domenica 29 giugno 2014

Vitruvius and Cauchy region

Vitruvius Cauchy domes (termed Vitruvius Vi 1-6 and Cauchy C1-19)

by Paolo Lazzarotti


by Mike Wirths


by Mike Wirths 

Vitruvius domes (termed Vi1-Vi6)
Dome
Longitude
Latitude
Diameter [km]
Heigth [m]
Slope[°]
Vitruvius 1
Vitruvius 2
Vitruvius 3
Vitruvius 4
Vitruvius 5
 32.41
32.49
32.25
33.39
33.54
13.85
14.48
14.29
13.96
14.59
5.8 ± 0.5
6.3 ± 0.5
6.0 ± 0.5
6.0 ± 0.5
5.0 ± 0.5
90 ± 10
130 ± 15
140± 15
70 ± 10
50 ± 5
1.7 ± 0.2
2.3 ± 0.2
2.7 ± 0.2
1.3 ± 0.1
1.1 ± 0.1
Vitruvius 6
33.39
13.96
7.3 ± 0.5
90 ± 10
1.5 ± 0.2


The domes termed Vitruvius 2 and 3 show a higher flank slope of 2.3°-2.7°, presumably as a consequence of higher viscosity of the lava from which they formed and the lower lava effusion rates. With their moderate lava viscosities and higher effusion rates, the other examined domes are characterized by lower flank slopes < 2°. The rheologic model indicates magma viscosity in the range from 1.0 x 104 to 9.4 x 105 Pa s, effusion rates of E = 45-100 m3 s-1, duration of the effusion processes of 0.6-2.0 years. The domes Vi1, Vi2, Vi3 and Vi6 in northern Mare Tranquillitatis belong to class C2, and their magma reservoirs are located below the lunar crust, while the neighbor Vi1, Vi4 and Vi5, with their smaller diameters, lower flank slopes and lower edifice volumes are situated between classes A, C2, and E2. Furthermore, the examined domes are aligned radially with respect to the Imbrium basin. A proposed explanation for these observations is that the domes were formed along crustal fractures generated by major impact events, hence running radially with respect to the basin locations. Another alternative explanation is that the examined domes are part of larger volcanic province of the Cauchy shield as introduced by Spudis et al. (Spudis, P. D., McGovern, P. J., Kiefer,  W. S., 2013. Large shield volcanoes on the Moon, J. Geophys. Res. Planets., 118).

Cauchy domes (termed C1-C19)
Dome
Longitude [°]
Latitude [°]
Slope [°]
Diameter [km]
Heigth [m]
Cauchy 1
Cauchy 2
Cauchy 3
37.48
38.32
36.73
7.11
7.23
7.58
0.35 ± 0.03
1.17 ± 0.1
1.28 ± 0.1
8.1 ± 0.5
12.2 ± 0.5
17.0 ± 0.5
25 ± 3
125 ± 10
190 ± 20
Cauchy 4
36.78
8.85
0.43 ± 0.05
13.3 ± 0.5
50 ± 5
Cauchy 5
33.02
10.56
1.03 ± 0.1
11.1 ± 0.5
100 ± 10
Cauchy 6
Cauchy 7 (Grace)
31.97
35.86
10.76
14.23
0.74 ± 0.1
2.00 ± 0.2
7.7 ± 0.5
8.0 ± 0.5
50 ± 5
140 ± 15
Cauchy 8
Cauchy 9
Cauchy 10
Cauchy 11
30.72
34.76
35.19
36.75
14.40
10.06
10.00
11.06
2.50 ± 0.2
0.15 ± 0.01
0.30 ± 0.3
0.70 ± 0.1
12.5 ± 0.5
13.3 ± 0.5
19.2 ± 0.5
12.2 ± 0.5
270 ± 30
15 ± 2
50 ± 5
75 ± 10
Cauchy 12
37.20
12.37
0.45 ± 0.05
6.3 ± 0.5
25 ± 3
Cauchy 13
39.32
13.50
1.00 ± 0.1
11.0 ± 0.5
95 ± 10
Cauchy 14
33.92
10.62
0.73 ± 0.1
7.0 ± 0.5
45 ± 5
Cauchy 15
Cauchy 16
33.19
32.35
11.76
11.95
0.48 ± 0.05
0.73 ± 0.1
13.0 ± 0.5
14.4 ± 0.5
55 ± 5
90 ± 10
Cauchy 17
32.44
12.49
0.82 ± 0.1
7.0 ± 0.5
50 ± 5
Cauchy 18
Cauchy 19
30.04
29.92
14.06
14.42
1.90 ± 0.2
2.00 ± 0.2
7.2 ± 0.5
4.0 ± 0.5
125 ± 10
70 ± 10
NTA1
35.05
14.73
0.34 ± 0.03
17.1 ± 0.5
50 ± 5
NTA2
35.30
14.36
0.70 ± 0.1
5.7 ± 0.5
35 ± 5
NTA3
36.13
14.01
0.62 ± 0.06
9.2 ± 0.5
50 ± 5
NTA4
36.47
13.68
0.62 ± 0.06
8.3 ± 0.5
45 ± 5
NTA5
36.72
13.57
0.50 ± 0.05
5.7 ± 0.5
25 ± 5
NTA6
37.49
13.07
0.49 ± 0.05
7.0 ± 0.5
30 ± 5
D (Diana)
35.57
14.31
1.31 ± 0.1
6.1 ± 0.5
70 ± 10

