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CARBONATE HOSTED SEDEX - MVT - KARST MINERALIZATIONS
The Middle East and the Balkans have historically been among the first regions where mineral wealth has been identified. Increasing demand for base metals, strategic elements such as zinc (Zn), lead (Pb), copper (Cu), and iron (Fe) resources are rapidly being depleted. With the decrease in known occurrences in this ancient geography where mining exploration and operations began, the targets are becoming more challenging. In this article, we will explore the unique characteristics of most known carbonate hosted depositions such as sedimentary exhalative (SedEx), Mississippi Valley Type (MVT), and subsequently developed karst fill deposits, focusing primarily on examples from Anatolia and the Middle East, especially Zn-Pb occurrences.

Beginning Insights

  • The prototypes of SedEx-MVT-Karst fill deposits formed in carbonate rocks in the Middle East are taken as a reference. Similar examples of these types of deposits will be found across the belt extending from the Balkans to the Far East.
  • The entire model is scaleless. Relief has been applied regionally in the representation of SedEx-MVT mineralization in terms of number, size, and faulting over regional tectonics for easier understanding.
  • From the formation model, until its current state, the ore-bearing plate will be subjected to pressure in many different directions, resulting in a curvature trend rather than a straight one.
  • Having theoretical knowledge about volcano-sedimentary or volcanogenic massive sulfide deposits will provide you with additional insights into the model to be presented.

1. Understanding the Origin of SedEx-MVT-Karst Fill Mineralizations Positioned with Trends Approximately Parallel to the Taurus-Southeast Anatolia-Zagros (Iran) Suture

  • During the Devonian-Permian period, they developed within the crust characterized by ocean floor spreading, normal faulting, and rifting.
  • They are subjected within the types of volcano-sedimentary or volcanogenic massive sulfide (VMS) deposits.
  • These are deposits formed by contact of saline waters with magmatic activity beneath the ocean floor, dissolving metals and developing into hydrothermal solutions (H2S) at temperatures between 50-200 degrees Celsius.
  • Among these mineralizations; SedEx, which is stratiform, is often confused with MVT, which is stratabound and open space fills.
  • Within the trend, primary metal accumulations at different concentrations exhibit clustering along a regional scale.
  • As the ore-bearing plate undergoes folding due to tectonic activity, the clustering direction of the deposits will give way to curves.
  • The presence of enrichments in ocean floor environments will also increase the amount of compounds containing SO4.

2. SedEx deposits form through the precipitation of sulfur-rich metal compounds from the clouds generated by black smokers onto the carbonate or less clastic seabed of the ocean floor

  • These are primary formations, showing bedding structures and partial layering, and they enrich in massive sulfide form.
  • Mineral zoning can be easily observed proportionally within the deposits.
  • Incorporating mineral zoning into your concept will be highly guiding for exploration.
  • You can observe stacking structures and carbonate, barite, and similar contributions that separate different phases/layers.
  • If oxidized/hydroxide ore minerals are observed, the mineralization may have been partially transported to other voids by groundwater.
  • Watching footages of actual deep-sea hydrothermal vents emitting sulfur-rich metal from black smokers can be inspiring for understanding the process.

3. MVT is formed by sulfur-rich metal dense hydrothermal fluids penetrating into fractures, fissures, and similar open spaces

  • MVTs are primary depositions, settling into faults, cracks, and voids, enriching in massive sulfide form.
  • It is difficult to follow mineral zoning across the deposit.
  • As hydrothermal open space fillings, they behave like primitive type volcanogenic massive sulfide deposits.

4. Karstic fill enrichments occur when the metal in the primary mineralization chamber is dissolved by groundwater and transported to the gaps and chambers formed by groundwater.

