The Shaytor Apatite-Magnetite Deposit in the Kashmar-Kerman Tectonic Zone (Central Iran): A Kiruna-Type Iron Deposit

The Shaytor apatite-rich iron deposit is located in the Kashmar-Kerman tectonic zone in the central of the Iranian plat, which is an important polymetallic belt in Iran. The ore bodies are interbedded with the upper inferacaamberian calc-alkaline igneous rocks that show well-preserved porphyritic and volcaniclastic textures. The iron ores have massive, disseminated, and brecciated structures. Magnetite from the Shaytor deposit is low in Ti (TiO2 = up to 0.70 wt.%) and different ore types show similar rare earth element (REE) and trace element-normalized patterns with weak-to-moderate enrichment in light REE and negative Eu anomalies, indicating a common source and genesis. The similar REE patterns for the magnetite and volcanic basaltic host rocks suggest their close genetic linkage and support a magmatic origin for the deposit. The Shaytor deposit shows the typical characteristics of Kiruna-type deposits with regard to the mineral assemblages, ore texture and structure, and the apatite and magnetite geochemistry. We propose that the Kiruna-type Shaytor apatite-rich iron deposit was derived from Fe-P-rich melt through liquid immiscibility and the activity of hydrothermal fluids.

宁芜盆地陶村铁矿床磷灰石的LA-ICP-MS研究

宁芜盆地是长江中下游成矿带中的重要矿集区,磷灰石是该区各矿床中的标志性矿物。本文以宁芜玢岩铁矿典型代表的陶村铁矿床为研究对象,利用激光剥蚀电感耦合等离子体质谱(LA-ICP-MS)微区分析新技术和电子探针分析对该矿床中辉石闪长玢岩中的磷灰石(Ap-I)、浸染状磁铁矿矿石中的磷灰石(Ap-D)和脉状磁铁矿矿石中的磷灰石(Ap-V)进行了微量元素和主量元素成分分析。其结果表明辉石闪长玢岩中的磷灰石(Ap-I)和两种类型矿石中磷灰石(Ap-D和Ap-V)的主要元素成分变化范围都很小,均为氟磷灰石,并含有少量的S和Cl。其中Ap-I含有较高的Na、Mg、Si、V、Mn、Fe、Ga、Ge、Sr、Y、Zr、Ba、REE、Pb、Th和U。Ap-D中除了含有较高的Na、Mg、Si、V、Mn、Fe、Ga、Ge、Sr、Y、Zr、Ba、REE、Pb、Th和U之外,还含有Al、Sc、Cr、Ni和Cu。Ap-V与Ap-D不同的是Al、Sc、Cr、Ni和Cu的含量较低,只有少数分析点值高于仪器的检测限。岩浆岩中的磷灰石(Ap-I)和两种类型矿石中磷灰石(Ap-D和Ap-V)中Zr、Y、Lu、Yb、Mn和δEu之间的演变关系以及稀土元素分配形式表明陶村铁矿床的成矿热液来源于辉石闪长玢岩,从浸染状矿化到脉状矿化,成矿热液的氧逸度升高,成矿热液中的Y,REE等微量元素的含量降低。陶村铁矿床为与辉石闪长玢岩密切相关的岩浆热液型矿床。将陶村铁矿床矿石中磷灰石(Ap-D和Ap-V)的F、Cl、S、REE组成与Kiruna型矿床和IOCG型矿床的同类成分进行对比发现,他们之间存在明显差异,表明以陶村铁矿床为代表的宁芜玢岩型铁矿床既不属于Kiruna型矿床,也不属于IOCG型矿床。