Earth's middle age
Earth's middle age
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DOI：
10.1130/g35402.1
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发表时间：
2014-06-01
期刊：
影响因子：
5.8
通讯作者：
Hawkesworth, Chris J.
中科院分区：
文献类型：
--
作者：
Cawood, Peter A.;Hawkesworth, Chris J.
地球的中年期从 1.7 Ga 延伸到 0.75 Ga，其特点是环境、进化和岩石圈的稳定性，与之前和之后时代的巨大变化形成鲜明对比。这一时期的特点是缺乏保存完好的被动边缘，古海水记录和碎屑锆石中的ε（Hf（t））中不存在显着的Sr异常，缺乏造山金和火山块状硫化物矿床，并且不存在冰川沉积物和铁矿层。相比之下，斜长岩和同类矿体发育良好，钼和铜矿化的主要脉动（包括世界上最大的此类矿床实例）是这一时期的特征。这些趋势归因于相对稳定的大陆组合，该组合是在大约 1997 年努纳超大陆组装期间开始的。 1.7 Ga 并一直持续到其密切相关的后继者罗迪尼亚 (Rodinia, ca) 解体。 0.75 Ga。被动边缘的整体低丰度与稳定的大陆构造一致，这也为环境和进化稳定性提供了框架。沿着超大陆边缘发育了一系列汇聚边缘增生造山带。板块边缘内侧发育丰富的斜长岩和相关岩石。它们的时间分布似乎与地幔的长期冷却有关，此时上覆的大陆岩石圈足够坚固，可以增厚并支持大型岩体进入地壳，但下面的地幔仍然足够温暖，足以导致下层增厚的地壳广泛融化。
Earth's middle age, extending from 1.7 to 0.75 Ga, was characterized by environmental, evolutionary, and lithospheric stability that contrasts with the dramatic changes in preceding and succeeding eras. The period is marked by a paucity of preserved passive margins, an absence of a significant Sr anomaly in the paleoseawater record and in the epsilon(Hf(t)) in detrital zircon, a lack of orogenic gold and volcanic-osted massive sulfide deposits, and an absence of glacial deposits and iron formations. In contrast, anorthosites and kindred bodies are well developed and major pulses of Mo and Cu mineralization, including the world's largest examples of these deposits, are features of this period. These trends are attributed to a relatively stable continental assemblage that was initiated during assembly of the Nuna supercontinent by ca. 1.7 Ga and continued until breakup of its closely related successor, Rodinia, ca. 0.75 Ga. The overall low abundance of passive margins is consistent with a stable continental configuration, which also provided a framework for environmental and evolutionary stability. A series of convergent margin accretionary orogens developed along the edge of the supercontinent. Abundant anorthosites and related rocks developed inboard of the plate margin. Their temporal distribution appears to link with the secular cooling of the mantle, at which time the overlying continental lithosphere was strong enough to be thickened and to support the emplacement of large plutons into the crust, yet the underlying mantle was still warm enough to result in widespread melting of the lower thickened crust.