  • When considering karst fillings, the masses have quite characteristic geometry and boundaries. Due to insufficient drilling density, you may not be able to detect this geometry from the surface.
  • What makes a difference here is examining the mass edges.
  • Because increasing the frequency of, drilling for relatively small-scale mineralizations would incur unnecessary additional costs.
  • The masses are irregular, sometimes observed settled into fractures of different widths (grikes/grykes), sometimes partially filling large karstic chambers.
  • It is not possible to estimate their age with stratigraphy, as examples exist just below the Mesozoic strata.
  • The ore mass consists of oxidized and carbonate minerals.
  • They contain micro and cryptocrystalline minerals such as smithsonite, cerussite, sphalerite, hydrozincite, with hematite and iron oxides giving dominant colors, also sulfates like anglesite can be seen.
  • While detection through drilling may not be difficult, estimating the grade due to the low core recovery of oxidized minerals is often unreliable.
  • If you can identify crusts such as limestone, calcite, aragonite developing on walls, it will be useful for clarification.
  • Studying karst formation from videos will provide you quite unique information of karst characteristics, which will be beneficial for all stages.

5. Determining the type of mineralization is essential for drilling planning, modeling, and mining operation

  • Let’s identify ore deposit structures, understand their geometry, mineralogical differences, and mineral zoning.
  • When initially formed, SedEx will have a horizontal ellipsoidal shape, MVT will appear as a vertically standing ellipsoid or a pin-shaped mass, and karst formations will exhibit a distinctive nodular or cavity-like geometry.
  • The detection of discontinuous mineralization or establishing a pattern of their locations may lead to potential new discoveries; examine the “sample scenario of prospection”.
  • A significant portion of the ore deposits in this belt, dating back to the Late Paleozoic, has been pushed to depths due to the collision of plates during the Alpine orogeny, while a certain portion identified so far has been brought to shallower depths through folding.
  • Geophysical methods (IP/Res) can be utilized for the discovery of SedEx and MVT deposits.
  • However, the drawback here is that the contrast of alteration halos specific to these types of mineralizations is limited, and if the size of the deposit is small, it may be missed between the lines.
  • Particularly, various geological studies such as the thickness and bedding of cover strata should be evaluated for planning the selection of methods and line directions; geophysical methods may not work for ore deposits expected at depth.
  • Since ore deposits are found in carbonate rocks, it is normal to observe many karstic structures in geophysical sections in the region.
  • Due to seasonal conditions or the independent effect of groundwater levels, water, clay, and other oxidized mineral content anomalies will appear.
  • Although your chances of filtering out these parasite anomalies based on the concept you create here may be low, they still exist.

Sample Scenario: SedEX - MVT - Karst Prospection

This is the prototype scenario for your mineral exploration activities, prefer to interpret the similarities correctly rather than having it develop so perfectly in nature. Evaluating all the parameters and making your decision with the help of experts will lead you to the result.

  • As an example, you identified the horizontal stratiform SedEx lens in its current form,
  • MVT masses, which are close to vertical and approximately parallel to the line direction, at lower elevations along the line presented by more than one SedEx mineralization,
  • We can see Karst fill mineralizations, where you can see karst skeleton/joint structures that are close to vertical, differing at low angles to MVT directions.

You can improve your exploration strategy by applying this template based on 3 different types of mineralization that you are sure of. Remember that the plate does not change direction in its block state and will duct within itself. You must obtain conscious and reliable data and evaluate all the data together.

IMPORTANT NOTICES

  • For mineralizations located close to each other along the trend, it is generally assumed that they are of the type first discovered.
  • Even if it is wrong, it can be neglected if ore continues to be mined, and it is unnecessary if you do not have a potential search target other than the resource you have.
  • Being rational and lucky, rather than knowing the type of mineralization and its local origin, has always been useful since the tens of thousands of years of history of mineral exploration.
  • Unlike everyone else, you need more to access what’s deep inside.
  • Remember that mining is different from agriculture, the resource is exploited and finished.
  • Moreover, the existence of operated mines does not mean that “there may be a few more mineralization around”.
  • You can estimate what difference it will make by interpreting the data you will obtain in mineral exploration and development in 3D by watching this simple modeling.
  • Develop your strategy, establish the most appropriate concept in the target region, collect data intentionally, and achieve positive results by evaluating it with experience and expertise.