Anorthosite and associated plutons, southern Nain complex, Labrador

1978 ◽  
Vol 15 (8) ◽  
pp. 1326-1340 ◽  
Author(s):  
Robert A. Wiebe
Keyword(s):  
Late Stage ◽  
Parent Magma ◽  
Average Composition ◽  
Small Bodies ◽  
Residual Magma ◽  
Southern Area ◽  
Crustal Origin ◽  
Plutonic Rocks ◽  
Heterogeneous Matrix ◽  
Anorthosite Complex

Plutonic rocks in a southern area of the Nain anorthosite complex consist of leuconorite, anorthosite, granite, and subordinate diorite. An older anorthosite intrusion (CI < 10) has been invaded and broken up by an extensive leuconorite intrusion (CI = 15). Ferrodiorite occurs as small bodies within or adjacent to the leuconorite and is a late stage differentiate of leuconorite, Large granitic plutons of separate crustal origin were emplaced prior to complete solidification of the leuconorite. Where these intrusions invaded leuconorite a marginal hybrid (diorite–granite) zone of heterogeneous matrix developed with chilled pillows of residual magma (mainly ferrodiorite) filter-pressed from the leuconorite. Chilled leuconorite dikes indicate that the parent magma of one leuconorite intrusion was approximately equivalent to its average composition. The older anorthosite body most probably represents a concentration of plagioclase crystals from a different magma; deformation of plagioclase crystals suggest that the mechanism of concentration was filter pressing.

U–Pb zircon age of the southwest lobe of the Havre-Saint-Pierre Anorthosite Complex, Grenville Province, Canada

1993 ◽  
Vol 30 (7) ◽  
pp. 1453-1457 ◽  
Author(s):  
Otto van Breemen ◽  
Michael D. Higgins
Keyword(s):  
Solid State ◽  
Shear Zone ◽  
Late Stage ◽  
Grenville Province ◽  
Zircon Age ◽  
Zircon Dating ◽  
Granitoid Intrusions ◽  
Anorthosite Complex ◽  
Massif Anorthosite ◽  
Magmatic Event

U–Pb zircon dating of the southwest lobe of the Havre-Saint-Pierre anorthosite intrusion indicates that it is 1062 ± 4 Ma old. Parallelism of magmatic and solid-state foliations with the adjacent Abbé–Huard lineament suggest that anorthosite parental magmas rose up this shear zone, which was active at that time. The age of igneous crystallization is much younger than that of a spatially associated mangerite intrusion, but accords with age data from other granitoid intrusions elsewhere in the Grenville Province. Evidence points to a widespread 1.09–1.05 Ga magmatic event that included massif anorthosite intrusions. This magmatic event coincided with late stage convergent tectonics in the southwestern Grenville Province.

scholarly journals 5. On the Early Scattering Processes of the Outer Planets

1977 ◽  
Vol 39 ◽  
pp. 485-490
Author(s):  
W. H. Ip
Keyword(s):  
Monte Carlo ◽  
Late Stage ◽  
Total Mass ◽  
Monte Carlo Calculation ◽  
Oort Cloud ◽  
Small Bodies ◽  
Outer Planets ◽  
Long Period ◽  
Asteroidal Belt ◽  
Mass Influx

The gradual scattering of small bodies by the Jovian planets in the late stage of their accretion is simulated by Monte Carlo calculation. The effects of collisional interaction of the scattered planetesimals with the inner planets and asteroidal belt are estimated. The total mass influx injected into the terrestrial zones from the outer planetary zone could be appreciable; however, if the damping effects due to the mutual inelastic or catastrophic collisions among the small bodies were significant, the total mass influx would be greatly reduced. The origin of the cometary Oort cloud in relation to these scattering processes is also discussed. The calculation indicates that, in addition to Jupiter, Uranus and Neptune were likely to be the major contributors to the population of long-period comets if they originated from such scattering processes.

Compositional Variation of pyroxene and mica from the Little Murun ultrapotassic complex, Aldan Shield, Russia

1996 ◽  
Vol 60 (403) ◽  
pp. 907-925 ◽  
Author(s):  
Roger H. Mitchell ◽  
Nikolai V. Vladykin
Keyword(s):  
Late Stage ◽  
Aldan Shield ◽  
Compositional Variation ◽  
Compositional Evolution ◽  
Compositional Trend ◽  
Plutonic Rocks ◽  
Alkaline Complexes

AbstractPyroxene and mica found in plutonic rocks of the Little Murun ultrapotassic pluton exhibit trends of compositional evolution that permit evaluation of the differentiation sequence of the complex. Pyroxene evolves from diopside in kalsilite and phlogopite pyroxenites through aegirine-diopside in shonkinite to aegirine in late stage charoitite and evolved hypabyssal rocks. The compositional trend is unusual in that the hedenbergite content of the pyroxenes never exceeds 15 mol.% and is thus unlike pyroxene compositional trends found in sodic alkaline complexes. Mica is Al- and Ti-poor and ranges in composition from Fe-rich phlogopite through biotite towards tetraferriannite. Compositional trends of mica found in ‘lamproite-like’ hypabyssal rocks are identical to those observed in the micaceous plutonic rocks; hence the former are considered to be representatives of the lamprophyric facies of the magmas which formed the plutonic series.

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