CAJ | 학술논문

对浙江常山黄泥塘剖面奥陶系砚瓦山组瘤状灰岩中瘤体和基质的矿物组成、结构、构造、化学成分及碳氧同位素等做了系统研究,并从其基本特征、尤其是碳氧同位素特征出发,结合前人研究成果,对瘤状灰岩的成因进行了初步探讨.研究表明,瘤状灰岩的瘤体和基质存在明显差异:瘤体主要由方解石组成(70%～98%),基质则以黏土矿物为主(40%～78%),方解石次之(20%～58%);瘤体和基质的δ~(13)CVPDB值分别为0.5‰～1.4‰和-0.4‰～1.1‰,平均值分别为0.9‰和0.2‰,δ~(18)OVPDB 值分别为-12.8‰～-8.0‰和-11.7‰～-9.0‰,平均值分别为-10.6‰和-10.3‰;每个样品中瘤体的碳同位素值和形成温度均比基质高.黄泥塘剖面砚瓦山组瘤状灰岩是沉积物沉积时期周期性底流溶解和成岩过程中差异性压实和压溶共同作用的产物,瘤体原岩中非碳酸盐组分含量及后期压溶作用强度的差异导致瘤状灰岩不同的存在形式,有条带状、断续状和杂乱状3种.
대절강상산황니당부면오도계연와산조류상회암중류체화기질적광물조성、결구、구조、화학성분급탄양동위소등주료계통연구,병종기기본특정、우기시탄양동위소특정출발,결합전인연구성과,대류상회암적성인진행료초보탐토.연구표명,류상회암적류체화기질존재명현차이:류체주요유방해석조성(70%～98%),기질칙이점토광물위주(40%～78%),방해석차지(20%～58%);류체화기질적δ~(13)CVPDB치분별위0.5‰～1.4‰화-0.4‰～1.1‰,평균치분별위0.9‰화0.2‰,δ~(18)OVPDB 치분별위-12.8‰～-8.0‰화-11.7‰～-9.0‰,평균치분별위-10.6‰화-10.3‰;매개양품중류체적탄동위소치화형성온도균비기질고.황니당부면연와산조류상회암시침적물침적시기주기성저류용해화성암과정중차이성압실화압용공동작용적산물,류체원암중비탄산염조분함량급후기압용작용강도적차이도치류상회암불동적존재형식,유조대상、단속상화잡란상3충.
In this paper,we discussed the genesis of the nodular limestones from the Ordovician Yanwashan Formation in the Huangnitang section(the first GSSP),Changshan,Zhejiang Province on the basis of mineral component,texture,structure,chemical composition,and particularly the stableC-O isotopic composition of both the nodule and matrix.The research results indicate that there is an apparent difference between the nodule and matrix of the nodular limestones.The nodules are mainly composed of micritic calcite(70%～98%),while the primary component of the matrix is clay mineral(40%～78%)with only 20%～58% calcite.Theδ~(13)CVPDB values of calcite of the nodule and matrix are 0.5‰ to 1.4‰(average 0.9‰)and -0.4‰ to 1.1‰(average 0.2‰),respectively.Theδ~(18)OVPDB values of calcite of the nodule and matrix are -12.8‰ to -8.0‰(average -10.6‰)and-11.7‰ to -9.0‰(average -10.3‰),respectively.The nodule always shows higher δ~(13)C value and formation temperature than those of the matrix for the same sample.All features imply that the nodular limestones from the studied section are formed due to a combined processes of the periodical dissolution of bottom current during the sedimentary period and the differential compaction and pressure solution during the diagenesis.There are three existing types of the nodular limestones: banded nodular limestone,discontinuous nodular limestone and random nodular limestone.The occurrence mode of the nodular limestone is determined by the insoluble residue content of country rock of nodules and the pressure solution intensity.