| The volcanic strata consist of sheet-like flows of andesite, dacite, basalts, and trachybasalts that are interbedded with agglomerates and tuffs. |
|
| They are marked by eruptions of cooler, stickier lavas such as andesite, dacite and rhyolite. |
|
| The canyon is carved out of dacite, and there are some large trees with yellow and green leaves. |
|
| Here colorless to yellow crusts of mimetite coat open spaces and coarse fragments in brecciated dacite. |
|
| These are called tension gashes and formed as the dacite split open allowing the quartz fluid to fill in the cracks. |
|
| The lava dome is made of dacite, a fine-grained volcanic rock that contains a sprinkling of larger, visible crystals, like chopped fruit in a cake. |
|
| Unchallengeable examples of what are assumed to have been beta quartz appear to be limited to occurrences in silicic volcanic rocks, such as rhyolite, liparite, and dacite. |
|
| Four common volcanic rock types are basalt, andesite, dacite, and rhyolite. |
|
| South of Tricouni Peak are andesite and dacite lava flows that form two non-overlapping sequences. |
|
| Look around the trail signs and benches and identify the pale tan coloured dacite. |
|
| These are overlain by flows of rhyolite, dacite, and andesite totalling about 900 m in thickness. |
|
| It comprises a series of ridges and vertical towers of dacite that cut through the centres of the older Mount Fee units. |
|
| A saddle separates this older dacite flow sequence from the main ridge of Mount Fee, which is the youngest exposed part of the volcano. |
|
| Two mineralized units were identified: a rhyolite unit primarily mineralized in zinc, followed by a dacite unit primarily mineralized in copper. |
|
| These are overlain by units from the Vulcan's Thumb stage which consist of lava flows, blocky agglutinated dacite breccia, and bedded and unbedded fine tephra. |
|
| The youngest volcanic rocks at Mount Cayley are those of the Shovelnose stage, and consist of a thick sequence of dacite flows extending down the Shovelnose and Turbid Creek valleys almost as far as the Squamish River. |
|
| A 5 cm wide quartz vein cuts through the surrounding grey dacite. |
|
| The magma is responsible of the formation of skarns with garnet, pyroxene, amphibole and magnetite in the ore bodies, and of the presence of veins of dacite or dolerite within the host rocks. |
|
| The dominant rock constituting the composite volcanoes is andesite, but in some younger island arcs basalt tends to be more common, and in older volcanic areas dacite or rhyolite becomes prominent. |
|
| During the explosive process, the Venus breccia formed when the ascending dacite magma reacted with groundwater to produce a phreatic eruption. |
|
|
|
| Hydrothermal circulation and fracturing soon followed, altering the dacite and depositing ore minerals and gangue in the veins. |
|
| The oldest volcanic rocks at Mount Cayley represent the Mount Cayley stage of eruption, and consist of a complex pile of porphyritic dacite flows, tephra, and breccia. |
|
| The gold mineralization is hosted in metasomatically altered dacite and andesite and is interpreted to be controlled by the northeast trending Aksuyski fault zone. |
|
| Pillow lavas are commonly of basaltic composition, although pillows formed of komatiite, picrite, boninite, basaltic andesite, andesite, dacite or even rhyolite are known. |
|
| The ore deposits reside in veins present in the dacite volcanic dome. |
|
| A microprobe analysis of sample material taken at the time concluded that Dacite was not the source for the gold in this region. |
|
| The summit of the fell is composed of one such lava flow, but only a few metres down slope the underlying lava flow is a portion of the Great Whinscale Dacite. |
|
