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以及随后经济级所谓氧化铁磷灰石（IOA）矿化的地质过程。 ）和氧化铁铜金 (IOCG) 矿床，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之后），包括：1) 锆石原位 U-Pb 地质年代学，来自未蚀变围岩、热液蚀变围岩以及 IOCG 和 IOA 矿石的独居石、磷灰石和钛矿；2) 原位微量元素和示踪同位素，包括相同副相的 Sm-Nd、Lu-Hf 和 Pb-Pb； （对于熔体包裹体中的 Pb-Pb）以及锆石中的原位 O 同位素；以及 3）整个岩石的主要成分和来自未蚀变围岩、热液蚀变母岩以及 IOCG 和 IOA 矿石的微量元素和 Sm-Nd、Lu-Hf、Pb-Pb 和 Rb-Sr 示踪同位素 本研究计划的拟议现场区域包括两个地点：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。 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主要从事 Kiirunavaara 和 Per Geijer 矿石研究的博士生所取得的成果的基础上。该研究结果通过原位 U-Pb 证实了北博滕地区 1880-1900 Ma 左右的地质事件。更有趣的是，最近几个矿石样本中独居石中的 U-Pb 结果表明，在 1624 ±22 Ma 发生了较晚的事件。此外，Sm-Nd 同位素全岩石数据显示了未改变的主岩之间的明显差异。 -6），强烈蚀变的主岩（〜3.5至-4）和矿石（eNd〜-3），可能表明贫乏的地幔影响后两者的 Nd 同位素组成差异可能是由矿石中独居石 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了解铁矿化的方式。通过调查瑞典北博滕地区的其他此类矿床（例如 Svappavaara），我们发现 IOA IOCG 与斑岩矿床之间的关系还远未明确。许多研究都使用了流体。例如，通过比较这一庞大的数据集，并像我们小组所做的基律纳工作那样，以系统的方式收集新数据，可以了解包裹体以及稳定和放射性同位素。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和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·拉科著名的近期（~2 Ma）火山，含有约 10 亿吨铁，具有磁铁矿熔岩流和磁铁矿火山岩等特征；2）第二个区域是智利地区，那里有大量的 IOCG 和 IOA 矿床（例如，Tropezón、Filomena、Carola、La Farola、Romera）最后，我计划生长和表征（使用粉末 XRD、EPMA、拉曼和 LA-ICPMS）合成锆石，在我的实验地球化学实验室中，我对独居石、钛矿和磷灰石进行了研究，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痕量元素，这些元素通常在 IOCG 和 IOA 矿石中发现。