美国爱达荷博伊西州立大学M.T. Mohr的团队成员，使用高精度U-Pb年代学方法将Laurentia西南大火成岩省的岩浆活动与大陆中部裂谷联系起来。相关论文发表在2024年1月9日出版的《地质学》杂志上。

研究人员表示，新的精确U-Pb锆石测年方法，揭示了ca.1098Ma(以死亡谷、加利福尼亚、大峡谷和亚利桑那州中部的大规模岩床为代表)和ca.1083Ma(以大峡谷的Cardenas玄武岩和加利福尼亚州死山的岩床为代表)基性岩中岩浆长英质分离的明显岩浆期次。ca.1098Ma的岩浆脉冲是短暂的，持续时间为0.25-0.24+0.67m.y,，体积大且分布广泛，死亡谷、大峡谷和亚利桑那州中部≥100米的岩床证明了这一点，这与上涌地幔柱的减压熔融一致。ca.1083Ma的岩浆活动可能是由次级脉冲或后地幔柱岩石圈伸展产生的。ca.1098 Ma的岩浆活动脉冲发生在Laurentia中部大陆裂谷大体积熔体生成的异常更新之前约2m.y.，这一异常是由ca.1096MaDuluth复杂层状基性侵入体记录的。

地幔柱润滑理论预测的地幔柱横向扩散速率支持了一个模型，即来自深地幔的地幔柱撞击了Laurentia西南部附近，然后扩散到变薄的大陆中部裂谷岩石圈，持续了约2m.y.，地幔温度升高并产生熔体。研究强调，这一地球动力学假说调和了Laurentia地区大规模岩浆活动之间的密切时间关系，并为大陆中部裂谷漫长的岩浆历史中高岩浆通量的异常更新提供了解释。

据悉，西南Laurentia大岩浆岩省(SWLLIP)由美国西南部和墨西哥北部广泛分布的约1.1 Ga岩浆活动组成。由于难以对基性岩进行高精度测年，SWLLIP岩浆活动的时间和速度及其与其他晚中元古代火成岩省的关系尚不清楚。

附：英文原文

Title: High-precision U-Pb geochronology links magmatism in the Southwestern Laurentia large igneous province and Midcontinent Rift

Author: M.T. Mohr, M.D. Schmitz, N.L. Swanson-Hysell, K.E. Karlstrom, F.A. Macdonald, M.E. Holland, Y. Zhang, N.S. Anderson

Issue&Volume: 2024-01-09

Abstract: The Southwestern Laurentia large igneous province (SWLLIP) comprises voluminous, widespread ca 1.1 Ga magmatism in the southwestern United States and northern Mexico. The timing and tempo of SWLLIP magmatism and its relationship to other late Mesoproterozoic igneous provinces have been unclear due to difficulties in dating mafic rocks at high precision. New precise U-Pb zircon dates for comagmatic felsic segregations within mafic rocks reveal distinct magmatic episodes at ca. 1098 Ma (represented by massive sills in Death Valley, California, the Grand Canyon, and central Arizona) and ca. 1083 Ma (represented by the Cardenas Basalts in the Grand Canyon and a sill in the Dead Mountains, California). The ca. 1098 Ma magmatic pulse was short-lived, lasting 0.25 –0.24 +0.67 m.y., and voluminous and widespread, evidenced by the ≥100 m sills in Death Valley, the Grand Canyon, and central Arizona, consistent with decompression melting of an upwelling mantle plume. The ca. 1083 Ma magmatism may have been generated by a secondary plume pulse or post-plume lithosphere extension.The ca. 1098 Ma pulse of magmatism in southwestern Laurentia occurred ～2 m.y. prior to an anomalous renewal of voluminous melt generation in the Midcontinent Rift of central Laurentia that is recorded by the ca. 1096 Ma Duluth Complex layered mafic intrusions. Rates of lateral plume spread predicted by mantle plume lubrication theory support a model where a plume derived from the deep mantle impinged near southwestern Laurentia, then spread to thinned Midcontinent Rift lithosphere over ～2 m.y. to elevate mantle temperatures and generate melt. This geodynamic hypothesis reconciles the close temporal relationships between voluminous magmatism across Laurentia and provides an explanation for that anomalous renewal of high magmatic flux within the protracted magmatic history of the Midcontinent Rift.

DOI: 10.1130/G51786.1

Source: https://pubs.geoscienceworld.org/gsa/geology/article/doi/10.1130/G51786.1/632536/High-precision-U-Pb-geochronology-links-magmatism