Fine-grained Mass Research Articles

Geotechnical aspects of fine-grained mass flow deposits: California Continental Borderland

Seismic reflection profiling demonstrates the importance of mass movement in the north-central California Borderland. Bulk properties of surficial hemipelagic sediments in the Santa Barbara, Santa Cruz, and San Nicolas basins show that different types of mass-transported sediments have different properties, although their general sedimentologic characteristics are very similar. Slump deposits have moderate water contents (48% wet weight basis), high plasticity indices (46%), and moderate activities (1.6). For debris flows these values are low: 28%, 5%, and 0.3, respectively, and for other types (liquefied flow, mudflows, and turbidities) the values are high: 54 to 63%, 49 to 58%, and 1.2 to 1.5, respectively.

Eudidymite and epididymite from the Ilímaussaq alkaline intrusion, South Greenland

Eudidymite has been discovered as lamellar or spherulitic aggregates in veins of albitite in alkali granite and in poikilitic nepheline-sodalite syenite (naujaite) in the Ilímaussaq alkaline intrusion, South Greenland. In the veins in granite it is associated with microcline, quartz, albite, arfvedsonite, ægirine, polylithionite, narsarsukite, monazite and elpidite. In naujaite eudidymite is associated with albite, microcline, fluorite, analcime, tugtupite, epididymite, genthelvite, neptunite, schizolite, lithium mica, ægirine, katapleiite, etc. Epididymite occurs as microcrystalline or fine-grained masses associated with analcime, albite, tugtupite, eudidymite leucophane, schizolite, etc. in veins of albitite in naujaite. The optical properties of the two minerals are: eudidymite: nα = 1.545, nγ = 1.549, 2 Vγ = 25°; epididymite: nα = 1.540, nγ = 1.544, 2 Vα = 16-26° with a pronounced crossed axial plane dispersion. Both minerals are polysynthetically twinned. Chemical analyses of the two minerals are recorded. The X-ray powder diagrams are identical with those of epididymite and eudidymite from Lovozero. Eudidymite and epididymite were formed during late albitization of naujaite. Their mode of occurrence recalls that of these two minerals at Lovozero, the Kola peninsula.