# Vesicles and Reservoirs of Basic Lava Flows in the Laobeishan and Huoshaoshan Volcano, NE China
## 5 Discussion
### Connectivity between Shrinkage Fractures and Vesicles
The longitudinal fractures all occur at a high angle of almost vertical elevation. The fractures are concentrated in the middle and upper zones of the lava flow. The fracture width is 0.2-3.2 cm, the fracture spacing is 14-28 cm, the apparent length is between 8.4-74.2 cm, the surface density is 18.91 m/m\({}^{2}\), and the linear density is 4.1 strip/m. The fracture surface density in the top zone is 36.74 m/m\({}^{2}\), and the linear density is 7.5 strip/m. Some fractures were deflected in the vesicle zone, and some were filled with mud in the basal vesicle zone. An image of the top vesicle zone was selected to analyze the influence of fractures on vesicle connectivity in the outcrop view (Figure 11a). The total number of vesicles in the image area was 406, and the number of connected vesicles was 63, accounting for 15.5% of the total. The proportion of connected vesicles was approximately 5.95%, accounting for 19% of the total surface porosity. The angle between the fractures and the directionally arranged vesicles was concentrated between 30\({}^{\circ}\) and 60\({}^{\circ}\). Some researchers have found that the angle between fractures and directionally arranged vesicles presents a greater connectivity effect within 30\({}^{\circ}\)-60\({}^{\circ}\), and the connectivity is highest when the angle is 45\({}^{\circ}\)[47]. There were 18 fractures in the proximal belt outcrop, 16 of which were longitudinal and two were transverse, and they also existed at high angles. The fracture width is 0.1-1.9 cm, the fracture spacing is 14-30 cm, the apparent length is between 2.1-91.6 cm, the surface density is 25.19 m/m\({}^{2}\), and the linear density is 12.7 strip/m. The fracture surface density in the top zone was 48.29 m/m\({}^{2}\), and the linear density was 18.2 strip/m. The top zone develops cavernous dissolution vesicles, and fractures can be seen connecting vesicles with larger apparent diameters. An image of the top vesicle zone was selected to analyze the influence of fractures on vesicle connectivity in the outcrop view (Figure 11b). The total number of vesicles was 705, and three fractures developed in the imaging area; there were 97 connected vesicles, accounting for 13.8%. The surface porosity of the connected vesicles was approximately 8.59%, accounting for 40.9% of total surface porosity. The angle between the directional vesicles and high-angle fractures was approximately 60\({}^{\circ}\), and that between the near-horizontal fractures was less than 30\({}^{\circ}\). There were 28 fractures in the distal belt outcrop, most of which existed at a high angle, and only five short transverse fractures, which were extremely irregular in distribution. The fracture width was less than 1.6 cm, the fracture spacing was about 10 cm, the apparent length was between 7.1-57 cm, the surface density was 43.28 m/m\({}^{2}\), and the linear density was 6.7 strip/m. We selected an image of the top vesicle zone to analyze the influence of fractures on vesicle connectivity in the outcrop view (Figure 11c). There were 649 vesicles, 5 fractures developed in the imaging area, and 64 connected vesicles (9.9%). The surface porosity of the connected vesicles is approximately 1.26%, accounting for 4.7% of the total surface porosity. The intersection angle between the fractures and vesicles was wide, and the connectivity was the worst among the three facies belts. The fracture distribution in hornito is affected by genetic mechanisms and the forming environment. Due to the condensation of the \"lava cake\" from the inner molten lava spilling over the surface and forming the closed structure. The high-temperature expansion of the cooling shrinkage core of the shell constrained the deformation and generated temperature stress, while the maximum principal tensile stress trace was distributed in a ring [48]. Under the action of temperature stress, the \"lava cake\" forms fractures. The fractures were distributed radially on the plane and approximately equidistant from each other.