Discovery of paleozoic Fe-Mg carpholite in Motalafjella, Svalbard Caledonides: A milestone for subduction-zone gradients

被引：34

作者：

Agard, P

Labrousse, L

Elvevold, S

Lepvrier, C

机构：

[1] Univ Paris 06, Lab Tecton, F-75252 Paris, France

[2] Norsk Polar Inst, N-9296 Tormo, Norway

来源：

GEOLOGY | 2005年 / 33卷 / 10期

关键词：

high-pressure-low-temperature metamorphism; blueschists; caledonides; carpholite; Svalbard;

D O I：

10.1130/G21693.1

中图分类号：

P5 [地质学];

学科分类号：

0709 ; 081803 ;

摘要：

Paleozoic blueschist facies rocks are relatively scarce on Earth due to warmer geothermal gradients at that time and/or later reequilibration. Ferro-magnesiocarpholite (Fe-Mg carpholite), the typical low-temperature blueschist facies index mineral in metapelites, was discovered 30 yr ago and is known only in Tethyan belts metamorphosed < 80 m.y. ago. Herein we report the discovery of Paleozoic Fe-Mg carpholite in the ca. 470 Ma blueschists of Motalafjella, Svalbard Caledonides, the oldest known occurrence on Earth. The carpholite-bearing rocks reached pressure-temperature (P-T) conditions of 15-16 kbar and 380-400 degrees C and followed a nearly isothermal exhumation path. In the cooling Earth perspective, these P-T estimates for Motalafjella blueschists demonstrate the existence of cold subduction-zone gradients (similar to 7 degrees C/km) from the middle Paleozoic onward.

引用

页码：761 / 764

页数：4

共 35 条

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