Other
Scientific paper
Feb 1986
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1986gecoa..50..231n&link_type=abstract
Geochimica et Cosmochimica Acta, vol. 50, Issue 2, pp.231-245
Other
26
Scientific paper
Pb, Nd and Sr isotopic compositions are reported for ultrapotassic rocks from a variety of tectonic settings. Olivine leucitites located within the Palaeozoic Lachlan Fold Belt of southeastern Australia have a range in initial 87 Sr / 86 Sr of from 0.7042 to 0.7056, Nd values of + 1.5 to -4.1 and 207 Pb / 204 Pb of 15.55 to 15.60. These isotopic characteristics overlap with those of contemporaneous alkali basalts and suggest derivation of the leucitites from sources which have been variably contaminated by either the hotspot which initiated volcanism or during earlier enrichment events. Lamproites from the West Kimberley region of Western Australia and leucitites from Gaussberg intrude stabilised Precambrian continental crust and have low 206 Pb / 204 Pb (<17.86 and <17.60 respectively and high 207 Pb / 204 Pb (>15.69 and >15.65). Pb isotope correlations displayed by the Western Australian lamproites are consistent with the mixing of an ancient (>2.1 byr old) high 207 Pb / 204 Pb , low 206 Pb / 204 Pb component with more typical mantle Pb. These ancient components probably evolved within the subcontinental lithosphere. Lamproites from southeastern Spain, which have geochemical features ( i.e . negative Ti- and Nb-anomalies) suggesting a subduction-related origin, possess isotopic compositions ( 87 Sr / 86 Sr = 0.7173 to 0.7207, 206 Pb / 204 Pb = 18.66 to 18.81, 207 Pb / 204 Pb = 15.67 to 15.74 and Nd = -11.2 to -12.6) and isotope correlations consistent with contamination of their sources by a component resembling modern oceanic sediments. This component is isotopically similar to that previously identified in the potassic rocks of Italy. A leucitite from a back-arc setting in the Sea of Japan has Pb isotopic composition similar to some ocean islands such as Kerguelen. The available isotopic data from this and other studies implicate enrichment processes frequently involving ancient, isotopically evolved components in the generation of continental potassic magmatism. These components are probably polygenetic with possible sources including subducted sediments, "megaliths" of recycled crust or the subcontinental lithosphere
McCulloch Malcolm T.
Nelson David R.
Sun Shen-Su
No associations
LandOfFree
The origins of ultrapotassic rocks as inferred from Sr, Nd and Pb isotopes does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with The origins of ultrapotassic rocks as inferred from Sr, Nd and Pb isotopes, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and The origins of ultrapotassic rocks as inferred from Sr, Nd and Pb isotopes will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-1675692