Crystallization, alteration, and ore-forming processes, of IOCG ores and related rocks

IOCG 矿石和相关岩石的结晶、蚀变和成矿过程

• 批准号: RGPIN-2014-04047
• 负责人: Hanchar, John
• 金额: $ 2.19万
• 依托单位: Memorial University of Newfoundland
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2014
• 资助国家: 加拿大
• 起止时间: 2014-01-01 至 2015-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=566263
• 关键词: Crystallization; alteration; ore; forming; processes

The overarching objective of my research program for the next five years is to train undergraduate and graduate students to better understand the geologic processes that lead to the hydrothermal alteration of host rocks, and subsequent mineralization, of economic grade so-called iron oxide apatite (IOA) and iron oxide copper gold (IOCG) deposits. To accomplish this, we will use a combination of analytical tools (after detailed field mapping and sample collection) including: 1) In situ U-Pb geochronology of zircon, monazite, apatite, and titanite from unaltered country rocks, hydrothermally altered host rocks, and IOCG and IOA ores; 2) in situ trace elements and tracer isotopes including Sm-Nd, Lu-Hf, and Pb-Pb, in the same accessory phases (and in the case of Pb-Pb in melt inclusions) and where appropriate, in situ O isotopes in zircon; and 3) whole rock major and trace elements and Sm-Nd, Lu-Hf, Pb-Pb and Rb-Sr tracer isotopes, from unaltered country rock, hydrothermally altered host rock, and IOCG and IOA ores. The proposed field areas for this research program includes two locations: 1) The Norrbotten region of northern Sweden and; 2) the Atacama Desert region of northern Chile. In the Norrbotten region (e.g., the Kiirunavaara and Per Geijer ores), and Svappavaara (e.g., the Gruvberget, Mertainen and Leveäniemi ores), the next phase of my research program will build on the results obtained by my current Ph.D. student who has been working primarily on the Kiirunavaara and Per Geijer ores. The results of that research has confirmed a geologic event around 1880-1900 Ma in the Norrbotten region by using in situ U-Pb geochronology of zircon and titanite. More interesting, recent U-Pb in monazite results from several ore samples suggests a later event at 1624 ±22 Ma. Furthermore, Sm-Nd isotopic whole rock data shows distinct differences between the unaltered host rocks (eNd ~ -6), strongly altered host rocks (~3.5 to -4), and the ore (eNd ~ -3), possibly indicating a depleted mantle influence for the latter two. This difference in the Nd isotopic composition may be caused by the same event that is recorded by the U-Pb system in monazite within the ore. Further study in this region is needed to confirm these findings and understand how the iron mineralization is related to the two events by investigating other such deposits in the Norrbotten region of Sweden such as Svappavaara. The relationship between IOA IOCG and porphyry deposits is far from clear. A number of studies have used fluid inclusions, and stable and radiogenic isotopes, to understand IOCG deposits in Canada, Australia and South America, for instance. Comparing this vast data set, and collecting new data in a systematic way like the Kiruna work that has been done by our group, could help to understand similarities and differences between the two deposit types and help understand their formation. To address this, I also plan to begin this work following a similar approach as in Sweden, in northern Chile in two field areas: 1) The first area is El Laco, a well-known recent (~2 Ma) volcano that contains roughly 1 billion tons of Fe and has features such as magnetite lava flows and magnetite lapilli; 2) The second field area is the region of Chile where there are numerous IOCG and IOA deposits (e.g., Tropezón, Filomena, Carola, La Farola, Romeral). Lastly, I plan to grow and characterize (using powder XRD, EPMA, Raman and LA-ICPMS) synthetic zircon, monazite, titanite, and apatite in my experimental geochemistry laboratory in order to better understand their crystal chemistry and charge balancing mechanisms that allow for the incorporation trace elements in the high concentrations they are often found in IOCG and IOA ores.

我未来五年研究计划的总体目标是培训本科生和研究生更好地了解导致主岩热液蚀变的地质过程，以及随后经济级氧化铁磷灰石 (IOA) 和氧化铁铜金 (IOCG) 矿床的矿化。为了实现这一目标，我们将使用多种分析工具（在详细的现场测绘和样本采集后），包括：1）对来自未蚀变围岩、热液蚀变围岩以及 IOCG 和 IOA 矿石的锆石、独居石、磷灰石和钛矿进行原位 U-Pb 地质年代学； 2) 原位微量元素和示踪同位素，包括相同副相中的 Sm-Nd、Lu-Hf 和 Pb-Pb（对于熔体包裹体中的 Pb-Pb），以及锆石中原位 O 同位素（如果适用）； 3) 来自未蚀变围岩、热液蚀变围岩以及 IOCG 和 IOA 矿石的全岩主量元素和微量元素以及 Sm-Nd、Lu-Hf、Pb-Pb 和 Rb-Sr 示踪同位素。该研究计划的拟议实地区域包括两个地点：1）瑞典北部的北博滕地区； 2）智利北部的阿塔卡马沙漠地区。在北博滕地区（例如 Kiirunavaara 和 Per Geijer 矿石）和 Svappavaara（例如 Gruvberget、Mertainen 和 Leveäniemi 矿石），我的下一阶段的研究计划将建立在我目前的博士学位获得的成果的基础上。主要从事 Kiirunavaara 和 Per Geijer 矿石工作的学生。该研究结果通过使用锆石和钛矿的原位 U-Pb 地质年代学，证实了北博滕地区大约 1880-1900 Ma 的地质事件。更有趣的是，最近从几个矿石样本中得出的独居石 U-Pb 结果表明，发生在 1624 ±22 Ma 的较晚事件。此外，Sm-Nd同位素全岩数据显示未蚀变围岩（eNd ~ -6）、强烈蚀变围岩（~3.5至-4）和矿石（eNd ~ -3）之间存在明显差异，可能表明后两者受到贫化地幔影响。 Nd 同位素组成的这种差异可能是由矿石内独居石 U-Pb 系统记录的同一事件引起的。需要对该地区进行进一步研究，以证实这些发现，并通过调查瑞典北博滕地区的其他此类矿床（例如斯瓦帕瓦拉）来了解铁矿化与这两个事件的关系。 IOA IOCG 与斑岩矿床之间的关系尚不清楚。例如，许多研究使用流体包裹体以及稳定的放射性同位素来了解加拿大、澳大利亚和南美洲的 IOCG 矿床。比较这个庞大的数据集，并像我们小组所做的基律纳工作那样系统地收集新数据，可以帮助了解两种矿床类型之间的异同，并帮助了解它们的形成。为了解决这个问题，我还计划按照与瑞典、智利北部两个领域类似的方法开始这项工作：1）第一个区域是埃尔拉科，一座著名的近年（~2 Ma）火山，含有大约 10 亿吨铁，具有磁铁矿熔岩流和磁铁矿熔岩等特征； 2）第二个领域是智利地区，那里有大量的IOCG和IOA矿床（例如Tropezón、Filomena、Carola、La Farola、Romera）。最后，我计划在我的实验地球化学实验室中生长和表征（使用粉末 XRD、EPMA、拉曼和 LA-ICPMS）合成锆石、独居石、钛矿和磷灰石，以便更好地了解它们的晶体化学和电荷平衡机制，从而能够掺入高浓度的微量元素（通常在 IOCG 和 IOA 矿石中发现）。