Nativeowner,
I agree wholeheartedly with with your post other than this bit (unless you have worded it in a way that I am misinterpreting)
".......
that is why they have been drilling all this time and they have explicitely stated that they are drilling the ironstone to see if it extends at depth. the results are due in late October. Once that is done they are planning on drilling the Anomaly that they found on the IP. Resource measurement is also due sometime in early 2019. They have been moving at quite a fast pace and have set clear timelines."
I thought that one of the two holes is into the SE Anomaly straight away in this current two hole programme.
Maybe I'm just reading it upside down
As for the Ironstone, if the strata that it sits withing starts to curve ESE it will confirm a long held view that the structure is folded (which might facilitate better intercepts further down).
As for the SE Anomaly, it really has all the signatures of an intrusion, which if it runs true to the textbook example, it should be mineralised (given the exploration work done to date).
Also the Resource Definition will most likely only be a small fraction of what could be extrapolated to exist given the nature of these structures tested to date and the wider setting.
The other leases that they are working up, are to a certain extent part of a larger structure that runs from south of Copper Blow right up to or just south of Fairy Hill .
The quality of the graphic below is much better in the document as are the other graphics.
Anyway the below text is just a sample of the doc if anybody is bothered to read it.
From DIGS:
Copper-Gold Prospectivity of the Broken Hill Block, NSW, Australia
R00019937 (GS2001/520)
5.2 Aeromagnetics and Gravity
Regional aeromagnetic and gravity data for the Broken Hill Block are included in
Figure 14 and Figure 15 respectively. High frequency enhancement of the magnetic
data using a Total Gradient filtering technique (Figure 16) resolves the fine detail not
visually evident in TMI data. These data have been qualitatively reviewed with the
aim of defining criteria applicable to the exploration models.
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At a regional scale the two geophysical data sets contribute to definition of:
· Province scale structural architecture, with major geophysical boundaries
inferred to represent potential penetrative structures, controlling both intrusive
activity and associated migration of mineralising fluids. Penetrative structures
active at the time of granite emplacement are key elements of the proposed fluid
flow mechanisms for ore formation (Figure 9).
· Inferred granitic intrusives delineated by circular to ovoid regions of low
gravity, coincident with either low magnetic relief, or coincident zones of aureole
or “rimmed” magnetic response, indicative of (oxidised) magnetite bearing
intrusives. The coincidence of concealed granites within positions of interpreted
penetrative structures has been further investigated in Figure 17. This shows the
location of a selected aeromagnetic profile crossing the Broken Hill Block and the
results of quantitative modelling of magnetic response due to three interpreted
magnetite bearing granite bodies, which are shown to account for the broad scale
variation in the TMI profile. The magnetic traverse is approximately coincident
with the regional seismic reflection line observed by AGSO (Gibson et al, 1998).
Interpretation of the seismic reflection section suggests the possibility of crustal
scale SE dipping structures, and the magnetic interpretation presented here
suggests that these structures may have controlled Proterozoic granite
emplacement. Although it is not intended to imply that this is a unique solution to
the observed magnetic relief, the modelled TMI profile indicates how “base level”
shifts in regional magnetic levels, can be quantitatively attributed to the influence
of these three concealed magnetic granites (Mulyungarie, Umberumberka and
Redan – Figure 17).
At a prospect scale, the Total Gradient processing technique (Figure 16) has
delineated high magnitude gradient anomalies coincident with, or adjacent to a
number of significant Cu-Au occurrences (Copper Blow, Copper King). The processing
also highlights the strong linear NNE trending breaks in magnetic character, which
appear to have a significant control on a number of known areas of Cu/Au
mineralisation.
Positive Total Gradient anomalies also arise from unusually magnetic lithological
trends, and are also observed in association with some mafic to ultra-mafic
intrusives. However, as a potential indicator of late-stage metasomatic magnetite,
local magnetic features with a similar high gradient magnitude response are
regarded as priority target areas. This is particularly the case where it can be
reasonably inferred that the magnetic features occur within regionally extensive
structures.
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5.3 Prospect Element Maps
Key features from the available data sets that are interpreted to be relevant to Cu-Au
exploration prospectivity have been compiled and summarised in "prospect element
maps". These critical exploration elements include the following:
· Interpreted granites: thermal and/or mineralised fluid source for Fe-oxide Cu-Au
deposits.
· Mapped and interpreted regional structures and/or shear zones: focus for fluid
flow from intrusives or basin de-watering.
· Metasediments of Sundown/Paragon Groups: favourable reductant “trap”
sequence for fluid flow.
· Mapped occurrences of ironstone and albite lithologies: possible indicators for Fe-
Na alteration associated with hydrothermal systems.
· Cu-Au mineral occurrences and defined geochemical anomalies.
· High Total Gradient aeromagnetic features: limited extent magnetite distributions
compatible with alteration by metasomatic Fe-rich fluid.
