A Knowledge Database for Applied Chemostratigraphy

element-mineral_link

Element-Mineral links

Understanding the relations between elements and minerals is a crucial part in chemostratigrahpy. Most elements are hosted in a range of minerals, but some general assumptions can be made. Here is a list the most common element-mineral links.

Introduction

Chemostratigraphy builds on element distributions and variations through the geological / stratigraphic record, e.g., strata,  beds, layer, formations, etc. defined as chemostratigraphic zones.  The element assemblage in a certain stratigraphic horizon is determined by the mineralogical composition of the rock. It is therefore important to understand the element-mineral links / associations for the chemostratigraphic interpretation of the element data.

Some definitions

Like outlined in my article ‘Element – Mineral Associations‘, a few terms should be clear. Here some basic definitions, just to make sure we are all on the same page.

  • Rock: A rock is a naturally occurring and coherent aggregate of one (mono-mineralic) or more minerals (poly-mineralic).
  • Mineral: A mineral is a naturally occurring homogeneous solid with a characteristic (but generally not fixed) chemical composition, crystalline atomic structure, and distinct physical properties.
    • Minerals can comprise of pure elements or complex chemical compounds.
  • Element: A chemical  element is a pure chemical substance consisting of a single type of atom distinguished by its atomic number (Z), which is the number of protons in its atomic nucleus.
    • Elements are divided into metals, metalloids, and non-metals

Though the following definitions are not that crucial for element chemostratigraphy, lets define the term for completeness.

  • Atom: The atom is the smallest unit of matter that consists of a dense central nucleus surrounded by a cloud of negatively charged electrons.
    • The atomic nucleus contains a mix of positively charged protons and electrically neutral neutrons (except in the case of hydrogen, which is the only stable nuclide with no neutrons).
    • An atom containing an equal number of protons and electrons is electrically neutral, otherwise it is positively or negatively charged and is known as an ion.
    • An atom is classified according to the number of protons and neutrons in its nucleus: the number of protons (Z) determines the chemical element, and the number of neutrons (N) determines the isotope of the element.
  • Isotope: Isotopes are atoms of the same element (same Z), but with deferring numbers of neutrons (N).

When talking about elements, a common differentiation is into major and trace elements.

  • Major elements: a common definition of major elements is that they have concentrations of more than 1% by weight. However, this does not hold true for all elements that are commonly referred to as major elements. For instance, Mn, Ti, and P usually have concentrations below 1 wt.%.
  • Trace elements: Trace elements commonly have abundancies of less than 0.1 % by weight. Their concentrations are usually expressed in parts per million (ppm) or even parts per billion (ppb); for the latter for instance the elements of the platinum group. 

List of elements

Below is are two lists of elements, one for major the other for trace elements. Each entry (unless grey) is linked to another page with details on the element’s mineral associations.

[THIS LIST IS NOT COMPLETED YET. IT IS WORK IN PROGRESS, so check again later if the element you are looking for is not listed yet, or let me know which one you want to see next.]

Major elements:

*: Although sulfur (S) does not belong to the major element series, I list it here, because it is often abundant (i.e. > 1 wt.%) and often reported as oxide SO3.

Trace elements (in alphabetic order of their symbols):

  • Arsenic (As)
  • Boron (B)
  • Barium (Ba)
  • Beryllium (Be)
  • Bromine (Br)
  • Carbon (C)
  • Cadmium (Cd)
  • Chlorine (Cl)
  • Cobalt (Co)
  • Chromium (Cr)
  • Caesium (Cs)
  • Copper (Co)
  • Fluorine (F)
  • Gallium (Ga)
  • Hafnium (Hf)
  • Molybdenum (Mo)
  • Niobium (Nb)
  • Nickel (Ni)
  • Lead (Pb)
  • Rubidium (Rb)
  • Strontium (Sr)
  • Tantalum (Ta)
  • Thorium (Th)
  • Uranium (U)
  • Vanadium (V)
  • Yttrium (Y)
  • Zinc (Zn)
  • Zirconium (Zr)
  • Rare Earth Elements (REE)
    • LREE
    • HREE

 

2 thoughts on Element-Mineral links

  1. Hi, many thanks for this website. As the application of this subject is quite new in my organization, this is truly helpful. I was just wondering if you also have a list of mobile and immobile elements (major and trace elements).

    Reply

    1. Hi Christly,
      Apologies for the late and short reply below, I am currently on vacations.
      I don’t have a list as such. The mobility of elements depends on several factors, such as ionic radius and ionic charge/valence, e.g. Large-Ion-Lithophile Elements (LILE) and High Field Strength Elements (HFSE). If you refer to alterations during weathering and diagenesis, the environmental conditions are important, such as pH, Eh, temperature, pressure.
      Anyway, thanks for giving me the idea to write an article about it in the future.

      Reply

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