The basal gabbro subdivision and associated magmatic nickel-copper sulphide mineralization of the Pants Lake intrusion, Labrador, Canada : a combined geological, petrological, geochemical, and metallogenic study

• Main Author: Smith, Roderick L.
• Format: Thesis
• Language: English
• Published: Memorial University of Newfoundland 2006
• Subjects: Canada; Nain
• Online Access: https://research.library.mun.ca/6686/; https://research.library.mun.ca/6686/1/RoderickLSmith.pdf; https://research.library.mun.ca/6686/3/RoderickLSmith.pdf

The Pants Lake Intrusion (PLI), located in northern Labrador, represents an early phase of the 1.34 to 1.29 billion-year Nain Plutonic Suite that is located amongst the 1.45 to 1.46 billion-year old Harp Lake Intrusive Suite, the 1.85 billion-year Nain-Churchill Province suture zone, and the 2.78 to 1.74 billion-year Churchill Province which actually hosts the intrusion. The early evolution of the Pants Lake Intrusion is similar to that described for the Voisey's Bay Intrusion. -- The PLI is composed of two separate intrusions termed the North and South Pants Lake Intrusion. A U/Pb zircon and baddeleyite igneous crystallization age of 1322.2 ± 2 million years was derived from the north intrusion, whereas a U/Pb baddeleyite igneous crystallization age of 1337 +4/-2 million years was derived from the south intrusion. Apart from geographical proximity, and common origin and host, the north and south intrusions do not share many characteristics; in fact, the north intrusion intrudes the south intrusion. -- The South Pants Lake Intrusion, located in the southern part of the study area, is a weakly layered mafic body that intrudes the Harp Lake Intrusive Suite. The south intrusion is characterized by olivine cumulate-textured peridotite and troctolite compositions, high MgO abundances (up to 21 wt %), elevated light rare earth elements, positive Eu anomalies (Eu/Eu* = 1.19), and Ce/Yb ratios that resembles the range reported for the troctolites of the Voisey's Bay Intrusion (Ce/Yb = 26-31). -- Disseminated, blotchy, net, and les abundant massive textured sulphides are widespread in the south intrusion and are dominated by pyrrhotite with lesser chalcopyrite and pentlandite. Nickel tenors of the sulphide minerals are slightly elevated compared to those in the north intrusion due to the greater percentage of nickel available to partition into the localized sulphide liquid (as indicated by the elevated modal olivine). Sulphur isotopic ratios of sulphide mineral separates from the south intrusion range from -5.25 to -1.99 ...