Geological Controls and Block Modeling - Mineral Resource Estimation - page 30

Table 3.2 Mineralization mapped, logged, and modeled, October 2001 Resource Model (used with permission from BHP Billiton)
Mineralization types Mapped/Logged abrev. codes Modeled (Oct 2001 Model)

Leach LX Modeled as such

Green Copper Oxides OX Modeled as such

Cuprite CP Modeled as Cuprite

Cuprita + Copper Oxides CPOX Modeled as Cuprite

Cuprite + Mixed CPMX Modeled as Cuprite

Cuprite + Chalcocite + Pyrite CPCCPY Modeled as Cuprite

Partial Leach PL Modeled as such

Mixed Copper Oxides + Sulfides MX Modeled as such

Chacolcite + Pyrite HE1 Modeled as High Enrichment

Chacolcite + Covelite + Pyrite HE2 Modeled as High Enrichment

Covelite + Pyrite HE3 Modeled as High Enrichment

Chalcocite + Chalcopyrite + Pyrite LE1 Modeled as Low Enrichment

Chacolcite + Covelite + Chalcopyrite + Pyrite LE2 Modeled as Low Enrichment

Covelite + Chalcopyrite + Pyrite LE3 Modeled as Low Enrichment

Pyrite PR1 Modeled as Primary Mineralization

Chalcopyrite + Pyrite PR2 Modeled as Primary Mineralization

Bornite + Chalcopyrite + Pyrite PR3 Modeled as such

Table 3.3 Alteration mapped, logged, and modeled, October 2001 Resource Model (used with permission from BHP Billiton)
Alteration zones Mapped/Logged abrev. codes Modeled (Oct 2001 Model)

Unaltered F Not modeled

Propilitic P Not explicitly modeled

Chlorite-Sericite-Clay SCC Modeled as such

Quartz-Sericite S Modeled as QSC

Potassic K Modeled as K-B

Biotitic B Modeled as K-B

Advanced Argillic AA Modeled as QSC

Clays AS Modeled as QSC

Silicified Q Modeled as QSC

Potassic-Sericite Transition in Porphyry QSC Modeled as QSC

Silicified Sericite-Chlorite-Clay in Andesites SSCC Modeled as SCC

Silicified Quartz-Sericite-Clay in Porphyry SQSC Modeled as QSC

cific for a porphyry-copper type orebody, but the process of
mapping, logging, and modeling geologic variables is gen-
eral and applies to other types of mineral deposits.
Figures 3.2 and 3.3 show a plan view and a cross sec-
tion of the resulting interpretation of lithology. Cross sec-
tions used to model lithology in this deposit are located 50 m
apart, while benches are 15 m high. Only the abundant high-
volume units can be represented. Both figures use the same
color codes, with Fig. 3.2 showing the correspondence be-
tween the unit names and the colors.

modeling, since it does not carry a measure of uncertainty.
The interpreted models are assumed to be exact and accurate.
Geologic interpretation and modeling uses the data and
general geologic knowledge gained from other studies in
context of the type of deposit. This outside information may
include geological knowledge, a plausible theory about the
genesis of the deposit, and past experience with similar de-
posits. Deterministic interpretations are preferred because
they are unique and easy to manage, although sometimes
difficult and time-consuming to build.
Some basic guidelines for creating good sectional or plan
views are worth noting. First, features of interest must be
properly drawn and clearly labelled. These features include
coordinate axes and a reference datum. The map should also
include a title block which includes the title of the drawing,
who it was drawn by, and the date it was drawn. Any third
party should be able to easily figure out what they are look-
ing at and from what view angle.

3.2 Geologic Interpretation and Modeling

A traditional approach to create a geologic model is to in-
terpret the geologic variables on cross sections and plan
maps, then, extend the interpretations to three-dimensional
volumes. This is sometimes called deterministic geologic