| dc.creator |
Manya, Shukrani |
|
| dc.date |
2016-03-03T11:02:39Z |
|
| dc.date |
2016-03-03T11:02:39Z |
|
| dc.date |
2008 |
|
| dc.date.accessioned |
2018-03-27T08:56:43Z |
|
| dc.date.available |
2018-03-27T08:56:43Z |
|
| dc.identifier |
Manya, S. "Geochemistry and Nd-isotopic composition of high silica rhyolites in the neoarchaean Musoma-Mara greenstone belt, northern Tanzania: evidence for the presence of older continental crust." Tanzania Journal of Science 34, no. 1 (2008). |
|
| dc.identifier |
0856 1761 |
|
| dc.identifier |
http://hdl.handle.net/123456789/570 |
|
| dc.identifier.uri |
http://hdl.handle.net/123456789/3968 |
|
| dc.description |
The high silica rhyolites of the Kibasuka Hill, although volumetrically minor, constitute a part
of the greenstone sequence in the northern Musoma-Mara Greenstone Belt (MMGB). They are
characterized by high silica contents (63.38 – 81.65 wt %), very low CaO (! 0.05 wt %),
variable to unusually high K2O (2.24 – 13.43 wt %) most likely attributed to strong sericite
alteration, and their major element composition are similar to those of melts derived from
partial melting of metapelites. The samples have very low concentration of the transition
elements, Sr (3.13 – 48.4 ppm) and very large negative Europium anomalies (Eu/Eu* = 0.27 –
0.48). Their Nd isotopic composition reveals that the T-depleted mantle (DM) model ages of the
samples are highly variable and range from 2867 Ma to 4015 Ma. These geochemical features
are consistent with generation of the high silica rhyolites by partial melting of a heterogeneous
source composed of juvenile Archaean rocks of the MMGB and older sedimentary rocks. The later
imparts to the rocks very old mean crustal residence ages. Partial melting of this suite took place
at low-pressure conditions within the continental crust where plagioclase was a stable phase.
Such old TDM model ages of up to 4015 Ma recorded by the high silica rhyolites suggest the
presence of very old continental crust in the MMGB which has so far not been identified
anywhere else in the Tanzania Craton. |
|
| dc.language |
en |
|
| dc.publisher |
College of Natural and Applied Sciences (CoNAS) of the University of Dar es Salaam (UDSM) |
|
| dc.subject |
Geochemistry |
|
| dc.subject |
Isotopic |
|
| dc.subject |
Greenstone Belt |
|
| dc.title |
Geochemistry and Nd-isotopic Composition of High Silica Rhyolites in the Neoarchaean Musoma-Mara Greenstone Belt, Northern Tanzania: Evidence for the Presence of Older Continental Crust |
|
| dc.type |
Journal Article |
|