Abstract: Deep gcomagnetic field is picked from ΔT_A anomalies on actual data with extended abnormal classification operators，and a quantitative estimation and comprehensive analysis of it are carried out in geologic theory of rift. It is concluded that deep gcomagnetic field in Tarim area is the evidence of Taklamakan Pre-Sinian paleorift, which is the basis for fotmation and evolution of Paleozoic platfarm and part of Mesozoic oil-farming depression as well as for controlling tectonic evolution in Tarim basin. Its discovery provides a guideline towards large-scale oil and gas fields in Tarim basin.

Key words: Tarim basin, Taklamakan paieorift, Deep geomagnetic field, Abnormal classification operator, Frequency spectrum