Introduction

Ever since the publication of the memoir by Wager and Deer (1939), the Skaergaard intrusion has held a central position in igneous petrology. It remains the most researched igneous rock body in the world for reasons largely anticipated by Wager and Deer themselves (1959, p. 5): "Once the difficulties of reaching this part of Greenland have been overcome, the Skaergaard intrusion, among the known layered intrusions of the world, is probably the easiest to study because of its relatively small size and because the Tertiary rocks composing it are fresh and magnificently exposed in a region of high relief". The present situation has been made clear by Wilson (1993) in a recent review of magmatic differentiation. She  made clear the overwhelming importance of  Skaergaard studies to the development of ideas and understanding of the differentiation of basic magmas and writes for example: "The Skaergaard intrusion, east Greenland, has, for the past 50 years, been cited as the classic example of in-situ differentiation of basic magma" and goes on to show that the evidence, which continues to accumulate, is by no means unequivocal and we are still a long way from achieving a consensus in exactly how to interpret this evidence. Implicit in this is the continued importance of work on Skaergaard, where a vast corpus of information already exists.

In the course of time interest in layered intrusions has greatly increased, partly because they are now recognized as being much more common than was realized in the 1930s. Also, with the continuing debate on magmatic processes, especially at mid-ocean ridges, and with the introduction of fluid dynamic concepts in recent years, layered intrusions have acquired new importance in providing the best evidence of pre-eruptive processes in magma chambers, complementary to studies of volcanic sequences. Indeed, unless greatly improved methods are found to study processes at depth in currently active volcanic terrains, layered intrusions are likely to remain central to studies of igneous processes. The movements of magma from the Earth's interior and its evolution in near-surface environments is one of the most important steps in the geochemical evolution of our planet, also one of the most poorly understood.

Although in recent years seismic work on mid-ocean ridges has suggested that large magma chambers may not exist in this setting (e.g. Detrick, 1991) the presence of major intrusive bodies such as Skaergaard still provide evidence for differentiation mechanisms in the crust.

For these reasons alone, there is no sign that interest in Skaergaard is declining. Indeed, in recent years, the converse is true. In the late 1980s the discovery of economically interesting concentrations of precious metals in the Skaergaard intrusion (Brooks, 1990) has led to greater interest and major improvements in logistics in the Skaergaard area and shown that significant  new discoveries can still be made in this, the world's most studied intrusion.

Earlier, the major obstacle to studies of Skaergaard was access. This has been greatly improved in recent years by the establishment of a STOL (= Short Take-Off and Landing) airstrip at Sødalen, Miki Fjord*, carried out prior to the recent commercial activities and probably a significant factor in attracting mineral  exploration interests. Although this airstrip is about 15 km by line of flight from the Skaergaard peninsula over rugged mountains, glaciers and ice-filled sea, it is an enormous improvement. Previously special ice-strengthened ships were necessary and expeditions had the attendant uncertainties and unforeseen expenses related to weather and bureaucracy. Under these conditions there was actually no guarantee of even arriving. In 1973, for example, four geologists spent more than three weeks on a ship and, in the end, only one of them was able to spend a few hours in the field in Kangerlussuaq. In 1989, this author (Kent Brooks) left Copenhagen at midday and was at Skaergaard in the evening.

This website presents a collection of photos and diagrams of some of the spectacular structures that are exposed in the Skaergaard intrusion. In addition, a collection of abstracts documents both the central role of the Skaergaard intrusion in research on igneous processes and the increasing interest in the intrusion in recent years. The abstracts were assembled both to collect the results of existing Skaergaard research from a wide range of literature sources and to form a useful starting point for new workers on Skaergaard and a reference for existing workers, many of whom seem poorly informed on the wealth of information gathered by their predecessors. Over fifty years of research is represented here and it is important not to loose sight of the history of ideas, which must form a foundation for new lines of thought. To form a background to the collection, largely for newcomers to the area, the website also includes introductions to the human and natural history of the area.