浙江浦江—富阳地区早新元古代沉积岩石学与盆地演化

发布时间：2018-06-17 09:56

本文选题：新元古代 + 浦江　；参考：《浙江大学》2017年硕士论文

【摘要】：浙西北的新元古代地层零星并且孤立地分散在富阳、浦江、建德、衢州、开化等地。囿于地层对比标志的缺乏,对这些地层的划分及形成存在不少争议。本文综合运用了岩石学、年代学以及沉积学等方法,对比研究了富阳骆家门组、虹赤村组和蒙山陈塘坞组的地层序列、沉积特征、碎屑锆石年龄特征、粘土矿物特征、重矿物特征,进而分析浦江-蒙山新元古代盆地的沉积、构造环境及演化特征,并提出了可能的演化模式。主要认识如下:1.浦江陈塘坞组由岩屑砂岩、细砂岩、泥质粉砂岩、泥岩等组成,发育韵律层理、沙纹层理、水平层理等。富阳骆家门组主要由砂岩、粉砂岩、泥岩组成,也发育韵律层理、水平层理、沙纹层理等。除陈塘坞组直接平行整合在以细碧岩为主的蒙山组之上,骆家门组底部出现洪冲积扇砾岩外,浦江的陈塘坞组和富阳的骆家门组在沉积岩组合、沉积构造及沉积序列方面基本相同。2.X射线及红外测试表明,浦江陈塘坞组、富阳骆家门组上段及虹赤村组泥岩组成基本一致,其粘土矿物主要为伊利石、鲕绿泥石,含少量碎屑矿物石英、长石。鲕绿泥石属自生矿物,形成于浅海环境,结合沉积岩组合,分析得出浦江蒙山组的形成环境为次深海环境,陈塘坞组为浊积-浅海环境;富阳骆家门组的形成环境为冲洪积扇、滨岸水下扇环境到浊积-浅海环境,虹赤村组的形成环境为海滩和潮坪环境。3.陈塘坞组重矿物组合为锆石、金红石、锐钛矿、石榴子石、磷灰石、磁黄铁矿和闪锌矿等,富阳骆家门组磁铁矿、锆石、磁黄铁矿、闪锌矿、石榴子石和绿帘石等,虹赤村组重矿物组合为锆石、磷灰石、磁铁矿、锐钛矿和闪锌矿,指示陈塘坞组与骆家门组及虹赤村组的物源都来自火成岩区。骨架颗粒统计结果表明,浦江陈塘坞组与富阳骆家门组的碎屑岩物源区构造属性一致,均为岩浆弧,这个岩浆弧很有可能就是靠近扬子地块东南缘的双溪坞群。4.陈塘坞组底部砂岩中的碎屑锆石都是岩浆锆石,其锆石U-Pb年龄分布在830～870Ma之间,最年轻的年龄为829Ma;骆家门组底部砂岩中碎屑锆石亦为岩浆锆石,年龄主要分布在840～890Ma,最年轻的年龄为824Ma;富阳虹赤村组的砂岩中的碎屑锆石也是岩浆锆石,其U-Pb年龄主要分布在830～930Ma之间。最年轻的碎屑锆石年龄可近似指示盆地开启的年龄,由此表明浦江盆地与富阳盆地接受沉积的时间基本一致。5.结合浦江陈塘坞组和富阳骆家门组两套地层的沉积岩组合、粘土及重砂矿物特征、物源、沉积相分析,推断它们属同一套地层,两地层所代表的盆地为同一盆地,称其为富阳-浦江盆地,开启于840～835Ma左右(由细碧岩年龄指示),并于830～824Ma左右开始接受沉积,为新元古代盆地。在此基础上,提出富阳-浦江新元古代盆地可能的演化过程和模式:距今835Ma,地壳受到拉张作用伸展,形成裂谷;持续扩张,沉积浊积岩,形成浊积裂谷盆地,期间发生裂谷环境下的岩浆活动;距今800Ma左右,强烈拉张结束,盆地被虹赤村组填满;800～760Ma期间,大规模双峰式火山喷发,标志着本次裂谷事件的结束。
[Abstract]:The Neoproterozoic strata in northwestern Zhejiang are scattered and isolated in Fuyang, Pujiang, Jiande, Quzhou, and Kaihua, and there are many disputes on the division and formation of these strata. In this paper, petrology, chronology and sedimentology are used in this paper to compare the Locke of Fuyang and Hong Chi Village. The stratigraphic sequence, sedimentary characteristics, detrital zircon age characteristics, clay mineral characteristics and heavy mineral characteristics of the detrital zircon, and then analyze the sedimentary, tectonic environment and evolution characteristics of the Pujiang montmont Neoproterozoic basin, and put forward the possible evolution patterns. The main understanding is as follows: 1. Pujiang Chen Tangwu formation is composed of lithic sandstone, fine sandstone and mud powder. Sandstone, mudstone and so on, developed rhythmic bedding, sand texture, horizontal bedding, and so on. The Fuyang Locke group is mainly composed of sandstone, siltstone and mudstone, also developed rhythmic bedding, horizontal bedding and sand texture. The basic same.2.X ray and infrared measurements of the sedimentary rock assemblage, sedimentary structure and sedimentary sequence in Pujiang's Chen Tangwu formation and Fuyang's Locke group show that the composition of the mudstone of the Chen Tangwu formation in Pujiang, the upper part of the Fuyang Locke group and the Hong Chek village is basically the same, and the clay minerals are mainly illite, oolitic debris, and a small amount of debris mineral quartz. Feldspar oolitic mudstone belongs to the authigenic mineral, which is formed in shallow sea environment, combining