...M. E. Hodson The rhythmic modal layering in the Nunarssuit syenite has a vertical extent of >150 m and a lateral extent of >15 km. Individual layers average 20 cm thick and grade from a relatively melanocratic base into more leucocratic syenite over a distance of up to 5 cm. The major cumulus...

...Mark E. Hodson Abstract The chemistry and textures of the minerals in the layered syenites of Nunarssuit and West Kungnat record a complex post-crystallisation history. The initial cumulus phases were alkali feldspar, pyroxene and olivine, apatite and opaque oxides. Grain size distributions...

...I. Parsons; A. W. Butterfield Abstract SUMMARY: The sediment-like features of two layered syenites are described and reviewed in the light of recent suggestions that layering in gabbros maybe produced by in situ crystal growth in a near-rigid medium. In the Nunarssuit Syenite igneous layering...

... undersaturated and oversaturated) and gabbros —which indicates a primitive (mantle) origin for the parental Gardar magmas. Intermediate ratios (0.704 to 0.707) are observed in fewer centers, particularly in the Nunarssuit complex (gabbro, oversaturated syenites, and granites). For these centers, the possibility...

... granites to saturated and undersaturated syenites, and also include small occurrences of carbonatite. The larger complexes are dealt with in this paper ( Fig. 1b ), and they comprise Gronnedal-Ika consisting of nepheline syenites and carbonatite ( Emeleus 1964 ), Nunarssuit made up of alkaline...

... activity. Consequently several of the complexes consist of many individual units and cover areas of up to 45o km'. The majority of the central complexes are located at the intersections of three ENE.-trending, regional dyke swarms (the Ivigtut, Nunarssuit-Isortoq and Tugtut6q-Motzfeldt swarms...

...F ig . 13. Amphibole analyses from the Kûngnât.Complex. Symbols as for Fig. 12 . The red line marks the trend of Kûngnât amphiboles towards alkali depletion and Fe-enrichment. Comparative trends: SQ, South Qôroq; IL, Ilímaussaq; NUN, Nunarssuit-Alangorssuaq (image reproduced with the permission...

..., syenites, and carbonatites ( Upton et al. 2003 ). Samples analyzed in this study include basalts from the volcano-sedimentary Eriksfjord Formation (EF) and gabbroic dike rocks (diabase) from the Nunarssuit–Isortoq dike swarm (Fig.  1 ). The EF represents a ∼3500 m thick sequence of supracrustal rocks...

... microperthite cryptoperthite exsolution References Anderson, J.G. 1974. The geology of Alangorssuaq, Northern Nunarssuit complex, South Greenland. PhD Thesis. University of Aberdeen. Brown W.L. Parsons I. Parsons I . Feldspars in igneous rocks Feldspars and their reactions...

...Fig. 1.  Simplified geological map of southern Greenland, after Chadwick & Garde (1996) , showing the principal divisions of the Ketilidian orogen and the location of the main areas of Gardar rocks. The Nunarssuit–Isortôq (N–I) and Tugtutôq–Ilímaussaq–Nunataq (T–I–N) dyke swarms are shown...

... in the west of the region. The late Gardar episode between 1170 and 1160 Ma ago began with crustal dilation through intrusion of ENE trending groups of giant dykes of alkali-gabbro com- position, one axially concentrated on TugtutSq in the east and another near Nunarssuit in the centre of the region. Some...

...+ become dominant over the substitution CaMg = CaFe 2+ ? Many workers ( Aoki, 1964 ; Yagi, 1966 ; Nash and Wilkinson, 1970 ; Larsen, 1976 ) have postulated that f O2 is the controlling factor. From work on the Nunarssuit Complex of South Greenland, Anderson (1974) suggested that the pyroxene trend...

..., and rhyolitic) and also include lamprophyres and carbonatites. These strike mostly WNW-ESE and NE-SW following zones of inferred lithospheric thinning and graben development ( Upton et al. 2003 ; Upton 2013 ). Two major dike swarms are located in the Tugtutôq-Ilímaussaq and the Nunarssuit-Isortoq zones...

...–1145 Ma; Upton et al. , 2003 ) was concentrated in two southwest–northeast trending zones within the Ketilidian mobile belt: the Nunarssuit-Isortôq (N-I) zone in the west and the Tugtutôq-Ilímaussaq-Nunataq (T-I-N) zone in the east. In this area, carbonatite occurs only as a plug cutting...

... , France . Hodson , M. ( 1997 ) Post-crystallisation modification of the igneous layering in the Nunarssuit and West Kungnat syenites, South Greenland . Mineralogical Magazine , 61 , 467 – 483 . Högdahl , K. , Gromet , L.P. , and Broman , C. ( 2001 ) Low P-T Caledonian...

... earths and thorium. Arizona Bureau of Mines Bulletin , 180 , 245 –251. Alimarin, I.P. ( 1935 ) The chemical composition of chevkinite. Comptes rendus de l’académie des sciences U.S.S.R. , 1 , 648 –651 (in Russian). Anderson, J.G. ( 1974 ) The geology of Alongorssuaq, northern Nunarssuit complex...

... . Hodson , M.E. , 1998 , The origin of igneous layering in the Nunarssuit syenite, South Greenland : Mineralogical Magazine , v. 62 , p. 9 – 27 , https://doi.org/10.1180/002646198547431 . Holness , M.B. , Clemens , J.D. , and Vernon , R.H. , 2018 , How deceptive...

... ( Fig. 1 ). Table 2. Sequence of intrusions in the Gardar rift. Gardar intrusion episode Age in ∼Ma Rocks and structures Intrusions Shear zones Nain batholith 3 1144 Syenite ring complex Paatusoq 1185–1165 Syenite ring complexes Klokken, Ilímaussaq, Nunarssuit...