IGA Diamond Jubilee Special Lecture- “The Leinster Granite: Sixty Years of Wondering” by Dr. Pádhraig Kennan

IGA Diamond Jubilee Special Lecture: “The Leinster Granite: Sixty Years of Wondering”

By Dr. Pádhraig Kennan

Abstract:

There was a time when batholiths were batholiths – large bodies of coarse-grained granite that had slowly crystallised deep in the earth’s crust from liquid rock (magma) intruded from even greater depths. These bodies were commonly seen as having outward-dipping contacts, and question marks as lower limits. However, even before the IGA era, 2 kg hammers, petrological microscopes and countless pairs of boots had established that most of these batholiths were aggregates of smaller, essentially coeval, plutons. Later development of larger hammers (e.g., spectrometers of various hues, ion probes,
electron microscopes, and the like) served to define more complex patterns of aggregation of components not always coeval. But oftentimes, the boots could not see the joins and still cannot – just one of many enigmas. The questions that
are still questions and matters of debate wherever granites occur are still many.

Where exactly did the liquid magmas originate, and how far did they journey upwards? How did the magmas intrude – as inverted tear drops, or sheets, or otherwise? What exactly melted in the first place? Did magmas mingle and mix,
or segregate and evolve? When did intrusion occur and over what time span? Why so many different granite varieties – all textural interplays of quartz, feldspar and mica that recur worldwide? This talk will attempt to address some,
and only some (ignorance), of these questions. In doing so, the role of the enclosing envelope will be given some emphasis and it will be a major surprise to the speaker if Sr isotopes and coticule are not mentioned. A model incorporating some of the features of the Leinster Granite, and of one or two others, that might have wide application is the aim.

Acknowledgement: In 1959 and throughout the 1960s (and beyond), the IGA enabled a young student and university teacher to experience the rocks of many parts of Ireland on excursions led by experts from all the universities and
Geological Surveys of Ireland, and from some abroad. These excursions were augmented by countless lectures. He met many giants. Little of that would have happened so soon without the IGA. The experience was priceless. Thank you.

When and where (PLEASE NOTE VENUE!!!):

The School of Earth Sciences, University College Dublin, on Wednesday, 20 November 2019, between 20:00 and 21:00. Coffee and biscuits will be available from 19:00. All are welcome!

Location: https://www.ucd.ie/earthsciences/contact/

Image Credit: www.countywicklowheritage.org