Q: There was a discovery of large amounts of magnetite at Bekisopa, Madagascar by Akora Resources, who subsequently drilled another area with magnetic anomalies at nearby Satrokala. They reported an interesting result from the Satrokala drilling, were the field portable magnetic susceptibility measurements were lower than expected for the degree ofapparent mineralisation, compared to similar Bekisopa core sections. This could imply thatother minerals than the highly magnetic magnetite may be present. They also discovered some pyrite and pyrrhotite, these minerals being less magnetic iron sulphides, observed in some drill core sections. Does the pyrite and pyrrhotite discoveries suggest the potential of an IOCG deposits at Satrokala?
A: The discovery of pyrite and pyrrhotite at Satrokala, alongside significant magnetite at Bekisopa, does suggest a potential for IOCG (Iron Oxide Copper Gold) deposits, but further investigation would be necessary to confirm this.IOCG deposits typically contain a mixture of iron oxides (like magnetite and hematite) and sulfide minerals (including pyrite and pyrrhotite), along with copper and sometimes gold. The presence of pyrite and pyrrhotite, which are less magnetic iron sulfides, could indeed indicate a complex mineralogical environment typical of IOCG systems. Key characteristics of IOCG deposits include:1. **Iron Oxides**: High concentrations of magnetite and/or hematite.2. **Copper and Gold**: Economic grades of copper and sometimes gold.3. **Sulfide Minerals**: Presence of minerals like pyrite and pyrrhotite.4. **Alteration Zones**: Extensive alteration of host rocks, often showing sodic (sodium-rich) or calcic (calcium-rich) alteration.The presence of lower-than-expected magnetic susceptibility in areas with apparent mineralization could suggest that the mineralization includes sulfide minerals, which do not have strong magnetic properties, alongside magnetite. This mix is typical of IOCG deposits, where both iron oxides and sulfides are present.### Implications of Pyrite and Pyrrhotite- **Pyrite and Pyrrhotite**: These minerals are commonly found in IOCG deposits and indicate the potential for hydrothermal processes that can concentrate other valuable metals.- **Geophysical Anomalies**: The magnetic anomalies, combined with the sulfide minerals, support the potential for an IOCG system, which often shows complex geophysical signatures due to the presence of both magnetic and non-magnetic minerals.### Further ExplorationTo confirm the potential for an IOCG deposit, further exploration would involve:- **Geochemical Analysis**: Detailed chemical analysis of the drill cores to identify copper, gold, and other trace elements.- **Geophysical Surveys**: Advanced geophysical methods to map the extent of the mineralization and alteration zones.- **Mineralogical Studies**: Detailed study of the mineralogy to understand the relationship between iron oxides and sulfides.The discovery at Satrokala is promising and aligns with characteristics of IOCG deposits, but comprehensive exploration and analysis are required to make a definitive determination.
Q: Is there any evidence of magmatic-hydrothermal systems in Madagascar?
Madagascar has geological features that suggest the presence of magmatic-hydrothermal systems. These systems are critical in the formation of various mineral deposits, including IOCG (Iron Oxide Copper Gold) deposits. Here are some points of evidence indicating the presence of such systems in Madagascar:1. **Tectonic Setting**: Madagascar's geological history involves significant tectonic activity, including rifting and magmatism. The island's position at the junction of several major tectonic plates has led to extensive magmatic and hydrothermal activity over geological time scales【19†source】.2. **Presence of Large Igneous Provinces (LIPs)**: Madagascar hosts large igneous provinces, such as the Karoo-Ferrar LIP, associated with significant magmatic activity. These provinces can provide the heat and fluid flow necessary for hydrothermal systems【19†source】.3. **Existing Mineral Deposits**: - **Nickel-Cobalt Deposits**: The Ambatovy deposit is one of the world's largest nickel-cobalt deposits, formed through lateritic processes over ultramafic rocks. These types of deposits often have underlying magmatic-hydrothermal systems. - **Graphite Deposits**: Madagascar is known for its high-quality graphite deposits, such as those at Ambatolampy. Graphite deposits can be associated with hydrothermal fluids emanating from deeper magmatic sources.4. **Geochemical Anomalies**: Areas with significant geochemical anomalies, particularly of metals like copper, gold, and rare earth elements, often indicate past hydrothermal activity driven by magmatic sources. Exploration companies have identified such anomalies in various regions of Madagascar, hinting at magmatic-hydrothermal processes【19†source】.5. **Volcanic Activity**: Historical and recent volcanic activity in Madagascar provides additional evidence of magmatic systems. The Ankaratra and Itasy volcanic fields are examples where ongoing magmatic activity suggests the potential for related hydrothermal systems.6. **Scientific Studies**: Research studies have documented hydrothermal alteration and mineralization in several regions of Madagascar, often associated with intrusive igneous rocks. These studies provide direct evidence of magmatic-hydrothermal processes at work.### Examples of Magmatic-Hydrothermal Evidence1. **Ankaratra Volcanic Field**: This field has documented evidence of hydrothermal alteration zones, often associated with volcanic and sub-volcanic intrusions, indicative of active magmatic-hydrothermal systems.2. **Bekisopa and Satrokala Areas**: The discovery of magnetite, pyrite, and pyrrhotite at Bekisopa and Satrokala by Akora Resources indicates a potential hydrothermal system. The differences in magnetic susceptibility and the presence of sulfide minerals suggest a complex mineralizing system, possibly magmatic-hydrothermal in nature.### ConclusionWhile there is no direct confirmation of IOCG deposits in Madagascar, the presence of significant magmatic activity, hydrothermal alteration, and diverse mineral deposits strongly suggest that magmatic-hydrothermal systems are present. These systems are conducive to forming various types of mineral deposits, including potential IOCG deposits. Further exploration and research are needed to identify and characterize these systems fully.
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