塔里木盆地西北缘库孜贡苏剖面晚白垩世--早中新世沉积物岩石磁学研究

Rock-magnetic Characteristics of the Late Cretaceous-Early Miocene Sediments on the Kuzigongsu Section of the Northwestern Tarim Basin

对塔里木盆地西北缘库孜贡苏剖面晚白垩世—早中新世沉积物进行了热退磁及岩石磁学研究,结果表明岩石热退磁及岩石磁学特征随沉积环境可分为三种类型:潮下、台地边缘浅滩相岩石主要磁性矿物为磁铁矿及少量针铁矿、磁赤铁矿,磁性矿物含量较少、颗粒较小(假单畴),其天然剩磁强度较小,一般小于1×10-2A/m,在250℃～500℃能获得稳定特征剩磁方向,特征剩磁由磁铁矿携带;潮间、潮上带岩石主要磁性矿物为磁铁矿,并含有少量磁赤铁矿、赤铁矿、针铁矿,磁性矿物颗粒为假单畴和多畴,天然剩磁强度一般在1×10-2～1 A/m之间,在250℃～580℃能获得稳定特征剩磁方向,特征剩磁由磁铁矿携带;河湖相岩石主要磁性矿物为磁铁矿、赤铁矿,并含有少量磁赤铁矿、针铁矿,磁性矿物含量较多、颗粒较小(假单畴),天然剩磁强度一般在1×10-1A/m以上,多数样品特征剩磁由赤铁矿携带,少数由磁铁矿与赤铁矿共同携带。岩石磁学研究对于在沉积环境复杂剖面进行古地磁研究具有重要的意义。

We have carried out an rock magnetism investigation and thermal demagnetization for the Late Cretaceous to Early Miocene sediments on Kuzigongsu section from the Northwestern Tarim basin, Western China. The results in- dicate that thermal demagnetization and rock magnetic characteristics of rocks can be divided into three types specific- ally. Rocks from sublittoral zone, shallow of platform edge are dominated by the pseudo-single domain （PSD） magne- tite with a little amount of goethite and maghematite. Its natural remanence intensity is smaller than 1 x 10 -~A/m gen- erally, and the characteristic remanent magnetism （ChRM） are carried by magnetite and can be isolated from 250~C 500~C. Rocks from intertidal zone and supratidal zone are dominated by pseudo-single domain and multi-domain （ PSD ＋ MD） magnetite generally, with a little amount of goethite, maghematite and hematite. It＇ s natural remanence intensity is between 1 x 10-2 N 1A/m, and the characteristic remanent magnetism （ChRM） are carried by magnetite and can be isolated from 250~C - 580^（：. Rocks from the fluvial and lacustrine facies are dominated by the pseudo-sin- gle domain （PSD） magnetite, the hematite, with a little amount of maghemite, the goethite, Its natural remanence in- tensity is greater than 1 101A/m generally, and the characteristic remanent magnetism （ChRM） are carried by hema- tite in most samples, and carried by magnetite and hematite in some samples. So investigation of rock magnetism on sediments from different sedimentary environments is important for the paloemagnetic research.