Based on these exploration elements, priority magnetic and geochemical anomalies
have been delineated, and compared with the current exploration drill-hole database
to determine what level of drilling assessment may already have been carried out.
Open file exploration drill hole locations are seen to be concentrated in a relatively
small number of areas, which do not show any correlation with defined Cu-Au target
areas. This is not an unexpected result, given that the great majority of historical
exploration drilling within the Broken Hill Block has been concentrated in areas of
interpreted Broken Hill “mine sequence” stratigraphy.
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6.0 DETAILED PROSPECT EVALUATIONS
Exploration element data and selected target areas for each of the three principal ore
model types are summarised in Figure 18 (Fe-Oxide-Cu-Au), Figure 19 (Sediment
Hosted Cu) and Figure 20 (Porphyry/Skarn). In these summaries, individual prospect
areas have been selected on the basis of local aeromagnetic anomalies and/or
geochemical anomalous zones, that are coincident with other favourable exploration
elements for the ore model. Priorities have then be assigned to selected target areas
according to the degree to which the exploration elements are defined for the area,
and the level to which existing drill holes allow for further exploration potential. Due
to time constraints for the project, no assessment of actual drilling results has been
attempted other than a qualitative review of drill hole positioning relative to
interpreted target area extents.
6.1 Fe-Oxide-Cu-Au
Favourable exploration elements for the “Fe-Oxide-Cu-Au” ore model are summarised
in Figure 18, for the entire area of the Broken Hill Block, with a total of 16 prospect
areas delineated as first order target areas. Area selection is based on the following
combinations or coincidences of key exploration elements:
· Locally anomalous aeromagnetic features defined in either TMI or, more
commonly, Total Gradient images.
· Coincidence with geochemical anomalism, defined by mineral occurrence of
surface geochemistry.
· Positioning on regional structures and/or flexures in structures
· Coincidence with ironstone/albite lithologies.
· Proximity to inferred or mapped intrusive granites.
On this basis, a total of 16 priority target areas with potential for significant
mineralisation of the Fe-Oxide-Cu-Au type have been delineated within the Broken
Hill Block. The target areas include 10 known occurrences, included in prospect
descriptions by Willis (2000) and others, plus a total of 6 “new” prospect areas.
Details on the exploration element data and perceived priorities for individual areas
are detailed below, for known and new prospects.
6.1.1 Known Prospects
The exploration element approach employed here has delineated additional possible
target areas within the vicinity of ten historic Cu/Au occurrences. Descriptions of
recorded prospect geology, alteration and mineralisation are included with the
current assessment of exploration element data, for individual prospect areas and
their surrounds.
Copper Blow (Figure 21)
The Copper Blow prospect represents the most significant known Cu/Au producer in
the Broken Hill Block, and as indicated above “is one of the most extensively
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explored systems of its kind in the Broken Hill Domain” (Skirrow et al 2001). The
prospect is described in detail by Burton (1994) and Willis (2000) and comprises
“multiple gossanous lodes over 1000m strike length, in an extended mineralised zone
of ~ 4000m” (Willis, op cit). Drilling details included in the prospect description of
Burton (op cit) show a number of drill holes in the south-western portion of the
prospect, of which only a sub-set is included in the NSWDMR database (holes
CB1,CB2,CB3 – Figure 21). Although Burton (op cit) indicates a more complete
distribution of drill holes in the southwestern limit of the magnetic trend, the
northeastern portion of the trend is apparently untested (Figure 21). Given the high
grades intersected in a relatively small number of holes in the southwestern portion
of the area, and possibilities for multiple lode development, the exploration potential
within this northeastern zone of 2 kilometre length is regarded as very high.
Copper King (Figure 22)
The Copper King prospect area is described by Willis (2000) as a “Great Eastern”
style, epigenetic, syn- to late-tectonic stratabound Fe-Cu-Au occurrence, and consists
of a number of mineral shows along a 1 kilometre ENE trend, from Charlies Lode to
the actual Copper King workings (Figure 22). This trend has been tested with limited
R/C drilling (Burton, 1994), however these drill locations are not included in the
existing digital drill hole data set. The compilation shown in Figure 22 outlines a
strong local aeromagnetic anomaly, of approximately 4000 nTs magnitude, over an
area of 400 x 200 metres, centred approximately 500 metres south of the known Cu-
Au occurrences. Four drill holes are recorded within the data set in this area, collared
to the south of the aeromagnetic anomaly, but oriented to the south-east away from
the magnetic source region (holes RW12,RW13,RW14 and RW15 – Figure 22). This
geophysical target therefore appears to be un-tested, and retains high potential for
magnetite dominant Fe-oxide Cu-Au style mineralisation.
