雷州半岛中西部第四纪火山岩的^(40)Ar/^(39)Ar年龄及地质意义  

^(40)Ar/^(39)Ar ages of Quaternary volcanic rocks from the midwest of the Leizhou Peninsula,and their geologic significance

作　　者：李响[1,2] 张宗言[1,2] 李海勇 张楗钰[1] 白秀娟[5] LI Xiang;ZHANG Zongyan;LI Haiyong;ZHANG Jianyu;BAI Xiujuan(Wuhan Center of China Geological Survey,Wuhan 430205,Hubei,China;Research Center of Granitic Diagenesis and Mineralization,China Geological Survey,Wuhan 430205,Hubei,China;South China Sea Institute of Oceanology,Chinese Academy of Sciences,Guangzhou 511458,Guangdong,China;Key Laboratory of Ocean and Marginal Sea Geology,Guangzhou 511458,Guangdong,China;Key Laboratory of Tectonics and Petroleum Resources of Ministry of Education,China University of Geosciences(Wuhan),Wuhan 430074,Hubei,China)

机构地区：[1]中国地质调查局武汉地质调查中心,湖北武汉430205 [2]中国地质调查局花岗岩成岩成矿研究中心,湖北武汉430205 [3]中国科学院南海海洋研究所,广东广州511458 [4]中国科学院边缘海与大洋地质重点实验室,广东广州511458 [5]中国地质大学(武汉)资源学院,构造与油气资源教育部重点实验室,湖北武汉430074

出　　处：《地质力学学报》2023年第4期512-521,共10页Journal of Geomechanics

基　　金：中国地质调查局地质调查项目(DD20230204,DD20221634,DD20160035);珠海市城市地质调查(含信息化)项目(MZCD-2201-008);广东省基础与应用基础研究基金(2019A1515011244);广州市基础与应用基础研究基金(202201010720);国家自然科学基金项目(91958212)。

摘　　要：雷州半岛地区第四纪火山岩广泛分布,但对火山岩形成的时代还存在争议。文章利用高精度的激光阶段加热^(40)Ar/^(39)Ar法对雷州半岛中西部火山岩的年龄进行了测定,并结合与相邻地层的接触关系,划分了2个火山活动旋回。第Ⅰ旋回火山岩呈夹层产于湛江组内部,仅见于钻孔ZKC12中,岩性为橄榄拉斑玄武岩;第Ⅱ旋回火山岩在区内分布最广,覆盖在湛江组之上,^(40)Ar/^(39)Ar年龄为2.02~0.88 Ma,时代为早更新世早期至早更新世晚期,结合与周围地层的接触关系,进一步划分为4个喷发期。第1喷发期(Ⅱ_(1))规模最大,出露面积最广,形成2个喷发中心,^(40)Ar/^(39)Ar年龄为2.02±0.03 Ma;第2喷发期(Ⅱ_(2))主要分布于锅盖岭和北插一带,^(40)Ar/^(39)Ar年龄分别为1.77±0.03 Ma、1.70±0.03 Ma;第3喷发期(Ⅱ_(3))喷发中心位于火炬农场,^(40)Ar/^(39)Ar年龄为1.51±0.07 Ma;第4喷发期(Ⅱ_(4))岩性以沿裂隙喷发形成的溢流相的玄武质熔岩为主,^(40)Ar/^(39)Ar年龄为0.88±0.14 Ma。火山活动明显受北东向和北西向基底断裂的控制。研究成果为雷州半岛地区火山活动时代、期次和活动规律研究提供了重要年龄证据。Quaternary volcanic rocks are widely distributed in the Leizhou Peninsula,but the age of volcanic formation remains controversial.This study used the high-precision laser stepwise heating ^(40)Ar/^(39)Ar method to date the age of volcanic samples from the midwest of the Leizhou Peninsula,and two volcanic cycles were determined by combining the contact relationship with the neighboring strata.Volcanic rocks of the first cycle(Ⅰ)occur as interlayers in the Zhanjiang Formation,only seen in Borehole ZKC12,and the lithology is olivine tholeiite;volcanic rocks of the second cycle(Ⅱ)are the most widely distributed in the study area,unconformably overlaying on the Zhanjiang Formation,with ^(40)Ar/^(39)Ar ages ranging from 2.02 to 0.88 Ma,indicating that they were erupted from the early stage of the early Pleistocene to the end of the early Pleistocene.On the combination of contact relationship with surrounding strata,the second cycle can be further divided into four eruption stages.The first eruption stage(Ⅱ_(1))has the largest scale and the most extensive area,forming two eruption centers with ^(40)Ar/^(39)Ar age of 2.02±0.03 Ma.The second eruption stage(Ⅱ_(2))centers in the areas of Guokailing and Beicha with ^(40)Ar/^(39)Ar ages of 1.77±0.03 Ma and 1.70±0.03 Ma,respectively.The eruptional center of the third eruption stage(Ⅱ_(3))lies at Huoju Farm,and the age of ^(40)Ar/^(39)Ar is 1.51±0.07 Ma.The lithology of the fourth eruption stage(Ⅱ_(4))is dominated by basaltic lava of overflow phase formed by fissure eruption,and the ^(40)Ar/^(39)Ar age is 0.88±0.14 Ma.The volcanic activity is obviously controlled by NE-trending and NW-trending basement faults.These results provide reliable age data to constrain Leizhou Peninsula’s forming age,eruption periods,and the law of volcanic activity.

关 键 词：火山岩 ^(40)Ar/^(39)Ar法 火山旋回 第四纪 雷州半岛 年代学 

分 类 号：P597[天文地球—地球化学] P534[天文地球—地质学]