THE GRAFTON-MACLEAN METALLOGENIC MAP

THE GRAFTON-MACLEAN METALLOGENIC MAP

The NSW Geological Survey has compiled an extensive series of reports which can be used to assist in the search for new mineral deposits or simply to locate existing ones. The Grafton-Maclean Metallogenic Map group of documents may be downloaded from DIGS (here) using this reference number: R00056102. The files take up about 65 MB and consist of many related documents apart from the map itself. These represent the original report broken up into sections.

The map includes the Torrington and Emmaville districts and extends southwards to Glencoe. The western edge of the sheet joins the Inverell map, and it extends to the coast in the east. The Inverell map will be the subject of a later blog.

The map provides a vast amount of information – geology, structure and mineral deposits as well as the underlying topography, roads, watercourses etc. This can make locating something quite difficult and frustrating, so it’s important to become familiar with the meaning of the colours and symbols provided around the margins of the map. Here is an example of what the map contains:

The rest of the documents in the downloaded folder provide information on the background geology and the individual mineral deposits. Take, for example the deposit number 1837, roughly in the centre of the extract. The table of mineral deposits (left of map) describes this as “Back Plain Creek sapphire (Zr)”.

You will find the deposit listed in the file titled “Text_4.3MB_zip_of_4_deposit;_pdf” (the first of four of these). When the file is open, scan through until you come to “GR 1837”, which is the extract below.

More information can be found by looking up the Mineral Occurrence List in the second part of the above file, using the same deposit number (1837).

 You could expand your knowledge of the area by searching other deposit numbers nearby, whether you can find them on the map or not.

Another possibilty is to search the Mindat data base (here) using the mine name. This is what you will find for Back Plain Creek:

“Located approximately 15kms NNW of Glen Innes.
Operated as a small open cut and shallow pits 1971 to 1990s.

Mineral List

Corundum
var: Sapphire

Zircon

2 entries listed. 1 valid mineral.

The above list contains all mineral locality references listed on mindat.org. This does not claim to be a complete list. If you know of more minerals from this site, please register so you can add to our database. This locality information is for reference purposes only. You should never attempt to visit any sites listed in mindat.org without first ensuring that you have the permission of the land and/or mineral rights holders for access and that you are aware of all safety precautions necessary.

References

Metallogenic Study and Mineral Deposit Data Sheets: Grafton-Maclean Metallogenic Map (SH/56-6, SH/56-7), Geological Survey of New South Wales, 2001: HF Henley, RE Brown, JW Brownlow, RG Barnes and WJ Stroud. Published by the Geological Survey of New South Wales.”

Finally, you might like to check out my blog on the Back Plain Creek area here.
Here is a link to a slide show of pictures from the data package: here.

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Limestone Caves of NSW

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Shoalhaven District Geology.

SAPPHIRE DEPOSITS AT BACK PLAIN NEAR GLEN INNES NSW AUSTRALIA

SAPPHIRE DEPOSITS AT BACK PLAIN 

NEAR GLEN INNES NSW AUSTRALIA

Before you read this blog, I recommend that you read my blog entry “The Red Rock Sapphire Deposit” (here). It deals with gemstone deposits in the same general area as I am covering here.

A good starting point in understanding the sapphire deposits at Back Plain (not Back Plains, by the way) is the map at the back of “Records of the Geological Survey of NSW, 14 Part 1 (1971)”, DIGS reference R00050764. If you haven’t downloaded this document yet, you should do so. The map shows only that Wellingrove Creek (left) and the Wellingrove Fossicking Area (on the letters Pgw)) are sources of sapphire. Both are marked in green. The reddish area near the centre of the map (marked Ts) is apparently an area of Tertiary sediments associated with the basalt.

The next map is extracted from the “Quarterly Notes of the Geological Survey of NSW 103, April 1997” (page 13). The DIGS Reference is R00040935. My extract from the map shows the following sapphire bearing areas of interest to us here: Back Plain Creek in the centre, with a tributary to the west of it and the creek flowing down from the Wellingrove Fossicking Area into Wellingrove Creek.

The third map has been extracted from the Grafton-Maclean Metallogenic Map (DIGS reference R00056102).  To help you align it with the other maps, the Wellingrove Fossicking Area is approximately in the centre, shown as 1835. 1836 is identified in the accompanying notes as Pablos Mine and 1837 as the Back Plain Creek deposit, elsewhere called the Truro Mine. We can distinguish two types of sapphire deposits on this map. Firstly, the close cross hatched areas (Wellingrove Creek, the stream draining the Wellingrove Fossicking Area and Back Plain Creek, not named on the map) which are regular alluvial deposits, and secondly, the broad hatched areas (one around Pablos Mine and the other near the top of the map adjoining an area of Tertiary basalt labelled Tb. These are locations where spinel, sapphire and zircon are to be found in the soil, possibly derived from tuffaceous sediments intercalated with the earliest basalt flows. The Red Rock deposit (see above) is like that and the Wellingrove Fossicking Area deposit could be a contemporaneous alluvial concentration derived from such sediments.

