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An investigation of the Felsic Ramiane Pluton in the Monapo Structure, northern Moçambique

Karlsson, Jonnina P. (2006) In Dissertations in Geology at Lund University
Department of Geology
Abstract (Swedish)
Monapostrukturen ligger i Nampula provinsen i norra Moçambique, och utgör en del av Mocambique
bältet. Strukturen är ca 35-40 km i diameter och har en mycket låg topografi. Trots detta syns den väl på
satellitbilder och flygfotografier. Relationer mellan samt utbredning av de enskilda bergartsleden är inte
helt klarlagd och frågor såsom transportriktning, litostratigrafisk uppdelning samt tektonisk miljö debatteras
fortfarande.
Ramianeplutonen ligger i de östra delarna av Monapostrukturen, och utgör en stor del av den felsiska,
A-typ, Ramianegruppen. Plutonen består till mesta del av alkalina graniter, men det finns även andra
bergarter representerade. Petrografi har påvisat vätskeinklusioner i granat och kvarts från plutonen. Detta... (More)
Monapostrukturen ligger i Nampula provinsen i norra Moçambique, och utgör en del av Mocambique
bältet. Strukturen är ca 35-40 km i diameter och har en mycket låg topografi. Trots detta syns den väl på
satellitbilder och flygfotografier. Relationer mellan samt utbredning av de enskilda bergartsleden är inte
helt klarlagd och frågor såsom transportriktning, litostratigrafisk uppdelning samt tektonisk miljö debatteras
fortfarande.
Ramianeplutonen ligger i de östra delarna av Monapostrukturen, och utgör en stor del av den felsiska,
A-typ, Ramianegruppen. Plutonen består till mesta del av alkalina graniter, men det finns även andra
bergarter representerade. Petrografi har påvisat vätskeinklusioner i granat och kvarts från plutonen. Detta
indikerar därmed att det troligen rör sig om en pluton som var vätskerik vid intrusionen. Den almandinandradit
rika granaten i plutonen är i stor utsträckning koncentrerad till leukokratiska områden i bergarten.
Kristalliseringen av granat har tolkats som en retrograd process som ägt rum vid ökad ƒO2. Kemiska
analyser på de olika mineralen i bergarten visar att den intrusiva temperaturen och trycket för plutonen
har varit höga. Tryck och temperatur vid bildandet av granat har blivit beräknade och visar relativt stora
skillnader beroende på vatten aktiviteten i plutonen, samt om plutonen var vätskerik eller vätskefattig.
Modellerande av en möjlig protolit till Ramianeplutonen indikerar en juvenil protolit som inte verkar vara
besläktad med vare sig bergarter från Nampula provinsen eller från Monapostrukturen. SHRIMP U-Pb
dateringar av zirkoner rån Ramianeplutonen har gett en intrusiv ålder på 636.8 ± 5.3 Ma samt en yngre
ålder på 596 ± 5 Ma. Båda dessa åldrar faller inom det Pan-afrikanska åldersspannet. De är även mycket
lika åldrarna från Metacheriakomplexet som Ramianeplutonen tros ha intruderat i. För att bestämma de två
bergarternas relation till varandra måste mer forskning utföras på Metacheriakomplexet. (Less)
Abstract
The Monapo Structure is situated in the Nampula Subprovince in northern Moçambique, and makes up a
part of the Moçambique Orogenic Belt. It is a 35 x 40 km subcircular structure, with a very flat topography,
and it clearly shows up on aerial photos. The regional setting of the Monapo Structure is not yet clearly
settled and many questions regarding transportation directions, lithostratigraphic groupings and tectonic
setting of the area are still under debate.
The Ramiane Pluton is situated in the eastern parts of the Monapo Structure and makes up a large part
of the felsic, A-type, Ramiane Suite. The pluton comprises mostly alkaline granites, but other rock types
also exist. Petrographic studies have shown fluid inclusions in garnet... (More)
The Monapo Structure is situated in the Nampula Subprovince in northern Moçambique, and makes up a
part of the Moçambique Orogenic Belt. It is a 35 x 40 km subcircular structure, with a very flat topography,
and it clearly shows up on aerial photos. The regional setting of the Monapo Structure is not yet clearly
settled and many questions regarding transportation directions, lithostratigraphic groupings and tectonic
setting of the area are still under debate.
