Detrital zircon U‐Pb geochronology of Cambrian to Triassic miogeoclinal and eugeoclinal strata of Sonora, Mexico
Detrital zircon U‐Pb geochronology of Cambrian to Triassic miogeoclinal and eugeoclinal strata of Sonora, Mexico
复制标题
墨西哥索诺拉寒武纪至三叠纪淡地斜和优地斜地层碎屑锆石U-Pb年代学
DOI：
10.1029/97jb03251
复制
发表时间：
1998
影响因子：
--
通讯作者：
J. H. Stewart
中科院分区：
文献类型：
--
作者：
G. Gehrels;J. H. Stewart
本文分析了索诺拉西北部寒武纪-二叠纪浅地斜地层、奥陶纪优地斜岩和三叠纪造山后沉积物中的182个碎屑锆石颗粒。在寒武纪、泥盆纪、二叠纪和三叠纪时期，大部分聚集在沿着这部分科迪勒拉边缘的锆石是从1.40-1.45和1.62-1.78 Ga的火成岩中脱落的，这些火成岩广泛分布于美国西南部和墨西哥西北部。锆石的年龄约为1.11 Ga是常见的寒武纪地层，显然是从花岗岩体附近的样品现场脱落。在我们的三叠纪样品中，225-280 Ma锆石的来源更成问题，因为在墨西哥西北部几乎没有发现这些年龄的火成岩。这种来源可能存在但未被识别，或者颗粒可能来自西北部莫哈韦沙漠地区，东部奇瓦瓦州和科阿韦拉，或南部增生（？）弧型波纹管由于我们的寒武纪和泥盆纪到三叠纪样品中的锆石颗粒可能在其目前位置附近的基底岩石附近或在加州南部的死亡谷地区积累，我们的数据不支持或反驳莫哈韦-索诺拉巨震的存在。奥陶系中具有深斜和深斜性质的地层主要由大于1.77Ga的碎屑锆石组成，它们的年龄比本区大多数基底岩石的年龄大得多。锆石颗粒在moogeoclinal样品显然是来自加拿大西北部的和平河拱区和沿岸流向南输送。优地斜颗粒也可能来自和平河拱门地区，通过沉积或构造过程向南迁移，或者它们可能是从大陆（也许是南极洲？）在新元古代裂谷作用期间从科迪勒拉边缘移出。也有可能奥陶纪优地斜地层是远距离旅行和异国情调的北美。
One hundred and eighty two individual detrital zircon grains from Cambrian through Permian miogeoclinal strata, Ordovician eugeoclinal rocks, and Triassic post-orogenic sediments in northwestern Sonora have been analyzed. During Cambrian, Devonian, Permian, and Triassic time, most zircons accumulating along this part of the Cordilleran margin were shed from 1.40–1.45 and 1.62–1.78 Ga igneous rocks that are widespread in the southwestern United States and northwestern Mexico. Zircons with ages of approximately 1.11 Ga are common in Cambrian strata and were apparently shed from granite bodies near the sample site. The sources of 225–280 Ma zircons in our Triassic sample are more problematic, as few igneous rocks of these ages are recognized in northwestern Mexico. Such sources may be present but unrecognized, or the grains could have been derived from igneous rocks of the appropriate ages to the northwest in the Mojave Desert region, to the east in Chihuahua and Coahuila, or to the south in accreted(?) arc-type terranes. Because the zircon grains in our Cambrian and Devonian to Triassic samples could have accumulated in proximity to basement rocks near their present position or in the Death Valley region of southern California, our data do not support or refute the existence of the Mojave-Sonora megashear. Ordovician strata of both miogeoclinal and eugeoclinal affinity are dominated by >1.77 Ga detrital zircons, which are considerably older than most basement rocks in the region. Zircon grains in the miogeoclinal sample were apparently derived from the Peace River arch area of northwestern Canada and transported southward by longshore currents. The eugeoclinal grains may also have come from the Peace River arch region, with southward transport by either sedimentary or tectonic processes, or they may have been shed from off-shelf slivers of continents (perhaps Antarctica?) removed from the Cordilleran margin during Neoproterozoic rifting. It is also possible that the Ordovician eugeoclinal strata are far traveled and exotic to North America.