南海北部陆区岩石磁化率的矿物学研究  

Mineralogy study of magnetic susceptibility of rocks along the coast of the northern South China Sea

作　　者：郎元强[1] 胡大千[1] 刘畅[2] 张斌[1,3] 鲁宝亮[1] 王璞珺[1] 

机构地区：[1]吉林大学地球科学学院,长春130061 [2]北京林业大学生物科学与技术学院,北京100083 [3]辽河油田勘探开发研究院,盘锦124010

出　　处：《地球物理学报》2011年第2期573-587,共15页Chinese Journal of Geophysics

基　　金：国家科技重大专项(2008ZX05025)和国家"973"项目(2009CB21 9303)联合资助;获"东北亚生物演化与环境教育部重点实验室";吉林大学"211"工程三期建设项目;2009年教育部基本科研业经费("吉林大学创新团队发展计划")支持

摘　　要：基于2517套现场测量资料，245块岩石样品的体积磁化率测量和详细的岩矿鉴定及硅酸盐全分析结果，结合单矿物磁化率特征及各岩石之间的对比研究，发现岩石磁化率主要受组成岩石的矿物磁化率控制．即岩石磁化率（峰）与组成岩石各个矿物磁化率（峰）及其体积含量（G）成正比．例如侵入岩磁化率，kr=-5．68×10^2Cq＋2．86×10^2C1＋3．28×10^2Ca＋1．18×10^4Cb＋1．27×10^4Cam＋5．35×10^5Cm；其中多项式各项的系数是与该矿物磁化率值成正比的常数，C为该矿物在该岩石中的体积含量，依次为石英q（k=-1.3）、斜长石f（k=0．01）、碱性长石a（k=0．01）、黑云母b（k=100）、角闪石am（k=80）和磁铁矿m（k=100000）．对区内火山岩、侵入岩、沉积岩和变质岩磁化率研究发现，其他三类岩石磁化率与其组成矿物磁化率的关系和侵入岩的情况相同，矿物对岩石磁化率的贡献顺序为铁磁性矿物〉顺磁性矿物〉逆磁性矿物．其中，火成岩磁化率变化大，主要取决于岩石中磁铁矿、角闪石和黑云母的含量；沉积岩多为无磁性、弱磁性，其磁化率主要由黑云母、碱性长石及岩屑提供；变质岩的磁性变化较大，从无磁性到极强磁性，主要决定于其原岩的类型，副变质岩（沉积原岩）磁化率类似于沉积岩类，正变质岩（火成原岩）类似于火成岩类；石英岩和碳酸盐岩是所有岩石中磁性最弱的．岩石蚀变会对其磁化率产生显著性影响，通常，黑云母、角闪石等铁镁硅酸盐矿物经蚀变会因形成含铁质氧化物而使岩石的磁化率升高；长石等弱顺磁矿物的粘土矿化、绢云母化会升高磁化率而碳酸盐化、高岭土化作用会使磁化率降低；岩石的绿泥石化会增加磁化率；含铁磁性矿物的岩石风化时会因高磁性组分破碎、流失而致使岩石的磁化率降低．从岩石磁化率与其组成矿物�On the basis of 2517 series of field measured data, bulk magnetic susceptibility values of 245 rock samples, detailed rock-mineral identification and total silicate analysis, combining with single mineral magnetic susceptibility and comparison research of each rock, we found thatrock magnetic susceptibility mainly depends on mineral magnetic susceptibility. That is, rock magnetic susceptibility （Kr） is proportional to the product of every mineral magnetic susceptibility （Ki） of rocks and their volume content （Ci）. For example, for intrusive rocks, Kr =-5. 68 × 10^2 Cq ＋ 2. 86 ×10^2 C1 ＋ 3. 28×10^2Ca＋1. 18× 10^4Cb＋1. 27 × 10^4Cam＋5. 35 × 10^5Cm, where the polynomial coefficients are constants positively proportional to the susceptibility of magnetic minerals,C stands for the volume content of minerals, in the order of quartz q （k=-1.3） （4π 10^-6 SI units）, plagioclase f （k=0. 01）, alkali feldspar a （k=0. 01）, biotite b （k=100）, amphibole am （k=80） and magnetite m （k= 100000）. On the other hand, from the magnetic susceptibility study of volcanic rocks, intrusive rocks, sedimentary rocks and metamorphic rocks, it is found that for the other three types of rocks the relationship of rock magnetic susceptibility with the magnetic susceptibility of mineral composition is similar to that of intrusive rocks. The contribution of mineral to rock magnetic susceptibility has the sequence of ferromagnetic minerals〉paramagnetic minerals 〉 diamagnetic minerals. Due to the change of volume content of magnetite, amphibole and biotite, the magnetic susceptibility of igneous rocks is extremely variable. While sedimentary rocks are mostly non-magnetic and weakly magnetic, and their magnetic susceptibility mainly origins from biotite, alkali feldspar and cuttings. Magnetic susceptibility of metamorphic rocks is also variable. It may range from non-magnetic to very strongly magnetic, this is mainly determined by the type of original rock. Susceptibility of para- metamorphic r

关 键 词：南海北部陆区 岩石磁化率 矿物磁化率 

分 类 号：P631[天文地球—地质矿产勘探]