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首页> 外文期刊>Earth, planets and space: EPS >Rock magnetism and microscopy of the Jacupiranga alkaline-carbonatitic complex, southern Brazil
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Rock magnetism and microscopy of the Jacupiranga alkaline-carbonatitic complex, southern Brazil

机译：巴西南部Jacupiranga碱性碳酸盐复合体的岩石磁学和显微学

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This study of the Cajati deposit provides evidence that the ore was neither purely hydrothermal, nor volcanic in origin, as previous workers have proposed. The ores were formed from magnetite-rich magmas, hydrothermally altered and intruded at an indicated crustal depth in excess of 500 m. The mineralogical and textural association between magnetite and magnesioferrite in the carbonatite, and between the titanomagnetite and magnesioferrite-Ti mineralization in the pyroxenite of hedenbergite, seems to be analog mineralizations strongly related to the ionic substitution of Fe2+ by Mg. Relatively high Q ratios (>= 5) for Jacupirangite-pyroxenite may indicate a thermo remanent magnetization (TRM) by the ore during post-metamorphic cooling, however it call also be developed from chemical remanent magnetization (CRM). Vector plots for the pyroxenite samples show reasonably linear and stable magnetic components. The intensity decay Curves show that only two components of magnetizations are likely present. Continuous susceptibility measurements with increasing temperature show that the main magnetic phase seems to be magnetite. Maghemite is probably produced during the cooling process. Susceptibility recorded from low temperature (liquid nitrogen (- 196 degrees C)) to room temperature produces typical Curves. indicating Verwey transition of magnetite. Hysteresis parameters point Out that nearly all values fill in a novel region of the Day plot, parallel to but below magnetite SD + MD mixing curves.
机译：对Cajati矿床的这项研究提供了证据，证明该矿石既不是纯粹的热液矿，也不像以前的工作人员所提议的那样是火山成因的。矿石是由富含磁铁矿的岩浆形成的，经过热液蚀变后侵入指示的地壳深度超过500 m。碳酸盐岩中磁铁矿与镁铁矿之间，钛铁矿与辉锰矿中钛铁矿与钛铁矿之间的矿物学和组织学上的联系似乎与镁对Fe2 +的离子取代作用密切相关。 Jacupirangite-pyrenite的相对较高的Q比（> = 5）可能表明矿石在后变质冷却过程中具有热剩余磁化强度（TRM），但也称为化学剩余磁化强度（CRM）。黄铁矿样品的矢量图显示了合理的线性和稳定的磁性成分。强度衰减曲线表明，可能仅存在两个磁化分量。随温度升高而进行的连续磁化率测量表明，主磁相似乎是磁铁矿。磁赤铁矿可能是在冷却过程中产生的。从低温（液氮（-196摄氏度））到室温记录的磁化率会产生典型的曲线。指示磁铁矿的Verwey转变。磁滞参数指出，几乎所有值都填充在Day图的一个新颖区域中，该区域与磁铁矿SD + MD混合曲线平行但在其下方。

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