with sedimentary rock assemblage. It is concluded that the formation environment of Mengshan formation in Pujiang is the sub sea environment, the Chen Tangwu formation is turbid and shallow sea environment, and the formation environment of Fuyang Locke group is the alluvial fan, the coastal underwater fan ring to turbid shallow sea environment, and the formation environment of Hong Chi Village formation. The heavy minerals in the beach and tidal flat.3. are composed of zircon, Jin Hongshi, anatase, pomegranite, apatite, magnetite and sphalerite, and the magnetite, zircon, magnetite, pyrite, sphalerite, garnet and epidote in the Fuyang Locke group. The heavy minerals in Hong Chi Village are composed of zircon, apatite, magnetite, anatase and sphalerite. It indicates that the source of the Chen Tangwu formation and the Locke group and the Hong Kun village are all derived from the igneous rock area. The statistical results of the skeleton particles show that the structural properties of the detrital rocks in the Pujiang Chen Tangwu formation are the same as the magma arc in the Fuyang Locke group, and this magma arc is likely to be the bottom of the.4. Tangtang formation near the southeastern margin of the Yanzi block. The detrital zircon in the Ministry sandstone is all magmatic zircon, whose zircon U-Pb age is between 830 and 870Ma, the youngest age is 829Ma, and the detrital zircon is also magmatic zircon in the bottom sandstone of the Locke group, the age is mainly from 840 to 890Ma and the youngest age is 824Ma; the detrital zircons in the sandstone of Hong Chek village in Fuyang are also zircons of magma. The U-Pb age is mainly between 830 and 930Ma. The youngest age of the detrital zircon can approximate the age of the basin, which indicates that the time of the Pujiang basin and the Fuyang basin is basically the same as the sedimentary rocks of the two sets of the Pujiang Tangtang and Fuyang Locke groups, the characteristics of clay and heavy sand minerals. Source and sedimentary facies analysis, it is inferred that they belong to the same set of strata. The basin represented by the two layers is the same basin, which is called the Fuyang Pujiang basin, which is opened at about 840 ~ 835Ma (from the age indication of the fine birock), and from about 830 to 824Ma, the deposit is accepted as a Neoproterozoic basin. On this basis, the possibility of the Neoproterozoic basin of Fuyang Pujiang was proposed. The evolution process and model: 835Ma, the earth's crust was stretched and stretched to form a rift valley, which continued to expand, deposited turbidite, and formed a turbidite basin. During the period of the rift valley, the magma activity occurred; around 800Ma, the intense tension ended, the basin was filled with the Hong Chi Village Group; during the period of 800 ~ 760Ma, large-scale Shuangfeng volcano eruption was marked. The end of this rift event.
【学位授予单位】：浙江大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：P512.2

【参考文献】