Two well-known domes in this region are Cauchy ω (C2) and τ (C3). The vents of C1, C4, C13 and C15 are all aligned in about the same direction. This direction is parallel to Rima and Rupes Cauchy and also to the direction in which the eight domes in northern Mare Tranquillitatis (NTA domes), including Diana and Grace are aligned. This direction is approximately radial to Mare Imbrium.So an explanation of the alignment is that domes were formed along crustal fractures generated by major impact events, hence running radially with respect to the basin locations. Evidence for this is particularly strong at the Cauchy region, which is characterized by a set of large graben/lava fissures (Rimae Cauchy I and II) that are radial to Imbrium basin. North of Rima Cauchy, another alignment of lunar mare domes is situated, termed Northern Tranquillitatis Alignment (NTA). C2 (Cauchy ω) has a diameter of 12.2 km, a height of 125 m, an average flank slope of 1.17° and an edifice volume corresponding to 7.2 km3, while its neighbor C3 (Cauchy τ) is characterized by larger diameter (17 km), with height of 190 m corresponding to a flank slope of 1.3°. Another alternative explanation is that these domes are part of larger volcanic province of the Cauchy shield. The examined domes span a continuous range of properties from spectrally blue (class A) to red (class E) soils and from very low (class A) to steep (class E1) or shallow (class E2) flank slopes. The class E domes represent the smallest volcanic edifices formed by effusive mechanisms observed to date. Domes of class C2 are characterized by gentle flank slopes, moderate volumes which are higher than those of class A. Moreover the corresponding effusion rates are comparable to those estimated for the class A domes, but the class C2 domes were formed over longer periods of time between about 0.8 and 5 years. Modeling results indicate that some domes belong to class A (C1, C4, C6, C14, C15, C17), while C2, C3, C5, C7, C8 belong to class C2. C12 belongs to class E2 while Diana with its smaller diameter, lower flank slope is situated between classes A, C2, and E2. The domes termed C13, NTA2, NTA5 and NTA6 are situated between classes A and E2, NTA1 between classes A, C1, and C2, while the domes NTA3 and NTA4 between classes B2 and C1

The domes C11 and C16 show elongated shape and dimensions, flat summit and very low slopes. So they could be considered candidate intrusive domes and belong to class In2. The domes C9 and C10 have extraordinarily low flank slopes and their outlines are strongly elongated, and make the occurrence of intrusions at least plausible, and belong to the class In3.