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A survey of anomalous K-Ar "dates" indicates they are common, particularly in basalts, xenoliths and xenocrysts such as diamonds that are regarded as coming from the upper mantle.

In fact, it is now well established that there are large quantities of excess K and not yet outgassed.

A metamorphic rock characterized by a very fine alignment of its minerals, which allows it to be easily split into flakes or slabs.

Because schist often contains abundant mica, it usually has a shiny, gray appearance.

And there are mantle-crust domains between, and within, which argon circulates during global tectonic processes, magma genesis and mixing of crustal materials.

This has significant implications for the validity of K-Ar and Mt Ngauruhoe is an andesite stratovolcano of 2,291 m elevation, rising above the Tongariro volcanic massif within the Tongariro Volcanic Center of the Taupo Volcanic Zone, North Island, New Zealand (Figure 1) [38, 97].

The zone extends approximately 300 km north-northeast across the North Island from Ohakune to White Island (Figure 1) and is up to 50 km wide in the central part, narrowing northwards and southwards.

This volcano-tectonic depression (Taupo-Rotorua depression [42]) comprises four rhyolitic centers (Rotorua, Okataina, Maroa and Taupo), plus the calc-alkaline Tongariro Volcanic Center, part of a young (The Tongariro Volcanic Center extends for 65 km south-southwest from Lake Taupo at the southern end of the Taupo Volcanic Zone (Figure 1) and consists of four large predominantly andesite volcanoes - Kakaramea, Pihanga, Tongariro and Ruapehu (Figure 2); two smaller eroded centers at Maungakatote and Hauhungatahi; a satellite cone and associated flows at Pukeonake and four craters at Ohakune (Figure 2) [15, 46]. The location of Mt Ngauruhoe in the Taupo Volcanic Zone (TVZ), New Zealand, showing the main structural features.

Potassium-argon "dating" of five of these flows and deposits yielded K-Ar model "ages" from Ar* content.The shaded area is the andesite arc, and the inset shows the major components of the boundary between the Australian and Pacific Plates in the New Zealand region (arrows indicate relative motions).