The Sisters (Figure 23)
Cu/Au mineralisation at the Sisters prospect is described as “overprinting premetamorphic
iron formations” (Willis, 2000), with the iron formations exposed in a
north-south oriented fold structure. Total gradient processing of the aeromagnetic
data (Figure 23) shows a strongly anomalous response over the strike length of the
“iron formations” and a local high in the area of complex structure within the unit
immediately to the northeast of the “Sisters” workings. The magnetic response
outlines a total strike length in excess of 2.5 kilometres for the iron formation “host”,
with no apparent drill testing. The width and magnitude of the observed magnetic
response is suggestive of more pervasive magnetite alteration surrounding the iron
formations, and potential for significant mineralisation within this “system” is high.
Sentinel (Figure 24)
The Sentinel prospect area comprises an extensive linear NE/SW trending “ironstone”
subcrop, with a coincident aeromagnetic anomaly of approximately 2500nTs
magnitude. Nine drill holes are included in the NSWDMT database, along the 2-
kilometre strike of the prospect, and the area has been covered with relatively
23
detailed “RAB” drilling (Figure 24). Geochemical data for the latter define a
discontinuous anomaly in copper, in the immediate “footwall” to the SE of the
ironstone position, which does not appear to have been targeted by existing drill
holes. Additional geochemical anomalies are defined to the north and northwest of
the Sentinel area, coincident with lower order magnetic features.
Coultra (Figure 25)
The Coultra prospect is centred on historical workings of near-surface, oxide copper
mineralisation, which have been tested by a limited number of drill-holes (C1-C5,CO1
– Figure 25). Aeromagnetic data indicate that the known prospect lies to the
immediate east of a moderate order “curvi-linear” magnetic horizon, extending from
1 kilometre north of the prospect, to 1.5 kilometres to the south-west, with a local
amplitude high in the former area. In the southern portion of the magnetic trend,
existing “RAB” geochemical anomalies also delineate two additional target areas.
Isolated magnetic anomalies to the north of the Coultra prospect (Figure 25) also
appear to warrant further investigation. Limited “RAB” coverage has delineated
isolated anomalous samples within the vicinity of these discrete magnetic responses,
which have no identifiable source in surface outcrop, or drill hole tests.
Great Eastern (Figure 26)
The Great Eastern mineral occurrence “comprises several parallel lodes within a zone
about 100 m long and 50 m wide” (Burton 1994), within a relatively major NE
trending retrograde schist zone (Figure 26). The aeromagnetic data indicate a more
significant development of magnetite bearing “lode” rocks within this structure, over
a strike length of approximately 1.5 kilometres, with a minor mineral occurrence
recorded near the northeastern limit of the magnetic trend. Drill testing of the extent
of this magnetite development has apparently not been carried out.
Golden King (Figure 27)
Mineralisation at the Golden king prospect, in the southern portion of the Euriowie
Block, is classified by Willis (2000) as a “post-tectonic Cu-Au vein occurrence”, and
“the system has good size (800m long, main vein system 1-10m wide) and excellent
reported spot grades (30-330 gpt Au)”. Details of prospect geology, past production
and exploration included in Burton (2000) indicate that sporadic attempts at
production from Golden King returned small parcels of high grade Cu/Au ore, and
limited exploration drilling returned significant mineralisation (eg Spinifex Exploration
–DDH02, 7.3m at 0.51%Cu – Burton op cit). These details suggest considerable
scope for economic mineralisation within the immediate area of the prospect.
The current assessment (Figure 27) has identified local aeromagnetic anomalies to
the east and north-east of the Golden King occurrence. These are interpreted as
possible reflections of Fe-Oxide-Cu-Au style mineralisation, with the Golden King vein
representing a distal expression of a larger mineralised system in this region. Drill
24
based evaluation of both the Golden King vein occurrence and the apparently
untested aeromagnetic features is clearly warranted.
Fairy Hill (Figure 28)
Copper mineralisation at the Fairy Hill prospect, also in the southern Euriowie Block,
is hosted within quartz-hematite-sulphide veins, hosted within “migmatitic albitites”
(Willis 2000). Although Willis (op cit) classifies the deposit as a probable posttectonic
vein style occurrence, Burton (2000) notes some similarities with the
Diamond Jubilee prospect, and therefore more compatible with the Fe-Oxide-Cu-Au
model. Although small scale mining operations extracted approximately 4000 tonnes
of ore grading approximately 2.3% Cu in the early 1970s (Burton op cit), no drill
testing of the prospect is recorded. The current assessment (Figure 28) indicates that
the prospect lies immediately to the south-west of a major north-west south-east
trending zone of “ironstone” subcrop, and associated magnetic anomalies. Although
these magnetic features are of only moderate amplitude in TMI (300nTs), this is
consistent with the more hematitic nature of the lode development at Fairy Hill.
Significant potential for ore development exists in the areas of aeromagnetic
anomalies.
Diamond Jubilee
MI
(20min delay)