keyword(s):  
Coarse Grained ◽  
Main Body ◽  
Chronological Order ◽  
Orientation Field ◽  
Rapid Crystallization ◽  
Magmatic Rocks ◽  
Microgranular Enclaves ◽  
Mafic Microgranular Enclaves ◽  
Basic Rocks

The Paulo Lopes Suite (SPL), composed of the Paulo Lopes Granite (GPL), Garopaba Granitoids (GG) and Silveira Gabbro (GS), is an association of contemporaneous acid and basic rocks, comprising monzo and syenogranites associated to basic dikes, with abundant mafic microgranular enclaves, interpreted as co-mingling products. The contacts between the granitoids and the basic rocks are evidences of coeval and interactive magmas. The Silveira Gabbro occurs in the study area as a main body and several narrow dikes of NNE orientation. Field relations define a chronological order of magmatic events, where the GPL is the first magmatic pulse and, while steel partially crystallized, was intruded by mingled magmas, represented by the GG and the GS. The basic components are medium-grained, equigranular rocks, with subophitic and ophitic textures. The centre of the main body contains medium- to coarse-grained, equigranular rocks, where agglomerates of early-formed clinopyroxene and plagioclase crystals are found. In the chilled margins, they are microporphyritc rocks of aphanitic groundmass, indicative of rapid crystallization. The Silveira Gabbro rocks are composed of labradorite-andesine, orthopyroxene, augite, pigeonite, olivine (occasionally serpentinized), Fe-hornblende and magnesian hornblende, red biotite, magnetite, ilmenite, apatite, and baddeleyite. The composition is tholeiitic, similar to the high-Ti-P basalts of the Serra Geral Formation. Their high contents of K, Rb, Sr and Ba, as well as negative anomalies of Nb and Ta in multielemental diagrams are similar to the ones observed in magmatic rocks from mature arcs or post-collisional environments. The Neoproterozoic basic rocks may be discriminated from the ones belonging to the Cretaceous Serra Geral Formation by their higher contents of alcalis, Cs, U, Th, and by their fractionated REEpatterns, expressed in the La/LuN ratio. The associated granitoids are structural and compositionally compatible with the ones found in post collisional settings, which indicates that the SPL magmatism developed in such environment.

scholarly journals The alkaline igneous complex of Kûngnât Fjeld, South Greenland

1960 ◽  
Vol 27 ◽  
pp. 1-145
Author(s):  
B.G.J Upton
Keyword(s):  
Parental Magma ◽  
Layered Intrusion ◽  
Optical Data ◽  
Basalt Magma ◽  
Grey Zone ◽  
Magma Chambers ◽  
Quartz Syenite ◽  
Outward Diffusion ◽  
Layered Series ◽  
Ring Dyke

An intrusive complex of saturated syenites and gabbros near Ivigtut in S.W. Greenland forms the mountain of Kûngnât Fjeld. The rocks were intruded into the basement gneisses towards the close of the Gardar period, thought to be of Pre-Cambrian age. The complex consists of three steep-sided syenite bodies. These were intruded successively with progressive easterly shift of centre and were succeeded by an alkali gabbro intrusion which, occurring as a ring-dyke, almost entirely surrounds the syenites. Emplacement of each of these intrusions is thought to have been by ring-faulting and cauldron subsidence. The S.W. marginal syenite, regarded as the earliest of the three syenite intrusions, is a small, poorly exposed body. It consists of quartz syenite containing fayalite and aegirine-augite. The second syenite intrusion formed the western layered syenite stock. This is a larger mass thought to have been originally ca. 2.6 X 3.5 kms. It possesses the characteristics of a layered intrusion of Skærgaard type with inwardly directed rhythmic banding, cryptic layering, feldspar lamination and an overall increase in mafic index from top to bottom. The base of the layered rocks is not exposed. The intrusion is divided horizontally, by a raft-like mass of gneiss blocks, into an upper and a lower layered series. This raft, the "grey-zone", is believed to represent a subsided mass of roofing material which sank only a relatively short distance before coming to rest, suspended in the magma chamber. Differentiation by bottom accumulation of fayalite, clinopyroxene, high-temperature alkali feldspars etc. continued independently above and below this raft. In each case it resulted in pronounced fractionation of the magma. In both series the rocks grade up from quartz-free to quartz-bearing types. The ultimate differentiates of the upper layered series have been lost by erosion, but those of the lower series are represented by transgressive soda-granite dykes and sheets. These latter, which remained unconsolidated until very late in the cooling history of the complex, include riebeckite-astrophyllite granites of close affinity to some of the Nigerian examples. The differentiated sequence of the lower layered series is analogous to the larvikite-nordmarkite-ekerite sequence of the Oslo region. The eastern syenite intrusion is also layered in its central part with somewhat higher average dips than in the western intrusion. For the most part it consists of more basic syenites with more magnesian pyroxenes and olivines and more calcic feldspars. However, fractionation in situ again produced quartz syenites of less basic type. The eastern stock possesses a marginal border group on its eastern flanks. An irregular zone of pegmatite surrounds the eastern intrusion and is thought to have been caused by outward diffusion of volatiles and alkali silicates. In the syenites partial analyses indicate a range in feldspar composition from Ab59 Or29 An10·5 Cn1·5 to ca. Ab59 Or37·5 An3·5, (mol. comp.). Optical data show a pyroxene range from augites of ca. Ca42 Mg20 Fe38 through ferroaugites to hedenbergitic types, and with progressive Na enrichment through to aegirine-augites. The olivines range from ca. Fa80-Fa100. Convection, occurring within the main western and eastern syenite magma chambers, is believed to have been responsible for the steep inclination of the layering by promoting marginal deposition of primary precipitate crystals. Evidence for strong magmatic currents is mainly provided by the trough-banding. Consideration of the feldspars suggests that in the two layered intrusions the magma chambers became filled with accumulated crystal mush over. a temperature range between 800-700°C. The behaviour of the trace-elements is broadly similar to that found in the Skærgaard series, except that at Kûngnât Ba and Sr were progressively removed from the magma. Li and Zr are strongly concentrated in the latest fractionates of the western lower layered series. The syenite melts were continuously depleted in F by the bottom accumulation of fluorapatite. The ring-dyke consists of a suite of gabbroic and syeno-gabbroic rocks thought to have been derived by the fractionation of alkali-basalt magma at depth. Some contamination by syenitic material is suspected. In places the ring-dyke rocks suffered strong metasomatism from residual syenitic and granitic liquids. Apart from water, this alteration involved the addition of Li and Rb. Spectrographic analyses of the feldspars from the whole complex showed that there are all gradations from those with severe Rb depletion to those with moderate Rb enrichment. A surprising Ag-Cu content in some of the feldspars is attributed to the presence of submicroscopic sulphide inclusions. The four Kûngnât intrusions were apparently intruded in order of increasing basicity. A possible explanation is that the four magma portions were tapped off from successively deeper levels of an already differentiated parental magma. The Kûngnât complex is probably coeval and comagmatic with the alkaline intrusions at Nunarssuit, Ilímaussaq and Tugtutôq. The development of nepheline syenites in this region of south Greenland is considered to be closely linked to that of the saturated syenites such as those at Kûngnât.

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