Journal ArticleDOI
Crustal contamination versus enriched mantle: 143 Nd/ 144 Nd and 87 Sr/ 86 Sr evidence from the Italian volcanics
Chris J. Hawkesworth,R. Vollmer +1 more
TLDR
In this article, a wide variety of Pliocene-Recent volcanic rocks from central Italy are presented, and they are tentatively subdivided into three zones: (1) N. Tuscany where the magmas are believed to reflect crustal anatexis.Abstract:
143Nd/144Nd, 87Sr/86Sr, and REE analyses are presented on a wide variety of Pliocene-Recent volcanic rocks from central Italy. 143Nd/144Nd varies from 0.51214–0.51289 and 87Sr/86Sr from 0.7255-0.7036; while the rare earth elements are characterised by light RE enrichment and a significant negative Eu anomaly. These Italian volcanics are tentatively subdivided into three zones: (1) N. Tuscany where the magmas are believed to reflect crustal anatexis. (2) A central zone in which hybrid (crust/ mantle) rocks have been recognised. (3) A southern zone, south of Rome, where mantle-derived magmas are identified which have been largely unaffected by interaction with continental crust. At Roccamonfina, in zone 3, Rb/Sr and Sm/Nd pseudo isochrons are observed but since the calculated ages are 0.5 and 2.0 b.y. respectively it is argued that a simple isochron model is not applicable and that the data are most easily explained by a recent mixing event within the upper mantle. It is envisaged that this occurred during metasomatism of the upper mantle source region by a fluid that had high 87Sr/86Sr and low 143Nd/144Nd and was enriched in K, Rb, and LREE's but relatively depleted in Sr2+ and Eu2+.read more
Citations
More filters
Journal ArticleDOI
The ultrapotassic rocks: Characteristics, classification, and constraints for petrogenetic models
TL;DR: In this paper, the chemical properties of ultrapotassic rocks are defined using the chemical screens K 2 O > 3 wt.%, MgO > 3 Wt.% and Na 2 O/Na 2 O 2 > 2 for whole-rock analyses.
Journal ArticleDOI
Some remarks on the movement of small melt fractions in the mantle
TL;DR: In a plate whose temperature changes little with time melt solidifies to produce a metasomatic layer as mentioned in this paper, which is likely to be best developed in Archaean lithosphere, but is probably present in some form even within old oceanic plates.
Journal ArticleDOI
Post-Collisional Potassic and Ultrapotassic Magmatism in SW Tibet: Geochemical and Sr–Nd–Pb–O Isotopic Constraints for Mantle Source Characteristics and Petrogenesis
TL;DR: In this paper, chemical data for post-collisional ultrapotassic, silicic, and high plateau of Tibet, the Himalaya and the Kapotassic and high-K calc-alkaline volcanic rocks from SW Tibet, rakoram Ranges are presented.
Journal ArticleDOI
Magmatism and metamorphism in the Ladakh Himalayas (the Indus-Tsangpo suture zone)
TL;DR: A detailed study of the evolution of the northern Himalayan orogeny has been carried out using petrographic, geochemical and isotope analytical techniques in the Ladakh region of India as discussed by the authors.
Journal ArticleDOI
Nd isotopic characteristics of S- and I-type granites
TL;DR: In this article, the initial Nd and Sr isotopic composition has been determined in S- and I-type granites from the Paleozoic Berridale and Kosciusko Batholiths of southeast Australia.
References
More filters
Journal ArticleDOI
Nd isotopic variations and petrogenetic models
TL;DR: In this article, the authors analyzed the geochemical properties of a chondritic reservoir with high Fe, high Fe basalt, Ti basalt and alkali basalts and compared the results with the present value of the source regions of the earth.
Journal ArticleDOI
Trace element fractionation and the origin of tholeiitic and alkaline magma types
TL;DR: In this article, it was shown that the abundance of large ion elements in alkaline basalts cannot be consistently explained by fractional crystallization processes and that these characteristics are produced by previous partial melting episodes.
Journal ArticleDOI
A general mixing equation with applications to Icelandic basalts
TL;DR: The mixing equation applied by Vollmer [1] to Pb and Sr isotope ratios is shown to be a general equation applicable to consideration of element and isotope ratio.
Journal ArticleDOI
143Nd/146Nd, a natural tracer: an application to oceanic basalts*
TL;DR: In this paper, the possibility of using 143Nd/146Nd as a natural tracer was examined by analyzing two Hercynian granitic rocks, one carbonatite, three alkali basalts and nine tholeiites.
Journal ArticleDOI
Variations in143Nd/144Nd and87Sr/86Sr ratios in oceanic basalts
TL;DR: In this article, a strong negative correlation exists between 87Sr/86Sr ratios in oceanic basalt from Iceland and the Reykjanes Ridge, but such a clear correlation does not exist for samples from the Hawaiian Islands.