CAJ | 학술논문

本文报道冀北崇礼-赤城地区晚古生代花岗岩类岩石的锆石U-Pb年龄和Sr-Nd-Hf同位素组成特征.它们出露在华北陆块北缘的构造单元内,侵位于中高级变质基底岩石红旗营子群中.锆石LA-ICP-MS定年结果表明,海流图花岗岩岩体记录了两期岩浆作用,即299±3Ma和254±11Ma;镇宁堡片麻状二长花岗岩和白花沟片麻状黑云母石英二长闪长岩分别形成于287±1Ma和252±3Ma.这些晚古生代花岗岩类岩石具有较低的初始~(87)Sr/~(86)Sr值(0.7062～0.7076)、低的ε_(Nd)(t)值(-18.1至-9.6)和古老的Nd亏损地幔模式年龄(2.49～1.87Ga).其锆石的ε~(Hf)(t)值变化在-13.2至-7.4之间,Hf平均地壳模式年龄值(T_(DM)~C)在2.15Ga至1.79Ga之间.锆石Hf同位素特征与全岩Nd同位素特征指示古老的华北陆块地壳物质是花岗岩浆的主要物源.在形成时代和地球化学特征上,崇礼-赤城地区晚古生代花岗岩与出露在东部丰宁-承德地区的花岗岩类岩石既有相似性,又有不同之处,可能代表华北陆块北缘不同构造背景下岩浆作用的产物.
본문보도기북숭례-적성지구만고생대화강암류암석적고석U-Pb년령화Sr-Nd-Hf동위소조성특정.타문출로재화북륙괴북연적구조단원내,침위우중고급변질기저암석홍기영자군중.고석LA-ICP-MS정년결과표명,해류도화강암암체기록료량기암장작용,즉299±3Ma화254±11Ma;진저보편마상이장화강암화백화구편마상흑운모석영이장섬장암분별형성우287±1Ma화252±3Ma.저사만고생대화강암류암석구유교저적초시~(87)Sr/~(86)Sr치(0.7062～0.7076)、저적ε_(Nd)(t)치(-18.1지-9.6)화고로적Nd우손지만모식년령(2.49～1.87Ga).기고석적ε~(Hf)(t)치변화재-13.2지-7.4지간,Hf평균지각모식년령치(T_(DM)~C)재2.15Ga지1.79Ga지간.고석Hf동위소특정여전암Nd동위소특정지시고로적화북륙괴지각물질시화강암장적주요물원.재형성시대화지구화학특정상,숭례-적성지구만고생대화강암여출로재동부봉저-승덕지구적화강암류암석기유상사성,우유불동지처,가능대표화북륙괴북연불동구조배경하암장작용적산물.
This study presents zircon U-Pb ages and Sr-Nd-Hf isotopic composition of late Paleozoic granitoids in the ChongliChieheng area of northern Hebei Province.These granitoids intrude in the medium-to high-grade metamorphic basement rocks of the Hongqiyingzi Group exposed in the tectonic unit within the northern into margin of the North China block.Zircon LA-ICP-MS dating results show that the Hailiutu granitic pluton records two stages of magmatism forming in 299±3Ma and 250±11Ma.The Zhenningpu gneissie granite and the Baihuaguo gneissie diorite are also dated at 287±1Ma and 253±3Ma,respectively.The late Paleozoic granitoid have low initial ~(87)Sr/~(86)Sr values of 0.7062 to 0.7076,low ε_(Nd)(t)values of-18.1 to-9.6,and old Nd depleted mantle model ages of 2.49Ga to 1.87Ga.ε_(Hf)(t)values and Hf average crust model ages(T_(DM) ~C)range from-13.2 to-7.4 and 2.15 Ga to 1.79Ga.A combination of zircon Hf and whole-rock Nd isotopic compositions indicates old crustal rocks of the North China block as major source material for the granitic magmas.From the evidence of the formation ages and geochemical composition,late Paleozoic granitoids in the Chongli-Chicheng area are similar to those exposed in the Fenning-Chengde area with some differences,both likely represent magmatic products forming in different tectonic regimes along the northern margin of the North China block.