Single Zircon Evaporation and SHRIMP Ages for Granulite‐Facies Rocks in the Mozambique Belt of Tanzania

2001 ◽  
Vol 109 (2) ◽  
pp. 171-189 ◽  
Author(s):  
Sospeter Muhongo ◽  
Alfred Kröner ◽  
A. A. Nemchin
Keyword(s):  
Granulite Facies ◽  
Mozambique Belt ◽  
Single Zircon ◽  
Zircon Evaporation

Single zircon evaporation ages constraining the growth of the Archaean Aravalli craton, northwestern Indian shield

1996 ◽  
Vol 133 (3) ◽  
pp. 333-342 ◽  
Author(s):  
A. B. Roy ◽  
A. Kröner
Keyword(s):  
Indian Shield ◽  
Basement Rocks ◽  
Single Zircon ◽  
Single Grain ◽  
Aravalli Craton ◽  
Zircon Evaporation

AbstractSingle grain 207Pb/206Pb zircon ages were determined for granitoids and gneisses which constitute the Archaean basement rocks of the Aravalli craton of Rajasthan, northwestern Indian Shield. The protolith ages for two gneisses, collected from east of Udaipur, are ˜3230 Ma and 2887 Ma respectively. The granitoids display an intrusive relationship with the gneisses and yielded ages ranging between 2666 Ma and 2620 Ma. These ages provide the basis for a geochronological model of evolution of the oldest basement of the Aravalli craton.

scholarly journals O STOCK NEFELINA-SIENÍTICO RIO PARDO, PROVÍNCIA ALCALINA DO SUL DO ESTADO DA BAHIA

2012 ◽  
Author(s):  
Rita da Cunha Leal Menezes ◽  
Herbet Conceição ◽  
Maria de Lourdes da Silva Rosa ◽  
Marco Antonio Galarza ◽  
Débora Correia Rios ◽  
...  
Keyword(s):  
Rare Earth ◽  
Trace Element ◽  
Nepheline Syenite ◽  
Crystallization Process ◽  
The South ◽  
Trace Element Contents ◽  
Single Zircon ◽  
Age Range ◽  
Fractional Crystallization Process ◽  
Zircon Evaporation

O Stock Nefelina-Sienítico Rio Pardo se localiza na porção sul do conjunto de intrusões alcalinas que constitui a Província Alcalina do Sul do Estado da Bahia. Esse corpo aflora numa área de 46 km2, sendo constituído por sienito, sienito com nefelina, nefelina sienito e sodalita sienito. A idade Pb-Pb obtida em monocristal de zircão para esse stock foi de 725 ± 2 Ma, a qual se insere no intervalo de idades para o magmatismo da parte sul dessa província alcalina (732 Ma a 720 Ma). Os dados litoquímicos obtidos para esse stock o posicionam na suíte alcalina subsaturada em SiO2 da Província Alcalina do Sul do Estado da Bahia. Os conteúdos de elementos traços asseguram sua afinidade anorogênica. Sua evolução, controlada por cristalização fracionada, se marca por acentuado enriquecimento em Na2O (até 15%) e Al2O3 (até 25%) e marcantes decréscimos em SiO2 (63% a 45%) e Elementos Terras Raras.Palavras-chave: nefelina sienito, idade Pb-Pb, Rio Pardo, BahiaABSTRACT: THE RIO PARDO NEPHELINE-SYENITIC STOCK, SOUTH BAHIA ALKALINE PROVINCE. The Rio Pardo nepheline-syenitic intrusion is located in the southern sector of the South Bahia Alkaline Province. It crops out over an area of 46 km2 and consists of syenite, nepheline-bearing syenite, nepheline syenite and blue-sodalite syenite. The Pb-Pb single-zircon evaporation age of 725 ± 2 Ma obtained for the Rio Pardo stock is in agreement with the age range (732 Ma to 720 Ma) for the southern part of province. Lithochemical data provide evidence to consider the Rio Pardo stock as a body of the SiO2 sub-saturated alkaline suite of the South Bahia Alkaline Province. Trace element contents indicate anorogenic afinity and the stock evolution, controlled by a fractional crystallization process, resulted in an outstanding enrichment of Na2O (up to 15%) and Al2O3 (up to 25%), and an important depletion of SiO2 (63% to 45%) and Rare Earth Elements.Keywords: nepheline syenite, Pb-Pb age, Rio Pardo, Bahia State.,

