UPb geochronology of layered mafic intrusions in the eastern Baltic Shield: implications for the timing and duration of Paleoproterozoic continental rifting
UPb geochronology of layered mafic intrusions in the eastern Baltic Shield: implications for the timing and duration of Paleoproterozoic continental rifting
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DOI：
10.1016/0301-9268(95)00015-w
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发表时间：
1995-11
影响因子：
3.8
通讯作者：
Y. Amelin;L. Heaman;V. Semenov
中科院分区：
文献类型：
--
作者：
Y. Amelin;L. Heaman;V. Semenov
古元古代层状镁铁质-超镁铁质侵入体广泛分布于波罗的海（芬诺斯堪的纳维亚）盾东部，标志着大陆裂谷和大量溢流玄武岩涌出的初始阶段。对科拉半岛的Pechenga-Imandra-Varzuga带和卡累利阿的Sumi-Sariola带的7个层状镁铁质侵入体和一个次火山长英质岩进行了锆石U-Pb/斜锆石年龄测定。Sumi-Sariola带中的层状侵入体的年龄从位于带东南边缘的Burakovka杂岩的2449.0 ± 1.1 Ma，到位于带东北部的北方Karelia的Olanga杂岩的Lukkulaisvaara和Tsipringa侵入体的2442.1 ± 1.4 Ma和2441.3 ± 1.2 Ma。这些年龄的结果表明，总的基性岩岩浆活动的时间沿着CA。卡累利阿的800公里带小于1000万年。科拉半岛的Pechenga-Imandra-Varzuga带包含两个不同时代的层状镁铁质侵入体和相关岩石。其中较年轻的部分与奥兰加侵入体获得的年龄重叠，包括2441.0 ± 1.6 Ma的伊曼德拉岩片和一个2442.2 ± 1.7 Ma的空间相关长英质次火山单元。科拉半岛较老的镁铁质层状岩体包括2501.5 ± 1.7 Ma的Pana冻原岩体、2504.4 ± 1.5 Ma的Monche岩体和2505.1 ± 1.6 Ma的General'skaya山岩体。波罗的海地盾2.50-2.44 Ga与裂谷有关的岩浆活动的时空分布既与地幔柱启动模型相一致，也与受预先存在的岩石圈弱点控制的被动裂谷作用模型相一致。
Paleoproterozoic layered mafic-ultramafic intrusions are widespread in the eastern Baltic (Fennoscandian) Shield and mark the initial stages of continental rifting and outpouring of voluminous flood basalts. UPb zircon/baddeleyite ages have been determined for seven layered mafic intrusions and a subvolcanic felsic unit associated with two Paleoproterozoic volcanic-sedimentary belts: the Pechenga-Imandra-Varzuga belt in the Kola Peninsula, and the Sumi-Sariola belt in Karelia. The layered intrusions in the Sumi-Sariola belt show an age progression from 2449.0 ± 1.1 Ma for the Burakovka complex, located at the southeastern edge of the belt, to 2442.1 ± 1.4 Ma and 2441.3 ± 1.2 Ma for the Lukkulaisvaara and Tsipringa intrusions of the Olanga complex in northern Karelia (northeastern part of the belt). These age results indicate a total duration of mafic magmatism along the ca. 800 km belt in Karelia to be less than 10 m.y. The Pechenga-Imandra-Varzuga belt, Kola Peninsula, contains two distinct age groups of layered mafic intrusions and related rocks. The younger of these overlaps with the ages obtained for the Olanga intrusions and includes the 2441.0 ± 1.6 Ma Imandra lopolith and a spatially associated felsic subvolcanic unit dated at 2442.2 ± 1.7 Ma. The older group of mafic layered intrusions in the Kola Peninsula includes the 2501.5 ± 1.7 Ma Pana tundra intrusion, the 2504.4 ± 1.5 Ma Monche pluton and the 2505.1 ± 1.6 Ma General'skaya mountain intrusion. The temporal and spatial distribution of the 2.50-2.44 Ga rift-related igneous activity in the Baltic Shield is consistent both with the model of starting mantle plume, and with the model of passive rifting controlled by pre-existing lithospheric weaknesses.