Magnetic properties of the oceanic igneous rocks (Table 1)

Hysteresis measurements have been carried out on a suite of ocean-floor basalts with ages ranging from Quaternary to Cretaceous. Approximately linear, yet separate, relationships between coercivity (Bc) and the ratio of saturation remanence/saturation magnetization (Mrs/Ms) are observed for massive doleritic basalts with low-Ti magnetite and for pillow basalts with multi-domain titanomagnetites (with x= 0.6). Even when the MORB has undergone lowtemperature oxidation resulting in titanomaghemite, the parameters are still distinguishable, although offset from the trend for unoxidized multidomain titanomagnetite. The parameters for these iron oxides with different titanium content reveal contrasting trends that can be explained by the different saturation magnetizations of the mineral types. This plot provides a previously underutilized and non-destructive method to detect the presence of low-titanium magnetite in igneous rocks, notably MORB.

本研究对一套时代跨度为第四纪至白垩纪的洋底玄武岩岩样开展了磁滞测量。针对含低钛磁铁矿的块状辉绿质玄武岩，以及含多畴钛磁铁矿（x=0.6）的枕状玄武岩，本研究观察到矫顽力（coercivity, Bc）与饱和剩磁与饱和磁化强度的比值（Mrs/Ms）之间存在近似线性且相互独立的相关关系。即便洋中脊玄武岩（MORB）经历低温氧化作用形成钛磁赤铁矿，其相关参数仍可与未氧化的多畴钛磁铁矿的变化趋势区分开来，尽管参数点会偏离该未氧化样品的趋势线。这些不同钛含量的铁氧化物的相关参数呈现出截然不同的变化趋势，这一现象可通过不同矿物类型的饱和磁化强度差异得到合理解释。该磁滞参数图解提供了一种此前未被充分利用的非破坏性检测方法，可用于识别火成岩（尤其是洋中脊玄武岩（MORB））中低钛磁铁矿的赋存情况。