Metamorphic evolution and zircon geochronology of early Proterozoic granulites in the Aravalli Mountains of northwestern India

2005 ◽  
Vol 142 (3) ◽  
pp. 287-302 ◽  
Author(s):  
A. B. ROY ◽  
ALFRED KRÖNER ◽  
P. K. BHATTACHAYA ◽  
SANJEEV RATHORE
Keyword(s):  
Granite Gneiss ◽  
Granulite Facies ◽  
Granulite Facies Metamorphism ◽  
Granulite Metamorphism ◽  
History Of ◽  
Single Zircon ◽  
Northwest India ◽  
Orogenic Cycle ◽  
Age Range ◽  
Rock Association

Granulites including a charnockite suite, mafic granulites, pelitic granulites, metanorite dykes and their retrograde varieties occur as discontinuous shear zone-bounded bodies within the Archaean basement comprising a granite gneiss–amphibolite–metasedimentary rock association in the central part of the Aravalli Mountains, northwest India. The entire suite, named the Sandmata Complex, preserves a complex history of tectonothermal evolution. Except for their strongly foliated margins, the granulite bodies are largely massive. Partial melting in the ‘country rocks’ led to the development of migmatite gneisses close to the contact of the granulite, a feature not as common in the rocks further away from the granulite contact. Geothermobarometry of massive granulites indicates Tmax>900°C and Pmax∼7.5 kbar. The retrograde granulites, which formed at lower amphibolite/upper greenschist-facies conditions, experienced channelized hydration reactions concomitant with shearing. These rocks locally appear as hornblende–biotite-bearing foliated granulite with or without Cpx or Opx. The rocks seem to have followed an inverse PTt path and have undergone an earlier phase of near-isobaric cooling. Our single zircon Pb–Pb ages indicate that the exhumation of granulites to the shallower amphibolite-facies levels with concomitant melting in the country rocks took place between 1690 Ma and 1621 Ma. Assuming that the granulite-facies metamorphism took place at around 1725 Ma, we relate the entire process of granulite metamorphism and exhumation covering an age range between 1725 and 1621 Ma to the rift basin opening stages of the Delhi Orogenic cycle that culminated at c. 1450 Ma.

Triassic rift-related meta-granites in the Internal Hellenides, Greece

2009 ◽  
Vol 146 (2) ◽  
pp. 252-265 ◽  
Author(s):  
F. HIMMERKUS ◽  
T. REISCHMANN ◽  
D. KOSTOPOULOS
Keyword(s):  
Eastern Mediterranean ◽  
Primary Crystallization ◽  
Trace Element Geochemistry ◽  
Initial Ratio ◽  
Element Geochemistry ◽  
Northern Greece ◽  
The West ◽  
Basement Complex ◽  
Single Zircon ◽  
Zircon Evaporation

AbstractThe Serbo-Macedonian Massif is a basement complex in the Internal Hellenides of northern Greece, situated between the Vardar Zone to the west and the Rhodope Massif to the east. The Serbo-Macedonian Massif comprises several distinct basement units interpreted as terranes, the largest of which is the Gondwana-derived Vertiskos Terrane in the northwestern and central parts of the massif. A series of leucocratic meta-granites intrude the Silurian orthogneiss basement of the Vertiskos Terrane. No similar granites are found in any of the other units of the Internal Hellenides. The meta-granites have a pronounced crustal within-plate signature which is visible in lithology, major- and trace-element geochemistry and the Sr isotopic compositions. These intrusions were dated using the Pb–Pb single-zircon evaporation method, and yielded a Triassic age of between 240.7 ± 2.6 Ma and 221.7 ± 1.9 Ma on 17 samples, with a mean age of 228.3 ± 5.6 Ma. The zircons are purely magmatic, indicating that ages are primary crystallization ages. A Rb–Sr errorchron of the whole-rock samples of the Arnea granite yielded an age of 231.6 ± 9.9 Ma (MSWD = 82), and a mean 87Sr/86Sr initial ratio is 0.7142, indicating a crust-dominated source, and suggesting an A-type origin for the granites. The A-type meta-granites together with mafic intrusive bodies (amphibolites) in the Vertiskos Terrane may be evidence of Triassic rifting that led to the formation of a branch of Neotethys (Vardar–Meliata Ocean). Similar rock associations are also exposed in the Cyclades, and in massifs of the wider eastern Mediterranean realm related to the Gondwana-derived Hun Terrane, indicating that the Arnea-type granites are representatives of a major regional rifting event in Triassic times.

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