Method for identifying hydrothermal alteration areas of the earth

• US 4,581,531 A
• Filed: 11/16/1983
• Issued: 04/08/1986
• Est. Priority Date: 11/16/1983
• Status: Expired due to Fees

• Current Assignee: Exxonmobil Oil Corporation (Exxon Mobil Corporation)
• Original Assignee: Mobil Oil Corporation (Exxon Mobil Corporation)
• Inventors: Dion, Eric P.
• Primary Examiner(s): Smith, Alfred E.
• Assistant Examiner(s): HANIG, RICHARD E
• Application Number:
  US06/552,522
• Time in Patent Office: 874 Days
• Field of Search: 250/253
• US Class Current: 250/253
• CPC Class Codes: G01V 5/02 specially adapted for surface logging, e.g. from aircraft

Abstract

An aerial natural gamma radiation survey is conducted over an exploration region. A change in the measured T1-208/K-40 ratio in the exploration region in contrast to a region known not to be hydrothermally altered identifies the exploration region as a hydrothermal alteration. A surface natural gamma radiation survey is conducted over the hydrothermally altered exploration region. A change in the T1-208/K-40 ratio at specific sites within the exploration region indicates the location of alteration products.

Claims

1. A method for identifying hydrothermal alteration areas of the earth comprising the steps of:

(a) conducting a first aerial natural gamma radiation survey over a known non-hydrothermal alteration area,

(b) identifying a first T1-208/K-40 ratio of said known non-hydrothermal alteration area from the measured natural gamma radiation of said first aerial survey,

(c) conducting a second aerial natural gamma radiation survey over an exploration area,

(d) identifying a second T1-208/K-40 ratio over said exploration area from the measured natural gamma radiation of said second aerial survey,

(e) comparing said second T1-208/K-40 ratio from the second survey over said exploration area with said first T1-208/K-40 ratio from the first survey over said known non-hydrothermal alteration area,

(f) identifying said exploration area as a hydrothermal alteration region wherever said second T1-208/K-40 ratio for said exploration area is changed from said first T1-208/K-40 ratio for said known non-hydrothermal alteration area,

(g) conducting a third surface natural gamma radiation survey over said exploration area,

(h) identifying a third T1208/K-40 ratio over said exploration area from the measured natural gamma radiation of said third surface survey,

(i) comparing said third T1-208/K-40 ratio from the third surface survey over said exploration area with said second T1-208/K-40 ratio from the second survey over said exploration area,

(j) identifying an ore deposition site within said exploration area wherever said third T1-208/K-40 ratio for said site is changed in a first direction from said second T1-208/K-40 ratio from the second survey for said exploration area, and

(k) identifying an ore leaching site within said exploration area whenever said third T1208/K-40 ratio for said site is changed in a second direction from said second T1-208/K-40 ratio from the second survey for said exploration area.

2. The method of claim 1 wherein said alteration product site is identified as a site of ore deposition wherever the T1208/K-40 ratio for said site is higher than that of said hydrothermal alteration region and is identified as a site of ore leaching whenever the T1208/K-40 ratio for said site is lower than that of said hydrothermal alteration region.