摘要
对伊豆小笠原海脊(ODP 782A孔)上新世以来沉积物中黏土矿物的组成、含量及矿物学特征进行了分析,结果表明:黏土矿物以伊利石(42%)和蒙皂石(42%)为主,绿泥石的平均含量为14%,高岭石的含量最低,平均仅为2%。伊利石的结晶度较好,平均为0.25°Δ2θ;化学指数较低,平均为0.31;表明伊利石主要形成于干冷的气候环境。通过将ODP 782A孔黏土矿物组合特征和含量与周边可能源区对比,并结合伊利石和蒙皂石的矿物学参数特征,我们认为蒙皂石主要来源于伊豆小笠原海脊周边岛弧火山物质;伊利石、绿泥石和高岭石主要来自亚洲大陆风尘。上新世以来(伊利石+绿泥石)/蒙皂石比值总体上呈增加的趋势,并且在5.3~3.6、3.6~1.6、1.6~0 Ma的三个阶段表现出不同的变化特征,该比值与全球深海δ^(18)O值所记录的全球变冷、北太平洋ODP 885/886孔风尘通量和灵台黄土沉积速率,以及日本海U1430站伊利石/蒙皂石比值所指示的亚洲内陆干旱变化的总体变化趋势和阶段性变化的时间点大致同步,表明该比值敏感地响应了全球变冷和亚洲内陆的干旱。上新世以来(伊利石+绿泥石)/高岭石比值表现为高/低交替变化,分别与中国灵台黄土磁化率高/低变化相对应,由于黄土磁化率记录了亚洲内陆干/湿变化,因此该黏土矿物比值敏感地响应了亚洲内陆的古气候变化,因而可以作为可靠的亚洲大陆干/湿变化示踪指标。
The composition and mineralogical characteristics of clay minerals in sediments from ODP Hole 782A,Izu-Ogasawara Ridge since the Pliocene were analyzed.According to the results,the clay minerals were mainly composed of illite(average 42%)and smectite(average 42%),with moderate chlorite(average 14%)and minor kaolinite(average 2%).The low crystallinity(average 0.25°Δ2θ)and chemical index(average 0.31)of illite indicated the mineral was mainly from a cold,dry environment.By comparing clay mineralogy and clay mineral assemblages and contents between ODP Hole 782A and potential source areas,we argue that smectite is mainly derived from island arc volcanic materials around Izu-Ogasawara Ridge,and that illite,chlorite and kaolinite are mainly from aeolian dust of the Asian continent.The(illite+chlorite)/smectite ratio increased overall since the Pliocene and varied in three stages:5.33.6 Ma,3.61.6 Ma and 1.60 Ma.The variations are roughly synchronized with the global cooling recorded by deep sea δ^(18)O,the enhanced aridity in Asia recorded by dust flux in ODP Hole 885/886 in North Pacific,the sedimentary rate of Lingtai loess,and the illite/smectite ratio in IODP Site U1430 in Japan Sea.These evidences suggested that the(illite+chlorite)/smectite ratio in ODP Hole 782A is sensitive to global cooling and aridity in Asia.Since the Pliocene,the(illite+chlorite)/kaolinite ratio oscillates between high and low in accordance with the high/low changes of magnetic susceptibility of Lingtai loess.As the loess magnetic susceptibility records the dry/wet changes in Asia,we argue that the(illite+chlorite)/kaolinite ratio in ODP Hole 782A is sensitive to the paleoclimate changes in Asian inland,and,therefore,can be used as a reliable proxy of the dry/wet changes in Asia.
作者
杨佳毅
蒋富清
颜钰
郑昊
常凤鸣
YANG Jiayi;JIANG Fuqing;YAN Yu;ZHENG Hao;CHANG Fengming(Key Laboratory of Marine Geology and Environment,Institute of Oceanology,Chinese Academy of Sciences,Qingdao 266071,China;Center for Ocean Mega-Science,Chinese Academy of Sciences,Qingdao 266071,China;University of Chinese Academy of Sciences,Beijing 100049,China;Pilot National laboratory for Marine Science and Technology(Qingdao),Qingdao 266061,China)
出处
《地学前缘》
EI
CAS
CSCD
北大核心
2022年第4期73-83,共11页
Earth Science Frontiers
基金
国家自然科学基金项目(41776065,42076049,42076051)
中国科学院战略性先导科技专项“印太交汇区海洋物质能量中心形成演化过程与机制(XDB42000000)”
中国科学院海洋地质与环境重点实验室开放基金(MGE2020KG15)。
