Geochemistry and Nd-isotopic composition of potassic magmatism in the Neoarchaean Musoma-Mara Greenstone Belt, northern Tanzania

Shukrani Manya, Makenya A H Maboko, Eizou Nakamura

Research output: Contribution to journalArticle

17 Citations (Scopus)

Abstract

The Neoarchaean Musoma-Mara Greenstone Belt (MMGB) of northern Tanzania is underlain in part by the ∼2649 Ma post-orogenic potassic-rich granites, which are the most abundant intrusive rocks in the belt. The rocks are composed of plagioclase + K-feldspar + quartz + biotite ± sphene ± zircon ± hornblende ± chlorite. They are characterized by high contents of SiO2 (68.90-77.76 wt%), K2O (3.71-5.44 wt%) and low Na2O (3.27-5.70 wt%) leading to low ratios of Na2O/K2O (0.63-1.02). The rocks are depleted in CaO (0.22-2.41 wt%) as well as in Sr (15-412 ppm), Cr (≤16 ppm) and Ni (≤5 ppm); and their major element composition are similar to those of experimental melts derived from partial melting of tonalite. On chondrite-normalized REE patterns, these rocks show fractionated patterns (La/YbCN = 1.22-41.32) that are characterised by moderate to strongly negative Eu anomalies (Eu/Eu* = 0.04-0.86). On primitive mantle-normalized spidergrams, these rocks are generally enriched in Th, U, K and Pb and depleted in Ba, Sr, Nb, Ta and Ti relative to adjacent elements. The K-rich granites have εNdo (at 2.649 Ga) values of +0.55 to +1.70 that compare well with those of associated volcanic rocks and TTG (εNd = +0.44 to +2.66) which predate the emplacement of the K-rich granitoids. Their mean crustal residence ages are 170 to 450 Ma older than their emplacement ages. The overall geochemical features of this suite of rocks, together with evidence from experimental results, are consistent with their generation by partial melting of relatively juvenile igneous rocks within the continental crust at pressures corresponding to depths

Original languageEnglish
Pages (from-to)231-240
Number of pages10
JournalPrecambrian Research
Volume159
Issue number3-4
DOIs
Publication statusPublished - Nov 15 2007

Fingerprint

Geochemistry
greenstone belt
magmatism
isotopic composition
geochemistry
Rocks
Chemical analysis
rock
partial melting
emplacement
Melting
Igneous rocks
Volcanic rocks
Quartz
tonalite
titanite
Prednisolone
chondrite
hornblende
igneous rock

Keywords

  • Geochemistry
  • Greenstone Belt
  • K-granites
  • Nd-isotopes
  • Tanzania Craton

ASJC Scopus subject areas

  • Geochemistry and Petrology
  • Geology

Cite this

Geochemistry and Nd-isotopic composition of potassic magmatism in the Neoarchaean Musoma-Mara Greenstone Belt, northern Tanzania. / Manya, Shukrani; Maboko, Makenya A H; Nakamura, Eizou.

In: Precambrian Research, Vol. 159, No. 3-4, 15.11.2007, p. 231-240.

Research output: Contribution to journalArticle

@article{57e95d9742604873b504bc8ddbf3de96,
title = "Geochemistry and Nd-isotopic composition of potassic magmatism in the Neoarchaean Musoma-Mara Greenstone Belt, northern Tanzania",
abstract = "The Neoarchaean Musoma-Mara Greenstone Belt (MMGB) of northern Tanzania is underlain in part by the ∼2649 Ma post-orogenic potassic-rich granites, which are the most abundant intrusive rocks in the belt. The rocks are composed of plagioclase + K-feldspar + quartz + biotite ± sphene ± zircon ± hornblende ± chlorite. They are characterized by high contents of SiO2 (68.90-77.76 wt{\%}), K2O (3.71-5.44 wt{\%}) and low Na2O (3.27-5.70 wt{\%}) leading to low ratios of Na2O/K2O (0.63-1.02). The rocks are depleted in CaO (0.22-2.41 wt{\%}) as well as in Sr (15-412 ppm), Cr (≤16 ppm) and Ni (≤5 ppm); and their major element composition are similar to those of experimental melts derived from partial melting of tonalite. On chondrite-normalized REE patterns, these rocks show fractionated patterns (La/YbCN = 1.22-41.32) that are characterised by moderate to strongly negative Eu anomalies (Eu/Eu* = 0.04-0.86). On primitive mantle-normalized spidergrams, these rocks are generally enriched in Th, U, K and Pb and depleted in Ba, Sr, Nb, Ta and Ti relative to adjacent elements. The K-rich granites have εNdo (at 2.649 Ga) values of +0.55 to +1.70 that compare well with those of associated volcanic rocks and TTG (εNd = +0.44 to +2.66) which predate the emplacement of the K-rich granitoids. Their mean crustal residence ages are 170 to 450 Ma older than their emplacement ages. The overall geochemical features of this suite of rocks, together with evidence from experimental results, are consistent with their generation by partial melting of relatively juvenile igneous rocks within the continental crust at pressures corresponding to depths",
keywords = "Geochemistry, Greenstone Belt, K-granites, Nd-isotopes, Tanzania Craton",
author = "Shukrani Manya and Maboko, {Makenya A H} and Eizou Nakamura",
year = "2007",
month = "11",
day = "15",
doi = "10.1016/j.precamres.2007.07.001",
language = "English",
volume = "159",
pages = "231--240",
journal = "Precambrian Research",
issn = "0301-9268",
publisher = "Elsevier",
number = "3-4",

