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

我的研究计划在未来五年的总体目标是培养本科生和研究生，以更好地了解地质过程，导致热液蚀变的寄主岩石，以及随后的矿化，经济级所谓的氧化铁磷灰石（IOA）和氧化铁铜金（IOCG）矿床。为了实现这一点，我们将使用分析工具的组合（1）未蚀变围岩、热液蚀变围岩、IOCG和IOA矿石中锆石、独居石、磷灰石和钛铁矿的原位U-Pb年代学;（2）原地微量元素和示踪同位素Sm-Nd、Lu-Hf、Pb-Pb，在同一副相中（以及熔融包裹体中的Pb-Pb）和适当情况下锆石中的原位O同位素;（3）全岩常量、微量元素及Sm-Nd、Lu-Hf、Pb-Pb、Rb-Sr示踪同位素，分别来自未蚀变围岩、热液蚀变围岩以及IOCG和IOA矿石。本研究计划的拟议实地区域包括两个地点：1）瑞典北方的Norrbotten地区; 2）智利北方的阿塔卡马沙漠地区。在诺尔博滕地区（例如，Kiirunavaara和Per Geijer矿石），和Svappavaara（例如，Gruvberget，Mertainen和Leveäniemi矿石），我的研究计划的下一阶段将建立在我目前的博士学位所获得的成果之上。他是一名学生，主要从事基鲁纳瓦拉和佩尔盖杰尔矿石的研究。利用锆石和钛铁矿的原位U-Pb年代学研究结果，证实了诺尔博滕地区在1880-1900 Ma左右发生了一次地质事件。更有趣的是，最近几个矿石样品中独居石的U-Pb结果表明在1624 ±22 Ma发生了较晚的事件。此外，Sm-Nd同位素全岩数据显示，未蚀变容矿岩石（eNd ~-6）、强蚀变容矿岩石（~3.5 ~-4）和矿石（eNd ~-3）之间存在明显差异，可能表明后两者受到亏损地幔的影响。这种Nd同位素组成的差异可能是由矿石中独居石中U-Pb系统记录的同一事件引起的。需要在该地区进行进一步研究，以确认这些发现，并通过调查瑞典Norrbotten地区的其他此类矿床（如Svappavaara），了解铁矿化与这两个事件的关系。IOA、IOCG与斑岩矿床的关系尚不清楚。例如，许多研究使用流体包裹体、稳定同位素和放射性同位素来了解加拿大、澳大利亚和南美洲的IOCG矿床。比较这一庞大的数据集，并以系统的方式收集新的数据，如我们小组所做的基律纳工作，可以帮助理解这两种存款类型之间的相似性和差异，并帮助理解它们的形成。为了解决这个问题，我也计划开始这项工作，按照类似的方法，在瑞典，在智利北方的两个领域：1）第一个领域是埃尔拉科，一个著名的最近（~2 Ma）火山，含有大约10亿吨铁，并具有功能，如磁铁矿熔岩流和磁铁矿火山砾; 2）第二个油田区是智利地区，那里有许多IOCG和IOA矿床（例如，Tropezón，Filomena，Carola，La Farola，Romeral）.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、钛铁矿和磷灰石，以便更好地了解它们的晶体化学和电荷平衡机制，这些机制允许在IOCG和IOA矿石中发现高浓度的微量元素。

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.