Early Cretaceous Wulong intermediate-mafic dike swarms in the Liaodong Peninsula: Implications for rapid lithospheric delamination of the North China Craton
Early Cretaceous Wulong intermediate-mafic dike swarms in the Liaodong Peninsula: Implications for rapid lithospheric delamination of the North China Craton
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辽东半岛早白垩世武隆中基性岩脉群：华北克拉通岩石圈快速拆沉的意义
DOI：
10.1016/j.lithos.2020.105473
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发表时间：
2020-06
期刊：
影响因子：
3.5
通讯作者：
Xinming Zhang
中科院分区：
文献类型：
--
作者：
Yan Liu;Junhao Wei;Daohan Zhang;Jiajie Chen;Xinming Zhang
华北克拉通（NCC）的岩石圈结构发生了巨大变化，100多公里古老且难熔的岩石圈地幔被去除。然而，岩石圈减薄的时间和机制仍存在争议。利用辽东半岛早白垩世中基性岩脉群的全岩/原位地球化学和同位素数据，利用新的锆石键合Pb年龄，破译了华北克拉通岩石圈减薄的时间和机制。堤坝群在化学上被细分为约。 126Ma闪长斑岩和同期（约119Ma）低钛（TiO2<1.20wt%，Ti/Y<375）和高钛（TiO2>1.90wt%，Ti/Y>580）辉绿岩岩脉。闪长斑岩表现出中等的二氧化硅 (56.71–61.13 wt%) 和高 K 钙碱特征，具有低 TiO2 和总 Fe2O3 以及高 Cr 和 Ni 成分。它们富含大离子亲石元素 (LILE)（例如 Rb、K、Pb 和 Sr），并缺乏高场强元素 (HFSE)（例如 Nb、Ta、Ti 和 P）。它们具有高放射性 Sr 同位素（全岩 (87Sr/86Sr)i= 0.711553–0.714284、原位斜长石 (87Sr/86Sr)i=0.71392）、低 εNd(t) 值（−19.9 至 −14.5）和旧 Nd 模型年龄（1.81–2.25 Ga）。同时，一些斜长石斑晶具有富钠核心（An：35-48）和富钙边缘（An：48-57）的反向分区。这些特征表明，闪长斑岩是由太古代-古元古代下地壳和岩石圈地幔的岩浆混合生成的。低Ti辉绿岩岩脉的特点是中高K钙碱性系列，Al2O3含量高，TiO2含量低。它们显示出弧形微量元素特征，例如 LILE（Rb、K、Pb 和 Sr）的富集和 HFSE（Nb、Ta、Zr、Hf、Ti 和 P）的耗尽。与斑岩和负εNd(t)值（-13.6至-5.0）相比，它们还具有相对较低的初始87Sr/86Sr比（全岩和原位Sr同位素分别为0.706331-0.708315和0.70837），表明它们源自富集岩石圈地幔的部分熔融。它们的 Th/Yb 和 Th/Nb 比率变化，而 Sr/Nd 和 U/Th 值恒定，进一步表明地幔源可能先前已被俯冲相关的熔体改变。相比之下，高钛辉绿岩岩脉属于高钾钙碱性至钠钙质系列，其TiO2和总Fe2O3含量较高，但Al2O3含量较低。它们具有类似 OIB 的微量元素（例如，Nb 和 Ta 略有富集，没有 HFSE 损耗，Nb/U 值较高（42 ± 5））和单键 Nd 同位素组成（例如，正全岩 εNd(t) 值（+3.1 至 +4.3）），表明它们是由软流圈地幔源产生的。共存的武隆低钛和高钛镁铁质岩脉具有相似的形成年龄（约119 Ma），可能表明地幔来源从岩石圈向软流圈转变。结合前人对华北克拉通东地块中、新生代基性岩的研究，我们推测辽东半岛岩石圈减薄开始于约119 Ma，华北克拉通下方的这一过程持续了很短的时间（约 13 Ma）。古太平洋板块的快速俯冲和回滚造成的不稳定地幔流可能会引发增厚、改造的岩石圈失去重力稳定性，最终导致岩石圈分层和华北克拉通减薄。
The North China Craton (NCC) underwent a dramatic change in the lithospheric architecture, and more than 100 km of the ancient and refractory lithospheric mantle was removed. However, the timing and mechanism of the lithospheric thinning remain controversial. New zircon Usingle bondPb ages and whole-rock/in-situ geochemical and isotopic data of the Early Cretaceous intermediate-mafic dike swarms in the Liaodong Peninsula have been carried out to decipher the timing and mechanism of lithospheric thinning of the NCC. The dike swarms are chemically subdivided into the ca. 126 Ma diorite porphyry and coeval (ca. 119 Ma) low-Ti (TiO2< 1.20 wt%, Ti/Y < 375) and high-Ti (TiO2> 1.90 wt%, Ti/Y > 580) diabase dikes. The diorite porphyries exhibit a moderate silica (56.71–61.13 wt%) and high-K calc-alkalic signature, with low TiO2and total Fe2O3and high Cr and Ni compositions. They are enriched in large ion lithophile elements (LILEs) (e.g., Rb, K, Pb, and Sr) and depleted in high field strength elements (HFSEs) (e.g., Nb, Ta, Ti, and P). They have high radiogenic Sr isotopes (whole-rock (87Sr/86Sr)i= 