}

TY - JOUR

T1 - Geochemistry and Nd-isotopic composition of potassic magmatism in the Neoarchaean Musoma-Mara Greenstone Belt, northern Tanzania

AU - Manya, Shukrani

AU - Maboko, Makenya A H

AU - Nakamura, Eizou

PY - 2007/11/15

Y1 - 2007/11/15

N2 - The Neoarchaean Musoma-Mara Greenstone Belt (MMGB) of northern Tanzania is underlain in part by the ∼2649 Ma post-orogenic potassic-rich granites, which are the most abundant intrusive rocks in the belt. The rocks are composed of plagioclase + K-feldspar + quartz + biotite ± sphene ± zircon ± hornblende ± chlorite. They are characterized by high contents of SiO2 (68.90-77.76 wt%), K2O (3.71-5.44 wt%) and low Na2O (3.27-5.70 wt%) leading to low ratios of Na2O/K2O (0.63-1.02). The rocks are depleted in CaO (0.22-2.41 wt%) as well as in Sr (15-412 ppm), Cr (≤16 ppm) and Ni (≤5 ppm); and their major element composition are similar to those of experimental melts derived from partial melting of tonalite. On chondrite-normalized REE patterns, these rocks show fractionated patterns (La/YbCN = 1.22-41.32) that are characterised by moderate to strongly negative Eu anomalies (Eu/Eu* = 0.04-0.86). On primitive mantle-normalized spidergrams, these rocks are generally enriched in Th, U, K and Pb and depleted in Ba, Sr, Nb, Ta and Ti relative to adjacent elements. The K-rich granites have εNdo (at 2.649 Ga) values of +0.55 to +1.70 that compare well with those of associated volcanic rocks and TTG (εNd = +0.44 to +2.66) which predate the emplacement of the K-rich granitoids. Their mean crustal residence ages are 170 to 450 Ma older than their emplacement ages. The overall geochemical features of this suite of rocks, together with evidence from experimental results, are consistent with their generation by partial melting of relatively juvenile igneous rocks within the continental crust at pressures corresponding to depths

AB - The Neoarchaean Musoma-Mara Greenstone Belt (MMGB) of northern Tanzania is underlain in part by the ∼2649 Ma post-orogenic potassic-rich granites, which are the most abundant intrusive rocks in the belt. The rocks are composed of plagioclase + K-feldspar + quartz + biotite ± sphene ± zircon ± hornblende ± chlorite. They are characterized by high contents of SiO2 (68.90-77.76 wt%), K2O (3.71-5.44 wt%) and low Na2O (3.27-5.70 wt%) leading to low ratios of Na2O/K2O (0.63-1.02). The rocks are depleted in CaO (0.22-2.41 wt%) as well as in Sr (15-412 ppm), Cr (≤16 ppm) and Ni (≤5 ppm); and their major element composition are similar to those of experimental melts derived from partial melting of tonalite. On chondrite-normalized REE patterns, these rocks show fractionated patterns (La/YbCN = 1.22-41.32) that are characterised by moderate to strongly negative Eu anomalies (Eu/Eu* = 0.04-0.86). On primitive mantle-normalized spidergrams, these rocks are generally enriched in Th, U, K and Pb and depleted in Ba, Sr, Nb, Ta and Ti relative to adjacent elements. The K-rich granites have εNdo (at 2.649 Ga) values of +0.55 to +1.70 that compare well with those of associated volcanic rocks and TTG (εNd = +0.44 to +2.66) which predate the emplacement of the K-rich granitoids. Their mean crustal residence ages are 170 to 450 Ma older than their emplacement ages. The overall geochemical features of this suite of rocks, together with evidence from experimental results, are consistent with their generation by partial melting of relatively juvenile igneous rocks within the continental crust at pressures corresponding to depths

KW - Geochemistry

KW - Greenstone Belt

KW - K-granites

KW - Nd-isotopes

KW - Tanzania Craton

UR - http://www.scopus.com/inward/record.url?scp=35348858294&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=35348858294&partnerID=8YFLogxK

U2 - 10.1016/j.precamres.2007.07.001

DO - 10.1016/j.precamres.2007.07.001

M3 - Article

AN - SCOPUS:35348858294

VL - 159

SP - 231

EP - 240

JO - Precambrian Research

JF - Precambrian Research

SN - 0301-9268

IS - 3-4

ER -