In high-temperature environments (i.e. hydrothermal systems or lower crustal settings), temperature logs can be recorded using the wireline slim-hole Hi-T Temperature Tool (HTT) developed at LDEO. The HTT can be used in temperature conditions of up to 275°C although the Teflon insulation in the wireline will begin to degrade beyond 232°C. Generally, this could present a problem after extended use in temperature conditions exceeding 235°C however, the HTT measuring system is only frequency dependant. Therefore, the tool can still transmit reliable measurements even after the cable has been considerably degraded.

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