浙北富阳地区新元古代骆家门组沉积时限的厘定SCIEI北大核心CSCD

中-新元古代四堡造山运动将扬子地块和华夏地块拼合成一个完整的华南板块。四堡造山运动结束后,位于华南板块东北部的浙北分区沉积了一套新元古代骆家门组地层,其底部以砾岩和砂质砾岩为特色,且以角度不整合直接覆盖于四堡造山单元双溪坞群之上。骆家门组地层的精确沉积时限对了解四堡造山结束后华南板块新一轮沉积盆地的形成和发展具有重要意义。本文对采自浙北富阳地区骆家门组底和顶部的两件沉凝灰岩样品进行SIMS锆石U-Pb定年工作,并据此分析骆家门组的起始沉积时间略早于845Ma,终止沉积时间略晚于830Ma。综合前人研究,我们认为浙北分区保存了华南板块新一轮沉积盆地(南华盆地)的早期沉积活动信息,骆家门组的初始沉积时限指示了南华盆地的开启时间略早于845Ma。

Depositional age of the Neoproterozoic Luojiamen Formation in the Fuyang area, northern Zhejiang

The Meso- to Neoproterozoic Sibao Orogeny amalgamated the Yangtze and Cathaysia blocks into a united South China Block. After the Sibao Orogeny, the northern Zhejiang region, located in the northeastern South China, preserves the Neoproterozoic Luojiamen Formation, featuring with conglomerates and sandy conglomerates at the bottom, sitting on top of the Sibao orogenic unit (the Shuangxiwu Group) with an angular unconformity. Therefore, the precise depositional age of the Luojiamen Formation is significant for understanding the evolution of the post-Sibao Orogeny sedimentary basin in South China. Taking one tuffite sample each from the bottom and top of the Luojiamen Formation, this study obtained the youngest age group of each sample (845±7Ma and 830±8Ma, respectively), and referred to the depositional window of the Luojiamen Formation as about 845~830Ma. In consideration of previous studies, we conclude that the northern Zhejiang region preserves the earliest information of the post-Sibao Orogeny sedimentary basin (the Nanhua Basin), and the initiation of the Nanhua Basin was probably a bit earlier than 845Ma.