There isn’t much information available about these deposits, except for one (Truro) and even that isn’t clear

Ruwenzorie Road turnoff (on right)

cut. Starting from the north, we have a site which has at least the potential to produce some gems. This is the area shown in broad hatching along Ruwenzorie Road, which branches off to the right (north) from the Strathbogie Road. This is before you come to the back road from Wellingrove (Polhill Road). This road crosses Back Plain Creek after 2.5km at a place where there are some rocky outcrops. I only went there once and found some colour easily enough (without getting wet or covered with leaches). It’s certainly worth a try, if it’s still accessible. Then there is the possibility of gems in the soil on the road side. You could try dry sieving and then take the concentrate to Back Plain Creek to see what’s in it.

Pablos Mine location (from Mindat)

Pablos Mine appears to be on a tributary of Back Plain Creek south of the Wellingrove Fossicking Area. All I can find from the metallogenic notes is that it was worked by Pablos Mining (1970-73) by shallow pits or scrapings. It’s described as a “modern placer (fluvial)”.

The problem starts with the Back Plain Mine. The metallogenic notes contain quite a bit of information – worked by SC Burgis (1971), Pablos Mining (1970-73) and Nunan Pty Ltd circa 1990. “This deposit comprises high grade sapphires and abundant zircon. The headwaters of the creek drain from a red soil 

Back Plain Mine location (from Mindat)

plateau where the deposits were quite rich. The abundant zircon contrasts strongly with Reddestone Creek immediately to the east where zircon is relatively minor. Alluvial placer”. The difficulty arises when you look at the Mindat information for the Back Plain Mine (here). It is clearly identified as the Back Plain Mine (Truro). This would be fine, except that we have a lot of information about the Truro Mine from the NSW Department of Minerals and Energy publication Minfo 27 (1990) which deals with the opening of the mine belonging to TJ and PV Nunan Pty Ltd. You can download the document from DIGS, reference number R00040997. The included map shows that the mine was on the right hand 

Truro Mine location (from Minfo 27)

side of the Strathbogie Road, past the Wellingrove turnoff. This is several kilometres from the indicated site of the Back Plain Mine. Perhaps the wash from the Back Plain Mine was trucked to Truro Mine for treatment. That there was a mine near Truro homestead is beyond doubt. You could see the activity from the Strathbogie Road, but when it closed down I can’t say.

My thanks go to the NSW Geological Survey, Mindat and Google Maps for information and illustrations used in this blog. Without these it would be difficult to make sense of this interesting area.

To explore the satellite images better, I suggest a Google search for "Mindat Pablos Mine NSW" and "Mindat Back Plain Mine NSW". You can then follow the "Maps" link, "Maps Pages" and select "satellite"to get to the images shown above.

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All New England and other Geology blogs and videos

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Limestone Caves of NSW

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Shoalhaven District Geology.

WEBB’S CONSOLS AND RELATED MINES, STRATHBOGIE NEAR EMMAVILLE

WEBB’S CONSOLS AND RELATED MINES, STRATHBOGIE NEAR EMMAVILLE

Mine cluster south of Strathbogie

A group of sulfide ore bodies has been mined or prospected about 15 km south west of Emmaville. I have not visited any of these places; I assume that they are all on private property and under mining leases or covered by exploration licences. If any reader can provide information about accessing these locations, please advise us in the comments area at the end of this blog.

Here is a list of prospects I have come up with – all appear to be in the same general area. Webb’s Consols, Wellingrove Silver Mine, Mt Galena, Matthews Mine, Seaton’s Mine, Munsies Prospect, Lucky Lucy, Castlereagh, Barton’s Quarry and Tangoa. In every case, there appears to be an association with the Webb’s Consols Leucogranite, most often by way of quartz rich veins and pipe-like structures. Some of the ore bodies have actually formed in the Permian volcanic rocks which the leucogranite has intruded. The map from which the extract opposite is taken is included in the downloadable report "Inverell Metallogenic Map 1:250 000" (DIGS reference R00050906).

Minerals recorded include galena, sphalerite, arsenopyrite, chalcopyrite and pyrite. Silver is almost always present in the ore in significant percentages and its presence was the main reason for mining.

The Webb’s Consols mine has been the most productive to date, though more than one hundred years have passed since profitable mining took place there. At least 19 000 tonnes of ore were extracted (yielding 100 000 ounces of silver), most of this before 1901.

The earliest reference I have found is in the Annual Report of the Department of Mines for 1875, page 111. It reads as follows. “About 14 or 15 miles westward of Glen Innes, in the neighbourhood of Wellingrove, a lode was found which showed on the surface indications of copper, and when sunk upon to a depth of 14 feet a vein of pure galena was met with and worked, but carriage of the ore to the coast being too expensive to allow a profitable return, operations are at present in abeyance.”  This is well before the coming of the railway to Glen Innes, so the ore would have had to be sent to Grafton, a long and expensive process. No doubt the reference is to the Wellingrove Silver Mine.

