Study of melt and a clast of 546 Ma magmatic arc rocks in the 65 Ma Chicxulub bolide breccia, northern Maya block, Mexico: western limit of Ediacaran arc peripheral to northern Gondwana
Study of melt and a clast of 546 Ma magmatic arc rocks in the 65 Ma Chicxulub bolide breccia, northern Maya block, Mexico: western limit of Ediacaran arc peripheral to northern Gondwana
复制标题
DOI：
10.1080/00206810903545527
复制
发表时间：
2011-08
影响因子：
2.6
通讯作者：
J. Keppie;J. Dostal;M. Norman;J. Urrutia‐Fucugauchi;Manuel Grajales-Nishimura
中科院分区：
文献类型：
--
作者：
J. Keppie;J. Dostal;M. Norman;J. Urrutia‐Fucugauchi;Manuel Grajales-Nishimura
墨西哥东部玛雅地块的基底一般被中生代和新生代的台地碳酸盐岩覆盖。然而，尤卡坦半岛北部的65.5 Ma希克苏鲁伯陨石撞击深入地壳，并将结晶基底碎片带入撞击角砾岩中。来自冲击熔体和岩心 (Y6) 的花岗岩碎屑的常见铅同位素数据具有高放射性，与太古代推导一致。来自钻芯 (Yaxcopoil-1) 的角砾岩中的花岗闪长岩碎屑产生了一系列一致的 206Pb/238U 激光烧蚀电感耦合等离子体质谱锆石年龄在 546 ± 5 Ma 和 465 Ma 之间，以及三个不一致的锆石，其 206Pb/238U 年龄在 130 Ma 和 345 Ma 之间。约。 546 Ma 年龄被解释为花岗闪长岩侵入的年龄，较年轻的年龄代表与陨石撞击相关的熔化过程中不同的 Pb 损失。这与之前的 U-Pb 锆石数据一致，希克苏鲁伯的上截距年龄为 550 ± 15 Ma，当与远端喷射物的锆石数据结合时，该年龄变为 545 ± 5 Ma。这种弧形岩石在玛雅地块南部并不存在，而在邻近的瓦哈萨基亚地体 (s.s.) 中，它们被 546 ± 5 Ma 羽流相关的岩脉群所取代。另一方面，埃迪卡拉弧岩继续穿过阿巴拉契亚山脉和欧洲（佛罗里达州、卡罗莱纳州、阿瓦隆尼亚州、伊比利亚州、阿莫里卡州、中央高原、波希米亚和非洲西北部）的近冈瓦纳地体。这些地区的弧岩浆作用在 570 Ma（纽芬兰）和 540 Ma（卡罗莱纳/英国）之间结束，因为俯冲带被冈瓦纳北部边缘的转换断层所取代。这个年龄范围与土卫八的两阶段诞生同步，表明两者都与主要板块重组有关。与羽流相关的岩脉的源头可能位于劳伦大陆、波罗的海大陆和冈瓦纳大陆之间的裂谷-裂谷-转换三重交界处。
The basement of the Maya block of eastern Mexico is generally covered by Mesozoic and Cenozoic platformal carbonate rocks. However, the 65.5 Ma Chicxulub meteorite impact in the northern Yucatan Peninsula excavated deep into the crust and brought crystalline basement fragments into the impact breccias. Common Pb isotopic data from impact melt and a granitic clast from drill core (Y6) are highly radiogenic, consistent with the Archaean derivation. A granodiorite clast in this breccia from drill core (Yaxcopoil-1) yielded a continuous range of concordant 206Pb/238U laser ablation inductively coupled plasma mass spectrometry zircon ages between 546 ± 5 Ma and 465 Ma, with three discordant zircons having 206Pb/238U ages between 130 Ma and 345 Ma. The ca. 546 Ma age is interpreted as the age of granodiorite intrusion, with younger ages representing variable Pb loss during melting associated with the meteorite impact. This is consistent with previous U–Pb zircon data that gave an upper intercept age of 550 ± 15 Ma at Chicxulub, which becomes 545 ± 5 Ma when combined with the zircon data from distal ejecta. Such arc rocks are absent in the southern Maya block, and in the neighbouring Oaxaquia terrane (s.s.) they are replaced by a 546 ± 5 Ma plume-related dike swarm. On the other hand, Ediacaran arc rocks continue through the peri-Gondwanan terranes of the Appalachians and Europe (Florida, Carolinia, Avalonia, Iberia, Armorica, Massif Central, Bohemia, and NW Africa). Arc magmatism in these areas ended between 570 Ma (Newfoundland) and 540 Ma (Carolinia/UK) as the subduction zone was replaced by a transform fault along the northern Gondwanan margin. This age range is synchronous with the two-stage birth of Iapetus, suggesting that both are related to major plate reorganization. The source of plume-related dikes may have been located at the rift–rift–transform triple junction between Laurentia, Baltica, and Gondwana.