POLYMETAMORPHIC EVOLUTION OF THE PAN-AFRICAN BASEMENT AND PALAEOZOIC–EARLY TERTIARY COVER SERIES OF THE MENDERES MASSIF

Osman CANDAN; Roland OBERHÄNSLI; O. Özcan DORA; Mete ÇETİNKAPLAN; Ersin KORALAY; Gaëtan RIMMELÉ; Fukun CHEN; Cüneyt AKAL

Makale detayları

POLYMETAMORPHIC EVOLUTION OF THE PAN-AFRICAN BASEMENT AND PALAEOZOIC–EARLY TERTIARY COVER SERIES OF THE MENDERES MASSIF

Yazarlar:

Osman CANDAN | Roland OBERHÄNSLI | O. Özcan DORA | Mete ÇETİNKAPLAN | Ersin KORALAY | Gaëtan RIMMELÉ | Fukun CHEN | Cüneyt AKAL

Yayıncı:

Maden Tetkik Arama Genel Müdürlüğü

Ana Başlıklar:

Uygulamalı fizik

Dergi:

Bulletin of the Mineral Research and Exploration 2011 Vol.142 Issue 142, pp.121-163

Belge Tipi:

Makale

Yayın Tarihi:

10/2011

Belge Dili:

İngilizce

Document ID (Org No.):

2000520618

Sıklık:

Üç Yıllık

pISSN:

0026-4563

Özet:

 


The Menderes Massif exposing in the Western Anatolia substantially presents a complex tectonostratigraphy
as a result of Late Alpine compressional tectonism. The lithostratigraphical succession of this crystalline
complex can be divided into two units: 1- The Pan-African basement (core series) and 2-Palaeozoic - Early
Tertiary metasedimentary rocks (cover series). The Pan-African basement of the Menderes Massif is made up of
a Late Neoproterozoic metaclastic sequence consisting of paragneisses and conformably overlying micaschists.
This high-grade metaclastic sequence is extensively migmatized and intruded by the syn- to post-Pan-African
gabbros and granitoids. The primary contact relationship between the core and cover series is a regional unconformity
in character. The Palaeozoic (?Upper Devonian - Permian) cover units, which are cut by the intrusion of
Triassic leucocratic metagranites are consisted of phyllites, quartzites and marbles. The Mesozoic cover units are
characterized by Triassic to Upper Cretaceous platform-type thick marbles at lower levels of the sequence. Upper
Campanian - Upper Maastrichtian pelagic carbonates and the overlying Middle Paleocene - Eocene flysch-type
blocky unit constitute the uppermost units of cover series. Relic mineral assemblages observed in the PanAfrican
basement reveal a complex polyphase metamorphic evolution of this basement under granulite, eclogite
and amphibolite-facies conditions. The high temperature metamorphism developing under granulite facies is
characterized by the presence of hypersthene type pyroxene. Pelitic granulites, orthopyroxene gneisses, orthopyroxene
paragneisses and metagabbroic / metanoritic rocks form typical granulite-facies relics observed in the
massif. Geothermobarometric estimations characterize an average temperature of 730 °C and pressure of 6 kbar
for the granulite-facies metamorphism. By means of SHRIMP II method, clustering ages of 583±5.7 Ma were
dated from the outer parts zircons in pelitic granulites which have no zoning but have overgrown under granulite
facies. High grade metamorphism relics in the Pan-African basement are characterized by eclogite and eclogitic
metagabbros. Fully recrystallized, fine grained massif eclogites, with non bearing relic texture belonging to
protolith are composed of 'omphacite (jd40-52) + garnet + clinozoisite + amphibole + quartz + rutile'. However; relic
texture and minerals are extensively observed in metagabbros derived from eclogitic gabbros. The pressuretemperature
(P-T) conditions of the Pan-African high-pressure metamorphism were estimated as 644°C with a
minimum pressure of about 15 kbar, which corresponds to a burial depth of about 50 km. 206Pb/ 238U zircon ages
obtained from eclogitic metagabbros by TIMS yield 529.9±22 Ma, reveal the high-pressure metamorphism as
Pan-African in age. The Barrowian type medium pressure metamorphism reaching up migmatization stage in
which anatectic granites developed caused extensive retrogradations. Geothermobarometric estimates from
garnet amphibolites, retrograded from eclogites indicate that this metamorphism developed under P/T conditions
of 7 kbar in pressure and 628°C in temperature. The crystallization ages of these anatectic granites range from
551 to 540 Ma. They were generated by migmatization of paragneisses and reveal that this medium-pressure
event is related to the last stage of polyphase Pan-African metamorphism. All metamorphic ages obtained from
the Pan-African basement are compatible with the latest stages of assemblage of Gondwana super continent. It
is considered that protoliths of paragneisses and schists of the Pan-African basement were deposited on a
passive continental margin of a basin occurring between East and West Gondwana during the Late Proterozoic
time (Mozambique Ocean). The Pan-African basement of the Menderes Massif was deeply buried and metamorphosed
under granulite, eclogite and amphibolite-facies conditions as a result of the closure of this basin and
collision of East and West Gondwana during Late Neoproterozoic time. Both core and cover series of the
Menderes Massif were affected by an Alpine aged old regional metamorphism. In the Palaeozoic sequence of cover series, this metamorphism is characterized by a Barrowian type medium-pressure metamorphism. This
metamorphism developed under greenschist to lower amphibolite-facies (6 kbar in pressure / 430-550 °C in temperature)
and described by the occurrences of garnet, staurolite and kyanite (disthene) in phyllites. MesozoicEarly
Tertiary cover series at the southern part of Çine submassif contain data associated with Alpine aged HP/LT
metamorphism. Carpholite-kyanite assemblage within Triassic quartz metaconglomerates shows a metamorphism
under a pressure of 10-12 kbar and temperature of 440 °C corresponding to a minimum depth of 30 km.
So far, there has not been detected any data for an Alpine HP / LT metamorphism, neither in the Pan-African
basement nor in the Palaeozoic sequence of the Menderes Massif. Based on the fossil content obtained from
youngest unit of the cover series and from the oldest non metamorphic sedimentary cover on the massif, the
Alpine metamorphism can biostratigraphically be constrained into Eocene and Oligocene time interval. Few
isotopic data (37±1 Ma, Late Eocene Rb/Sr biotite age; 36±2 Ma, Middle Eocene Ar/Ar muscovite age; 43-37 Ma,
Eocene Ar/Ar muscovite age) related to Alpine metamorphism are compatible with the related time interval. The
Alpine metamorphisms of tectonical zones belonging to Anatolides is substantially associated with the closure of
the northern branch of Neothethys Ocean and with the collision in Paleogene. In such a tectonic model, the
segment of the Anatolide-Tauride platform corresponding to the Menderes Massif was subjected to intense
internal imbrication during the subduction process of the northern branch of Neotethys and the following period
in which the continental collision occurred. The tectonical slices being formed were buried at different depths and
metamorphosed under varying conditions related with burial depths under the load of Afyon zone at north in
Eocene-Oligocene times, and of Lycian nappes passing south and of ophiolites. 

