Page 2
The Ilimaussaq Complex
The Ilimaussaq Complex in Southwestern Greenland is an 8x17km intrusion spanning two fjords - Kangerluarsuk fjord and Tunulliarfik fjord. Located near the city of Narsaq, access to certain parts of the complex (Kvanefjeld and Taseq) can be made by foot, while other areas (Kangerluarsuk and Tunulliarfik) requires travel by boat. It is without a doubt the most mineral-rich area in Greenland. Due to the rapid weathering of the friable (brittle and easily crumbled) syenites most of the mountains have no vegetation (no soil). The gray “rockscape” contrasts sharply with the deep blue fjords and gleaming white icebergs.
The 1.2 million year old intrusion consists of three different rock suites. Nepheline-bearing augite syenite first formed a shell along the sides and the roof, next a quartz bearing alkali granite and alkali syenite formed two thin sheets near the top, and finally the biggest part and center of the intrusion was formed by a layered series of under-saturated syenites. These three main rock suites represent three pulses of different kinds of magmas. The rocks close to the roof are the oldest. The most common rocks in these areas are a sodalite-nepheline syenite called naujaite, an arfvedsonite-aegirine bearing nepheline syenite called lujavrite, and a eudialyte-bearing nepheline syenite called kakortokite.
Geological map of the Ilimaussaq Complex – based of a map by Ferguson (1964) and since corrected and improved.
Ilimaussaq hosts the widest variety of minerals in Greenland - more than 200 so far, half of them silicates. The silica content of these minerals is much higher than elsewhere in the world. Numerous pegmatites and hydrothermal veins, streaks and patches are found all over the intrusion, but are most common in the areas of Kangerluarsuk and Kvanefjeld.
There are several key localities within the complex. Some of these areas are small intrusions perhaps only meters wide. Many minerals in these areas are found nowhere else in the world.
Each area within the Ilimaussaq Complex yields distinctly different varieties of the more commonly found minerals. Therefore, a discussion of each variety found in each of the four major areas (Kvanefjeld, Taseq Slopes, Tunulliarfik, and Kangerlussaq) is appropriate.
|
