All posts by John C. Menzies

Bananas – Build absolutely Nothing Anywhere Near Anybody

[Then].. “there are activists to consider, too—activists who might like wind and solar, but seem to like nature as it is more. And who have proved they can stop new mining developments. What’s more, activism of this sort is evolving, and now commentators have coined a new term to replace the widespread not-in-my-back-yard sentiment among both activists and regular taxpayers. Instead of NIMBY, they are now talking about BANANA, or Build Absolutely Nothing Anywhere Near Anybody”.

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The Secret Life of the Geology Hammer – A Quiz

My G-pick and I are the tools of discovery. We are the masters of our universe. We are the saviors of my life. So be it, until discovery and beyond we are inseparable!

1.  Before using your geology hammer what should you do?

  1. Put on your safety glasses
  2. Put on your safety boots
  3. Read the instructions
  4. Put on your pants

2. What should you not use your geology hammer for?

  1. To drive nails
  2. To crack open a beer
  3. To break rocks
  4. To fix a broken window

3. What is the most important safety rule when using your geology hammer?

  1. Wear safety glasses
  2. Don’t use it underwater (You know who you are!)
  3. Don’t use it as a weapon
  4. All of the above

4. When using your geology hammer, what should you do if it gets stuck in a rock?

  1. Pull hard and hope it comes out
  2. Find another rock to hit it with
  3. Put it in the freezer to loosen it
  4. Call a professional

5. What should you do if you drop your geology hammer?

  1. Pick it up and keep going
  2. Leave it where it is and never use it again
  3. Find a replacement
  4. Call in a professional

6. If you hit your thumb when using your geology hammer what should you do?

  1. Take in a deep breath and say absolutely nothing at all unless you are alone
  2. Scream then cry
  3. Hit the Emergency Action Button on your GPS transponder and wait for evacuation
  4. Its beer time!

7. How often should you check for wear and tear on your geology hammer?

  1. Once a day
  2. Once a week
  3. Once a month
  4. Who Cares

8. What should you do if your geology hammer starts to rust?

  1. Replace it
  2. Sand it down and have it gold plated for longevity
  3. Put it in the dishwasher
  4. A geology hammer without rust is embarassing

9. What should you use to sharpen the tip of your geology hammer?

  1. A file
  2. Your sense of humour
  3. A rock
  4. An oxy-torch

10. What should you do if you can’t find your geology hammer?

  1. Pray to the God
  2. Check the refrigerator
  3. Ask your 3 YO
  4. Get out the magnetometer

The “Answers”

1. C

2. A

3. D

4. D

5. A

6. D

7. D

8. B

9. A

10. C

Samples from the 20km2 Hills Intrusive Centre

Samples taken on a regular 500m by 250 m grid at the 20km2 Hills Intrusive Centre in the last three days. A High-Sulphidation alteration ecosystem. It is one of the 6 or so intrusive canters within the ~200km2 Khvav intrusive cluster all of which shows strong to advanced argillic alteration and vuggy silica.

This large alteration system is coincident with a large gravity anomaly which lies with a large 3,000 km2 gravity low which we interpret to be a large batholith in the mid crust. These gravity features are evident in a 48,000km2 airborne gravity data set and less evident in the 2.5 million km2 satellite gravity data collation we have acquired and reprocessed.

SWIR has detected alunite, pyrophyllite, diaspore, white mica, dickite and minor topaz in rocks from this area, indicative of hydrothermal fluids with temperature locally >300 °C. Alunite in this area is sodic rich.

The Jungle in the Summer

It hardly gets more challenging than SE Asian jungles at the height of summer. What’s important:

  • Water and electrolytes are very important and at the height of summer needs to have added electrolytes
  • Take more water than you need and drink early
  • We always keep ice and abundant water in the vehicle – ready to be dropped into a back-pack
  • Everyone is responsible for their own water
  • Coconuts are a fantastic source of potassium (1,200 mg /coconut!)
  • Sports drinks are NOT electrolyte replacements as they contain a poor electrolyte balance and way too much glucose.
  • Hats, long sleeve shirts, trousers, boots (and gaiters) are essential.
  • Gloves are great, they protect from the sun and against the inevitable ants and vines and trees with spikes and spines.
  • Do not push yourself, take it easy as it is all too easy to have little capacity left for the unexpected (bushfire, snake bite, injury etc.)
  • Wildlife is for observing (see the caption below)
Only another 50 metres to the target outcrop! Cambodian jungle. Slow going but its the guy are the front that does all the hard yards! There was cobra seen in this area earlier in the year. When striking it stood >1.5 metres high. The gent who was holding its’ tail was dead within 20 minutes!

