Bull. Minéral. (1984), 107, 327-340

Compositions of fluid inclusions in granites and quartz syenites from the gardar continental rift province

(South Greenland) (i)

Composition des inclusions fluides dans quelques granites et syénites quartziques de la province continentale de Gardar (Sud-Groenland) .

Introduction

Previous studies on fluid inclusions in igneous rocks from the Precambrian Gardar continental rift province in south Greenland are essentially those of Petersilie and Sorensen (1970), Sobolev et al. (1970), Konnerup-Madsen et al. (1979), and Konnerup-Madsen and Rose-Hansen (1982), all on fluid inclusions in minerals from the Si-undersaturated agpaitic Ilimaussaq intrusion. Compared to the largely C02-and H20-domi¬ nated fluids generally found in igneous rocks (e.g. Roedder, 1972), the fluid inclusions in the agpaitic Gardar rock types contain large amounts of hydrocarbons, especially CH4.

The aim of this paper is to extend these pre¬ vious studies to fluid inclusions in igneous matrix quartz from a series of granitic and quartz

(1 ) Contribution to the Mineralogy of Ilfmaussaq no 7 1 .

syenitic intrusions from the Gardar province. Major emphasis has been given to a general description of the types of fluids trapped and to their chemical compositions as inferred prima¬ rily from microthermometry.

The Gardar rift province : geological setting

The Precambrian Gardar rift province in south Greenland is largely situated within a zone of Ketilidian granitic basement except in its north¬ western part where older Archean gneisses form the basement (Emeleus and Upton, 1976). The oldest rocks of Gardar age are a sequence of interbedded continental sandstones, alkaline to subalkaline lavas and pyroclastic rocks, and constituting the Eriksfjord Formation (Poulsen, 1964). Outcrops of this sequence is now res-