Volcanic-plutonic Connections and Metal Fertility of Highly Evolved Magma Systems

a case study from the Herberton Sn-W-Mo Mineral Field, Queensland, Australia

Yanbo Cheng, Carl Spandler , Zhaoshan Chang, Gavin Clarke

Economic Geology Research Centre (EGRU) and Department of Geoscience, James Cook University

December 2017 Townsville

Geochemistry, crustal thickness, and fertility

High Sr/Y magmas are “fertile”

Loucks (2014)

Thick crust = “fertile” crust

Chiaradia (2015)

Occurrence of topaz, tourmaline, fluorite, Li–Fe mica and albite

Rich in SiO2 and alkali, normally K2O＞Na2O; rich in B, F, Cl, Li, Rb, Nb, Ta, Ga, Cs, U, Th, REE

Poor in Fe2O3, MgO, TiO2, CaO, Ni, Cr, Co, V, Sr, Ba and Eu

High Rb/Sr value. Low δEu value

Biotite, titanite and ilmenite are supposed to be good Sn carriers

(Taylor, 1978; Plimer and Elliott, 1979; Blevin et al., 1996)

Magma fertility of Sn-W associated granite

Ishihara, 1981 Blevin et al., 1996

Models for granite-related metal associates

Sn-W mineralization: ilmenite-series, highly evolved, and reduced granite

Mush model showing the connection of granite-rhyolite (from Bachmann and Bergantz, 2008; Castro, 2013)

Highly evolved rhyolite

Granite(Less evolved)

If no granite, how about volcanic rocks?

RESEARCH AIMS

Identifying fertility indicators inherent in the volcanic rocks associated with granite-related Sn-W polymetallic mineralization

Investigating the volcanic–plutonic connection in a highly evolved felsic magma system

It is a collection of Carboniferous to Permian aged felsic plutonic and volcanic rocks

This is a ~600 km long by 70-100 km wide belt in northeastern Queensland, Australia

The granitoids and volcanic rocks make up about 70% of basement exposure in the Herberton Mineral Field

The HerbertonMineral Field (HMF) hosts extensive Sn, W and Mo mineralization

Granitoids of the C-P age are considered to be the source of these metals (Blevin et al., 1992; Champion and Bultitude, 2012)

Comprehensive dating analyses have been conducted

Previous K-Ar or Rb-Sr dating results cannot present the precise timing sequence

Our new dating results have revealed new details

Part of data cited from Kemp (2011) and Murgolov et al. (2013)

Musc

Sn

W-Mo

The geochemical trends evident for

coeval granitoidsand volcanic rocks are broadly

antipathetic, which is also evident in

their metal endowments.

The early (327-317 Ma) O’Brien Creek supersuites, and the late (<310 Ma) Ootann supersuites.

327-317 Ma (Sn) 310-280 Ma (W-Mo)

Part of granite WR data cited from David Champion database

327-317 Ma (Sn)

310-280 Ma (W-Mo)

Part of granite WR data cited from David Champion’s database

327-317 Ma (Sn)

310-280 Ma (W-Mo)

Sources?

Part of granite WR data cited from David Champion’s database

To conclude:

• The results of zircon age-dating, whole rock geochemistry, zircon Hf isotope and zircon trace element analyses

revealed the genetic connection between the volcano-plutonic, and the occurrence of Sn-W-Mo mineralization.

• A new model is suggested to interpret the volcanic-plutonic connection of the highly evolved magma system. Insights can be gained from the new model as guides in the future

Sn versus W-Mo mineral exploration in potential mineral fields.

Acknowledgement

Gavin Clarke, Andrew White, Darcy Milburn, Vladimir Lisitsin, Colin Abbott, Joel Cullen, Scott Stephens, Greg Clapin, Graham Greaves, Ivan Searston, Mary Searton, Umberto Srhoj, Helen (Mt Moss), Ryan & Sueanne (Ewan), and many other EMP holders and land owners….

Gavin Clarke, Andrew White, Darcy Milburn, Vladimir Lisitsin, Colin Abbott, Joel Cullen, Scott Stephens, Greg Clapin, Graham Greaves, Ivan Searston, Mary Searton, Umberto Srhoj, Helen (Mt Moss), Ryan & Sueanne (Ewan), and many other EMP holders and land owners….