THE PERMIAN VOLCANICS OF CENTRAL ALBORZ: IMPLICATIONS FOR PASSIVE CONTINENTAL MARGIN ALONG THE SOUTHERN BORDER OF PALEOTETHYS


Delavari M., Dolati A., Mohammadi A. , Rostami F.

OFIOLITI, cilt.41, sa.2, ss.59-74, 2016 (SCI İndekslerine Giren Dergi) identifier identifier

  • Yayın Türü: Makale / Tam Makale
  • Cilt numarası: 41 Konu: 2
  • Basım Tarihi: 2016
  • Doi Numarası: 10.4454/ofioliti.v4li2.442
  • Dergi Adı: OFIOLITI
  • Sayfa Sayıları: ss.59-74

Özet

The Permian volcanics of Central Alborz (PVCA) crop out between the Ruteh and Nesen Formations in the Baladeh-Siahbisheh area. The volcanics are predominantly basaltic and plagioclase-phyric. Ferromagnesian minerals such as clinopyroxene and olivine are not modally abundant and sometimes are totally altered. Chemical composition of clinopyroxene is characterized by high TiO2 contents (4.9-7.2 wt.%). Based on whole rock geochemistry, the samples display sodic alkaline nature (Na2O = 3.7 to 7.8 wt.%). Chondrite-normalized rare earth element (REE) patterns are extremely LREE-enriched with (La/Yb)(N) of 8.3-20.5. Both normalized REE and multi-element diagrams represent ocean island basalt (OIB) characteristics. Modeling based on trace element values, and the content of some major elements reveal low partial melting degree (< 10%) of a deep garnet-bearing mantle source. As the samples geochemically show an intra-plate tectonomagmatic setting without subduction zone signatures, during the Permian (and earlier times), the Alborz area was possibly a passive continental margin along the southern border of Paleotethys. As a result, the Alborz Permian magmatism could have been reasonably induced by an extensional tectonic regime along the northward-moving Cimmerian terranes during the early stages of Neotethys development.