The Ramiane Pluton is situated in the eastern parts of the Monapo Structure and makes up a large part
of the felsic, A-type, Ramiane Suite. The pluton comprises mostly alkaline granites, but other rock types
also exist. Petrographic studies have shown fluid inclusions in garnet and quartz from the pluton, and
hence indicate that the pluton was rich in fluids when emplaced. The almandine-andradite rich garnet is
concentrated in leucocratic patches, interpreted as fluid-rich areas, where biotite, amphibole and oxides
are clearly absent. This has been interpreted as a retrograde process due to increased ƒO2. Calculations
of P and T have yielded results that show large variations that are dependent on the water activity and the
presence or absence of fluids. Nevertheless, the P-T’s indicate that the pluton intruded at granulite-facies
conditions. Modelling of a possible protolith of the Ramiane has indicated a relatively juvenile protolith
that does not appear to be related to either the rocks of the Nampula Subprovince or those of the Monapo
structure. SHRIMP U-Pb data from zircons have yielded an intrusive event at 636.8 ± 5.3 Ma as well as a
younger age of 596 ± 5 Ma. Both these ages are within the Pan-African time span. However, these ages
are very similar to those obtained on the Metacheria basement rocks, which are thought to pre-date the
Ramiane. The lithostratigraphic relationship between the Ramiane and the Metacheria basement are thus
unsettled. Further studies on the Metacheria basement are needed in order to resolve this question. (Less)
Please use this url to cite or link to this publication:
author
Karlsson, Jonnina P.
supervisor
organization
alternative title
En undersökning av den felsiska Raminae-plutonen i Manapo-strukturen, norra Moçambique
year
type
H1 - Master's Degree (One Year)
subject
keywords
Moçambique Orogenic Belt, Nampula Subprovince, Monapo Structure, Ramiane Pluton, Moçambique bältet, Nampula provinsen, Monapostrukturen, Ramianeplutonen
publication/series
Dissertations in Geology at Lund University
report number
202
language
English
additional info
Dr. Jodie A. Miller, Stellenbosch University, Stellenbosch, South Africa.
id
2338166
date added to LUP
2012-02-07 12:50:21
date last changed
2012-02-07 12:50:21
@misc{2338166,
  abstract     = {The Monapo Structure is situated in the Nampula Subprovince in northern Moçambique, and makes up a
part of the Moçambique Orogenic Belt. It is a 35 x 40 km subcircular structure, with a very flat topography,
and it clearly shows up on aerial photos. The regional setting of the Monapo Structure is not yet clearly
settled and many questions regarding transportation directions, lithostratigraphic groupings and tectonic
setting of the area are still under debate.
The Ramiane Pluton is situated in the eastern parts of the Monapo Structure and makes up a large part
of the felsic, A-type, Ramiane Suite. The pluton comprises mostly alkaline granites, but other rock types
also exist. Petrographic studies have shown fluid inclusions in garnet and quartz from the pluton, and
hence indicate that the pluton was rich in fluids when emplaced. The almandine-andradite rich garnet is
concentrated in leucocratic patches, interpreted as fluid-rich areas, where biotite, amphibole and oxides
are clearly absent. This has been interpreted as a retrograde process due to increased ƒO2. Calculations
of P and T have yielded results that show large variations that are dependent on the water activity and the
presence or absence of fluids. Nevertheless, the P-T’s indicate that the pluton intruded at granulite-facies
conditions. Modelling of a possible protolith of the Ramiane has indicated a relatively juvenile protolith
that does not appear to be related to either the rocks of the Nampula Subprovince or those of the Monapo
structure. SHRIMP U-Pb data from zircons have yielded an intrusive event at 636.8 ± 5.3 Ma as well as a
younger age of 596 ± 5 Ma. Both these ages are within the Pan-African time span. However, these ages
are very similar to those obtained on the Metacheria basement rocks, which are thought to pre-date the
Ramiane. The lithostratigraphic relationship between the Ramiane and the Metacheria basement are thus
unsettled. Further studies on the Metacheria basement are needed in order to resolve this question.},
  author       = {Karlsson, Jonnina P.},
  keyword      = {Moçambique Orogenic Belt,Nampula Subprovince,Monapo Structure,Ramiane Pluton,Moçambique bältet,Nampula provinsen,Monapostrukturen,Ramianeplutonen},
  language     = {eng},
  note         = {Student Paper},
  series       = {Dissertations in Geology at Lund University},
  title        = {An investigation of the Felsic Ramiane Pluton in the Monapo Structure, northern Moçambique},
  year         = {2006},
}