Growing magma chambers control the distribution of small-scale flood basalts.
Growing magma chambers control the distribution of small-scale flood basalts.
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不断增长的岩浆房控制了小规模溢流玄武岩的分布
DOI：
10.1038/srep16824
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发表时间：
2015-11-19
影响因子：
4.6
通讯作者：
Zeng G
中科院分区：
文献类型：
--
作者：
Yu X;Chen LH;Zeng G
小尺度大陆溢流玄武岩是一种全球性的现象，其时空分布具有规律性。然而，没有成因机制已被提出来解释这些大陆玄武岩火山作用的可见的，但被忽视的分布模式。本文以中国东部地区为例，结合主量元素和微量元素分析，结合Ar-Ar和K-Ar定年，说明小规模溢流玄武岩的时空分布受长寿命岩浆房的生长控制。演化玄武岩（SiO2> 47.5重量%）浙江新昌-嵊州地区新生代小型溢流玄武岩场的玄武岩在9.4- 3.0Ma期间表现出向北隆起的趋势。随着向北迁移，岩浆在大约6 Myr（9.4- 3.3Ma）期间仅轻微演化（（Na_2 O + K_2 O）/MgO = 0.40-0.66; TiO_2/MgO = 0.23-0.35）。当溢流玄武岩到达该省的北方端时，岩浆迅速演化（3.3-3.0 Ma），其成分范围很广（（Na_2 O + K_2 O）/MgO = 0.60-1.28; TiO_2/MgO = 0.30-0.57）。迁移溢流玄武岩的分布和两个阶段的成分演化记录了持续的岩浆补充，对岩浆演化起到缓冲作用，并导致岩浆房的生长。研究结果表明，岩浆侵位-岩浆房生长模型解释了小尺度溢流玄武岩的时空分布。
Small-scale continental flood basalts are a global phenomenon characterized by regular spatio-temporal distributions. However, no genetic mechanism has been proposed to explain the visible but overlooked distribution patterns of these continental basaltic volcanism. Here we present a case study from eastern China, combining major and trace element analyses with Ar–Ar and K–Ar dating to show that the spatio-temporal distribution of small-scale flood basalts is controlled by the growth of long-lived magma chambers. Evolved basalts (SiO2> 47.5 wt.%) from Xinchang–Shengzhou, a small-scale Cenozoic flood basalt field in Zhejiang province, eastern China, show a northward younging trend over the period 9.4–3.0 Ma. With northward migration, the magmas evolved only slightly ((Na2O + K2O)/MgO = 0.40–0.66; TiO2/MgO = 0.23–0.35) during about 6 Myr (9.4–3.3 Ma). When the flood basalts reached the northern end of the province, the magmas evolved rapidly (3.3–3.0 Ma) through a broad range of compositions ((Na2O + K2O)/MgO = 0.60–1.28; TiO2/MgO = 0.30–0.57). The distribution and two-stage compositional evolution of the migrating flood basalts record continuous magma replenishment that buffered against magmatic evolution and induced magma chamber growth. Our results demonstrate that the magma replenishment–magma chamber growth model explains the spatio-temporal distribution of small-scale flood basalts.