High Sulphidation, Vuggy Silica – Textural Atlas

Updated: Spectacular new samples (courtesy Doug Kirwin) from Lepanto in Philippines, Seruyung and Bacan, Indonesia and La Yaqui in the Mulatos District of Mexico. The updates are identified by NEW!

Lepanto-Silica Enargite Diatreme Breccia Credit: Doug Kirwin

Vuggy silica textures are formed by the dissolution of phenocrysts and entire clasts by hot and strongly acidic fluids that are generated during the cooling and crystallization of near surface intrusive bodies. Vuggy silica is often mineralized but is also a strong indicator of a very active hydrothermal system and epithermal Cu-Au-Ag and porphyry Cu-Au deposits at depth.

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A Miarolitic Cavity in Section

Siem Reap has 98km of new roads  and new sidewalks much of which has been paved with interesting felsic intrusive rocks from quarries in Shandong Province in China.  The composition ranges from granodiorite to tonalite and is locally granophyric and pegmatitic.  The intrusive consists dominantly of plagioclase, quartz, pyroxene and hornblende. Ovoid structures known as Miarolitic Cavities are evident in the sidewalks to the observant and indicates that the parental magma was hydrous.

Here we have attempted to reassemble a miarolitic cavity over ~1 metre of its length. Just bear in mind that this is dimension stone and its now the pavement. There are many places where there are a large number of slabs that are clearly related. Reassembling them is quite instructive and reveals much about the evolution of these structures.

We have previously published libraries of miarolitic cavities.

Unravelling the Mystery of Graphite-Rich Magmatic-Hydrothermal Mineral Systems: MT Imaging Results from Australia and the US

MT Section through Olympic Dam. Note the very large sub-horizontal conductor in the mid crust with near vertical conductors beneath known deposits. After Selway (2015)

This post is a summary and review of Murphy, B., Hjuizenga, J. and Bedrosian, P., 2022. Graphite as an electrically conductive indicator of ancient crustal-scale fluid flow within mineral systems. Earth and Planetary Science Letters.


  • Magnetotelluric (MT) imaging has shown an apparent connection between crustal-scale electrical conductivity anomalies and major magmatic-hydrothermal iron oxide-apatite/iron oxide-copper-gold (IOA-IOCG) deposits in Australia and the United States
  • The exact cause of these anomalies has been unclear
  • Murphy et al (2022), interpret the conductors to be the result of graphite precipitation from CO2-rich magmatic fluids during cooling
  • These fluids exsolved from mafic magmas at mid- to lower-crustal depths
  • Saline magmatic fluids that could drive mineralization were likely derived from more evolved intrusions at shallower crustal levels
  • The conductivity anomalies mark zones that once were the deep roots of ancient magmatic-hydrothermal mineral systems
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Is this an Analogue for the Massive Mt Isa Cu-Pb-Ag Deposit

The Mt Isa bedrock copper anomaly (>65ppm) plotted over the 20km long magnetotelluric anomaly at 1,000 metres (Simpson, J. and Brown, D., 2023). Note the coincident large SQUITEM-EM Anomalies and hydrogeochemistry copper anomalies

The purpose of this post is to delineate the key characteristics of the Mt Isa deposit from an explorer’s pragmatic perspective and then discuss a possible analogue in the Eastern Succession, north of Cloncurry. Beside the fascinating tectonic, geological and structural history of the Mt Isa region,  it represents the largest repository of Pb-Zn metal.

Continue reading Is this an Analogue for the Massive Mt Isa Cu-Pb-Ag Deposit