干旱区生态环境知识资源中心

One of the most productive and well-sampled dense collection areas for meteorites on Earth is the Franconia strewn field in Mohave County, Arizona, which since 2002 has yielded hundreds of meteorites in an ellipsoidal area approximately 5x16km across. Based on petrographic, mineral-chemical, and terrestrial age data, we conclude that among 14 meteorites examined, there are at least 6 and possibly 8 distinct meteorites represented, which fell over a period of approximately 020kyr ago. These include equilibrated H-chondrites such as Franconia (H5) and Buck Mountains (BM) 001 (H6); H36 breccias such as Buck Mountains Wash and BM 004; and L6 chondrites such as BM 002 and BM 003 (which may be paired), Palo Verde Mine, and BM 005. To confidently pair such meteorites often requires thorough petrographic examination, mineral-chemical analyses, and terrestrial ages. We estimate that 50 +/- 10% of the larger specimens in this area are paired, yielding a relatively high value of approximately 2.32.9 distinct meteoriteskm2. The meteorite flux estimated for Franconia area is higher than the flux inferred from contemporary fireball data for larger masses. We suggest that one large H36 meteoroid fell in the area, most likely that of Buck Mountains Wash approximately 4kyr ago, which produced an elliptical strewn field with masses generally increasing toward one end, and which raised the meteorite productivity in the recovery area.