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.

接下来的五年我研究计划的总体目标是培训本科生和研究生，以更好地了解导致宿主岩石的水热改变的地质过程，以及随后的经济级别氧化铁氧化铁磷灰石（IOA）和氧化铁氧化铁铜（IOCG）的矿化。为此，我们将使用分析工具（详细的现场映射和样本收集之后）的组合，包括：1）原位U-Pb的锆石，独居石，磷灰石和钛的原位，来自未经改变的乡村岩石，水热改变的宿主岩石，以及IOCG和IOA ORES； 2）在相同的附件阶段（以及在熔体夹杂物中的Pb-Pb中）以及适当的地方，原位元素和示踪剂的同位素以及包括SM-ND，Lu-HF和PB-PB在内的原位元素和PB-PB。 3）整个岩石专业和微量元素以及SM-ND，LU-HF，PB-PB和RB-SR示踪剂同位素，来自未改变的乡村岩石，水热改变的宿主岩石以及IOCG和IOA矿石。该研究计划的拟议现场区域包括两个地点：1）北瑞典的Norrbotten地区； 2）北智利的阿塔卡马沙漠地区。在Norrbotten地区（例如Kiirunavaara和Per Geijer矿石），以及Svappavaara（例如Gruvberget，Menteryen和LeveäniemiOres），我的研究计划的下一阶段将基于我当前的Ph.D.D.D.主要在Kiirunavaara和Per Geijer矿石上工作的学生。该研究的结果通过使用氧化锆和钛的原位U-PB地质学，证实了1880-1900 MA左右的地质事件。更有趣的，最近的u-pb来自几个矿石样品的结果表明，以后的事件在1624±22 ma。此外，SM -ND同位素全岩数据显示出未改变的宿主岩石（末端〜 -6），强烈改变的宿主岩石（〜3.5至-4）和矿石（端〜 -3）之间的差异很大，这可能表明后两两者的底漆耗尽。 ND同位素组合物中的这种差异可能是由矿石中U-PB系统记录的相同事件引起的。需要在该地区进行进一步的研究来确认这些发现，并通过研究瑞典诺尔布特地区（例如Svappavaara）的其他此类沉积物来了解铁矿化与这两个事件的关系。 IOA IOCG和斑岩沉积物之间的关系远非清晰。例如，许多研究都使用了流体夹杂物以及稳定的放射异位素，例如了解加拿大，澳大利亚和南美的IOCG沉积物。比较这个庞大的数据集，并以系统的方式收集新数据，例如我们小组完成的Kiruna工作，可以帮助了解两种存款类型之间的相似性和差异，并帮助理解其形成。为了解决这个问题，我还计划按照与瑞典的类似方法开始这项工作，在智利北部的两个领域：1）第一个区域是El Laco，El Laco是El Laco，这是一座著名的（〜2 MA）火山，其中包含大约10亿吨的Fe，并且具有磁铁矿薰衣草流和磁场Lapilli等特征； 2）第二个野外地区是智利地区有许多IOCG和IOA沉积物（例如Tropezón，Filomena，Carola，La Farola，Romanal）。 Lastly, I plan to grow and characterize (using powder XRD, EPMA, Raman and LA-ICPMS) synthetic zircon, monazite, titanium, and apatite in my experimental geochemistry laboratory in order to better understand their crystal chemistry and charge balancing mechanisms that allow for the employment trace elements in the high concentrations they are often found in IOCG and IOA ores.