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Makale detayları

POLYMETAMORPHIC EVOLUTION OF THE PAN-AFRICAN BASEMENT AND PALAEOZOIC–EARLY TERTIARY COVER SERIES OF THE MENDERES MASSIF

Yazarlar: Osman CANDAN | Roland OBERHÄNSLI | O. Özcan DORA | Mete ÇETİNKAPLAN | Ersin KORALAY | Gaëtan RIMMELÉ | Fukun CHEN | Cüneyt AKAL

Yayıncı: Maden Tetkik Arama Genel Müdürlüğü

Ana Başlıklar: Uygulamalı fizik

Dergi: Bulletin of the Mineral Research and Exploration 2011 Vol.142 Issue 142, pp.121-163

Belge Tipi: Makale

Yayın Tarihi: 10/2011

Belge Dili: İngilizce

Document ID (Org No.): 2000520618

Sıklık: Üç Yıllık

pISSN: 0026-4563

Sayı

Yazarlar:

Osman CANDAN | Roland OBERHÄNSLI | O. Özcan DORA | Mete ÇETİNKAPLAN | Ersin KORALAY | Gaëtan RIMMELÉ | Fukun CHEN | Cüneyt AKAL

Yayıncı:

Maden Tetkik Arama Genel Müdürlüğü

Ana Başlıklar:

Uygulamalı fizik

Dergi:

Bulletin of the Mineral Research and Exploration 2011 Vol.142 Issue 142, pp.121-163

Belge Tipi:

Makale

Yayın Tarihi:

10/2011

Belge Dili:

İngilizce

Document ID (Org No.):

2000520618

Sıklık:

Üç Yıllık

pISSN:

0026-4563