Share Certificate from an early company

A problem common to all these mines was the difficulty experienced in separating the lead ore (galena) from the zinc (sphalerite). This was the same problem experienced at Broken Hill, where for many years the zinc concentrate was dumped, despite its containing valuable lead and silver. The flotation process, now normal practice in the industry, was unknown when these small mines were active, though to what extent it would have helped is unclear, considering the relatively small quantities of ore available.

Some of these old mines, especially Webb’s Consols, are currently under investigation by Silver Mines Ltd, though the present (November 2014) price of silver is not exactly encouraging.

There are numerous references from which you may gather information. An interesting newspaper report from 1891 may be found here. There are many references in old Geological Survey reports. Go to DIGS (first find it!) and put in “Webb’s Consols” for location and you will find lots of information. One of the best of these is called “Webb's Consols - Wellingrove and Mount Galena Mines. Extracts of Annual Reports from 1875 to 1954”. The DIGS reference number is R00025719.

Another well-presented report is to be found in EF Pittman’s “The Mineral Resources of New South Wales”, 1901.  The DIGS reference number is R0005137. The section dealing with this group of mines begins on page 112. The photograph of the mine is also found in this book.

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Shoalhaven District Geology.

From the "Horse and Buggy" days, minus the horse

THE RED ROCK SAPPHIRE DEPOSIT NEAR WELLINGROVE, NEW ENGLAND DISTRICT NSW AUSTRALIA

THE RED ROCK SAPPHIRE DEPOSIT NEAR WELLINGROVE, NEW ENGLAND DISTRICT NSW AUSTRALIA

This is an unofficial name for a place that lies on a stock route north west of Glen Innes. It is accessed by a gate on the right hand side of the Bonshaw road (also known as Strathbogie and Wellingrove road) about 15km from Glen Innes. It is a km or 2 after the Reddestone Creek bridge, just before the road begins to descend to Back Plain Creek. There may or may not be a sign (reading Red Rock West) on the gate. Once through the gate, the location may be found by taking left hand branch tracks back towards the road. Total distance from the gate would be around 500 metres.

The gate, courtesy of Google Earth

Access is difficult when there is enough water to use for sieving (this is boggy country) and when access is easy the gully will probably be dry. This spot is at the head of a gully draining down to Back Plain Creek at the bottom of the hill. The country rock is basalt, often deeply weathered to a reddish soil loaded with ironstone nodules.

In the soil, scattered among the ironstone nodules, (which are the result of the weathering of the basalt) are small amounts of spinel, sapphire and zircon. How did they get here? This is not a normal alluvial deposit, of the sort we are familiar with in Yarrow Creek. It has some resemblance to 

Wellingrove Fossicking Area - "wash" at the bottom

the so-called “wash” at the Wellingrove Fossicking Area, which is 2-3 km away, as the crow flies. There, the overlying basalt ends at the point where the entry track leaves the sealed road. The underlying rock in the reserve is granite, which intrudes the Emmaville Volcanics on the northern edge. The “wash” may be thought of as a reworked volcanic ash layer, erupted before or along with the neighbouring basalt flow. There has been some concentration of the dense minerals, possibly by rain water at the time of the eruption, but there are few of the normal alluvial indicators such as pebbles of quartz which might have been expected to have been derived from the granite.

At Red Rock there may have been ash layers associated with the basalt, either below or between flows, which could be the source of the gems, or they may be derived from the basalt itself where they formed xenocrysts in the lava. See my blog on Dog’s Tooth Sapphires at Pretty Valley (here) for links to articles which throw some light on this subject.

Extract from the Grafton Metallogenic Map

The extract from the Grafton Metallogenic Map show the geology of the immediate area. The numbers refer to mineral localities. 1835 is the Wellingrove Fossicking Area, 1836 Pablo’s Sapphire Mine, 1837 an alluvial sapphire mine on Back Plain Creek, 1839 the Wellingrove limonite deposit and 1840 Hamel’s Gully, an alluvial deposit, probably on a former course of Reddestone Creek. Tb indicates “Tertiary basalt"). Note also the cross hatching, representing “alluvial” sapphire deposits. I’m only guessing, because I haven’t explored the area, that the prospect at Pablo’s Mine and the areas near it showing cross hatching (south of the Wellingrove Fossicking Area) are similar to Red Rock and that gems will be found near the edge of the basalt in other places in the area. None are likely to be productive enough to mine.

Minerama ran a field trip to Red Rock in 2003. Most people found a few colours but the lack of water was the real issue. I believe some cutters were found, however. Our fossicking group went there several times, with the same result – a few sapphires and zircons and a lot of mud and ironstone, enough to make it interesting even if we found no cutters.

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All New England and other Geology blogs and videos

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Limestone Caves of NSW

https://www.blogger.com/blog/post/edit/1147003616874115974/2430103125095714141

Song Studies. Bible studies based on hymns and songs

https://www.blogger.com/blog/posts/1515863000684737715

Shoalhaven District Geology.