CAJ | 학술논문

本文报道了华北克拉通中部焦作地区太古宙变质岩的锆石U-Pb定年和Hf同位素分析结果。二云钾长片麻岩的碎屑锆石和变质锆石年龄分别为3.3～3.4 Ga和2.47±0.02 Ga，碎屑锆石的εHf（3.40Ga）和tDM2（CC）值分别为－2．4～＋13．9和2.89～3.84 Ga，变质锆石的εHf（2.47Ga）和tDM2（CC）值分别为－18．8～－6．4和3.38～4.13 Ma。黑云角闪片麻岩中只存在变质锆石，年龄为2.49±0.01 Ga，变质锆石的εHf（2.49Ga）和tDM2（CC）值分别为－15．0～－3．8和3.23～3.91 Ga。结合地球化学和前人研究成果，可得出如下结论：①碎屑物质来自以3.4 Ga花岗质岩浆岩为主的物源区，物源区岩石具有相当的规模，是壳幔混合作用的产物，形成过程中有更古老（始太古代）陆壳物质参与；②岩石遭受约2.5 Ga强烈构造热事件作用，深熔作用导致花岗质脉体形成；③可把变质碎屑沉积岩形成（沉积）时代限制在2.5～3.3 Ga之间；④变质锆石的Hf同位素组成与核部锆石的十分类似，变质增生边主要形成于核部锆石的溶解—再沉淀作用。
본문보도료화북극랍통중부초작지구태고주변질암적고석U-Pb정년화Hf동위소분석결과。이운갑장편마암적쇄설고석화변질고석년령분별위3.3～3.4 Ga화2.47±0.02 Ga，쇄설고석적εHf（3.40Ga）화tDM2（CC）치분별위－2．4～＋13．9화2.89～3.84 Ga，변질고석적εHf（2.47Ga）화tDM2（CC）치분별위－18．8～－6．4화3.38～4.13 Ma。흑운각섬편마암중지존재변질고석，년령위2.49±0.01 Ga，변질고석적εHf（2.49Ga）화tDM2（CC）치분별위－15．0～－3．8화3.23～3.91 Ga。결합지구화학화전인연구성과，가득출여하결론：①쇄설물질래자이3.4 Ga화강질암장암위주적물원구，물원구암석구유상당적규모，시각만혼합작용적산물，형성과정중유경고로（시태고대）륙각물질삼여；②암석조수약2.5 Ga강렬구조열사건작용，심용작용도치화강질맥체형성；③가파변질쇄설침적암형성（침적）시대한제재2.5～3.3 Ga지간；④변질고석적Hf동위소조성여핵부고석적십분유사，변질증생변주요형성우핵부고석적용해—재침정작용。
We present an integrated study of zircon U-Pb dating and O—Hf isotopic analysis on metamorphic rocks in the Jiaozuo area,Henan,central North China Craton.A two-mica K-feldspar gneiss sample contains 3.3~3.4 Ga detrital zircon and 2.47 ±0.02 Ga metamorphic zircon.The detrital zircon has εHf (3.40Ga)and tDM2(CC)ranging from -2.4 to 13.9 and 2.89 to 3.84 Ga,respectively;whereas the metamorphic zircon has εHf (2.47Ga)and tDM2(CC) ranging from -18.8 to -6.4 and 3.38 to 4.13 Ga,respectively.A biotite hornblende gneiss sample only contains metamorphic zircon with an age of 2.49 ±0.01 Ga and εHf(2.49Ga)of -15.0 to-3.8 and tDM2(CC)of 3.23 to 3.91 Ga.Combined with geochemical data and early studies,some conclusions can be drawn as follows.(1 )Detrital sediments were derived from a source region where 3 .4 Ga granitoidic rocks widely occurred,formed as a result of mixture of mantle and crustal material;(2)the sedimentary rocks underwent a strong tectono—thermal event at the end of the Neoarchean (~2.5 Ga),with anatexis resulting in the formation of granite veins;(3)the formation (deposition)time of the metasedimentary rocks can be limited to between 2.5~3.3 Ga;(4)metamorphic zircon is similar in Hf isotope composition to the detrital zircon,suggesting that the overgrowth rims were formed through the dissolution—reprecipitation of zircon cores.