Paleoproterozoic gabbro–diorite–granite magmatism of the Batomga Rise (NE Aldan Shield): Sm–Nd isotope geochemical evidence

AbstractThe geochemistry of Tertiary igneous rocks from Arran, western Scotland, provides a probe for the structure of the crust in the region of the Highland Boundary Fault (HBF). New Nd isotope data, coupled with other geochemical evidence, point to variable contamination of primitive mantle-derived magmas during magmatic differentiation in the crust. Two different isotopic contamination trends are seen. The northern granite was generated by contamination of basic differentiates by crust resembling exposed Dalradian units. Data for the central granite, and several other minor intrusions from south of the HBF, trend towards the reported isotopic signatures of granulite-facies xenoliths from the Midland Valley. However, quartz porphyry intrusions in the south of the island are compositionally similar to the nothern granite, and were probably intruded southwards across the HBF in dykes. Hence the isotopic signatures of the Tertiary intrusions reflect the different character of the crustal units on either side of the fault.

Download Full-text

Mantle Heterogeneity and Crustal Contamination in the Genesis of Low-Ti Continental Flood Basalts from the Paran Plateau (Brazil): Sr-Nd Isotope and Geochemical Evidence

Journal of Petrology ◽

10.1093/petrology/28.4.701 ◽

1987 ◽

Vol 28 (4) ◽

pp. 701-726 ◽

Cited By ~ 54

Author(s):

R. PETRINI ◽

L. CIVETTA ◽

E. M. PICCIRILLO ◽

G. BELLIENI ◽

P. COMIN-CHIARAMONTI ◽

...

Keyword(s):

Crustal Contamination ◽

Mantle Heterogeneity ◽

Flood Basalts ◽

Nd Isotope ◽

Continental Flood Basalts ◽

Geochemical Evidence

Download Full-text

Sm–Nd isotope characteristics of late Cadomian granite magmatism in northern France and the Channel Islands

Geological Magazine ◽

10.1017/s0016756800023165 ◽

1993 ◽

Vol 130 (6) ◽

pp. 797-804 ◽

Cited By ~ 37

Author(s):

R. S. d'Lemos ◽

M. Brown

Keyword(s):

Partial Melting ◽

Lower Crust ◽

Channel Islands ◽

Common Source ◽

Nd Isotope ◽

Late Precambrian ◽

The North ◽

Isotopic Studies ◽

Granite Magmatism ◽

Armorican Massif

AbstractSm–Nd isotopic studies of granites within the late Precambrian, Cadomian, orogenic belt of the North Armorican Massif (northwestern France) and Channel Islands reveal differences between arc-related granite magmatism in outboard terranes and intracrustal granite magmatism in inboard terranes. Late Cadomian (c. 570 Ma), arc-related granitoids exhibit a range of εnd( - 2 to - 6) and Nd model ages (TDM1.0–1.3 Ga) reflecting variable contamination between late Precambrian mantle derived magmas and ancient (c. 2.0 Ga?) continental crust. The contamination did not involve exposed granitic Icartian basement to anygreat degree, a more likely contaminant being unexposed lower crust of intermediate to acidic granulitic composition, or early Cadomian plutons which were themselves contaminated by lower crust. Voluminous granites of the Mancellian region (c. 550–540 Ma) share common isotopic characteristics (εNd-4 to -7, TDM1.5–1.7 Ga) with migmatites and anatectic granites produced by partial melting of metasedimentary sequences within the St Malo region consistent with a common source.

Download Full-text