0.711553–0.714284, in-situ (87Sr/86Sr)iof plagioclase = 0.71392), lowεNd(t) values (−19.9 to −14.5), and old Nd model ages (1.81–2.25 Ga). Meanwhile, some plagioclase phenocrysts have reverse zonings with Na-rich cores (An: 35–48) and Ca-rich rims (An: 48–57). These features imply that the diorite porphyries were generated by mixing between magmas from the Archean–Paleoproterozoic lower crust and the lithospheric mantle. The low-Ti diabase dikes are characterized by medium to high-K calc-alkaline series with high Al2O3but low TiO2contents. They show arc-like trace element signatures, such as enrichment in LILEs (Rb, K, Pb, and Sr) and depletion in HFSEs (Nb, Ta, Zr, Hf, Ti, and P). They also have relatively lower initial87Sr/86Sr ratios (0.706331–0.708315 and 0.70837 for the whole-rock and in-situ Sr isotopes, respectively) compared to the porphyries and negativeεNd(t) values (−13.6 to −5.0), indicating that they were derived from partial melting of an enriched lithospheric mantle. Their variable Th/Yb and Th/Nb ratios with constant Sr/Nd and U/Th values further suggest that the mantle source might have been previously modified by the subduction-related melt. In contrast, the high-Ti diabase dikes belong to the high-K calc-alkaline to shoshonitic series, with higher TiO2and total Fe2O3but lower Al2O3contents. They have OIB-like trace elements (e.g., slight enrichments of Nb and Ta with no HFSE depletion, high Nb/U values (42 ± 5)) and Srsingle bondNd isotopic compositions (e.g., positive whole-rockεNd(t) values (+3.1 to +4.3)), suggesting that they were generated from an asthenospheric mantle source. The coexisting Wulong low-Ti and high-Ti mafic dikes with similar formation ages (ca. 119 Ma) may indicate a transition from lithospheric to asthenospheric mantle source. In combination with previous studies on the Mesozoic–Cenozoic mafic rocks in the Eastern Block of the NCC, we propose that the lithospheric thinning beneath the Liaodong Peninsula initiated at ca. 119 Ma and this process beneath the NCC lasted for a narrow duration (ca. 13 Ma). The unsteady mantle flows due to the rapid subduction and rollback of the Paleo-Pacific plate might trigger the thickened, modified lithosphere to lose its gravitational stability, eventually leading to lithospheric delamination and thinning of the NCC.
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影响因子：
5.3
作者：
STEIGER, RH;JAGER, E
通讯作者：
JAGER, E
DOI：
10.1016/s0419-0254(99)80014-7
发表时间：
1999
期刊：
Developments in Geotectonics
影响因子：
--
作者：
T. Furman;D. Graham
通讯作者：
T. Furman;D. Graham
影响因子：
3.9
作者：
Jin-Hui Yang;Fu-Yuan Wu;Sun‐Lin Chung;S. Wilde;M. Chu;C. Lo;B. Song
通讯作者：
Jin-Hui Yang;Fu-Yuan Wu;Sun‐Lin Chung;S. Wilde;M. Chu;C. Lo;B. Song
影响因子：
3.5
作者：
Jin-Hui Yang;Fu-Yuan Wu;Sun‐Lin Chung;S. Wilde;M. Chu
通讯作者：
Jin-Hui Yang;Fu-Yuan Wu;Sun‐Lin Chung;S. Wilde;M. Chu
影响因子：
5.7
作者：
Rixiang Zhu;Chen Ling;FuYuan Wu;Junlai Liu
通讯作者：
Rixiang Zhu;Chen Ling;FuYuan Wu;Junlai Liu