太平洋板块中生代俯冲构造事件的响应：来自黑龙江东部饶河三叠纪层状燧石的古地磁证据

The identification of Mesozoic Pacific plate subduction: Evidence from paleomagnetism of the Late Triassic bedded cherts in Raohe area, eastern Heilongjiang Province

摘要: 提要：黑龙江东部饶河境内的层状燧石是中生代完达山造山带蛇绿混杂岩的重要组成部分，这些层状燧石的构造意义成为人们关注的热点。对完达山造山带饶河三叠纪大佳河组层状燧石280余块定向手标本开展深入的古地磁研究，结果表明这些层状燧石遭受不同程度的重磁化，重磁化的时间推测为晚侏罗世中期—早白垩世之间。说明对黑龙江东部晚侏罗世—早白垩世存在太平洋板块俯冲的响应。本区重磁化的机制是太平洋板块向西俯冲导致的地体增生、拼贴过程中的造山带流体造成的区域性重磁化现象。

Abstract: Abstract: The bedded cherts in Raohe area of eastern Heilongjiang Province constitute a significant component of Mesozoic Wandashan orogenic ophiolitic melange. A new paleomagnetic investigation was carried out for a Triassic red chert sequence in the western part of the WOB, with totally 200 samples collected. The bedded cherts of Lower Triassic Dajiahe Formation in Wandashan Orogenic Belt (WOB) in eastern Heilongjiang Province have been partially or completely subjected to remagnetization. In combination with the data of tectonic evolution of Wandashan Orogenic Belt and micropaleontology, the authors hold that the time of remagnetization was Late Jurassic-Early Cretaceous, caused by the orogenic fluid related to the westward subduction of the Pacific Plate.