摘要
古元古代大气圈快速大量充氧,地球表生系统发生一系列重要变化,其中之一是2.3~2.06Ga碳酸盐岩碳同位素正异常现象,称Lomagundi-Jatuli事件,颇受瞩目,成为当前国际研究前沿。胶北地体荆山群普遍经历高角闪岩相-麻粒岩相变质作用,其下部禄格庄组碳酸盐地层发育。本文研究了山后地区荆山群禄格庄组26件大理岩和7件白云质石英岩样品,获得δ^13Ccarb值在-0.8^+3.4‰(V-PDB),平均+1.4‰,其中大理岩δ^13C平均值为+1.6‰,白云质石英岩δ^13C平均值为+0.9‰。氧同位素值变化于9.3‰~20.2‰(V-SMOW),平均14.0‰。样品碳-氧同位素值之间具有很好的正相关性,且有13件样品Mn/Sr比值大于6,说明高角闪岩相的变质作用可能使δ^13Ccarb下降了3‰~5‰,原始沉积碳酸盐的δ^13Ccarb值高达+8.4‰,明显正异常,是全球性Lomagundi-Jatuli事件的响应。
The rapid rise of atmospheric oxygen content in Paleoproterozoic(i.e.,Great Oxidation Event)resulted in many dramatic changes in earth’s surficial system,including the 2.3~2.06Ma positiveδ^13Ccarb excursion,termed Lomagundi-Jatuli Event,which has been a focus of international geological and geochemical studies.The Lugezhuang Formation,lower portion of the Jingshan Group,is a high amphibolite to granulite facies metamorphic carbonate association.Herewith we report the results obtained from isotope and element geochemical study of 26 marble and 7 dolomitic quartzite samples from the Lugzhuang Formation at Shanhou village.Theδ^13Ccarb values of the samples range from-0.8‰to+3.4‰(V-PDB),with an average of+1.4‰.Theδ^13Ccarb averages of marbles and dolomitic quartzites are+1.6‰and+0.9‰,respectively.Theδ^18Ocarb values range from 9.3‰to 20.2‰(V-SMOW),with an average of 14.0‰.Theδ^18Ocarb andδ^13Ccarb values positively correlate,and 13 samples show Mn/Sr ratios of>6.This indicates that theδ^13Ccarb values of carbonates have been intensely modified by metamorphism,possibly causing a decrease ofδ^13Ccarb values by 3‰to 5‰.Hence,theδ^13Ccarb values originally sedimentary carbonates are possibly up to+8.4‰,showing positiveδ^13Ccarb excursion characterizing the global Lomagundi-Jatuli Event.
作者
李凯月
汤好书
陈衍景
薛莅治
王玭
孙之夫
LI KaiYue;TANG HaoShu;CHEN YanJing;XUE LiZhi;WANG Pin;SUN ZhiFu(MOE Key Laboratory of Orogenic Belts and Crustal Evolution,Peking University,Beijing 100871,China;State Key Laboratory of Ore Deposit Geochemistry,Institute of Geochemistry,Chinese Academy of Science,Guiyang 550008,China;Key Laboratory of Ocean and Marginal Sea Geology,South China Sea Institute of Oceanology,Chinese Academy of Sciences,Guangzhou 510301,China;Shandong Gold Group Co.,Ltd,Laizhou 261442,China)
出处
《岩石学报》
SCIE
EI
CAS
CSCD
北大核心
2020年第4期1059-1075,共17页
Acta Petrologica Sinica
基金
国家自然科学基金项目(U1906207、41890833、41872085)
国家重点基础研究发展计划(2012CB416602)联合资助.
