Pre-Sturtian (800-730 Ma) depositional age of carbonates in sedimentary sequences hosting stratiform iron ores in the Uppermost Allochthon of the Norwegian Caledonides: A chemostratigraphic approach

被引：26

作者：

Melezhik, V. A. ^{[1
]}

Ihlen, P. M. ^{[1
]}

Kuznetsov, A. B. ^{[2
]}

Gjelle, S. ^{[1
]}

Solli, A. ^{[1
]}

Gorokhov, I. M. ^{[2
]}

Fallick, A. E. ^{[3
]}

Sandstad, J. S. ^{[1
]}

Bjerkgard, T. ^{[1
]}

机构：

[1] Geol Survey Norway, N-7491 Trondheim, Norway

[2] Russian Acad Sci, Inst Precambrian Geol & Geochronol, St Petersburg 199034, Russia

[3] Scottish Univ, Environm Res Ctr, E Kilbride G75 0QF, Lanark, Scotland

来源：

PRECAMBRIAN RESEARCH | 2015年 / 261卷

基金：

俄罗斯基础研究基金会;

关键词：

Caledonides; Marbles; Iron formation; Carbon; Strontium; Isotopes; LOWER CAMBRIAN CARBONATES; HIGH-GRADE MARBLES; ISOTOPIC VARIATIONS; SR-ISOTOPE; NEOPROTEROZOIC GLACIATIONS; SCANDINAVIAN CALEDONIDES; PROTEROZOIC CARBONATES; DALRADIAN SUPERGROUP; NORTHWESTERN CANADA; LAURENTIAN ANCESTRY;

D O I：

10.1016/j.precamres.2015.02.015

中图分类号：

P [天文学、地球科学];

学科分类号：

07 ;

摘要：

Carbon and strontium isotope chemostratigraphy (52 delta C-13(carb) and delta O-18, and 50 Sr-87/Sr-86 analyses of carbonate components in whole-rock samples) was applied for constraining an apparent depositional age of the carbonate protolith to amphibolite-grade, calcite marbles occurring in siliciclastic sedimentary sequences hosting iron formations (the Dunderlandsdalen type iron ores) of previously unknown age in the Rodingsfjallet Nappe Complex of the Rana region, Nordland, Norway. The least altered Sr-87/Sr-86 (0.70676) and delta C-13 (+2.5 to +5.6%.) values of the marbles (Dunderland Marble 2a) in the hanging wall sequence of the Stensundtjern iron formation in the Rana region are consistent with seawater composition in the time interval 800-730 Ma, hence the Middle Cryogenian (pre-Sturtian). The least altered Sr- and C-isotopic values obtained from two other marbles units (Marble 3 and 4) of the Rodningsfjallet Nappe Complex are consistent with the Late Cryogenian (c. 660 and 670-700 Ma, respectively). The ages obtained provide the first insight into the depositional time of sediment-hosted iron formations of the Uppermost Allochthon in the North-Central Norwegian Caledonides. The Middle Cryogenian-age of marbles associated with iron formations in the Rana region and those located c. 250 km to the north (the Hafjellet iron ore horizon) share similar Sr-87/Sr-86 and delta C-13 ratios and hence similar chemostratigraphic ages. These iron formations were originally accumulated outside of Baltica, on a glacially influenced carbonate-siliciclastic shelf, apparently on a margin of an unknown microcontinent. The Scandinavian Dunderlandsdalen and the Hafjellet iron ores of Middle Cryogenian age (800-730 Ma) were accumulated in an open marine environment distant from volcanic centres, and hence represent an outstanding exception to other reported Neoproterozoic iron formations which were all accumulated in volcanically active continental rift settings. (C) 2015 Elsevier B.V. All rights reserved.

引用

页码：272 / 299

页数：28

共 97 条

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